STUDIES RELATED to the SYNTHESIS of a Thesis Presented

STUDIES RELATED TO THE SYNTHESIS OF

TETRACYCLINE

a thesis presented by

NORMAN JAMES ALBERT GUTTERIDGE

in partial fulfilment of the requirements for the degree of

DOCTOR OF PHILOSOPHY

Chemistry Department, Imperial College, LONDON June, 1966. To Jo ABSTRACT

A review of some important reactions of tetracycline are presented. An account of the attempts to synthesise tetracycline follows with a summary of the progress contributed by workers in these laboratories. The new contribution to this work commences with a study of the reduction of the 9-oxo function in 2-phenyl- 3-cyano-3-tetrahydropyranyloxy-9-oxo-2a18,8a-trihydro- naphthacene[4,4a$5,bc]furan (A).

(A)

An attempted conversion of 2-phenyl-3,8a-(N-phenyl- isoxazolidine)-9-oxo-2a1 3,8,8a-tetrahydronaphthaceno[4,4a,- 5,b0]-furan (B) into 2-phenyl-3/9-dioxo-2a0,8a-trihydronaphthaceno[4,4a,5,bc]furan (C) is then described together with a re-examination of previous work on these derivatives. (B)

(C)

To assist studies in this series of compounds, 1-N- phenylamino-1,2,3,4-tetrahydronaphthalene was synthesised. A preparation of 2-phenyl-4-(31 15'-diacetoxy-21- ethylene-acetal-4'-carbomethoxybenzy1)-5-oxo-naphtho- [4,10,5,bc]furan (D), a suitable precursor for the recently described photocyclisation process, is described in detail.

(D)

0 — C Ph

Finally, studies in the 2 -phenyl -4,6 -dihydroxy-5 -carbo - methoxy -3,8a -(N -phanylisoxazolidine)-9 -oxo -2a,3,8,8a - tetrahydronaphthaceno[4,4a,5,bc]furan series (E) were commenced.

(E) ACKNOWLEDGEMNTS

thank Professor D.H.R. Barton, F.R.S., for the privilege of working for him and for his constant interest, guidance and encouragement. I also thank Dr. J. E. Baldwin for his helpful advice and enthusiasm at all times. I wish also to thank other members of the Laboratory (1963-1966) for helpful discussions. Thanks are due to the technical staff for their assistance; in particular to Mr. D. Aldrich, Mr. P.R. Boshoff, Mrs. 1. Boston, Mr. E. Pilch and the analytical staff of the department.

A Science Research Council grant is gratefully acknowledged. CONTENTS Page Introduction 1 Some reactions of the tetracyclines 8 1.Reduction 10 2.Oxidation 14 3.Aromatisation 16 4.Epimerisation 20 5.Reactions on nitrogen atoms 21 6.Reactions on oxygen atoms 24 7.6-Methylenetetracyclines 27 8.Halogenation 29 9.Nitration 30 10.Photolyses 32 11.Chelation 33 Synthesis of tetracyclines 36 References 52 Outline of previous work 62 Studies related to the synthesis of tetracyclines 78 Experimental 184 References 290 1

INTRODUCTION

The name 'tetracycline, has been assigned(1) to a group of antibiotics characterised by their common hydronaphthacene skeleton. These pale yellow crystalline antibiotics possess broad spectra of antibacterial activity and are produced by strains of streptomyces. The first example of this class of compound, aureomycin (1), was isolated in 1948 by Duggar(2) from streptomyces aureofaciens. A similar compound, terramycin (2), was isolated from streptomyces rimosus in 1950 in Chas. Pfizer and Co. Laboratories:(3) In 1952, the structures of these complex natural products were elucidated by Woodward and his co-workersS4) The parent compound of the family, tetracycline (3), was isolated from streptomyces albo-niger(5) and shown to be identical to the hydrogenolysis product of aureomycin.(6,7) Terramycin and aureomycin have thus the generic names oxytetracycline and chlorotetracycline respectively. The accepted numbering system for the carbon skeleton of tetracycline is as depicted in (4). These antibiotics have been extensively used in the chemotherapy of infectious diseases on account of their 2 —

Cl OH\ Tie N(Me) 2 OH (1)

CONH2 O H OH OH 0

( 3 )

( 4 ) powerful activity against a broad spectrum of pathogenic organisms. Tetracycline itself has largely replaced the other two tetracycline antibiotics in clinical practice and now is one alternative to penicillin for treating acute throat infections and is standard treatment for chronic bronchitis.(8) Tetracycline is readily absorbed from the gastro intestinal tract and the blood stream, is highly stable and well tolerated by any route of administration.(9) The low side effects are mainly due to the effect of the drug on the alimentary tract and its flora. The tetracyclines have also found favour as preser- vatives of fish and meat.(10) Studies on the biosynthesis of 7-chlorotetracycline have demonstrated that [1-14C]- and [2-14C]acetate,(11) [2-140]glycine and [CH3-140]methionine(12) all produced high levels of 14a incorporation. The skeleton is largely built up from ahead to tail' linkage of acetate units. Birch has shown that the methyl and chlorine atoms were introduced directly and suggested that whereas the greater part of the molecule was derived from the poly-3-carbonyl framework (5), a large part of ring A was derived from glutamic acid.(13) Gatenbeck's results, on the other hand, indicate that the hydronaphthacene ring system was - 4 — [Mei [Me] [0]

o o o ( 5 ) *-[CO 2H]

0 [0 ] 0

Me 1 OH (6) CONH2 0H

( 7 )

Me H OH H OH (9) CONH2 OH derived entirely from acetate units and the carboxamido group was formed from carbon dioxide produced in the fermentation. Support for the later theory comes from the demonstration that compound (6) is a direct precursor to tetracycline. McCormick has established that oxidative hydroxylation of 5a,6-anhydrotetracycline (7) at C-6, succeeded by reduction of the resulting 5a,11a-dehydrotetracycline (8), were the final steps in the biogenesis of these antibiotics.(15) Chemical and X-ray studies(16,17) as well as the recent application of N.M.R. (18,19,20) have confirmed the relative stereochemistry depicted in structures (1,2,3). In all probability the other naturally occurring tetracyclines(21) (e.g. 9, 10, 11) possess the same con- figurations at all common asymmetric centres. In 5- hydroxytetracycline, however, differences in interpretation of the X-ray data for the 0-5 configuration has led to an N.M.R. study. The protons at C-5a and C-4a have been shown in 4-dedimethylamino-5-hydroxy-12a-22175a16- anhydrotetracycline (12) to be trans-diaxial. The con- formations of several 5-hydroxytetracyclines in solution appear to be different from that derived tentatively by X-ray studies.(17) Cl CH 1.1 NMe2

(10) CONH OH 2 OH OH

Bt OH Me 1IMe2

(12) Shemyakin(22) has shown that structure (1) also expresses the absolute configuration of these antibiotics by O.R.D. studies on 7-chlorotetracycline. Tetracyclines have recently been subjected to treatment by mass spectrometry(23) as well as some related compounds .(24) All the derivatives of tetracycline examined were reasonably volatile without extensive thermal decomposition except for 5-hydroxytetracycline which was partially cleaved before entry into the ion chamber. Strong molecular ion peaks were observed and almost all cleavages occurred in rings A and B, since the aromatic ring D and the ease of aromatisation of ring C conferred stability on the molecule. - 8 -

Some reactions of the tetrac clines

The reactions may be divided into a) skeletal re- arrangements, including reactions causing extensive decomposition of the molecule and b) transformations involving the existing functional groups. In the former group the reactions have been used primarily for structure elucidation. Reaction conditions to be controlled with care in synthetic work include the use of both acids and bases. In mildly alkaline (pH 8) solution the C ring of the tetracyclines are opened to yield the biologically inactive iso-tetracyclines (13). This reaction is markedly accelerated by the presence of substituents at C-7.(25) Acid catalysed dehydration occurs readily as expected of a t-benzyl alcohol. In the tetracyclic series the 5a,6-anhydrotetracyclines are formed but the 5-hydroxy-5a,6-anhydrotetracyclines react further under these conditions to give the ado-terramycins (14).(9) In the latter category numerous compounds have been prepared in order to provide a base for a detailed insight into structure-activity relationships. Some of these important reactions will be reviewed here and procedures that might be used to complete a total synthesis will be noted.

Me (me)2

( 13 )

H (14) ONH2

N(1,1e)2 H (15)

ONH2 a) X = 01 ID) X =Br -10 -

The reactions presented are classified as far as possible according to general types of reaction although it is recognised, however, that in such a classification many reactions affect the total molecule. A consideration of separated functional groups is not possible in some cases and instead their mutual interactions are discussed.

1. Reduction Many functional groups of the tetracyclines have been reduced quite specifically, so that a study of the effect of these groups on antibacterial activity can be made. The reductive removal of halogen in 7-.halogenotetracyclines to give tetracycline illustrates the non-essential role of halogen for hiological activity. This reduction can be carried out in neutral solution(25) with a Pd/C catalyst, but it was usual to add a bse e.g. triethylamine or triethanolamine.(6) In a similar way,(26,27,28) ila-halogenoderivatives (15) may be hydrogenolysed. An alternative means of replacement of the lla-halogen substituent was treatment with zinc in acetic acid or with aqueous sodium hydro- sulphite.(28) The lla-halogen thus offers a convenient way of protecting the 11,12-P-dicarbonyl system In synthetic work. — 11 -

Zinc in glacial acetic acid also effected removal of the 4-dimethylamino and the 12a-hydroxyl functions.(25) A superior method for the reductive removal of the 4- dimethylamino group was the reduction of the methiodide (P.23) with zinc in aqueous acetic acid. All 4-dedimethylamino derivatives appear to have little biological activity. 12a-Deoxytetracyclines may be conveniently prepared by reduction of tetracycline with zinc in aqueous ammonium hydroxide(29) or hydrogenolysis of 12a.0-formyl(30 or 12a-0-phenylcarbamoyl derivatives.(31) There is a claim,(32) however, that in the former case, tetracycline yields the 4-al derivative under these conditions. The 12a-deoxy derivatives are devoid of activity, due presumably to the altered pattern of enolisation and consequent alteration of the geometry of the molecule. Another reductive removal of a functional group in tetracyclines is the removal of the 6-hydroxyl group. Hydrogenolysis of tetracyclines in the presence of dilute acid(33'34) gave 6-deoxy-6-a1-tetracyclines.(35,36) A feature of this reaction was a tendency for the 6-hydroxyl to be removed by dehydration(34) rather than by hydrogenolysis to give reduction products of 5a,6-anhydrotetracycline(37) (16a,b,c). This side reaction was - 12 - N(Me) 2

(16)

2 OH R R' 0 a) R = H; RI = OH b) R = OH; R' =H a) R = H; =H

(17)

(18)

CH OH N( Me ) 2 4 OH (19) CONH I A n 2 OH 0

OH NS Me )2

( 20 ) 1 ~`CONH OH 2 OH OH a) R= H; R' = Me b) R = Me; R = H catalysed not only by hydrogen ions but also by noble metals and hydro gen and in view of the apparent invariable coproduction of anhydro compounds with 6-deoxytetracyclines it has been speculated that both may arise from a common intermediate on the catalyst surface.(35) Tetracyclines which do not contain a C-6 methyl group undergo reductive removal of the secondary benzylic hydroxyl in better yields .(35) Reduction has proved a useful way of degrading tetracyclines but reduction may also be used in synthetic work to generate tetracyclines from their dehydro derivatives. 33411a-Dehydro -7-chloro tetracycline (17 ) absorbed two molecules of hydrogen in the presence of a Pd/C catalyst to give a mixture of tetracycline and 33.- 21-tetracycline (18) . (38) This derivative (18) has only about half the biological activity of tetracycline but as the hydroxyl group is cis to the hydrogen in the 5a-position, 5a-apl-tetracycline was not readily dehy- drated in the presence of strong acids. Mixtures of 0-6 epimers of tetracyclines were formed on hydrogenation of the 6-methylene derivatives (p. 27 ) • Hydrogenation of 6-methylene-5-hydroxytetracycline (19) yielded a 111 mixture of C-6 epimers of 6-deoxy-5-hydroxytetracycline (20). Apparently both faces of the molecule are of - 14 - equal accessibility in these hydVogenation reactions.

2. Oxidation Strong oxidising agents caused degradation of the tetracyclic molecule to give no readily identified products Mild oxidising conditions recently enabled a new interesting class of tetracyclines to be prepared. Treatment of 6-demethyltetracycline (21) with mercuric acetate(39) gave the tetracycloxides (22), the new 4,6- hemiketal derivatives of tetracycline (p.27 ). 12a-Oxygenation has received much study on account of its important place in a successful synthesis of tetracycline. Many procedures have now been devised for accomplishing this addition of an oxygen atom in the 12a-position. Woodward(4O) used molecular oxygen in the presence of cerous chloride to introduce the 12a-hydroxyl in the synthesis of (±) 6-deoxy-6-demethyltetracycline (23). Other methods include oxygen with sodium nitrite,(41) and other salts,(42) oxygen and a noble metal,(43) inorganic oxidising agents,(41) and a microbiological method using aurcularia lunata.(44) Muxfeldt(32) has found that perbenzoic acid hydroxylated 4-dedimethylamino- 12a-deoxytetracycline (24) but gave a mixture of the expected product and its 12a-epimer (25). - 15 -

(21)

(22)

(23)

OH (24)

CONH2

Me OH

(25) -16 -

Another specific oxidation reaction which proved useful for confirmation of structures, was ozonolysis. The 6-methylenetetracyclines (p.27 ) on ozonolysis(45) yielded formaldehyde which was isolated as its dimidone adduct. Other oxidation procedures e.g. photo-oxidation and aromatisation are considered later in the appropriate sections.

3. Aromatisation Tetracycline derivatives containing an aromatic ring A were readily formed after removal of the 12a-oxygen atom. Treatment of the 12a-deoxytetracycline (26) with perbenzoic acid afforded the 4a,12a-anhydro-4-dedimethyl- aminotetracycline (27). It is thought that the N_-oxide is an intermediate in this reaction(29) and its ready formation indicates why perbenzoic acid cannot be used to oxygenate 4-dimethylamino derivatives in the 12a-position. Alternative routes to ring A aromatic derivatives are the treatment of 1247-deoxytetracycline (26) with methyl iodide and propylene oxide in refluxing tetrahydrofuran(46) and base treatment(47) of the 12a-bromo- 12a-deoxy-4-dedimethylamtnotetracycline (28) to give compaund (27). (26)

0 Me

(27)

(28)

Me nMe) 2

(29) -CONH OH I 2 OH 0

(30) - 18 -

The facile acid catalysed dehydration(4) of tetracyclines to give 5a,6-anhydro derivatives is the most convenient route to these biologically inactive derivatives. When dehydration was effected by anhydrous hydrogen chloride in acetone, acetone derivatives of the anhydro compound were isolated, but these could be converted into anhydro tetracyclines by aqueous acid.(48) Dehalogenation(49) as well as dehydration takes place when 7-halogenotetracyclines were treated with concentrated hydriodic acid. The product isolated from this reaction was 5a,6-anhydrotetracycline (29). The work of Scott(50) and Wittenau(51) has shown that a powerful new route to tetracyclines is now available by photo oxidation of 5a,6-anhydrotetracyclines. Only mild acid conditions are necessary to bring about the formation of fully aromatic tetracyclic molecules from 4a112a-anhydroderivatives. Terrarubein (30) has been formed from 4a,12a-anhydrotetracycline (31) in this way.(30) Strains of streptomyces aureofaciens have been shown to convert 4-dedimethylaminoterrarubein (6) into 7-chlorotetracycline.(52) This elegant combination of chemical and microbiological methods for the synthesis of tetracyclines opens a relatively simple - 19 -

( 31 )

'CON;

( 32 )

( 33 )

( 34 ) - 20 -

route to the preparation of a range of semisynthetic analogues and also affords further insight into the biogenesis of tetracyclines. The aromatic hydrocarbon, naphthacene isolated after the zinc distillation of 4-dedimethylaminoterrarubein (6), demonstrated the linearly fused tetracyclic system.(4)

4. aimerisation Epimers of the 4,5a,6 and 12a positions in synthetic and natural tetracyclines have been reported widely. The 4-position is of interest since in solution the tetracyclines undergo reversible epimerisation in the pH range 2-6 to give the 4--tetracyclines (quatri- :veins).(53) Epimers have been separated from their equilibrium mixtures by fractional distillation, counter- current extraction procedures or paper chromatography. Partition chromatography followed by counter-current extraction separated 4-dedimethylamino-4-221-amino-5a,6- anhydrotetracycline (32) from the normal 4-substituted compound.(54) The observed 0-4 proton downfield shifts in the N.M.R. spectrum upon epimerisation were consistent with the 1 p.p.m. shift shown in 5a,6-anhydrotetracycline.(20) - 21 -

The 4-221-tetracyclines are more stable to acids and bases but have much less biological activity than the tetracyclines.

5. Reactions on nitrogen atoms Before it had been established that the reversible epimerisation observed in tetracyclines in the pH range 2-6 involved the configuration at C-4, another possibility was suggested. Changes in the orientation of the 2- carboxamido group could lead to two interconvertible species since the free rotation of this group might be prevented by strong hydrogen bonding with the two adjacent oxygen functions. An attempt to exclude the carboxamide orientation possibility was the dehydration of the non-symmetric carboxamide group to the linear nitrile group which could rotate freely: Dehydration was achieved with p-toluene sulphonyl chloride(25) or methane sulphonyl chloride,(55) as well as by other reagents.(56'57) 5-hydroxytetracycline,In 6-deoxytetracycline and 6-deoxy-7-chlorotetracycline on treatment with an aryl sulphonyl chloride gave the 10- aryl sulphonyl ester of the nitrile.(4) Tetracyclino- nitrilea and their supposed 4-epimers were shown to be isomeric and distinguishable but neither could be reversibly - 22 -

interconverted under conditions which equilibrated the tetracyclines. The experiment, however, demonstrated that the intact carboxamido group may be involved in the ready interconversion of the parent compounds but is not essential to the existence of isomeric pairs. Nitrile analogues are versatile intermediates in the 6-deoxytetracycline series since in addition to their ready conversion to the parent amides by routes involving strong acids, they may be used to form N-alkyl amide derivatives via the Ritter reactim.(35) Acid hydrolysis of these N-substituted amides regenerate the corresponding tetracycline.(58) These reconversions open up other potential relay points for total synthesis efforts. The Ritter reaction using 2-decarboxamido-2-cyano- 6-deoxytetracycline (33), concentrated sulphuric acid, isobutylene and glacial acetic acid produced N-t-buty1- 6-demethy1-6-deoxytetracycline (34).(35) This compound represented the first example of a simple alkylated amide derivative of a fully active tetracycline. It was of considerable interest from a structure-activity viewpoint because the antibacterial spectrum was much narrower than tetracycline being active against gram-positive organisms only. - 23-

The 6-hydroxytetracycline nitriles gave the 2-N- alkylcarboxamido-5a,6-anhydrotetracyclines(59) under the Ritter conditions since dehydration also occurred in the presence of strong acids. The reaction between tetracycline nitriles, formaldehyde and secondary amines or amino acids gives rise to a series of water soluble Mannich bases(60,61,62,63,64) that have undiminished antibacterial activity. 2-(N- Morpholinomethyl)carboxamidotetracycline (35) has been formed in this way and regeneration of the tetracycline may be achieved by treatment with aqueous sodium bisulphite or Raney-nickel. The ease of reduction of the methiodides to 4-dedi- methylaminotetracyclines has been previously mentioned (p.II ) and on account of the short reaction time required only slight loss of the 12a-hydroxyl group takes place under these conditions. Not all tetracyclines gave stable methiodide derivatives but those which did were best formed by mixing tetracyclines with methyl iodide in dioxan at room temperature.(65) 5-Hydroxytetracyclines yielded only the crystalline tetramethylammonium iodide on treatment with methylindide. Initial quaternisation followed by elimination of trimethylamine resulted in this prot%uOt - 24 - being formed. Betaines produced from these quaternary derivatives may be reconverted by the action of hydriodic acid. The quaternary derivatives are relatively inactive as antibacterial agents as compared to the tetracyclines from which they are prepared.

6. Reaction on oxygen atoms Many of the 0-substituted tetracyclines are active biologically but this is probably due to their ready hydrolysis. Among the ester derivatives of the tetracyclines, the diacetate derivatives of 5-hydroxytetracycline are of greatest interest. The 10,12a-diacetyl compound was produced on acetylation with acetic anhydride in pyridine which on contact with one mole of sodium hydroxide containing magnesium chloride rearranged to give the 5,12a-diacetate.(4'66'67) Hydrolysis with 1N sodium hydroxide(4) regenerated 5-hydroxytetracycline in ten minutes. These diacetates offer a possibility of protecting the 5,12a-hydroxy groups of 5-hydroxytetracycline in synthetic work. During initial work on the constitution of 5-hydroxytetracycline this compound was reacted with diazomethane. A 10% yield of a dimethyl ether was obtained which has been shown to be probably the 5,12-dimethylether. (4,68,69) - 25 -

The formation of hemiketals has uniquely established the stereochemical assignments in the tetracyclines. Interaction of perchloryl fluoride with tetracyclines under basic conditions results in two classes of lla-fluorotetracyclines. Simple lla-fluorotetracyclines were obtained only when the C-6 hydroxyl was not present. In all cases in which the starting tetracycline con- tains a C-6 hydroxyl, more involved products result from the perchloryl fluoride reaction.(26) The compounds isolated from these reactions clearly indicate the lla- fIuoro-6,12-hemiketal structure. Formation of hemiketals such as compound (36) illustrates the stereochemical assignment at C-6 and C-5a in the tetracycline series since 6,12-hemiketal ring formation is sterically possible only in the case where the C-5a hydrogen and C-6 hydroxyl are trans. The isolation of a 6-demethyl analogue was important for it provided the first experimental evidence that the C-6 hydroxyl in 6-demethyltetracycline derivatives had the same stereochemistry as in the parent series. A remarkable effect of solvent occurs in reactions employing N-halogenosuccinimide. In 1,2-dimethoxyethane N-chlorosuccinimide(28) afforded with tetracycline, the lla-chlorotetracycline-6,12-hemiketal (37). Reduction - 26 -

( 3 6 )

( 3 7 )

( 3 8 )

OH ( 3 9 ) CO NH2

( 40 ) - 27 - of these derivatives gave back the parent tetracycline but dehydration occurred with liquid hydrogen fluoride to give the lla-chloro-6-methylenetetracyclines (38)(45) (p • 14 ) • Treatment of tetracycline hydrochloride with N- chlorosuccinimide in water generated the 4-oxo-4-dedi- methylaminotetracycline-4,6-hemiketal (39)(70) (P.A.- ). A novel way of introduction of nitrogen at 0-4 was discovered when these tetracycloxides (39) were treated with hydrazine or hydroxylamine. Subsequent reduction gave the corresponding 4-2217-amino derivative (40). The suggested mechanism of the formation of the 4,6-hemiketals is via the imine intermediate (Scheme 1).(71) The proposed structures of the 7-halogeno derivatives of compound (39) have been confirmed by single crystal X-ray analysis.(72) The 4-dimethylaminotetracycloxides(22) have also been prepared.(59'75)

7. 6-Nethylenetetracyclines The 6-methylene derivatives are useful intermediates in the formation of novel substituted tetracyclines. Their preparation from 6,12-hemiketal derivatives and their conversion to 6-deoxytetracyclines have been mentioned above. lla-chloro-6--methylenetetracycline (38) - 28 - _SCHEME 1

NH(Me)Me ) 2 NH (Me ) 2 Me-N-Me 0

9H 6 4

H ( 41 ) CONH2

PhCH S CH2 10H 1y(Me ) 2 H ( 42 ) 000111 CONH OH 2 OH OH

( 43 ) - 29 -

upon reduction afforded the fully biologically active 6-methylenetetracycline (41). These derivatives react with thiols and thioacids by a typical free-radical addition across the olefinic bond. This addition could be catalysed by oxygen, peroxides or 2,2,-azo-bis(2- methylpropionitrile).(45) Support of the structure of these thio derivatives (e .g.42) came when after desulphurisation with Raney-nickel the corresponding 6-deoxytetracyclines were formed.

8. Halogenation The most common reagents for halogenation of tetracyclines appear to be perchloryl fluoride and the N- halogenosuccinimides. The use of perchloryl fluoride in basic media, as indicated earlier, converts 6-deoxytetracyclines into their lla-fluoro derivatives (43).(74) There is a tendency for the N-halogenosuccinimides (27,75,76,77) to react differently with a tetracycline according to the acidity of the reaction medium. When a 6-deoxytetracycline was treated with E-bromosuccinimide in concentrated sulphuric acid at 000, a 7-bromo-6-deoxytetracycline was formed.(76) The proof that the bromine atom was in the 7-position in these compounds was obtained by carrying out the reaction with 6-demethy1-6-deoxy- [7-3H]-tetracycline and isolating the inactive halogen -30 - derivative. On treatment of 6-demethyl-6-deoxytetracycline under less acidic conditions (e.g. in acetic acid), with N-bromosuccinimide gave the lla-bromo derivative (44).(76) This different behaviour of N-halogenosuccinimide has been explained by the protonation of the 11,12-(3-dicarbonyl system making the 0-11a atom more inert to electrophilic halogen. The formation of tetracycloxides with H7chlorosuccinimide demonstrates another effect of acidity in reactions of tetracycline. In this case, the hydrochloride assists enolisation in ring A and promotes attack at 0-4 (Scheme 1).

9. Nitration The enhanced acid stability of the 6-deoxytetracyclines has rendered possible many acid-catalysed transformations with retention of biological activity. Electrophilic substitutions in the aromatic ring D have been accomplished to give halogeno, sulpho and nitro compounds. For example, nitration of 6-demethy1- 6-deoxytetracycline in concentrated sulphuric acid with one equivalent of potassium nitrate yielded the 7—nitro and the 9-nitro compounds in 25% and 29% yields respectively.(76) Other D-ring substituted products(58,76,79) have been obtained by reduction of nitro to amino groups — 31 — N.(Me) 2 OH (44)

CONH2 I I Br OH 0 0 0

( 45 )

( 46)

( 47 )

( 48) -32-

and subsequent diazotisation and Sandmeyer type reactions.

10. Photolyses. A new important route to tetracycline derivatives containing the 6-hydroxyl group became available when Scott and Bedford(50) discovered the photo oxidation of 7-chloro-5a,6-anhydrotetracycline (7). The 6-hydroperoxy derivative (45) was formed, which on catalytic reduction yielded the 7-chloro-dehydrotetracycline (8), identical in every respect to the stre rtomyces metabolite. The position of the double bond in compound (8) is not certain.

(50,51,80) 3,4-Benzpyrene as sensitiser accelerated this photo oxidation 51) Suitable 5a,6-anhydrotetracyclines may now be converted into tetracyclines since the reduction of 7-chloro•-dehydrotetracycline has been accomplished.08) Photolysis of the lla-bromo-6-deoxytetracycline (46) in acetonitrile gave the 5a,6-anhydro derivative (47) whereas in methanol or acetic acid, the 7-bromo-6-deoxy-

tetracycline (48) was formed.(81) A transient hypo- bromite may be the effective halogenation agent in this photochemical process which is a convenient method for obtaining biologically active halogen derivatives in the 6-deoxytetracyclic series. -33-

Photolysis of the diazonium salt (49) in formic acid, acetic acid or dichloroacetic acid caused displacement of the diazonium group by a formyloxy, acetoxy or dichloroacetoxy group.(82,83) The 7-fluoro-derivative (50) was formed on photo decomposition of the 6-demethyl- 6-deoxytetracycline diazonium fluoroborate in acetic acid.(83)

11. Chelation The tetracyclines form chelate complexes with metallic ions, the tetracycline:metal ratio beta* either 1:1 or 2:1. Their stability varies with the metal used e.g. Fe3+ > A13+ > Cu2+ > Fe2+ > Co2+ > Mn2+ > Mg2+, (84) the nature of the tetracycline being of little importance. The specific group the tetracycline uses to bind the metal has not been established with certainty. The 11,12-p-dicarbonyl system was suggested on results from absorption spectra.(69) Potentiometric titrations(85) of tetracycline in presence and absence of certain metallic ions appear to indicate that the binding group for at least Cu2+, Ni2+ , Zn2+ is the 4-dimethylamino nitrogen and the hydrox y 1 oxygen at C-3 or C-12a. How- ever, these assignments were based on acidity constants(68) which have now been questioned. (20,86) The electronic - 34 -

ED N=N

( 49)

(50) -- 35 spectra indicates that the octahedral complexes isolated coordinate through oxygen probably in the 1,2,3 tricar- bonylmethane gystam. (87) The antibiotic activity of the tetracycline may be due to the disturbance of certain enzyme systems by chelation of vital trace metals.(84) - 36 -

Synthesis of Tetracyclines

The complex array of functional groups in tetracyclines together with marked tendency of these system toward acidic or alkaline degradation provides a serious challenge to total synthesis of biologically active tetracycline derivatives. The task of total synthesis is rendered formidable by the minimum of five asymmetric centres present in these molecules. The stereo selective formation of these centres must be a prerequisite of any successful synthetic scheme especially those at 0-4a and C-5a as they are not subject to direct chemical manipulations when part of an intact tetracycline molecule. The total chemical synthesis of a complete tetracycline has not yet been reported, but several degradation products of natural tetracycline have been synthesised as well as many related tetracyclic and other model systems. Most success so far has been obtained by the generalised Claisen condensation involving the stepwise fusion of rings C, B and A to a benzene derivative carrying the ring .D substituents. The first total synthesis of a tetracycline derivative, the biologically active (±).4-dedimethylamino-6-demethy1- 12a-deoxy-5a,6-anhydro-7-chlorotetracycline (51), was - 37 - Cl H

(51)

OH OH 0

( 52 )

8Me

OH ( 3 )

CONH2

(54)

JMe OMe

( 55 ) (56) -38- reported in 1959 by BootheS88'89) The synthesis required 24 stages starting from 3-methyl-4-chloroanisole (52), but considerable modification of this route would be necessary to include the 4-dimethylamino group. Likewise, only 5a,6-anhydro derivatives with a 6-methyl group can be converted directly into tetracyclines(50,51) at present. Inclusion of some alterations in this route, however, culminated in the production of (±)4-dedimethylamino-6- demethy1-6,12-dideoxy-7-chlorotetracycline (53)590) In both these compounds (51,53), the 12a-hydroxyl function probably could have been introduced by methods outlined in the previous section (p.14-). (±)4-Dedimethylamino-12a-deoxy-5a16-anhydro-7-chlorotetracycline (54) was synthesised in 1959 by Muxfeldt(91) from 3-methoxyacetophenone (55) in 22 stages. In this case it is feasible that the photo oxidation method could dearomatise ring 0 with insertion of the 6-hydroxyl group. The introduction of the 12a-hydroxyl group was later demonstrated(92) but the addition of the 4-dimethylamino function would require many changes in this route. An important contribution towards the total synthesis of tetracycline came in 1962 when Woodward announced(40) the synthesis of (t)6-deoxy-6-demethyltetracycline (23). This synthetic racemic compound was observed to possess - 39 -

exactly half the activity against pathogenic organisms as its natural counterpart (93) . 21 Stages were required from methyl-3-methoxybenzoate (56) to synthesise this molecule that contained 4 asymmetric centres. The introduction of the 0-4 nitrogen function was achieved by the nucleophilic addition of dimethylamine to the intermediate (57) to give the desired base (58). Crystallisation direct from the reaction mixture was required since a rapid reversible reaction took place on the removal of the dimethylamine solvent. In his synthesis of (±)6-deoxy-6-demethyltetracycline (23) which appeared in 1965,(94) Muxfeldt used an entirely different means of 0-4 nitrogen introduction. The intermediate (59) was condensed with hippuric acid. in acetic anhydride containing lead acetate as catalyst and deketalised to give compound (60). Treatment with N-j- buty1-3-oxo-glutaramate (61) and then with sodium hydroxide yielded two 0-4 epimeric tetracyclic compounds which on subsequent removal of the N-benzoyl groups gave the 0-4 epimers (62). Alternative routes to tetracyclines have been examined. Muxfeldt has argued that the closing of ring B of tetracyclines after ring A is an advantage since the correct — 40 — Cl ?O0Bun

H' (57) 1 ,

tMe d

(58)

CHO (59)

Q 0 OMe j

Cl N ---4-Ph

(60)

ONe 0

CIDOMel CONH.C(CH3)3 (61) 1 - 41 - stereochemistry of the final product should predominate(32). The first synthesis of tetracycline like molecules (63a,b) in which the methyl group at position 6 were of known configuration,were prepared in this way. The 6- demethyl analogue (63c) was also described. Another approach developed by Muxfeldt is directed towards the complete synthesis of 5-hydroxy tetracycline. On the basis of studies on model compounds (95) it was predicted that the ester (64) would cyclise to the tetracyclic compound (65) on treatment with sodium hydride.(96) Further developments are expected in the near future to confirm this prediction. A further novel route to the tetracyclines was con- ceived by Bhati(97) who attempted to cyclise the diester (66) to the tetracyclic compound (67). The keto ester (68) was isolated after polyphosphoric acid treatment which, however, did not suffer further cyclisation with this reagent. Shemyakin and his school have carried out detailed researches on possible routes to the tetracyclines. An extension of a systematic study of model compounds led to the synthesis(98) of a tetracyclic compound (69) possessing only a few features of tetracycline. Further work has resulted in the introduction of the HO

eN00

(9)

'eN HN 0 0 '><(,

01000

079) H I HO ON HN

H =x(° H= feN = (ci. eryi = H= Ce

(c9) H

TO HET `II - 43 - Cl 3 1 (66) I --.-., COOPt COOEti JMe OMe

Cl r,7-0Me (67)

ciMe 0 OMe

(68)

(69)

(70) - 44 -

4-dimethylamino function in basically the same way as 17oodward (40) i.e. a nucleophilic addition reaction of dimethylamine to a suitably constructed unsaturated linkage. Descriptions of syntheses of other tetracyclic molecules loosely related to tetracycline have been published by Shemyakin of which three compounds (70 , 99 ) 71a(100) 71b, (2.01)) deserve mention. The hexahydronaphthacene ( 72) was the product formed after cyclising the intermediate (73) with polyphosphoric acid. (102) .Anoxime prepared from this diketo naphthacene carries a nitrogen atom in. the position occupied by the dimethylamino group in tetracycline . Yao-Tseng(103) has synthesised linear tetracyclic compounds (74,75,76,77) containing oxygen functions in more or less the same positions as in tetracycline. The most highly substituted compound (76) was made by con- densing 4-methyl-8-methoxy-naphthol-1 (78) with 3 5- dimethov-4-carboxyphthalic anhydride (79) • The synthesis of tetracyclines by a combined chemical and biological method has been published.(52) Initially this method has similarities to the condensation previously mentioned between a suitable naphthalene (80) with a substituted phthalic anhydride (81) to give a quinone (82). In this case, however, the npahthalene moiety becomes - 45 -

(71 I 1 0H a) R = Me b) R = H

(72)

(73)

(74)

JH d OMe

(75) — 46

(76)

(77)

,OMe 0 (79) \C'

(80) - 47 -

rings A and B instead of rings C and D in the final tetracyclic molecule. Reduction of the quinone (82) with hydriodic acid containing potassium hypophosphite gave the pentahydroxynaphthacene (83), identical in every respect with an authentic sample obtained by degradation of 6-demethyltetracycline.(27) The conversion of the nOphthacene (83) to 7-chlorotetracycline was achieved with str221211/22aaregfaciens. (104) Another hexahydranaphthacene (84) has been reported employing at one stage the condensation of a substituted benzaldehyde (85) with a tetralone (86). This bears some resemblance to our successful way of joining the substituted ring A to a potential CD system of a tetracycline via a benzylidene derivative (p.64-). A tricyclic model (87) having the principal facets .1.05) of the A, B and D rings of tetracyclines was synthesise in 5 stages from the carboxylic acid (88). This product showed no biological activity. Another Itricyclinev (89) containing the B, C and D ring system was prepared during Shemyakin's studies.(106) (107) A model compound (90) carrying five oxygen functions disposed in almost the same spatial arrangement as those of rings A and B of 5-hydroxytetracyclinephas been synthesised to examine the role played by the Ap B

-48 —

I I (82)

H 0 OH OH

OH (83)

CONH 2 OH OH OH OH

(84)

OMe Me

COOH

(85) CHO COOMe ONe 0 OMe

(86) - 49 - Cl 1

(89)

OH OH

(90)

H OH (92)

CONH2 OH 0

N(Nle), H ' OH

(93) OH (94) 50 ring substituents on conferring activity on the tetracycline molecule. Ring A models include the 1,3 diones(91,(108) 92, (98) 93, (98)1and the naphthalene (94) (109) Several compounds (951(110) 96, (111) 97,(112)) containing the chelating carbonyl and enolic oxygen functions of the tetracycline molecule have been synthesised and in common with many of the model compounds, no activities have been reported. — 51 —

(95)

OH 0 OH 0

(96)

Et (97)

OMe 0 OH -52-

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110. B.B. Smissman and R.B. Gabbard, J.Amer.Chem.Soc., 1957,79, 3203. 111. A.B. Sen and S.K. Gupta, J.Indian Chem.Soc., 1961, 38, 825. 112. U.S.P. 2,783,261/1957. - 62 --

Outline of previous work

The route postulated for the synthesis of tetracycline in these laboratories was based on the attachment of an aromatic ring A to a suitable CD system with formation of ring B by cyclisation. The intermediate aim was thus the synthesis of 4a,12a-anhydro-4-dedimethylaminotetra- cycline (1). The dearomatisation of ring A and the introduction of a dimethylamino group at 0-4 and a 12a- hydroxyl group would complete this synthesis of tetracycline. Although much work has been performed this scheme has remained essentially the same since its conception in 1956. Notable advances along this route have been made and the synthesis of useful model tetracyclic molecules indicates that our task may soon be completed. With the knowledge of the ease in which tetracycline rearranges in acid or base and its sensitivity to reductive and oxidative procedures it was decided to have as many as possible of the functional groups present before the cyclisation reaction. A search for the two suitable molecules representing rings C.Ds and ring A in tetracycline was started and the C,D system was soon discovered. It was thought that - 63 I' OH

(1) CONH2 OH 0 OH OH OH 0

( 2 )

( 3 ) ( 4 ) 0 - Ph

( 5 )

( 6 )

0 -C -- Ph -64- the condensation of 1,5-dihydroxynaphthalene with benzoic acid in the presence of zinc chloride might give the 2 -benzoyl derivative (2). The expected product was formed but in low yield. The major component of the mixture was the 2-phenyl -5 -oxo-5H perinaphthofuran (3), formed by attack at the 4-position in 1,5 -dihydroxynaph-T thalene.(192) The ideal C,D system was then generated by hydrogenation of the perinaphthofuran (3) with Raney- nickel as catalyst, to give the dihydroperinaphthofUran (4). The bear.ty of this compound lay in its ready transformation to the tetralone (5) via methyl magnesium iodide and ozonolysis. Initial experiments indicated that benzylidene derivatives (6) were conveniently formed from benzaldehydes employing Cromwellts(3) conditions of acetic and sulphuric acids. One of the more difficult problems has been the synthesis of an aromatic compound carrying the tetracycline ring A sabstituents as well as groups allowing the fusion to ring C. A great deal of effort has been expended in this direction with the formation of some highly substituted aromatic compounds, yet the perfect system has so far eluded us. The isoxazole (7), synthesised41) from orcinol (Scheme 1), has found most SCHEME 1

OH 1,2

COOMe OH OH

COO Me OH

OAC OAc 6,7 OAc

HC COOMe (7) \11 0

(8)

OAc

(9) COOMe

/NaHCO Reagents 1° CO2/KHCO3 2. Me2SO4 3 3. Zn(CN)2/A1013H01 4. NH2OH 5. Ac20/100°C. 6. Ac20/H2SO4 7. Cr03/H2SO4/AcOH. - 66 - success in this direction at the present time since the isoxazole ring provides an acid stable protecting group for either a formyl or a nitrile function. Model experiments with o-cyanobenzaldehyde and o-carbomethoxybenzaldehyde showed that phthalides (8) were isolated on condensation with dihydroperinaphthofuran whereas p-substituted benzaldehydes condensed in the normal way. Consequently the condensation of the isoxazole (7) with the dihydroperin.aphthofuran (4) was examined(2) and the benzylidene compound (9) was formed. Reduction of the double bond was eventually shown to be effected with hydrogen iodide in acetic acid. The tetralone (10), formed from the isoxazole (9) (Scheme 2) did not cyclise with basic catalysts. This result was in parallel to the absence of reaction between cyclohexanone and benzonitrile. A condensation was,however, observed between cyclohexanone and benzoic esters with sodium hydride as catalyst. The carbomethoxy derivative (11) was made from the isoxazole (9) in eight stages (Scheme 3) but unfortunately also failed to cyclise under basic conditions. The more reactive formyl derivative appeared more attractive but although the formyldiacetate (12) was synthesised (Scheme 4), ozonolysis did not lead to the required tetralone (13). — 67 —

SCHEME 2 (9)

OAc

COOMe Ph OAc 13 H OAc

ON COOMe 0-- C — rh OAc 4 Me OH

CN COOMe (10) Ph.000 OAc

Reagents. 1. Hl/AcCH 2. Ac20/pyridine 3. MeNgl 4. 03 - 68 - SCHEME 3

OAc 1 (9) ---> I COOMe Ph N 0 j/2,3 OAc

COOMe OAc

4111111111 coscoo 111111 COOMe --Ph OAc 6,7 OAc OAc

COOMe

OAc

COOMe Ph.000 0 OAc (11) Reagents: 1. H1/AcOH 2. HvPd/C 3. Ac20/pyridine 4. Cr03 5. CH2N2 6. KBH4 7. Ac20/pyridine 8. 03.

69 --

SCHEME 4

COOMe 0 C 0 12 OH( OAc

00Me 1 0 — — Ph N--

OH t 3 OAc

CH COOMe 0 C — Ph OH 4 OAc OAc

OH COOMe (12) 0 0— Ph OAc 0.Ac T 5 OAc

(13) OHO COOMe Ph.000 OAc Reagents: 1. H1/AcOH 2. B2H6 3. H 1Pd/C 4. Ac20/pyri— dine. 5. 03. -70-

At this stage in the work a model of compound (12) was required, so o-phthaldialdehyde and dihydroperinaphthofuran were condensed using triethylamine as catalyst. The result was that condensation occurred with a rearrangement of the exocyclic double bond to give the model aldehyde (14)(4) With the formation of an m,p_unsaturated ketone,selective reduction of the double bond was attempted but this was not successful, even with Raney-nickel and hydrogen. The suitable position of the p carbon atom of the unsaturated carbonyl to the formyl function offered more attractive means of cyclisation. The advantage now was that the perinaphthofuran system still protected the oxygen functions at C-10, C-13 No success was achieved in an attempt to cyclise the aldehyde (14) directly with lithium in liquid ammonia. (5) Derivatives of the aldehyde of type (15) were synthesised, so that formation of a potential anion in the benzylic position could be employed in Michael type condensations with the unsaturated ketone of ring C. The oxime (16) did not cyclise in basic media nor did several hydrazones (17) under acidic or basic conditions.(5) The Michael condensation between a primary nitro methyl group on ring A and the active double bond of ring C should have given the tetracyclic molecule (18). This compound was

-71- 0

I I (14) off 0 I a —Ph

(15)

(16)

(17)

a) R=Me; R,=Me b) R=H; RI=Ph c) R=H; Rf=p.Me.Ph

(18) -72- not isolated since a facile oxidation and rearrangement took place with the formation of the aromatic compound (19).(4)

By analogy to the benzoin condensation it was predicted that treatment of the model aldehyde (14) with sodium cyanide in refluxing ethanol would give the diketo derivative (20). In fact, however, two compounds were isolated in poor yield.(4) The first was the previously discovered aromatic ketone (19) and the second the keto-lactone (21), formed by attack of cyanide ion at the a position of the unsaturated ketone system.(7) A more successful cyclisation procedure was the potassium t-butoxide promoted reaction of the cyanhydrin- pyranfiether (22) in refluxing ether.(7) The cyclised cyanhydrinpyranylether (23) was converted into the simple tetracycline model (24) (Scheme 4).(5) This compound had no biological activity. Synthesis of a substituted benzaldehyde consumed a great deal of time but eventually by a tedious route the cyanhydrinpyranylether (25) was formed (Scheme 5). The use of the well tried conditions unfortunately did not cause cyclisation nor did other basic reagents,(5) presumably because of steno hindrance caused by the presence of the o-methoxy group. -73-

(19)

( 20 )

( 21)

0 NC% Nph

( 22 )

( 23 ) -74— SCHEME 4

OAc H

1,2 (23) - -4

0-Ph CN `s.

3,4 OAc

OH OH

Reagents: 1. Li(t-Bu0)3A1H 2. Ac20/pyridine 3. 11+ 4. 03 5. A1203 6. Mild base.

-75- SCHEME

OH (9)

COOMe

2,3,4 0 OMe 'Y 1 CHO COOMe 0 C —Ph OMe 5

CH COOMe 0 --Ph OMe 1 6,7 0

211C11T 0_ Mlle,- 0 (25)

Reagents: 1. Hl/AcOH 2. Mel/Ag20 3. H2,Pd/0 4. Mel/Ag20 5. D.D.Q. 6. NaCN/H2SO4 7. Dihydropyran. 76-

A more elegant cyclisation was demonstrated when the nitrone derivative of the model aldehyde (14) reacted intramolecularly with the endocyclic double bond of ring C.(4) The 1,3 dipolar addition product, the isoxabo- lidene (26), was useful as a starting material for the synthesis of tetracyclic compounds. Reduction of the isoxazolidene, subsequently referred to as 'isoldin', gave a variety of products according to the conditions used. Treatment of isoldin with potassium t-butoxide gave the aromatic ketone (19) but with acetic anhydride in pyridine 'seco-isoldin' (27) was formed. If the mechanism suggested for the action of strong base on isoldin was correct, seco-isoldin should rapidly aromatise to the ketone (19) on contact with base. This was not studied but seco-isoldin was found to be a surprisingly stable compound.() The position at the start of my work was thstas far as cyclisation experiments were concerned, the cyanhydrin- pyrangiether cyclisation appeared not to be extendable to the substituted series and that the isoldin route could well merit further attention. - 77 - 0 Ph

( 26 )

0- -Ph H

(27)

,1 0 U -Ph 11. OH Ph 0

( 28 )

C -Phoir / o 0

( 29) (30)

I 1, 0 C - Ph o d — Ph

(31) -78-

STUDIES RELATED TO THE SYNTHESIS OF TETRACYCLINE

I'xe2L.ra'tioij.af9z2.a2Tp•inahthacenofu.ran derivatives The 6-deoxy-6-demethyltetracyclines(8) have been reported to possess a biological activity at least as great as tetracycline. The stability of these compounds to acids and bases has enabled many new reactions to be applied to these derivatives giving novel products retaining full biological activity. As this series of compounds were far more stable than the normal tetracyclines, it was considered important to study methods of obtaining these derivatives from the tetracyclic model compounds synthesised in these laboratories. Work was commenced in order to find the most convenient point of entry into this series. The success achieved by the cyanhydrinpyranylether cyclisation in the model series, suggested that a suitable compound for initiating these studies would be the cyclised pyranylether (23). These derivatives had been synthesised, as illustrated in Scheme 6 (p.7' ) from the aldehyde (14). The protection of the 3-keto function by the cyanhydrinpyranylether grouping, allowed direct reduction of the 9-keto function to be attempted. Some normal 79 -

SCHEME 6

(1.4)

I 0— —F11 ON OH

I I

(22) 0 C —Ph oN 0

(23) - 80 -

methods of reducing ketones to the corresponding methylene derivatives were first employed. Raney-nickel desulphurisation of thioketals is a (9,10) method commonly used for this conversion. The reaction between the pyranylether (23) and ethane-1,2- dithiol in acetic acid containing boron trifluoride etheraW as catalyst, was followed by ultra-violet spectra. There was no change in the ultra-violet spectrum during the reaction and the only product formed was the cyanhydrin (28), arising from the hydrolysis of the pyranylether function. (11'12) Hydrogenolysis has been used with success to form 6-deoxytetracyclines(8) from their parent compounds. (12) Conditions which should have resulted in the hydrogenolysis of benzylic oxygen functions, were applied to the tetracyclic derivative (23). No reaction, however, took place on hydrogenolysis with a 10% Pd/C catalyst in ethanol, tetrahydrofuran or dimethylformamide. The dihydroperinaphthofuran (29) was chosen for a more detailed examination of the hydrogenolysis reaction, as there seemed to be no reason why this reaction could not be effected in the tetracyclic series. Hydrogenation of the dihydroperinaphthofuran (29) in dimethylformamide with a 10% Pd/C catalyst gave the - 81- alcohol (30)(2) in good yield. Repeating the reaction with glacial acetic acid as solvent, gave the required perinaphthofuran (31). The infra-red spectrum showed no carbonyl or hydroxyl absorption but the ultra-violet spectrum indicated that the reduced perinaphthofuran chromophore was present (320 mp.). The N.M.R. spectrum gave three discrete multiplets of methylene protons ( = 7.95, 7.19, 7.03). The analytical evidence confirmed the molecular formula C 17H140. Modifications of this hydrogenolysis reaction were then investigated in order to try and bring about these reactions under neutral conditions. No formation of the perinaphthofuran (31) could be detected using chromous acetate or triphenyiphosphine in dry tetrahydrofuran. Reduction of the hypothetical intermediate (32) between diborane and the dihydroperinaphthofuran (29) was attempted. Only the usual diborane reduction product,(2) the alcohol (30), with no trace of the deoxy derivative (31), was formed on incorporating chromous acetate in this reaction. A means of producing the deoxy derivatives in model compounds was now available under acidic conditions, so extension to the tetracyclic cyanhydrinpyranylether (23) was contemplated. The probable intermediate in the

- 82 -

0 BH3 (32)

OtAc H

/',, 0 — C-PhaN 0 --"--°‘N" (33)

OAc H

I ( 34)

(35)

H 0— C -Ph 0

(36)

0 d_ Ph 0 83 - reaction, the acetate (33) was more suitable than the ketone (23). Hydrogenolysis should have been rapid since the acetate is a better leaving group than the hydroxyl group. A mixture of products was the outcome of the hydrogenolysis of this compound in acetic acid with a 10% Pd/C catalyst. Only the ketoacetate (34) and starting material could be isolated from this mixture. The melting point and spectral data of compound (34) were identical to an authentic sample.(5) The mixed melting point showed no depression. The rates of all the hydrogenolysis reactions were still very slow so alternative acidic solvent systems were studied on the model (29). One of the best systems discovered was tetrahydrofuran containing catalytic quantities of perchloric acid. The 5-deoxyperinaphthofuran (31) could be formed in good yield in a convenient period of time. The reaction was usually completed in a matter of a few bourn, compared with the previous reactions which often required over ten hours. Application to cyanhydrinpyranylether derivatives (e.g. 23) was not now attempted, since evidence had accrued which suggested that the cyanide group had a -84-

poisoning effect on the catalyst. The complete absence of hydrogenolysis of these derivatives (23,33) could not be explained satisfactorily in any other way. This explanation was probably correct since derivatives subsequently used for the hydrogenolysis, not containing the cyanhydrinpyranylether function, reacted rapidly under these conditions. The diketone (35) was then chosen for a study of the hydrogenolysis of the 9-keto function, since steric hindrance should prevent the 3-keto group participating to any great extent. Hydrogenolysis under these new conditions gave many products from which small yields of the monodeoxy (36) and dideoxy derivatives (37) were isolated by the thick-layer chromatography technique on alumina plates. The reduced perinaphthofuran chromophore (321 mil) in the ultra-violet spectrum of these compounds compared favourably with the value (320 mtl) in the model (31). No hydroxyl or carbonyl absorption was present in the infra-red spectrum of compound (37),but an absorption at 1686 am.-1 indicated that a keto group was present in compound (36). Support for these structures also rested on the analytical and mass spectral data of these derivatives. The effect of perchioric acid on the diketone (35) under these hydrogenolysis conditions showed that the 85

( 37 )

01 H

( 38 )

0 - C -Ph 0

H OMs

Hm (39)

C - Ph SO 2 CH3 ( 40 ) b )R:-.•.; SO 2 07H7 SCH2Ph

0 —C --- Ph ( 42 ) (43) - 86 -

starting material was quite stable to strong acids. The 9-hydro xyperinaphthacenofuran (38) and the 9-acetoxy- perinaphthacenofuran (34) also gave mixtures on hydrogenolysis, and in neither case was there an improved yield of the monodeoxy derivative (36). Thin-layer chromatography (T.L.0.) on silica gel plates, suggested that some decomposition took place during the work-up procedure. At each particular stage in the work-up, stringent precautions were taken to keep all solutions at 000, under inert atmospheres of carbon dioxide or nitrogen. In this way slightly better yields were found. Under these conditions the best yield (41%) of the ketone (36) was obtained from a hydrogenolysis reaction performed in acetic acid containing a catalytic quantity of hydrochloric acid. As only low yields could be achieved by means of the hydrogenolysis reaction, alternative methods of reaching the required 9-deoxyperinaphthacenofuran series were sought. The corresponding hydroxy derivatives offered other ways of achieving this object. By means of a displacement reaction of a 5-g7mesylate grouping(13) by hydride ion (39), the 5-deoxyperinaphthofuran might be obtained from the 5-hydroxy derivative (30). -87-

The mesylate (40a) was formed in solution and reacted with sodium borohydride in diglyme at various temperatures, but only starting material could be recovered in small amounts. When triethylamine was used as the base instead of pyridine, no change occurred except that the recovery of starting material was quantitative. The solution of the tosylate derivative (40b) again gave starting material under the same conditions. Isolation of the intermediate mesylate (40a) and tosylate (40b) could not be achieved and in every attempt to do so starting material resulted. Participation of the lone pair of electrons of the oxygen in the furan promotes the leaving ability of the mesylate anion and so increases its instability. The intermediate (41) would then be rapidly quenched in aqueous solution. Another displacement of these suiphonates was en- visaged. If the mesylate (40a) or tosylate (40b) were treated with thiol, the thioether should result which on contact with Raney-nickel should desulphurise to give the required deoxyderivative (31). The mesylate (40a) on contact with benzylthiol gave the expected thioether (42) in low yield. A more convenient way to this derivative was then suggested. The acid catalysed displacement of the alcohol (30) with - 88 -

thiol, should give the corresponding thioether (42) directly. This was found to be the case, for the thioether (42) was formed in high yield and shown to be a stable compound in the pure state. The N.M.R. spectrum supported the structure (42) as the presence of an extra methylene signal ( = 6.22), together with the appearance of a triplet ( 1# = 5.84, J = 7 c.p.s.) due to the proton in the 0-5 position, were readily discernible. The integration established that ten aromatic protons were present in the molecule. No further doubt existed about the structure when the analytical data came to hand. Raney-nickel(14) desulphurised the thioether (42), as expected, to give a high yield of the deoxy compound (31). With a new route to deoxy derivatives now developed, application to the tetracyclic series was the next stage in the work. Treatment of the 9-hydroxyperinaphthacenofuran (38) or its 9-acetoxy derivative (34) with benzylthiol in benzene containing p-toluenesulphonic acid, failed to give the expected thioether (43). When benzylthiol was used as solvent for this reaction, again no thioether formation was detected. In all these reactions, two other compounds were formedl so blank experiments without thiol -89 -

present were performed. The two compounds were again produced, indicating that they must be only acid catalysed reaction products. The two compounds were designated A and B for convenience at this time. The major component, compound A, was separated from compound B by chromatography on an alumina (Grade III) column. The infra-red sriectrum of compound A showed absorptions st 1661 am.-1 and 1634 cm.-1 whereas compound B absorbed infra-red radiation at 3500 cm.-1 and 1660 cm.-1. This indicated that cotpound A was probably an unsaturated ketone as probably was compound B. In addition, a hydroxyl group must be accommodated in the structure of compound B. The ultra-violet spectrum was not particularly useful at this stage although new chromophores were now present. Compound A had 7,max. at 412 rap, 320 nap, 309 mil, and 281 mµ, whereas compound B had'Xmax. at 306 mµ, 287 mµ and 256 mµ. The identity of compound A seemed to have been narrowed down to one of the two possible structures (44) or (45); the former being supported by the N.M.R. spectrum. A signal in the N.M.R. spectrum at "r = 3.29 integrating for one proton, suggested that an olefinic proton was present.

-90-

( 44)

0 0 -Ph 0

( 45)

0 — C - Ph 0

( 46 )

( 47 )

0 ----- C - Ph OR a) R = Ac b) R = H — 91—

Initial equilibration studies showed that these compounds did not equilibrate in refluxing benzene, but with addition of a trace of acetic acid, compound A was partially converted into compound B. A very slow conversion of compound B to compound A also occurred in the presence of a trace of acetic acid. Chemical evidence for the structure of compound A was now sought. If structure (45) represented compound A, treatment with calcium in liquid ammonia should give the required ketone (56). Only a mixture of alcohols were fonned,boweel$the components of which could not be separated by crystallisation or column chromatography. This experiment led to no useful information except that the structure for compound A was probably not (45). The effect of zinc in acetic acid was investigated but again a mixture of alcohols resulted which could not be separated. Sodium borohydride treatment was expected to give the corresponding alcohol but no reaction took place on contact of compound A with this reagent. The application of an onol acetylation reaction should prove useful for structural assignments. Treat- ment of compound A with acetic anhydride in acetic acid produced a deep red crystalline solid, which was assigned _92_ structure (46) on physical evidence. The infra-red spectrum showed absorptions at 1764 -1 -1 cm. and 1642 am. . This supported the presence of an acetate attached to a carbon-carbon double bond, and possibly another unsaturated system. The ultra-violet spectrum showed a new chromophore was now present. The absorption in the visible region of the spectrum could be attributed to the o-quinonoid type structure (i.e. 513 mil, 479:Jaill 405 m4). The mass spectrum gave the molecular weight to be 390. Hydrolysis of the enol acetate (46) to starting material could not be effected with acid or base at room temperature. A consideration of the structure of compound B, shown to be formed from compound A, should assist the allocation of a structure to compound A. As hydroxyl absorption appeared to be present in -the infra-red spectrum of compound B, the characterisation of its acetate would give more structural information. Acetylation of compound B with acetic anhydride in pyridine gave an acetate derivative as colourless crystalline plates. The tafra-red spectrum of this derivative showed absorption at 1760 an.-1 consistent with an acetate group attached to an unsaturated carbon system. -93-

The absence of infra-red absorptiaft,at 1660 cm.-1 in this acetate derivative,coupled with the identical ultra- violet spectrum of compound B and its acetate, showed that no carbonyl groups were present in compound B. The absorption observed at 1660 an.-1 must therefore be due to an unusually high carbon-carbon double bond stretching vibration. This evidence immediately led to the allocation of structure (47a) to the acetate derivative which was confirmed by analysis. Rationalisation of the acid catalysed formation of compounds A and B was now possible. Compound A was formed by an acid catalysed elimination reaction and had structure (44). By a 1,3 proton shift, compound A was then converted into structure (45), which immediately aromatised under the reaction conditions to give the phenol (47b), i.e. compound B. Pyrolysis of the acetate derivative (34) also gave the (3,Y-unsaturated ketone (44) in small amounts. If the double bond of the unsaturated ketone (44) could be selectively reduced, the preliminary aim of this work would have been achieved. Unfortunately hydrogenation with a 10% Pd/C or a, Pt02 catalyst under neutral or acidic conditions failed to give the required compound (36). - 94 -

Low yields of the ketone (36) had previously been obtained by hydrogenolysis, so it was decided to leave this series and to investigate the alternative means of acquiring useful tetracyclic compounds, i.e. the iso- oxazolidine (isoldin) series.

Studies in the isoldin series

It had been shown(4/7) that the isoxazolidine-(26) glepared by the intramolecular 1,3-dipolar addition of a nitrone(15,16) to the double bond of an a, 3-unsaturated ketone (Scheme 7). was a potentially useful tetracyclic molecule. The reductive cleavage of the oxygen-nitrogen bond had given tetracyclic compounds not far removed from model tetracycline derivatives. (4,7) It was decided to reinvestigate some of the reactions found to take place in this series and to devise a route to more useful tetracyclic derivatives. The ultimate goal was to find a convenient route to the diketone (35). The formation of isoldin (26) from the aldehyde (14) and phenyl hydroxylamine was first examined. It was found that a yield of 85% could be obtained by prolonging the reaction time to five days at room temperature. In an attempt to speed up this reaction, the ethanolic suspension

- 95 - SCIIElv2 7 0 0 - z -' 0 - R It 0 R 9 R J1--... '..17.----- R 1__.,. e. R,,,-- / ‘,_, „Rut Rt e --Rut

SCHEME 8 0 0 Rng R 99

0 ,-"-c-D rot Rit

SCHEME 9

CB° H I I

(48) 0 Ph Ph -96-

of reactants was refluxed, but only a low yield of isoldin was isolated after cooling the reaction mixture. Con- centration of the filtrate and cooling at 00C, deposited a further crop, which was shown by T.L.C. to contain two compounds. These compounds had similar Rf values and the slower running one was isoldin. Attempted separation by fractional crystallisation of this mixture was not successful. Chromatography on an alumina (Grade III) column gave a clean separation of these two components, but removal of solvent from both fractions caused conversion to the original mixture. However, removal of solvent at room temperature gave the two separate components as pale yellow solids. The equilibrium which appeared to have occurred on heating, was conclusively established when on refluxing either component in ethanol, the same mixture was produced. The new isomer was called isoldin B at this stage. Physical evidence, principally N.M.R.,indicated that compound B was the hitherto unobserved product (49) arising from the alternative mode of a 1,3-dipolar addition of the nitrone intermediate (48) to the double bond (Scheme 8). The benzylic protons gave rise to an AB system (T 6.17, 6.69, JAB = 19 c.p.s.) in a different environment tothat in isoldin B ( 'r 6.57, 6.79, JAB = 16- c.p.s.).

- 97 -

S I H. \ (49) •H O Ph

I (50)

\0 CD

SO I (51) OHI OHI

(52)

0 C

(53)

I I Ph Ph 98

Further support for the intramolecular rearrangement via the nitrone (48) and the absence of a base catalysed elimination-addition rearrangement (Scheme 9) came when isoldin A was refluxed in ethanol-D. Examination of the equilibrium mixture by N.M.R. indicated no deuterium incorporation in either isoldin A or B. Further evidence was expected from a study of the rate and position of equilibrium in solution at various pH values. Treatment of isoldin A (26) or isoldin B (49) in refluxing ethanol or benzene with dilute hydrochloric acid or sodium hydroxide produced no change in the equilibrium position or the rate. This suggested that the rearrangement was molecular and not a base catalysed rearrangement. The 1,3-dipolar addition of nitrones to olefines has been reported in both intermolecular and intramolecular cases.(15,16) Recently evidence for reversibility of the additions such as was observed here under pyrolysis conditions, has been demonstrated.(17) A second, minor by-product isolated from these reactions was shown to be azoxybenzene (50) formed from phenylhydroxylamine by oxidation. Similarly oxidation of the bis-phenylhydroxylamine (51) has been reported(18) to give the cyclic azoxybenzene (52). -99-

This observation showed how isoldin A could be obtained in a purer state from this reaction. Phenyl hydroxylamine, when added at regular intervals during the reaction prevented a large build up of azoxybenzene, without a measurable change in the formation rate of isoldin. Isoldin A formed in this way was a very pale yellow solid,homogeneous by T.L.O. The presence of nitrones has been demonstrated by the formation of adducts with styrene monomer.(19) On refluxing isoldin A in benzene containing excess styrene monomer, no adduct was produced and only a mixture of isoldin A and B was isolated. Steric hindrance was probably the reason why no adduct was formed as the monomer probably could not approach close enough to the nitrone (48) because of the bulky 2-phenyl substituent. An investigation of some derivatives of isoldin A was now commenced with first,a study of seco-isoldin (53). The clue to the structure of seco-isoldin (53) was given on a consideration of the reaction conditions in which it was prepared. Acetic anhydride in pyridine at reflux temperatures converted isoldin(26) into seco- isoldin,formulated as (53) by Martin(4) , conditions where the nitrone (48) probably was formed in appreciable amounts. 'The nitrone (48) possibly had some influence -100 - on the preparation of this derivative, since seco- !_soldin was formed from both isoldin A and isoldin B. The spectral properties of seco-isoldin (53) were re- examined. The N.M.R. spectrum showed benzylic methylene protons as a singlet ( T 5.87) rather than an AB system as in the tetracyclic series and a proton at low field ( T -0.51) which was exchangeable with deuterium. The mass spectrum gave a molecular weight of 455 and showed that a preferential loss of a fragment of 93 units due to aniline, was formed in the first cleavage of the molecule. The above evidence could not all be satisfactorily accommodated in the previous structure (53). It was proposed that on examination of the above evidence that the ring opened N-phenylamide (54) was the probable structure for eeco-isoldin. It was obvious that as far as this synthetic work was concerned, seco-isoldin (54) was of little use. The reduction of isoldin A had been investigated by Martin(4) and Aufderhaar(7) and depending on the conditions, dihydroisoldin (55) or isoldinol (56) could be formed. Dihydroisoldin (55) had been produced from isoldin A (26) by hydrogenation with a 5% Pd/C catalyst in a variety of - 101 -

( 5 4 )

( 56 )

( 55 )

OH OH

( 57 )

( 58 ) -102 - solvents. The reduction was studied at various stages in the reaction, by T.L.C. Dihydroisoldin (55) was formed, but at all times it was contaminated with other products, one of which was isoldinol (56). When this reaction was allowed to go to completion, a new compound was observed. The new product was shown to be the glycol (57) by spectral and analytical data. The ultraviolet spectrum indicated a reduced perinaphthofuran system was present ('max. 301 mµ) and the infra-red npeotfum howed stron hydroxyl absorption at 3500 cm.-1 but no carbonyl absorption. The glycol (57) had arisen from the absorption of three moles of hydrogen by isoldin A. The monoacetate (58), formed on acetylation of the glycol (57) with acetic anhydride in pyridine, completed the characterisation. The infra-red spectrum showed absorption at 3610 cm. -1and 1742 am.-1 due to hydroxyl and acetate carbonyl absorption respectively. There was no change in the ultra-violet spectrum on acetylation. The N.M.R. spectrum showed an acetate methyl signal at r = 7.61 which integrated for only three protons. Confirmation of structure resided with the analytical results. Another reported reduction giving dihydroisoldin (55) was the chromous chloride treatment of isoldin A (26). On investigation of this reaction by T.L.O., it was shown -103- that this reduction was extremely fast. Emplpying a rapid workup procedure, a high yield of dihydroisoldin (55) was obtained after a contact time of one minute between isoldin A and this reagent. A longer reaction time resulted in the production of complex mixtures, two components of which were later shown to be the deoxy derivative (59) and its epimer (60). Only low yields of dihydroisoldin (55) could be obtained when isoldin A (26) was reacted with chromous acetate in dry dimethylsulphoxide. This reaction illustrated the need for acidic conditions in this reduction, presumably Protonation of the nitrogen atom occurred which weakened the oxygen-nitrogen bond, thus facilitating homolytic fission in the presence of chromous ion. The necessity for the chromium atom to be temporarily bound to the carbonyl oxygen in isoldin A before reaction, was demonstrated when no reaction was observed between isoldin B and chromous chloride. In the development of the chromous chloride reduction it was considered that the reaction might be performed in situ, i.e. the reactant added to the chromic chloride solution as it was reduced in the presence of zinc amalgam. Accordingly, the effect of strong acid in the presence and absence of zinc amalgam was studied din isoldin. A (26). - 104 - 0

(59)

H C---Ph NH Ph

(60)

(61)

(62)

II C -Ph H Ph OH Ii

(63)

fi - C -Ph NH Ph - 105-

Isoldin (26) reacted on contact with acetic and hydrochloric acids at above room temperature, to give the aldehyde (14). Nevertheless, zinc amalgam in acetic acid containing a small quantity of hydrochloric acid reacted extremely slowly with isoldin A, in accord with Martinis observation(4) that isoldin was inert to zinc in acetic acid. A reaction was carried out in situ, but T.L.C. indicated it was very complex with no dihydroisoldin present after a short period of time. To elucidate the course of this reduction, further blank experiments were performed. Dihydroisoldin (55) did not react with acetic acid containing hydrochloric acid, but on addition of zinc or zinc amalgam, a rapid reaction was observed. The first product that was formed was the epi-deoxy-dihydroisoldin (60), subsequently isolated in good yield after a reaction time of one minute. The deoxyderivative (59) and alcohols were then produced as the reaction proceeded. An interesting epimerisation was observed during chromatographic separation of the mixtures produced in this reaction. Chromatography on an alumina (Grade III) column converted the 221-deoxyderivative (60) into its epimer, the deoxyderivative (59), in quantitative yield. The infra-red spectrum of both compounds contained - 106 - absorption at 3400 cm.-1 and 1685 cm.-1 consistent with amine and saturated carbonyl absorptions. The ultra- violet spectra of these epimers contained absorption at 348 mµ due to the perinaphthofuran chromophane. The N.M.R. spectra of these compounds were complex and little idea of the stereochemistry of the products could be gleaned from these spectra. A suitably deuterated derivative would eliminate some of the complex proton interactions and so afford evidence for stereochemical assignments. The deoxy derivative (59) was refluxed in tetrahydrofuran containing deuterium chloride, prepared in situ from deuterium oxide and thionylchloride, and a deuterated derivative (61) was isolated. Pour deuterium atoms had been incorporated at the indicated positions according to the mass spectrum of this compound. The N.M.R. spectrum was now considerably simplified. An. AB system ( 7 5.79, 6.87, JAB = 19 c.p.s.) was readily discernible and the 0-2a,3 protons were easily distinguished. Their positions ( r 5.60, 4.91) were very similar to the positions of these protons in dihydroisoldin ( 5.89, 4.50). It was apparent that the epimerisation which had been demonstrated involved the 8a proton, and that the deoxy derivative (59) contained now a cis fused B,C ring. -107-

The reduction which had produced these deoxy derivatives was performed at various temperatures to see if the epimerisation that followed the formation of the p217-deoxy derivative (60) could be slowed down. No appreciable change in the epimerisation rate could be effected even at -20°C„although as expected, the formation of the 221.- deoxyderivative was much slower. The next step required to convert the amine (59) into the diketone (35) was the specific oxidation of a secondary amine. It was considered adyisable first to protect the keto function as its acetate derivative. The keto amine (59) was subjected to various reducing agents in order to form the corresponding aminoalcohol. Sodium borohydride treatment of the keto amine (59) gave only a poor yield of an alcohol (62) possessing the trans- fused B,C ring system since oxidation with manganese dioxide slowly produced the epi-deoxy derivative (60). In contrast, lithium aluminium hydride gave an excellent yield of the hydroxy derivative (63) which was readily converted back to starting material on contact with manganese dioxide. Zinc in acetic acid gave a low yield of another alcohol of probable structure (64). Treatment with manganese dioxide afforded starting material indicating - 108 - ?H H

( 64) A ' 0 ----- C - Ph NH Ph OAc

( 65 )

C - ph NH Ph OAc

( 66 )

H 0 C - Ph N7 Cl_ • Ph 0.A.c 1;1 ( 67 ) 04111 0 — 0 Ph ly Ph

( 68 ) -109 - that this derivative (64) also contained the cis-fused B,C ring system. The three alcohols (62,63,64) had very similar spectral properties. The infra-red spectra exhibited both hydroxyl and amine absorption at 3600 cm.-1 and 3400 cm. -1respectively, in these derivatives. The ultra- violet spectra were very similar showing the usual reduced perinaphthofuran chkomophores in the expected region, i.e. 300 mµ to 320 mil. The alcohol (63) gave an N.M.R. spectrum which had a signal at 1- 5.87 integrating for two protons. Both protons giving rise to this resonance were exchanged with deuterium, supporting the two exchangeable protons, i.e. the amino and hydroxyl protons, present in compound (63). The analytical data gave the molecular formula to be C31H2502N. No reduction could be effected under the Meerwein- Porndorff conditions with aluminium iso-propoxide in iso- propanol and starting material (59) Was recovered. Acetylation of the alcohol (63) with acetic anhydride in pyridine at 95°C gave the acetate (65) in good yield. The infra-red spectrum showed the expected absorption at 1735 am.-1 due to the ester carbonyl and the absorption at 3430 cm.-1 was in accord with the presence of an amino -110 -

group in compound (65). The ultra-violet spectrum gave absorption at 320 m as required of a reduced perinaphthofuran system. The N.M.R. spectrum contained a signal at 1- 5.61 integrating for one Droton, which was exchanged by deuterium. The downfield shift of the proton in the 9 position from 1- 4.94 to T 3.50 in the acetate derivative (65), i.e. a shift of 1.54 P.P .m.,was consistent with that expected. Analytical data gave C33H2703N as the molecular formula. Having the required acetate derivative (65) the problem that now had to be tacMed was the specific oxidation of the amine. Both direct and indirect methods of oxidising secondary amines were examined. Manganese dioxide, a versatile mild oxidising agent, was first used. The acetate (65) was found to be quite inert to this reagent although the ketoamine (59) gave the aromatic ketone (19) with manganese dioxide. t-Butyl hypochlorite(20) has been used to Chlorinate amines selectively. It was hoped that the N-chloro derivative (66) would eliminate hydrochloric acid on going to the imine (67) which could be cleaved with acid to give the ketone (35). This reagent gave mixtures of unstable oils with the amino acetate (65) which were unaffected by acid or zinc in acetic acid. This indicated that neither the imine (67) nor the N-chloroderivative- (66) were present. It was suggested that chlorination of the anilino residue had occurred in this reaction. No reaction took place with the amine (65) and sodium hypochlorite at room temperature and starting material was isolated after 18 hours. Oxidation with peracids was expected to give the corresponding N-hydroxy derivative (68) which was hoped would eliminate water to give the imine (67). Mixtures of products were formed using peracetic acid and m- chloroperbenzoic acid, which were inseparable by chromatography on silica gel or alumina (Grade III) columns. Mercuric acetate and chromium trioxide failed to give any useful products, the starting material being recovered. Excess reagent only caused slight decomposition of starting material. Formation of an N-mesylate derivative (69) on treat- 21 ment of the ketoamine (65) with mesylchlorie was expected to eliminate quickly to the required imine (67). Attempted formation of the N-mesylate compound (69) with mesyl chloride at various temperatures was unsuccessful. A quantitative recovery of starting material was achieved on working up these reactions. - 112 - OAc H

(69)

OAc

( 7 0 )

OAc H OAc

( 71)

C -Ph N-NO

OAc Ph H

I • (72)

NO -113-

In prOiaus work in the group,(5) 2,3-dichloro-5,6- dicyanoquinone,(22) was found to be a useful dehydro- genating reagent. It was hoped to dehydrogenate the carbon-nitrogen bond of the amine (65) with this reagent to give the irnine (67) directly. Acid hydrolysis should then have generated the diketone (35). A reaction did take place with this reagent but only a mixture of products were formed which were stable to acid. A recent report(23) on the cleavage of dibenzylamine to benzaldehyde with argentic picolinate, prompted the use of this reagent in the present work. Unfortunately no reaction could be effected between this reagent and the aminoacetate (65). No reaction was also observed between Premy's salt(24) and the aminoacetate (65), likewise attempted oxygenation of the aminoacetate (65) with platinum black(25) as catalyst was unsuccessful. It was predicted that lead tetra acetate would form the p-acetoxy derivative (70) of the aromatic amine (65) and so offer a means of oxidising the amino function. No reaction occurred at room temperature with this reagent in benzene, or acetic acid. On addition of dilute hydrochloric acid9 mixtures of products were formed. - 114 -

A small quantity of an unstable product was isolated from the reaction in acetic acid containing hydrochloric acid. According to the mass spectrumpthis product had incorporated chlorine. The molecular ion at 592 lost a fragment of 36 units to give strong lines centred at 556 units, in the cracking pattern. Apparently the molecular weight had increased by 107 units in this reaction but no suitable structure could be advanced for this unstable compound. atrous acid treatment of aromatic secondary amines give the corresponding N-nitroso derivatives as well as the p-nitroso compounds. These reactions appeared to offer another method of oxidising the amino function. The aminoacetate (65) on subjection to the action of sodium nitrite in acids gave mixtures from which the N-nitroso (71) and the p-nitroso derivatives (72) were isolated. At this stage in the work it was decided that as the oxidation of the aminoacetate (65) was turning out to be more difficult than expected, a simpler compound should be used to investigate new oxidation procedures. A model system was required which would possess the secondary amine function in an environment similar to that experienced by the amino group in the aminoacetate derivative (65). -115 -

The amine (73) seemed to offer a suitable model system for testing further oxidation reactions. The first suggested scheme for the preparation of this amine (73) was via the anil (74) formed from 1- tetralone and aniline. Reduction of this imine (74), should give the amine (73) directly. A literature method for a preparation of an anil was found to employ boron trifluoride etherate as catalyst.(26) The reaction between fluorenone (75) and p-chloroaniline in refluxing chloroform with this catalyst gave the anil (76) in reasonable yield. Under these conditions, however, there was no reaction between 1-tetralone and aniline. p-Toluene sulphonic acid in refluxing toluene brought about no condensation either, even with a Dean and Stark apparatus and soxhlets containing drying agents. Barnes(27) has used N-bromosuccinimide as a dehydro- genating agent to convert tetralin by way of the 1,4-dibromo derivative (77) to naphthalene. This reaction was repeated with one equivalent of N-bromosuccinimide to give a colourless unstable oil, the 1-bromo tetralin' (78), which was immediately treated with excess aniline. The l-N-phenylaminotetralin (73) was isolated from this reaction, initially as a viscous oil. A crystalline

-116--

1 i., II (73) (74)

Ph Ph

(76)

N Ph - Cl

(77) (78)

1TH.Ph

(79) (80)

NH.Ph NH2

(81) (82) N NO

Ph NO - 117 - by-pro duct was also formed and shown to be 1,4-di-N- phenylaminotetralin (79) arising from formation of the. 1,4-dibromo derivative (77). Both these amines (73,79) absorbed infra-red radiation at 3400 cm.-1 and 1605 cm.-1 consistent with the presence of the amino function and a carbon-carbon double bond of an aromatic amine. Strong ultra-violet absorption at 253 mµ was present, which supported the presence of an isolated aniline residue. (Aniline absorbs at 247 mµ in the ultra-violet.) The extinction value at this frequency (253 mµ) for compound (79) was approximately double that for the amine (73) i.e. E = 31,400 compared with E = 16,400. The N.M.R. spectra showed methylene mu.ltiplets integrating for the expected number of protons. The correct number of aromatic protons, 9 in the monoamine (73) and 14 in the diamine (79) supported these structures. Analytical data gave the molecular formulae for compounds (73) and (79) as 016H17N and 022H22N2, respectively. Separation of these amines was first achieved by fractional distillation and later by column chromatography on an alumina (Grade III) column. For characterisation purposes the monoamine (73) was treated with picric acid but no picrate derivative could be isolated. This paralleled the absence of a reported picrate derivative - 118 -

for l-aminotetralin (80)S28) Passage of dry hydrogen chloride through an ethereal solution of the amine (73) gave a crystalline hydrochloride, as colourless transparent needles. The oxidation of the amine (73) through its nitroso derivatives to compounds offering access to 1-tetralone appeared to hold out most hope of success at this time. The first reaction conditions to be used on the model amine (73) were the nitrosation procedures previously applied to the tetracyclic derivative (65). The amine (73) was readily nitro sated on nitrogen and in the aromatic ring. Development of these reactions resulted in the model N-nitroso derivative (81) and the p-nitroso derivative (82) being formed in good yield. Nitrous acid generated by sodium nitrite in aqueous acetic acid (10%) at room temperature converted the model amine (73) into the N-nitroso derivative (81). The infra-red spectrum of compound (81) exhibited no amine absorption, but a band at 1600 am.-1 suggested the presence of a carbon-carbon double bond af an anilino_ derivative. The ultra-violet spectruiti showed-the absence o- ¢ simple aniline chromophore at 247 mg. The N.M.R. spectrum showed only methylene and aromatic protons integrating - 119 - in the expected ratio of 7:9. The analysis gave

16H16N20 as the molecular formula. Dry hydrogen chloride through an. alcoholic solution of the N-nitroso derivative (81) caused the p-nitroso derivative (82) to be formed by the Fischer-Hepp rearrangement .(29) This unstable p-nitroso derivative (82) was also prepared in one step frora the amine employing sodium nitrite in acetic and hydro chloric acids. The p-nitro so derivative (82) gave amine absorption at 3300 cm.-1 in the infra-red spectrum. The absorption at 1603 cm.-1 in this spectrum suggested the presence of the carbon-carbon double bond of an anilino derivative. As expected, the ultra-violet exhibited absorption at 424 nIP, ( E 34,200) in the visible region, consistent with the absorption of p-nitroso derivatives. The N.M.R. spectrum was compatible with this structure (82). A single proton signal at 4.70 which was exchanged with deuterium was ascribed to the proton on nitrogen. The analytical evidence gave C161-116N20 as the molecular formula. A more convenient method of preparing the p-nitroso compound (82) should be by treatment of the amine (73) with nitrosyl chloride. The N-nitroso derivative (81) was immediately formed when the amine was treated with -120 - this reagent. On further treatment, however, a mixture resulted, with none of the p-nitroso derivative (82) present according to T.L.C. As the N-nitroso model compound (81) was the most easily obtained model nitroso compound, attempts were made to degrade this molecule to 1-tetralone. Photolysis of N-nitroso compounds has recently been reported(30,31) and Chow(31) observed that in strongly acidic media these compounds gave the corresponding ketones. The model compound (81) was photolysed in quartz apparatus by a high pressure lamp, but no 1-tetralone could be detected. The only other compound formed was small amounts of the amine (73), according to T.L.C. A later paper(32) by the same author reported that N-nitroso-N-methylaniline (83) did not undergo photolysis and suggested that an electronic factor contributed by the benzene ring prevented this reaction occurring. The N-nitroso amine (81) was treated with acetic anhydride containing sodium acetate in an attempt to form an acetyl derivative (84) on the oxygen of the nitroso group. This should allow formation of an imine (85) to occur readily. No reaction took place at room temperature between this reagent and the compound (81). At,reflux temperatures, T.L.O. indicated that a complex reaction mixture soon

— 121 —

(83)

(84) (85) NN AT" e Ph Ph OAc OAc

(86) (87)

N . CO 0.1i 3 Ph 01\13"

( 88 )

N— NO2 Ph

(89) -122- developed. A low yield of a crystalline product was isolated from this mixture by chromatography on an alumina (Grade III) column. This was readily shown to be the N-acetyl derivative (86) by acetylation of the amine (73) with acetic anhydride caataining sodium acetate. The infra-red spectrum of the N-acetyl derivative (86) showed the expected amide carbonyl absorption at 1653 an.-1 The signal at "t- 8.04 in the N.M.R. spectrum integrated for three protons in accordance with the presence of N--acetyl methyl protons. Analysis confirmed this structure (86)„. The corresponding mSylate (87) could not be formed from the N-nitroso derivative (81) and mesyl chloride. No oxidation took place with ferric chloride or chromium trioxide in two phase systems. An attempted oxidation of the N-nitroso derivative (81) with hydrogen peroxide to the nitro-derivative (88) was not successful. It had been hoped that elimination might then occur with base to give the imine (74). It was suggested that N-nitroso derivatives might react with hydrazoic acid to give the azide derivative (89) which might decompose with elimination of nitrogen to give the imine (74). -123 -

Subjection of the model compound (81) to sodium azide in sulphuric acid gave a new product in the form of a yellow viscous oil. Physical evidence indicated that this product was probably a hydrocarbon. The blank of the reaction was performed before further characterisation was undertaken. The N-nitroso compound (81) in sulphuric acid was shown to also give this product, which was then submitted for mass spectrum. The molecular ion in the spectrum was at 260 units, almost double that of starting material. N.M.R. indicated that the compound was probably a mixture of hydrocarbons. The two hydrocarbons (90, 91) which fitted the evidence were isomeric dimers of tetralin formed by the attack of an intermediate 1,2-dihydronaph- thalene (92) on the benzylic cation in another species (93). Further attack of compound (91) was also indicated since a small peak at 390 units was present in the mass spectrum. Anhydrous hydrazoic acid gave no reaction with the N-nitroso derivative (81). It was suggested that subjection of the N-nitroso derivative (81) to the action of sodium hydride should give the imine (74) via elimination of nitroxide anion caused by attack of the carbanion formed in the benzylic position. — 12 4 —

( 90 ) (91)

( 9 2 )

( 93 )

0.A.c H

I ( 9 4 )

0 - C NH Ph - 125 -

Sodium hydride in dimethylformamide did not react with the model compound (81) at room temperature,but at 95°0 a slow formation of a new compound took place. Physical and chemical evidence soon showed that this compound was the required imine (74). The infra-red spectrum showed absorption at 1632 am.-1 consistent with a carbon-nitrogen double bond stretching frequency. The H.M.R. spectrum showed three multiplets of methylene protons at 8.169 7.56, 7.21 which each integrated in the ratio:,)f 1:1:1. The only other resonances present were the aromatic protons which integrated correctly for

9 protons. The analytical evidence gave C1e1-15N. Acid hydrolysis readily gave 1-tetralone,characterised as the benzylidene derivative. A better yield of the imine (74) was found when dimethylacetamide was used as solvent; possibly because the reaction could then be performed at room temperature. Less decomposition of starting material and product then took place. At last a means of transforming the N-nitroso derivatives fmto their corresponding ketones had been found. Extension to the tetracyclic series (e.g. 65) was the next phase in this work. The re-examination of the nitrosation reaction in this series was necessary -126 - since only small yields of nitrosated materials had previously been isolated. The reaction conditions were then varied to find the best procedure for forming the N-nitrosoacetate (71). The method used for preparing the model N-nitroso derivative (81) was employed i.e. sodium nitrite in aqueous acetic acid (10%) at room temperature, but only the p- nitroso derivative (72) was formed. The infra-red spectrum showed the expected acetate carbonyl absorption -1 at 1738 cm. , together with amine absorption at 3420 cm.-1. The ultra-violet spectrum showed absorption at 417 mp as compared with the value 424 mp for the model p-nitroso derivative (82). The N.M.R. demonstrated the presence of an acetate methyl signal at -1-• 8.23 but the proton on nitrogen was in the aromatic region of the spectrum. Analytical data confirmed the molecular formula C33H26N204. Eventually the N-nitroso compound (71) was isolated in good yield ftom the reaction at 0°C with sodium nitrite in acetic acid/dioxan (1:1). The N-nitroso compound (71) showed no amine absorption in the infra-red spectrum although the acetate absorption at -1 1730 cm. was still present. The presence of the acetate was also shown in the N.M.R. spectrum for a singlet at T 8.22 integrating for three protons - 127 - appeared in the spectrum. No exchangeable protons were found in the N.H.R. spectrum. An unstable new compound isolated from the reaction between the amine (65) and sodium nitrite in glacial acetic acid was possibly the o-nitroso derivative (94). In compound (94) the infra- red spectrum showed acetate absorption at 1730 cm.-1 but apparently no amine absorption. This may possibly be due to strong hydrogen bonding between the proton on nitrogen and o-nitroso group. Unfortunately the structures of these three derivatives could not be supported by analytical data but the mass spectra were in accord. The three nitrosated compounds possessed very weak molecular ions due to the facile loss of the elements of NO and their cracking patterns were consistent with the postulated structures. The o-nitroso derivative (94) was virtually identical to that of the p-nitroso compound (72). Further nitrosation of these derivatives could not be achieved under a variety of conditions. The sodium hydride treatment which had been successful in the model work was now applied to this series of canpounds. On subjection of the N-nitroso compound (71) to sodium hydride in dimethylacetamide, a very complex -128 - reaction ensued. The products seen to be formed initially by T.L.C. reacted further to give highly complex mixtures. By applying careful work up procedures, small amounts of an unstable compound were isolated. The infra-red spectrum showed absorption at 3390 cm.-1 and 1723 cm.-1 consistent with amino and acetate carbonyl absorptions. The ultra-violet showed a modified perinaphthofuran absorption at 375 The mass spectrum gave a molecular ion at 483. This data was compatible with the enamine structure (95). In solution, this compound rapidly decomposed and treatment with hydrochloric acid caused no alternative mode of decomposition. The infra-red spectrum of the mixture so formed, showed no carbonyl absorption. The ease of oxidation of this series to aromatic ring B compounds, together with the possibility that the nitroxide anion was attacking elsewhere in the molecule, might account for the low yields encountered in this reaction. Assuming that the nitroxide anion was attacking the imine (67) or enamine (95),various additives were incorporated in the reactions in attempts to remove this nitroxide anion. If the nitroxide anion was attacking the enamine (95), the presence of an excess of a simple

— 129 --

(95)

NH Ph 0 0 Ac0 °Ac

(97) (98)

OH H

(99) H 0 -- 0—Ph N — NQ Ph

(No) -130 - enamine in the reaction mixture should remove this reactive entity. This was found not to be the case, however, since no change in the reaction course was brought about on addition of the model enamine (96). By analogy to the reaction with enol ethers 33) it was suggested at this point that enamines might be converted into their ketoacetates on treatment with lead tetra acetate. As the enamine (96) of cyclohexanone and morpholine was to hand, this possibility was examined. On contact with lead tetra acetate in benzene at room temperature, a mixture of compounds were formed. The expected product, 2-acetoxycyclohexanone (97) and possibly 2,6-diacetoxycyclohexanone (98) were isolated in the form of their 2,4-dinitrophenylhydrazone derivatives. 2-Acetoxycyclohexanone (97) in the form of its 2,4- dinitrophenylhydrazone derivative was identical in all respects to the authentic materialS34) The diacetoxy derivative (98) had an acetate carbonyl absorption at 1722 am.-1 in the infra-red spectrum. The ultra-violet spectrum of the 2,4-dinitrophenylhydrazones showed a chromophoric system very similar to compound (97) i.e. 361 mg, 276 mg, 260 mg and 230 mg compared with 358 mg, 275 mg, 260 mg and 239 mg in the monoacetoxy derivative (97). The addition of more than one equivalent of lead - 131 -•• tetra acetate did not lead to any increases in yield, so the reaction was not studied further. An attractive route leading to the insertion of the oxygen function in place of the anilino residue was suggested. It was considered possible to generate the keto function, by acid hydrolysis of a hemiketal type structure derived from the alcohol (99). Sodium hydride treatment of the alcohol (99) should give the anion on oxygen which would attack the intermediate imine (100) and so produce the required bridge structure (101). Acid hydrolysis should regenerate the imine (100) and immediately cleave this group before rearrangement to an enamine could take place. The N-nitrosoaCohol (99) was soon available, for on nitrous acid treatment the alcohol (63) was readily nitrosated. When the reaction time was prolonged small quantities of a compound, possibly the nitrite ester, were formed. The required derivative (99) was also prepared by the treatment of the acetate (71) with 4N sodium hydroxide at room temperature. The N-nitrosoalcohol (99) absorbed infra-red radiation at 3560 am.-1 in keeping with the presence of a hydroxyl group. The reduced perinaphthofUran chromophore was suggested by the absorption at 327 mµ in the ultra-violet -132 -

(101)

NH Ph Ph OH

(102)

H 0 0 - C; N t- 0 e Ph NH.Ph

(103)

H 1 0 -C NH Ph Ph OH

(104)

H o ----c NH Ph Ph H

(105)

H ----c Ph NH.Ph - 133 - spectrum. The analytical data did not confirm the formula C31HN0 mass spectrum molecular 3 but the showed the molecular weight to be 472. The cracking pattern showed the ready loss of 18 units corresponding to water, confirming the presence of the hydroxyl group. The conditions found to be successful for the previous sodium hydride base catalysed reactions were now applied to the N-nitrosoalcohol (57). The reaction was followedin the normal way by T.L.C., and an unusually complex reaction was observed. Initially an unstable fluorescent product was formed which rapidly disappeared to give non-fluorescent, more polar products. The reaction then continued slowly with a buildup of one very polar product. After 16 hours this compound was the major component of the mixture. Isolation of this compound was straightforward and was shown to be a stable crystalline solid. It was hoped that this new compound had the predicted hemiketal type structure (101) and so afford a route to the ketone (38). The initial physical evidence did not exclude this possibility. The infra- red spectrum showed absorption at 3300 cm.-1 and 1614 an.-1 which might be due to absorptions produced by an aromatic amine. The ultra-violet still indicated the presence of a reduced perinaphthofuran chromophore (325 mp). - 134 -

The analytical and mass spectral data, however, immediately ruled out this structure for they both supported a molecular formula of C311124N203. The new product was therefore isomeric with the N-nitrosoalcohol (99) and was hereafter referred to as the lisonitrosot derivative. Apparently either an inter- or an intramolecular rearrangement had taken place during the reaction. The T.L.C. evidence suggested the former had occurred as intermediate products had been observed during the reaction, but a decision based on this observation alone was in no way conclusive. The action of acid on the isonitroso derivative finally dismissed any possibility of a hemiketal type of structure being present. Only salt formation appeared to occur with dilute hydrochloric acid, as starting material was regenerated on base treatment. The isonitroso derivative exhibited a broad band at 3300 cm.-1 in the infra-red spectrum possibly due to hydroxyl or amine absorption, or both. To test whether the hydroxyl group of the alcohol (99) was involved in this rearrangement, acetylation should give either, or both, ester and amide absorption. A step towards an allocation of a structure to this new isonitroso compound would come on examination of its acetylation product. -135-

Acetylation of the isonitroso derivative with acetic anhydride in pyridine gave a derivative possessing infra- red absorption at 1725 cm.-1, the normal acetate carbonyl position in this series. The inference was that the hydroxyl group did not participate in the rearrangement. On the basis of the evidence so far collected, two possible structures were advanced (102,103). Reactions were then devised to establish if either of these two structures were correct. Reduction of both of these products should lead to loss of the N-oxide oxygen, to give the nmidine (104) or the hydrazone (105) derivative. Acid treatment might then lead either to ring opened products, a lactam or even the reauired ketone ( 38). Attempted hydrogenation of the isonitroso derivative using a 5% Pd/C catalyst in ethanol or a 10% Pd/C catalyst in acetic acid led to no uptake of hydrogen. Only starting material was isolated from both these reactions. Zinc in acetic acid, however, produced a new derivative, whose infra-red spectrum showed absorptions at 3440 am.-1 and 1623 am.-1. The ultra-violet spectrum exhibited the reduced perinaphthofuran chromophore at 325 These spectral properties were very similar to its precursor, but the analytical and mass spectral data showed the loss of an oxygen atom had occurred on this reftetion. — 13 6 —

Acid treatment now held the key to whether the structures postulated for the isonitroso derivative were correct and also as to whether this series would lead to useful tetracyclic derivatives. Acetic acid containing hydrochloric acid caused a reaction to take place. An unstable solid was isolated -1 having carbonyl absorption at 1670 cm. - in the infra-red spectrum as well as many absorptions between 3500 am.-1 and 3250 cm.-1. The ultra-violet spectrum showed no perinaphthofuran chromophore. When the N.M.R. and mass spectral evidence became availables it was clear that only a ring opened derivative, isomeric with the reduction product, had been formed. A ring opened product should result from structure (103) via the reduction product (104). A complete proof of the constitution had not yet been obtained although one possible structure (102) had been shown unlikely. The observation of the strong amine and/or hydroxyl absorption in the infra-red spectrum of the acid hydrolysis product, prompted the examination of its acetate derivative. Acetic anhydride in pyridine converted the acid hydrolysis product into a mixture of compounds at room temperature after 18 hours. The major component was -137- isolated by chromatography on an alumina (Grade III) column. No ester absorption was indicated in its infra- red spectrum; only amide absorption at 1677 cm.-1 and 1645 cm.-1. This supported structure (106) for the acid hydrolysis product and a tentative structure (107) was given to this acetylation product, although an infra-red absorption at 1706 cm.-1 in this derivative was left unexplained. The ring A of structure (106) was very similar to o-toluidine and so a study of the acetate derivative of o-toluidine might help to explain the anomalous band in the infra-red spectrum. o-Toluidine on treatment with acetic anhydride in pyridine at room temperature(35': gave the monoacetate derivative (108). No absorption in the infra-red spectrum of this compound appeared at 1706 cm.-1. Only at temperatures of about 95°C(35) did the di acetyl derivative (109) start to form. The infra-red spectrum of this product contained an absorption at 1707 cm.-1. This suggested that the acetate derivative had structure (110) and not (107). Confirmation of this assignment was given on an examination of its mass spectrum. The molecular ion appeared at 540 units instead of 498 units and the molecular formula calculation

(tTT) (CIT) (TT) (TTT) 11(1 'lay 11,3 TgaV 1 1 1 1 N OH- k H11 ON - .4 it i 1 a 1 D HO HO -1\I = T HO .., \ -q-ai 0 "id' NO NO NO

'Td'}1N 1,13 110 OD \ E H — 0 C11000 00

( OTT )

CH000 HO 00 HOOD 1 \

(601) (90-0

11.3* al 113 iloop,..., I H l___ 0 Hil 00 1 ..„---

( LOT ) ,s,.....-4

11c1' 1-11\1 rid 1 Ha OD I

( 9 OT ) -139--

0 together with the cracking pattern clearly (035}128N2 4) established structure (110) for this acetylation product. Beyond any reasonable doubt the structures of the degradation products of the isonitroso derivative could be explained on the basis of structure (103) for the isonitroso derivative. Reduction with zinc in acetic acid gave the amidine (104) which on acid hydrolysis, cleaved to give the amide (106). Dehydration also occurred at this stage to give the naphthalene by rearrangement of the double bond in the furan ring. This product was therefore isomeric to the amidine (104). Acetylation of the amine (106) gave the diacetyl derivative (110 ), which was surprising since the reaction was performed at room temperature, conditions which only monoacetylated o- to luidine . The structure of the isonitroso derivative,thus proven to be (103), showed that this compound was of very little use in our projected synthetic scheme. The nature of the rearrangement that took place during the formation of this derivative was now studied. The reattack of the nitroxide anion had been observed previOusly(32) and showed that this phenomenon was quite a common one. -140 -

Daeniker(36) has described a base catalysed rearrangement of the N-nitroso group which occurred in certain N- nitrosoaminoacetonitriles (111). The products from these reactions were the a-isonitrosoaminonitriles (112) formed by apparent readdition of the nitroxide anion. In contrast, however, he found that in the m-phenyl-N- nitrosoanilinoacetonitriles (113) no readdition occurred, so that the corresponding imines (114) were isolated. Rationalisation of these observations involved two alternative modes of attack of the a-carbanion on the N-nitroso group (Scheme 10). The formation of the isonitroso derivatives were suggested to come about by an intramolecular rearrangement via the three membered ring intermediate. There was no suggestion as to why one rearrangement should occur and not the other except the tentative invocation of an electronic effect asserted by the aromatic ring. In the preparation of the isonitroso derivative (103) a similar rearrangement should therefore occur to give the imine (100) because of the phenyl group attached to the carbanion. This was not found to be the case and it appears more likely that both alternative modes of decomposition of the N-nitroso derivatives proceed via a common three membered ring intermediate (115). If this is the case the decomposition of the intermediate (116) - 141

SCHEME 10

R- N -CH-ON N- CH-CN

R -NH C CN R 01-T- CN I < N

Ph N -- C - Ph Ph-N=_- C - Ph 7-1 N R R W

Ph 0 (115) x 1 N Ph5 C---) G - 142 -

0 H H

( 116 )

Yg II N -N-0

( 117 ) (118)

OH----0112 po NH N(Ne )2

( 119 ) ( 120 ) - 143 - must occur in one direction only, due possibly to the unique stereochemical environment experienced by this intermediate. Subsequent migration of the ring A phenyl group to the nitrogen of the intermediate 0-nitroso group then completed the formation of the isonitroso derivative (103). The imine (74) was previously prepared by a base catalysed reaction from the N-nitroso derivative (81). In this case no isonitroso derivatives could be observed. This reaction was repeated and the N-nitroso derivative (81) was left in contact with sodium hydride in dimethylacetamide for 3 days but only the imine (74) was formed. A similar reaction was found by Daeniker(36) who treated N-nitroso-benzalaniline (117) with sodamide in liquid ammonia. Benzalaniline (118) was the only product from this reaction, with no production of isonitroso derivatives. This observation showed why benzalaniline (118) when added to any of these base catalysed reactions, failed to remove the reactive nitrcz!de anion. This species, in accordance with the tentative mechanism of this reaction, is bound at all times to the intermediates. The reactions to with benzalaniline were added were shown to be interesting for another reason. The reaction between the N-nitroso derivative (81), benzalaniline -144-

and sodium hydride in dimethylacetamide was complex, but two crystalline compounds (A,B) were isolated by chromatography on an alumina (Grade III) column. A blank of this reaction between benzalaniline and sodium hydride in dimethylacetamide gave compound A in high yield. The structure (119) was assigned to this compound on the basis of the analytical and spectral data. The infra-red spectrum of compound (119) showed both amide and amine absorptions at 1650 cm.-1 and 3440 cm.-1. The ultra- violet spectrum was very similar to that of N-phenylbenzyl- amine. Absorptions at 297 mµ and 247 mµ agreeing well with 294 mil and 250 mil. The N.M.R. spectrum in pyridine showed N-methyl singlets at r 7.25, 7.47 and a proton attached to nitrogen at 1- 3.95 in the spectrum run in dimethylsulphoxide. Analysis gave 017H20N20 as the molecular formula of compound (119). Sodium hydride had generated the anion in dimethylacetamide a to the carbonyl group which had attacked the unsaturated linkage of the imine (74) in the formation of this structure (119). Compound B was also formed in the reaction between the imine (74), benzalaniline and sodium hydride in dimethylacetamide or dimethylformamide. This observation Indicated that there was no solvent participation in this -145-

case. Compound B was an orange crystalline solid which gave a dramatic colour change in solution on the addition of acid. The deep-red colour was discharged on the addition of alkali. This observation supported the vinylogous amidine structure (120), advanced on a study of its spectral data. The infra-red spectrum indicated an amino group was present as an absorption at 3410 cm.-1 occurred. The ultra-violet spectrum showed shifts in the absorption pattern on addition of acid. The absorptions at 392 mg, 250 mµ, 206 mµ being moved to 498 352 mil, 264 11111, 207 mil, consistent with the protonation of the amidine structure. The N.M.R. spectrum showed the presence of a proton attached to nitrogen by loss of the signal at ' 4.90 upon deuteration. Analytical evidence confirmed the molecular formula C29H24N2. The formation of the amidine type structure (120) had taken place by the oxidation of the addition product of benzalaniline (118) and the imine (74). It was still possible that the bridged structure (101) might be formed in a base catalysed reaction so for the sake of completeness, the effect of other bases on the N-nitrosoalcohol (99) were examined. -146-

Sodium ethoxide brought about no reaction at room temperature but potassium t-butoxide reacted with the alcohol (99) to give a mixture of compounds. The main product was isolated by chromatography on an alumina (Grade III) column and shown to be the aromatic ketone (19). The melting point and mixed melting point of this compound and an authentic sample proved the identity of this product (19). The infra-red and ultra-violet spectra were identical with the spectral data of this authentic -) specimen. Sodium hydroxide at room temperature did not react with the N-nitrosoalcohol (99) but at elevated temperatures a reaction was observed. T.L.O. showed that the main product had an identira Rf value and appearance to the amine (63). After isolation of this compound, spectral data confirmed this observation. The alcohol (63) was also formed in high yield when the N-nitrosoalcohol (99) was refluxed in ethanol, denitrosation being apparently readily effected. When the N-nitrosoalcohol (99) was stirred at room temperature with triethylpmine in the methanol for 24 hours, only starting material was recovered. These conditions had been previously used for formation of the imine (114) from the N-nitroso derivative (113). -147-

Synthesis of a re, rsor n T.X°992s

At this stage in the work our attention was drawn to another aspect of the work being dealt with in the group. A very convenient means of cyclisation of benzaldehydes of type (14) to the corresponding tetracyclic derivatives (35) by a photolytic procedure had been demonstrated.(37) Derivatives of the aldehyde, such as the acetal (121), also cyclised to the ketal (122) in high yield on photolysis. This discovery had changed the approach to the synthesis of tetracyclic molecules. A protecting group for the ketone was also present in these tetracyclic products making this cyclisation method doubly useful. The dimethylether (123) was also photolysed and the tetracyclic compound (124) was formed,(37) as expected, by this process. The substituted benzaldehydes suitable for this photocyclisation had been prepared previously(5) by a laborious route (Scheme 5, p.75) in low yield. A more simple, direct route to derivatives not containing methylether functions was now reauired. A valuable contribution towards the synthesis of a substituted benzaldehyde derivative suitable for photolysis — 148 —

(121)

0 — 0 Ph

1-% I

I I-167 (122) 0 \

(123)

0 H OMe (124)

0 Me 0 C / Phi -. 149 -

had been made(38) (Scheme 11). The important step left in this synthesis, the introduction of a formyl group, had not yet been successfully accomplished. A study of a possible introduction of this group into a model compound was commenced. It was predicted that treatment of a chloroformate (125) with sodium formate should give an interiaediate (126) which on decomposition might give the required o-substituted phenol (127) (Scheme 12). When anhydrous sodium formate was added to a solution of phenylchloroformate (128) in dry tetrahydrofuran or dimethylacetamide, a reaction was observed by T.L.C. A new product was isolated in low yield by chromatography on thick layer silica plates. Only a partial separation of this product from phenol, also formed in this reaction, could be made in this way. The infra-red spectrum and the mass spectral molecular weight 214 showed that this product was not salicylaldehyde (129). The infra-red spectrum showed no carbonyl absorption at 1666 am.- 13,(9) but only at 1736 an.-1. The molecular weight was consistent with diphenylcarbonate (130) yet the infra-red spectrum of this compound (130) had carbonyl absorption at 1775 mm. -1and not at 1736 an.-1 as in the new product. An authentic specimen of - 150 SCHEME 11 o OAc I CH Ac -;:/" , . OAc + II COOMe '1O--C I- Ph o OAo

C00I1e

J2 0,

H COOMe I O--C I Ph J3 0 OH ;:?'1 ~ <, COONe C-? OR Ph Reagents: 1. AcOH/H 2. AcOH/HCl/dioxan 2S04

— 151 —

SCHEME 12

CO R r) I --->R Cd (125) H (127) (126)

C -OHL

CHO (129)

(130 )

0 I OH

(131) COONle 0 C OH Ph 0

(132)

OH Ph - 152 - diphenylcarbonate (130) was shown to have the same T.L.O. behaviour as the new product. A further study of the infra-red spectra was therefore made. The original isolation of the unknown product failed to remove all the phenol that was present, consequently a small quantity of phenol had been present in the new product, as demonstrated by the mass spectrum. An authentic mixture of diphenylcarbonate (130) and phenol was prepared and the infra-red spectrum of the mixture taken. A dramatic shift of the carbonyl stretching frequency of diphenylcarbonate resulted. The original absorption at 1775 cm.-1 was shifted to a broad carbonyl absorption at 1740 cm.-1. The inference from this observation was that the new product formed in the reaction was diphenylcarbonate (130). On admixture with phenol, the characteristic carbonyl absorption of diphenylcarbonate (130) had shifted, presumably because of hydrogen bonding.

Gattermann• •••••••• ••-••••••• Reactions Gattermann reactions(40) have been used extensively for the insertion of formyl groups into phenols, and proved to be most effective in the ring A model work (e.g. Scheme 1, stage 3, p. 65.) . The available bisphenol (131) was predicted to yield the substituted benzaldehyde (132) under suitable -153-

Gattermann conditions. The Adams(41) modification which had previously been successful, was applied to this work. No reaction occurred at room temperature between the bisphenol (131), zinc cyanide and hydrogen chloride in nitrobenzene. On raising the temperature,a slow reaction was observed which did not go clearly to one product according to T.L.O. The mixture of compounds produced had infra-red absorptions at 1717 cm.-1, 1670 cm.-1, and 1634 an.-1 but very little perinaphthofuran chromophore in the ultra-violet spectrum. Aufderhaar(7) had treated the perinaphthofuran derivative (133) with sodium cyanide in ethanol and isolated the ketolactone (134) which had infra-red absorption at 1720 am.-1 Unfortunately separation of the crude mixture formed in the above Gattermann reaction was not possible, so it was tentatively assumed that tinder these conditions attack at the perinaphthofuran section of the molecule, to give derivatives of the phenol (135); had occurred. The usunl Gattermann conditions, employing liquid hydrogen cyanide were next used. No reaction again took place at room temperature in nitrobenzene and it was not until much higher temperatures had been attained - 15 4 -

OH (132a)

COOH

OH Ph 0

(133) I

0 C

(134)

OH (135)

COOMe

0 0 OH (136 )

CH COOMe

Ph -155-

(60°0 to 90°c), that a slow reaction_took place. A_low yield of a new product was isolated after a tedious workup, which was shown later to be the required substituted benzaldehyde (132). The infra-red spectrum showed absorption at._ 3370 cm.-1 consistent with the phenolic hydroxyl absorptions. The bands at 1665 cm.-1 and 1638 cm.-I were correlated with the overlapping carbonyl absorptions of the carbomethoxy group and the aldehyde at 1665 an.-1 and the m,P-unsaturated carbonyl at 1638 cm.-1. The ultra-violet spectrum exhibited absorption at 405 mµ as expected of the perinaphthofuran chromophore. _Due to the insolubility of this compound in the normal solvents used for N.M.R. spectroscopy only a little information could be extracted from the N.M.R. spectrum. A non-deuterium exchangeable_proton at -0.15 as expected of a formyl proton, was just visible. The mass spectral molecular weight of 454 eliminated the possibility that the product isolated was the imin.e (136).

The analytical evidence also supported 027H1807 as the molecular formula. _ Gattermann reactions have been successfully performed using the triazine complex formed from hydrogen cyanide and hydrogen chloride.(42,43) The aldehyde (132) was prepared in this reaction but many difficulties were - 156 -

encountered in the working-up of the reaction. The worst troubles were the formation of semisolid complexes and emulsions. in order to break down these complexes, treatment with acid was expected to liberate the bisphenol (13) from its aluminium complex. On 'heating the complex in dilute hydrochloric acid, a new compound was formed 027H2008 containing addition of the elements of water. The infra-red spectrum showed absorptions at 3420 am.-1 and 3230 cm.-1 consistent with the expected hydroxyl group absorption. The perinaphthofuran chromophore was altered so that weak absorption was now present at 409 mp instead of 405 mp. Strong absorptions at 247 mA and 231 mp, were now present. The analytical and mass spectral data supported 27C -H20 0-8 as the molecular formula. On heating the 'hydrated aldehyde', dehydration resulted as well as deformylation to give the original bisphenol (131). A detailed study of this Gattermann reaction was required but firstly,a systematic examination of the workup conditions was necessary since those previously used were quite unmanageable. It was decided to continue along the lines employed previously and then modify the procedure as required. -157-

The crude Gattermann reaction mixture on pouring into water gave a sticky brown solid, which after filtering and drying at 8000 was extracted with chloroform. The complex only broke down slowly to liberate the aldehyde (132), so extraction in a soxhlet apparatus with chloroform was attempted. From this treatment, however, only a low yield of the aldehyde (132), contarajnated with other products, was isolated. Aqueous acetone also had a similar effect in this extraction. Preferential complexing of the aluminium after the Gattermann reaction had been completed, offered the easiest way of preventing formation of solid organic complexes. Rochelle salt, salicylaldehyde, 8-hydroxyquino- line and acetylacetone were tested but were all used to no avail since sticky solids were still formed which contained most of the aldehyde (132). As one of the stages after the formation of the benzaldehyde was to be an acetylation step, direct acetylation of the Gattermann reaction mixture was attempted. With acetic anhydride, a very complex mixture of products was formed which could not be separated into its individual components. Acetyl chloride also brought about a very similar reaction. - 158 -

Finally, a study of direct acid hydrolysis of the reaction mixture was made. Ethanolic hydrochloric acid gave the previously observed 'hydrated aldehyde' 027H2008' Concentrated hydrochloric acid caused complete decomposition of the aldehyde (132) but addition of dilute hydrochloric acid appeared to slowly break down the complex. Freedom from troublesome complexes and consistent yields were found on working up the reaction mixture with dilute hydrochloric acid. Extraction of the resulting mixture with chloroform, removal of the solvents on a steam bath under high vacuum, and chromatography on a silica column gave the pure aldehyde (132) in reproducible yields (30-34%). The anomalous effect of acid was investigated in a model compound, to determine why in some circumstances hydration took place while in other cases no effect was observed. The conditions present in the Gattermann reaction were first tried. The perinaphthofuran (3) was stirred in a mixture of nitrobenzene and dilute hydrochloric acid for 24 hours but no change took place. Starting material was isolated in quantitative yield. Treatment of the perinaphthofuran (3) with dilute hydrochloric acid in -159- ethanol, brought about an immediate reaction. The new product was readily shown to be the naphthalene derivative (137)(38) formed by hydration of perinaphthofuran. Mass spectral and analytical data, combined with its ready transformation back to the perinaphthofuran (3) with strong acid, proved this structure. The infra-red spectrum supported this assignment by exhibiting hydroxyl absorption at 3290 cm.-1. The structure of the previously isolated 'hydrated aldehyde' was thus probably (138). The mass spectrum indicated a weak molecular ion at 472 units with a facile loss of 18 units due to loss of water. A convenient proof of structure (138) was thought obtainable by examination of the acetylation product which should show four separate acetate signals in its N.M.R. spectrum. Unfortunately, on attempted acetylation(38) a mixture of products resulted, presumably because acetylation of the formyl group had also occurred. With the Gattermann reaction workup procedure in operation, the conditions under which the reaction wam performed was then varied. The following chart shows six representative experiments under various conditions in nitrobenzene as solvent with the yields of pure aldehyde(132) obtained. — 160 — OH

(137) I

OH CO Ph OH

(138)

CH CO OH Ph

OH (139) COOEt

Ph 0

0 OAc (141) j H COOMe 0 d 0 0 OAc Th -161 -

ph art I

Time Temperature Equivalents Equivalents Yield of Aluminium of Gattermann chloride complex

2 hrs 7500 10 10 320 16 hrs 800C 10 10 8% 48 hrs 30-40°0 10 10 12% 20 mins 9500 10 10 34% (Solvent preheated) 10 mins 12000 10 10 30% 2 hrs 8000 10 30 9%

The best yield was obtained in the reaction in which the nitrobenzene solvent was preheated to 10000. The aluminium chloride and the Gattermann complex were added and when they had dissolved the bisphenol (131) was added. The well stirred mixture was then kept at 95°C. for 20 minutes. The number of equivalents of aluminium chloride used affected the speed of the reaction. 2 Equivalents produced no reaction but the reaction with 5 equivalents was substantially slower than that with 10 equivalents of aluminium chloride. Competitive formylation of the solvent ensu4(1 when toluene was used as the solvent instead of nitrobenzene. - 162 -

Highly polar byproducts were isolated from all these Gattermann reactions and in the case of the reaction performed in chlorobenzene, a crystalline solid was isolated. The infra-red spectrum gave a broad band centred at 1630 cm.-1 . The ultra-violet spectrum exhibited an absorption at 405 141 suggesting that the perinaphthofuran chromophore was present in this molecule. The N.M.R. spectrum showed signals at 1" 5.91; 'r 5.75; 1- 4.00; r 3.70; 1- 1.93 to 2.87, 'r 1.68; /- -0.40 and -4.17. Analytical data indicated nitrogen was present and suggested that the molecular formula C19H15N05 best represented this data. The mass spectrum, however, gave the molecular ion at 440 units, which did not correspond to the molecular formula as suggested by the analytical data. The cracking pattern in the mass spectrum held the clue to the identifi- cation of this molecule. In all previously encountered substituted ring A derivatives, a line could be found at 32 units less than the molecular ion. This was ascribed to the loss of methanol from the carbomethoxy group. In this spectrum, however, no peak was observed at 408 units, but rather one at 396 units. This information showed that the carbomethoxy group was absent and led to the formulation (132a) for this product. -163 -

The bisphenolaldehyde (132) had apparently suffered demethylation during the reaction, to give the carboxylic acid. Due probably to a thermal process on the probe, the acid (132a) decarboxylated to give the species of molecular weight 396 and so accounted for the observed loss of 44 units in the mass spectrum. Further support for this rationalisation was given on observation of further mass spectra taken a few minutes after the first. The molecular ion now appeared extremely weak, compared with the rest of the spectrum, whereas the line at 396 units had increased in intensity. This was in keeping with a thermal decarboxylation process. Similar reactions in the presence of aluminium chloride have been reported.(43a) The low yields in the previously described Gattermann reactions were now explained. The demethylated product did contain the formyl group, so all that would be necessary to increase the yields of these Gattermann reactions would be to selectively methylate the carboxyl group of the acid (132a). During investigations on the best chromatography systems to separate the benzaldehyde (132) fram unreacted starting material (131), the formation of a new product appeared to arise after chromatography on an alumina - 164 -

(Grade III) column. Only small amounts of this product were isolated, which possessed very similar physical properties to compound (131). Infra-red absorption at 1680 cm.-1 and 1640 em.-1 ascribed to the carbomethoxy carbonyl and the ap3-unsaturated ketone respectively, were in similar positions to those in the bis phenol (131). In fact, the infra-red spectrum was almost superimposable with starting material. The ultra-violet spectrum gave an absorption at 405 em.-1 in accord with the presence of the perinaphthofuran chromophore. The T.L.C. behaviour, however, was different since the new product had a slightly greater Rf value than the bisphenol (132). The solution to this problem came when the N.M.R. spectrum became available. A triplet centred at T 8.56 (3H) and a quartet at 5.47 (2H) coupled with the absence of a singlet at r 6.10 immediately showed itstacarboethoxy group rather than a carbomethoxy group was present in this compound. Confirmation of this structure (139) was given by the mass spectrum. The molecular ion was at 440 units and the cracking pattern indicated the loss of 46 units, &i.e to ethanol; rather than 32 units, methanol, from this molecular ion. Acetylation of the carboetboxy compound (139) gave - 165 -

the corresponding acetate (140) on treatment with acetic anhydride in pyridine at room temperature. The infra- red spectrum exhibited absorptions at 1772 cm.-1, 1722 am.-1, and 1641 cm.-1 consistent with carbonyl absorptions of ester, carboethoxy and a0-unsaturated ketone functions. The ultra-violet spectrum showed absorption at 400 mp, consistent with a perinaphthofuran chromophore. The mass spectrum indicated that the molecular weight was 524. The formation of this homologue was shown to occur readily on passage of compound (131) down an alumina (Grade III) column in ethanol. These conditions were apparently ideal for the transesterification reaction to take place. The next stage in the work was to form a derivative of the benzaldehyde (132) which would be a suitable precursor for the photolytic cyclisation procedure. The aim was then to prepare the diacetateacetal (141) which should be readily accessible from the benzaldehyde (132). Two stages were seen to be involved; an acetylation and an acetal formation which should aullu be attempted in either order. The formation of the acetal (142) was first attempted. The benzaldehyde (132) was refluxed in benzene containing ethyleneglycol and p-toluenesulphonic acid. ( 9i71) CH OD 0V c,T00Q11 HO 01\1000 eriooa

ovo

°HOOD HO

( ovO

CHDOO H0 00 aNOOD

ovo ua ovo 0 - 81\1000 OHO

Tla 0 0 0 °WOOD ( How

991 — -167 -

Examination of the reaction by T.L.C. indicated that the only new product being formed was probably the bisphenol (131). Proof that only deformylation occurred in this reaction came when on separation of the supposed bisphenol (131) from the benzaldehyde (132),the spectral data was identical to the authentic material (131). The acetal (142), however, was formed by refluxing the benzaldehyde (132) in benzene containing 2-butanone ethyleneketal and p-toluenesulphonic acid for 24 hours. The infra-red spectrum showed absorptions at 3410 cm.-1, 1663 am.-1 and 1641 am.-1 due to the absorptions of hydroxyl, ester and (1,p-unsaturated ketone groups respectively. The loss of the aldehyde carbonyl could not be verified in this spectrum since the carbonyls of the formyl and carbomethoxy groups absorbed at the same position. This absorption at 1663 an.-1 was weaker in compound (142) than in the benzaldehyde (132). The ultra-violet spectrum showed absorption at 405 mµ consistent with the presence of the perinaphthofuran chromophore. The mass spectrum gave the molecular weight of this compound as 498 and its molecular formula 029H2208, so supporting structure (142) for the new product. An attempted transketalisation with boron trifluoride etherate in 2-butanomm ethyleneketal was not successful. -168 -

The acetal (14.2) was an unstable compound which on contact with acid was immediately reconverted into the benzaldehyde (132). Acetylation of the acetal (142) with acetic anhydride containing sodium acetate gave the required diacetate derivative (141). The infra-red spectrum showed absorptions in the carbonyl region consistent with the carbonyl absorptions of the GO-unsaturated ketone (1642 cm.-1) carbomethoxy group (1728 cm.-1) and the phenolic acetates (1769 cm.-1). The usual shift of the carbomethoxy group absorption from 1665 am.-1 to 1728 am.-1 was associated with the loss of hydrogen bonding between this group and the phenolic hydroxyls. The mass spectra and analytical data supported the structure (141). As a low yield of the acetal-(142) and difficulties in its purification were experienced in the acetal formation step, the alternative scheme for the preparation of the diacetateacetal (141) was investigated. The bisphenolaldehyde (132) on acetylation was expected to give the diacetate (143) which should be readily converted into its acetal derivative (141). ,cetylation of the bisphenolaldehyde (132) gave mixtures of products with acetic anhydride containing sodium acetate, and also with acetic anhydride in pyridine. -169-

The following conditions were found eventually to give the separate acetylation products in good yields., Treatment of the benzaldehyde (132) with acetic anhydride containing sodium acetate at 95°C for 16 hours gave the formyldiacetate derivative (144) in high yield. The infra-red spectrum showed absorptions due to acetate -1 -1 carbonyl (1772 cm. ), carbomethoxycarbonyl (1729 cm. ) and on (10-unsaturated ketone (1642 cm.-1). The perinaphthofuran chromophore was indicated by an absorption at 403 mp, in the ultra-violet spectrum. The N.M.R. spectrum gave no formyl proton but a singlet integrating for six protons at 1- 8.10 was present, corresponding to the two new acetate methyls present in the molecule. The normal two acetate methyl singlets at -r 7.76 and T 7.62 'ere also present. Unfortunately, proof of structure was not forthcoming from the analytical evidence but the mass spectrum showed a weak molecular ion at 608 units, and a cracking pattern consistent with the presence of four acetate residues in the molecule. An attempted formation of the acetal (141) direct from the formyldiacetate (144) using 2-butanone ethyleneketal and a boron trifluoride etherate catalyst was unsuccessful. It was hoped that loss of the two acetate groups would occur to give the compound (142) which would -170 -

be transformed then into the acetal (141). As the formyldiacetate (144) was prepared in good yield,we endeavoured to make the diacetate derivative (143) by selective deacetylation of the formyldiacetate function. This proved to be difficult to achieve, however. Only starting material was isolated after stirring the formyldiacetate (144) with dilute acid in a two phase system. A one phase system was not tried since opening of the furan ring to give a naphthalene derivative would have immediately occurred, vide supra. A quantitative recovery of starting material also resulted when the formyldiacetate (144) was chromatographed on a silica column in ethylacetate. Chromatography on an alumina (Grade V) column, however, led to the formation of a small quantity of the monoacetate derivative (145) 6) The same compound was formed after treatment of the formyldiacetate (144) with sodium bicarbonate in aqueous ethanol. The infra-red spectrum showed absorptions at 1775 cm.-1 1684 cm.-11 1663 cm.-1, 1639 cm.-1 due to carbonyl absorptions of the ester group, carbomethoxy group, formyl group and the (1,-unsaturated ketone, respectively. The absorption at 405 mp in the ultra-violet spectrum indicated the presence of the perinaphthofuran chromophore. Support -171 -

for this structure also came by N.M.R., which showed one acetate methyl signal ( i 7.75), the cnrbomethoxy methyl signal ( 6.10) and the formyl proton signal (1- -0.25). A signal far one proton at '1" -0.48 was ascribed to the proton on oxygen in structure (145). The mass spectrum exhibited a molecular ion at 496 units as expected for this compound (145). Further confirmation of the monoacetate structure (145) was produced, when reacetylation of this derivative gave the formyldiacetate (144). The acetylation of the bisphenolaldehyde (132) appeared to proceed very rapidly to the formyldiacetate (144) even at room temperature. . This prompted the use of a ring A model, which possessed the same disposition of groups as in the bisphenolaldehyde (132), for a study of this acetylation reaction. The model aldehyde (146) prepared as depicted in Scheme 1, p.65, from oreinol, was chosen for this study. The model aldehyde (146) on treatment with either acetic anhydride containing sodium acetate or acetic anhydride in pyridine at room temperature failed to give any trace of the expected formyldiacetate (147) and only mixtures of the mono (148)(5) and diacetate (149) derivatives(58) were isolated. This was unfortunately another case where model compounds did not imitate the

— 172 —

Me OAc

COOMe CHC(C: COOMe

OH (148) OAc (149)

OH (150 )

COOMe I II 0 --- NH Ph Ph

COOMe COOMe NH OH1 F Ph (151) Ph (152)

(154) -173- action of the compounds of the larger series. The required diacetate (143) was eventually formed in the reaction between the bisphenol (132) and acetic anhydride containing sodium acetate. When the reaction mixture was stirred for 5 days at room temperature, a yellow solid was precipitated. After filtration, washing with water and crystallisation, the pure diacetate (143) was isolated. The infra-red spectrum showed absorption at 1765 am.-1, -1 -1 -1 1716 cm. 3) 1688 cm. and 1632 am. consistent with the presence of an ester, carbomethoxy and formyl carbonyls and an m, unsaturated ketone, respectively. The ultra- violet spectrum, as expected, showed that the chromophore of the perinaphthofuran was present by absorption at 403 mil. The N.M.R. showed signals at 'e 7.76, 7.65 due to acetate methyl protons, integrating for three pro tons each. The carbomethoxy methyl signal was present at

7 6.13 and the formyl proton appeared at -r" -0.32. The structure (143) was supported by the mass spectrum and analysis as the molecular formula 031H2209 was indicated. As expected, the acetal (141) was easily formed from the benzaldehyde (143). The transketalisation process with 2-butanone ethylene ketal and boron trifluoride -- 174 - etherate in benzene produced the acetal (141) in high yield from the benzaldehyde (143), in 5 minutes. Having completed the object of this work in synthe- sising the diacetateacetal (141), the further transformations of this compound were left to other hands.

Studies in the substituted isoldin series

Interesting developments in the formation of ring A compounds were taking place at about .the time the above (44) work was completed. Extensive studies had demonstrated that suitable bisphenols on treatment with Fremy's salt

((KS03)2N0) were converted into the corresponding quinones. These compounds were readily reduced to the triphenols (Scheme 13). It was argued that the driving force of the reduction to the hydroquinone might be directed towards the oxidation of the anilino function in suitably substituted isoldin derivatives (e.g. 150) (Scheme 14). This would offer a simple means of oxidising the amine, a reaction which had so far eluded us in this isoldin series. Before embarking on the route along the previously developed pathway to substituted isoldin derivatives, it was considered necessary to examine some model compounds for this transformation. A ring A compound which had — 175 —

SCHEME 13 OH Me OH Me

COOMe COOMe OH OH 1

SCHEME 14

COOMe

--- a NH Ph Ph

COOMe

N — H 0 Ph -176- the salient features of a substituted isoldin derivative was to be first oxidised with Fremy's salt. This was expected to serve as a guide to determine the sort of reactivity one might expect with this reagent. A suitable model compound to test these predictions was the amine (151). This compound was to be produced from the aldehyde (145) by condensation with aniline and reduction of the imine (151) so formed. The first step was simply accomplished by refluxing the aldehyde (146) with aniline in methanol for 30 minutes. On cooling the reaction mixture, the pale yellow imine (152) crystallised out. The infra-red absorption spectrum exhibited a band attributable to the imino group stretching frequency at 1640 cm.-1 and the ultra-violet spectrum showed a strong absorption at 412 mµ. The N.M.R. spectrum showed the presence of methyl signals due to the aromatic methyl ( 1- 7.66) and the carbomethoxy methyl (1- 6.00). There were 6 aromatic protons present according to the inteilxstion of this spectrum. The formyl proton absorption was also shown to be absent in the N.M.R. spectrum. Analytical data supported 016111504N as the molecular formula. Reduction of the imine (152) with sodium borohydride was expected to give the amine (151) directly. However, -177— on reduction with this reagent, two compounds were formed according to T.L.C. One product was shown to be the dimethyl derivative (155), by comparison with an authentic sample.(39) The other product was the required amine (151). The infra-red spectrum indicated absorptions due to -1 amine and hydroxyl groups 3120 cm.-1 and 3470 cm. respectively. The ultra-violet spectrum showed a strong absorption at 255 mµ which compared with the value 247 mµ for the aniline chromophore. The N.M.R. spectrum was compatible with the proposed structure (151). The aromatic methyl ( 1- 7.67) and carbomethoxy methyl (1- 5.79) were present as was a methylene signal at r 5.97. The molecular formula C16H17N 0 4 was supported by analytical and mass spectral evidence. This hydrogenolysis of the amine (151) was avoided by hydrogenation. A 5% Pd/C catalyst in benzene or a 1% Pd/C catalyst in ethanol when used for the hydrogenation of the imine (152), produced the amine (151) in good yield. The effect of Fremy's salt on this product could now be demonstrated. The treatment of the amine (151) with Fremy's salt resulted in a complex mixture of unstable products. No useful products could be isolated using the -178— usual solvents and conditions;namely, ethanol, ethanol/ sodium acetate, dimethylformamide/sodium acetate or dimethylformamide/sodium hydroxide. It was suspected that Fremyls salt was attacking the amino group, so the effect of the reagent on benzal aniline (118) was investigated. Once again mixtures of unstable brown oils were generated, and no clue as to the constitution of any of the products could be found. In contrast, to these complex reactions, treatment of the amine (151) with Premy9 s salt in the two phase system, methylene dichloride and aqueous sodium hydroxide, brought about no reaction. Starting material was isolated after 24 hours at room temperature. It was recalled that an experiment was performed to investigate the action of Fremygs salt on the amino— acetate (65). No reaction was observed in a one or a two phase system at room temperature. This result seemed surprising in view of the complex reaction that took place in a one phase system with the ring A model compound (151). On treatment of the aminoalcohol (63) with Fremy's salt in ethanolic sodium hydroxide, no reaction was ob— served to take place. After 24 hours starting material - 179 - was present, which was isolated quantitatively. As it had been noticed previously, the secondary amine appeared to be extremely inert. This may have been a consequence of the steric hindrance exerted by the 2-phenyl function. In the present case this inertness seemed to be an advantage as it would offer an 'internal protection' to the effect of a Fremyts salt oxidation of substituted isoldin derivatives. No demonstration had been given that Fremyts salt might bring about the oxidation-reduction step in producing an imino derivative (e.g. 154) in a substituted isoldin derivative; but it was suggested that work in this series should start for another reason. The suggestion was made that the bisphenolisoldin (155) on treatment with Fremy's salt should give the quinone (156) which on base treatment might open the isoxazolidine ring to give the imine (157). The bisphenol (132) was treated with phenylhydroxyl- Rmine under the usual .isoldin preparation conditions. The mixture was stirred at room temperature and the reaction followed by T.L.C. After 8 days,the reaction had not quite gone to completion but a new product was isolated by crystallisation of the crude precipitated product,,in low yield. The new product absorbed at 361 mµ in the ultra-violet spectrum as compared with ( 0 v o )11 o ; H 914000 (65i)

(HO ) ua 0 T-Id

0V0 0 eN 000

ua 0 Ild — 0 H

(LT)

H tra 0 H MOOD (95T)

HO ua b ua . HO FI ,D, ; H ii °WOO

qd. 0

- 02T - - 181-

365 mµ in isoldin A (26). The N.M.R. spectrum exhibited - an AB system ( r 6.26, 6.72, JAB 18 tip's.) due to the 0-8 protons which compared favourably with the AB system 1- present in isoldin A, i.e. (" 6.17, 6.69; JAB = 18 c.p.s.) Confirmation of the isoldin A structure (112) could not be obtained on analytical evidence but the molecular formula C33H23N04 as derived by the mass spectrum was in full accord with this structure. A likely way to speed up the isoldin preparation seemed to be possible by using a more soluble substituted benzaldehyde, since these reactions are dependent upon the solubility of the starting material. The diacetatealdehyde (143) was treated with phenylhydroxylamine in ethanol at room temperature and after 3 days no starting material was present according to T.L.C. On examination of the product by N.M.R. it was readily seen that none of the expected diacetate (158) was present. Only one acetate methyl signal could be seen which did not integrate for exactly 3 protons. The mixture from this reaction apparently consisted of essentially two products, the monoacetateisoldin derivative (159) and the previously isolated isoldin (155). These products could not be separated by fractional crystallisation. -182 -

The effect of Fremyts salt was now tested on the substituted isoldin (155). On addition of the reagent to a well stirred solution of the starting material in ethan- olio sodium hydroxide, a reaction occurred. No starting material was present after 15 minutes and the brown solid isolated from this reaction was possibly the quinone (156). Further work will be required to verify this formulation before attempting_further transformations. Now that this course of study was nearing its close, a comment on the present position_of the synthesis could be made. The isoldin route to useful tetracyclic compounds has proved rather disappointing. The final stage of the new route, i.e. the oxidation of the amino function to a ketone, could_not be accomplished, but work in ring A substituted isoldins, offer an alternative solution to this problem. The photo-cyclisation method now claims most of the attention at the present time since it is superior to the previous cyclisation procedures. It must be borne in mind, however, that this method is still in its development stages, even though some important tetracyclic derivatives have been,, synthesised. In future studies, products arising from the photo- ayclisation reaction may well require transformations -183 -

in ring A. If this is so, the substituted isoldins can offer a useful model tetracyclic system for these re- actiQns. The oxygen-nitrogen bridge connecting carbon• atoms 3,8a, conveniently protects the labile C-2a,3 and 8a positions in rings B and C. In conclusion, the studies in the ring A models, together with the photolytic cyclisation procedure, have demonstrated that a biologically active tetracycline may soon be realised. If, however, the new cyclisation procedure falls short of expectations, the isoldin route may well offer an alternative means of completing our object. - 184 -

EXPERIMENTAL

All melting points were determined on the Kofler block and are uncorrected. The infra-red spectra were taken on the Unicam S.P.200 spectrometer in a nujol mull, except where otherwise stated. The ultra-violet spectra were measured in absolute ethanol on the Unicnm S.P.700 spectrometer. The Varian A.60 spectrometer was used for the N.M.R. spectra which were mainly performed in deuterochioroform solution; the exceptions being mentioned at the relevant places. The A.E.I. M.S.9 double focussing spectrometer was employed for the mass spectra. -185 -

1. Preparati.9111f197Aponp.glItill2a1.911ma derivatives

Attem ted formation of 2-pheny1-3cyano=j7tetrahvdro- cenol4 49:p5pbcjfuran A solution of 2-phanyl-3-cyano-3-tetrahydropyranyloxy-9-oxo-2a,8,8a-trihydronaphthaceno[4,4a1 5,bc]fUran (64 mg.) in glacial acetic acid (60 ml.) was treated with 1,2-ethane dithiol (0.5 ml.). The mixture was stirred at room temperature and after 30 hours, poured into water. Extraction with chloroform gave an organic phase which was washed with water and dried over sodium sulphate. On evaporation of the solvent, a crude solid was formed which was crystallised from benzene. M.p. 219-220°C. Yield 39 mg. Mixed m.p. with authentic 2-Joaylzaamla:.3-hydroxy-„9-oxo-2a 8 8a-tri- Aydronhthaqpno[4,0q,5 bc]furan 28)(5) gave no depression. The infra-red spectrum showed absorptions at 3400 cm.-1, 1704 cm.-1, 1675 cm.-1. The ultra-violet spectrum Showed absorptions at 260 mil and 356 mµ. - 186 -

Hydrogenp1:vsis in the perinp,pp.t2n4uran series

1) 2-Pheni1-5-hvd.roTcy=3, 4.25.-_-trililidl?P.11-4,P,1#119_14119J 5, 'loc) furan 0

) 2-Phenyl-5-oxo -3 , 4-dihydro-naphtho[ 4,10 $ 5 be furan (25 mg.) in dry dimethylformamide (15 ml.) was hydrogenated in the presence of a prereduced 10% Pd/C catalyst. An uptake of one molar equivalent of hydrogen occurred after 16 hours. The catalyst was filtered and the filtrate poured into water (100 ml.). Dxtraction itith chloroform (50 ml.) gave an organic layer which was washed with water and dried over sodium sulphate. The solvent was evaporated to an oil which crystallised on contact with methanol. M.p.136°C. Yield 18 mg. The infra-red spectrum showed absorptions at 3367 cm.-1 and 1055 cm.-1. The ultra-violet spectrum showed absorptions at 322 mil and 308 mil. Mixed m.p. with authentic 2-phenyl-5-hydrox_y-3.144,5-trihyidrona_phth21,4,10.21Lbc furanagl(5) showed no depressicn.: b) Diborane was prepared by the treatment of sodium borohydride in diglyme with boron trifluoride etherate.(45) The gas was swept from the generator into the reaction vessel with a strean of nitrogen. — 187 —

2-Phenyl-5-oxo-3,4-dihydronaphtho[4,10,5,bc]furan (50 mg.) in dry tetrahydrofuran (6 ml.) was treated with diborane. After the gas had passed through the solution for one hour, excess chromous acetate was added. The mixture was filtered after a further 30 minutes and poured into water. Extraction with chloroform gave an organic layer which was dried over sodium sulphate. Evaporation of the solvent gave a solid. M.p. 134-136°C. Yield 40 mg. (80% Theory). Infra-red and ultra-violet were identical to the authentic 2-pheny1-5-hydroxy-3,4,5-trihydronaphtho[4,10,5,bd- furan (30)(2). -188 --

2 ) 2,..-21.9:x.d.h dr o1291.4t_]_-Qt2L12giggLal..

a) 2-Phenyl-5-oxo-3,4-dihydronaphtho[4,10,5,bc] furan (1.0 g.) in glacial acetic acid (120 ml.) was hydrogenated over a pre-reoduced 10% Pd/C catalyst. One molar equivalent of hydrogen was absorbed after 1 hour and a further equivalent taken up after 8 hours. After filtration to remove the catalyst, the solution was poured into water and extracted with chloroform. The organic layer was washed with water, sodium bicarbonate, and water again before drying over sodium sulphate. Evaporation of solvent gave an oil which was chromatographed on an alumina (Grade III) column made up in petroleum ether (60-80°C. B.p. range). The first fraction yielded an oil on evaporation of solvent. A solid formed on treatment of the oil with petroleum ether (30-40°C B.p. range). M.p. 55°C. Yield 811 mg. (84% Theory). The infra-red spectrum showed absorptions at 1621 cm.-1 and 1054 cm.-1 with no hydroxyl or carbonyl absorption. The ultra-violet spectrum showed absorptions at 320 mµ ( E 24,900); 306 12111 ( E 32,300); 253 mµ (E 12,700); 230 mµ (& 21,400). The N.M.R. showed signals at 7.95 r (2H), 7.19 (2H); 7.03 r (2H). -189 -

Faund C = 87.080; H = 5.77%. 017H140 requires C = 87.15%, H = 6.02%. b) 2-Phenyl-5-oxo-3,4-dihydronaphtho[4,10,5,bc] furan (250 mg.) in dry tetrahydrofuran (80 ml.) containing perchloric acid (1 ml.) was hydrogenated over a prereduced 10% Pd/C catalyst. Two molar equivalents of hydrogen were taken up in 5 hours. The catalyst was removed by filtration and water was added to the filtrate. Extraction with chloroform gave an organic phase which was washed with water, and dried over sodium sulphate. Evaporation of the solvent gave an oil which was chromatographed on an alumina (Grade III) column made up in petroleum ether (60-80°C.B.p. range). The main fraction was concentrated by evaporation of solvent to give a viscous oil which deposited a crystalline solid on addition of petroleum ether (30-40°C. B.p. range). H.p. 54-55°C. Yield 176 mg.(74% Theory). The infra-red and ultra-violet spectra were identical to those of the previous prepared 2-pheny1-31 4,5-trihydronaphtho[4,10,5,bc]furan (31).

11ydr9genolzsis in11222y1auLthanofuran series

1) Attempted formation of_g.7211enyl.7.5-p3mnotetn. PYranY4-wSX:2a98)8a/9-tetl:MalIMULLIMILia.-allEaKM -190 -

a) 2-Pheny1-3-cyano-5-tetrahydropyranyloxy-9-oxo- 2a,8,8a-trihydronaphthacen0[4, 4d,51 bc]furan (40 mg.) in ' absolute ethanol (15 ml.) was hydrogenated in the presence of a prereduced 10% Pd/C catalyst. No uptake of hydrogen occurred. After 21 hours the mixture was filtered to remove the catalyst and a solid was produced on evaporation of the solvent. The solid vas crystallised from a benzene/ether solvent mixture. N.p. 214-216°C. Yield 28 mg. Spectral data was identical to starting material. No reaction could also be effected in dry tetrahydrofuran or dry dimethylformamide. b) 2-Pheny1-3-cyano-5-tetrahydropyranyloxy-9- acetoxy-2a,8,8a,9-tetrahydronaphthaceno[4,4845,bc]furan (21 mg.) in glacial acetic acid (10 ml.) was hydrogenated over a prereduced 10% Pd/C catalyst. One molar equivalent of hydrogen was absorbed after 8 hours. After rAmoval of the catalyst by filtration, the filtrate was poured into water and extracted with chloroform. The chloroform extract was washed with water, dried over sodium sulphate and evaporated to an oil. T.Z.C. indicated at least seven compounds were present of which the one corresponding to starting material was the most intense. Chromatography on an alumina (Grade III) column

-191 -

made up in chloroform/benzene (1:1) gave fractions from which two pure compounds were isolated by removal of solvent. 1st Compound. N.p. 232-235°C. Yield 5 mg. The spectral data was identical with an authentic sample of 2,77 1.5nY122n2mg,Pet92a71q2...5_Laa.Lamtttn1=Dlz llaht, Do-furar134 (5). The mixed m.p. showed no depression. 2nd Compound. M.p.204-208°C. Yield 7 mg. The infra-red and ultra-violet spectra were identical to starting material.

2) Formation of 2-Then21-3-oxo-2ai8,8ar9-tet=Lanlz nalohthaeenPI4/4P:,591 111Mi36 i a) 2-Phenyl-3,9-dioxo-2a,8,8a-trihydronaphthaceno- [4,4a,5,bc]furan (30 mg.) in dry tetrahydrofuran (10 ml.) containing perchloric acid (0.1 ml.), was hydrogenated in the presence of a prereduced 10% Pd/C catalyst. Two molar equivalents of hydrogen were absorbed in 25 minutes. After removal of the catalyst by filtration, the solution was poured into water and extracted with chloroform. The chloroform extract was washed with water and dried over sodium sulphate. Evaporation of solvent gave an oil which contained at least six components according to -192-

T.L.C. The mixture was chromatographed on a thick layer chromatography silica plate and each component was isolated. The two main components were found to be solids on removal of solvent. First component. M.p. 125-126°C. Yield 5.1 mg. The infra-red spectrum showed no hydroxyl or carbonyl absorption. The ultra-violet spectrum showed absorptions at 321 mil, 306 294 mil, 247 mil, and 234 mil. Found C = 89.17%; H = 6.60%. C2511200 requires C = 89,25%, H = 5.99%. The spectral and analytical evidence supported 2-phen4y1-2a)3,8,8a,9-„pentahydronaphtha- 22 . (37) as the first component. Second component. M.p.189-19400. Yield 2.3 mg. The infra-red spectrum showed absorption at 1681 cm.-1. The ultra-violet spectrum showed absorptions at 322 mid,' 308 mtl, 295 m1.1, 248 mil and 236 mµ. Mass spectrum gave the molecular weight as 350. The above evidence indicated that the second component was 2-phenyl-3-oxo-2a,8,8a,9-tetrahydronaphthaceno[4,4a,5„bc] furan (36). 2-Theny1-3,9-dioxo-2a,8,8a-trihydronaphthaceno- [4,4a,5,bc]furan (15 mg.) in dry tetrahydrofuran (8 ml.) containing concentrated hydrochloric acid (0.05 ml.) was hydrogenated over a prereduced 10% Pd/C catalyst. Two - 193 - molar equivalents of hydrogen were absorbed after 7 hours. The catalyst was removed by filtration. The filtrate was poured into water and extracted with chloroform. The chloroform extract was washed with water and dried over sodium sulphate. Evaporation of the solvent gave an oil which was transferred to a thick layer chromatography silica plate. 6 bands were formed on development and each was removed and extracted with chloroform. Only one solution deposited a solid on evaporation of the solvent. H.p.190-196°C. Yield 2.3 mg. The infra-red spectrum showed an absorption at 1686 cm.-1 but no hydroxyLasorption. The ultra-violet spectrum showed absorptions at 320 mµ, 308 mil, 298 mµ, 247 mµ. This spectral data was consistent with that of authentic 2-pheny1-3-oxo-2a,8,8a,9-tetrahydronaphthacene- [4,4a,5,bc]furan (36). b) 2-Pheny1-3-oxo-9-hydroxy-2a,8,8a,9-tetrahydronaphthaceno[4,4a1 5,bc]furan (15 mg.) in dry tetrahydrofuran (10 ml.) containing perchloric acid (0.05 ml.),was hydrogenated over a prereduced 105 Pd/C catalyst. One molar equivalent of hydrogen was absorbed in 6 minutes. After removal of the catalyst by filtration, the solution was poured into water and extracted with chloroform. The organic extract was washed with water, dried over sodium -194- sulphate and the solvent removed by evaporation to give an oil. The thick layer chromatography technique separated the components of the mixture. One fraction gavea solid. M.p.188-190C. Yield 1.7 mg. The infra-red and ultra-violet spectra were identical to those of 2-pheny1-3-oxo-2a,8,8a,9-tetrahydronaphthaceno- [4,4a$5,bc]furan (36). e) 2-Pheny1-3-oxo-9-acetoxy-2a,8,8a19-tetrahydronaphthaceno[4,4a15,bc]furan (15 mg.) was ,hydrogenated as in the above experiment, one molar equivalent of hydrogen being absorbed in 25 minutes. 2-Phenyl-3-oxo-2a18,8a,9-tetrahydronaphthaceno[4,4a,5,bc] furan (36) was isolated via thick layer chromatography on silica plates. Yield 2.1 mg. The spectral data was identical to authentic material. 2-Pheny1-3-oxo-9-acetoxy-2a,8,8a,9-tetrahydronaphthaceno[4,4a,5,bc]furan (200 mg.) in glacial acetic acid (50 ml.) containing concentrated hydrochloric acid (1 ml.) was hydrogenated over a prereduced 10% Pd/C catalyst. One molar equivalent of hydrogen was absorbed after li- hours. The mixture was filtered through celite to remove the catalyst. The filtrate was cooled to 0°C by additions of solid carbon dioxide and poured into ice-cold water -195-

and extracted with chloroform. The organic extract was washed well with water, and dried over sodium sulphate. All solutions were kept at 0oC under inert atmospheres of nitrogen or carbon dioxide. Evaporation of the solvent at room temperature gave an oil, which was chromatographed on an alumina (Grade III) column with petroleum ether (60_80°0 B.p. range). The main fraction was reduced to low bulk on evaporation of the solvent at room temperature. Additions of petroleum ether (50-40°C. B.p. range) gave a crystalline solid. M.p.207-20800. Yield 70 mg. (41% Theory). The infra-red spectrum showed absorptions at 1678 cm.-1 and 1603 cm.-1. The ultra-violet spectrum showed absorptions at 320 mil (E 17,000); 306 mµ (E 27,000); 294 mµ (E 24,000); 257 mil (E 14,600); 247 11211 (C 19,700); 239 mµ (E 18,200) mµ. The N.M.R. spectrum showed signals

at 8.73 r (1H); 5.58 r (IH); 6.51 to 7.10 r (4H); 1.87 to 3.00q

Found C = 85.19%; H = 5.23%; 025111802 requires C = 85.69%; H = 5.18%. -196-

10,5,bc]furan (31) 1) 2-Pheny1-5-hydroxy-3,42 5-trihydronaphtho[4,105,bc]- furan (50 mg.) in dry diglyme (2.0 ml.) was cooled to 0°C and treated with redistilled triethylamine (0.033 mi.) and methanesulphonylchloride (0.018 ml.). The mixture was stirred at 0°C for 12 hours. Sodium borohydride (9.4 mg.) in dry diglyme (1 ml.) was added with stirring and kept at 0°C for a further 1 hour. The mixture was poured into ice-water and extracted with chloroform. The organic layer was washed well with water and dried over sodium sulphate. An oil was left after evaporation of the solvent on a rotary evaporator at room temperature. A solid was formed on contact of the oil with petroleum ether (40-60°C. B.p. range). N.p. 135-136°C. Yield 47 mg. The infra-red spectrum showed absorptions at 3650 cm.-1, 3484 am.-1, 1631 cm.-1 and 1605 am.-1. The ultra-violet spectrum showed absorptions at 322 rapt 308 mp, 294 mtl, 248 mp and 233 mil. No depression of mixed m.p. with authentic 2-phenyl- 5-hydroxy-354,59trihydronaphtho[4,10,5,bc]furan (30). The above reaction was repeated at room temperature with the:same result. - 197 -

Experiments with dry pyridine in place of triethylamine yielded no 2-pheny1-3,4,5-trihydronaphtho[4,10,5,bc]- furan (31). Similarly formation via the 2-pheny1-5-p- toluenesulphonate-3,4,5-trihydronaphtho[4,10,5,bc]furan (40b) was not successful. 2) 2-Pheny1-5-benzylthio-3,4,5-trihydronaphtho[4,10,5,bc]- furan (421 2-Pheny1-5-hydroxy-3,4,5-trihydronaphtho[4,10,5,bc]- furan (50 mg.) in dry diglyme (2.0 ml.) was treated at 0°C with redistilled triethylamine (0.033 ml.) and methane sulphonyl chloride (0.018 ml.). After the mixture had been stirred at 0°C for 1 hour, a suspension of sodium hydride (9.6 mg.; 50%) and benzyl thiol (0.023 ml.) in dry benzene (2.00 ml.) was added. The mixture was kept at 0°C for 1 hour and then poured into water (50 ml.) containing dilute hydrochloric acid (0.5 ml.). Extraction with chloroform gave an organic layer. After washing with sodium bicarbonate solution, and then water, the solution was dried over sodium sulphate. Evaporation of solvent yielded an oil. Chromatography on an alumina (Grade III) column in petroleum ether (60-80°C. B.p. range) gave a fraction which on evaporation of solvent gave a crystalline solid. M.p. 90-95°C. Yield 8 mg. - 198 -

The infra-red spectrum showed no hydroxyl or carbonyl absorption. The ultraviolet spectrum showed absorptions at 323 mp, 309 mp, 298 mp, 248 mp, 234 mp and 218 mp. 2-Pheny1-5-hydroxy-3,4,5-trihydronaphtho[4,10,5,bc]- furan (250 mg.) in dry benzene (25 ml.) containing benzylthiol (0.23 ml.) and p-toluenesulphonic acid (10 mg.) was refluxed for 3 hours. The cooled solution was poured into a sodium bicarbonate solution and extracted with chloroform. The chloroform extract was washed with water and dried over sodium sulphate. Evaporation of the solvent yielded an oil. A crystalline solid was formed on treatment of the oil with ether. M.p. 98°C. Yield 320 mg. (89%). The infra-red spectrum showed absorptions at 1626 cm.-1, 1603 cm.-1, 1004 cm.-1 and 836 cm.-1. The ultra- violet spectrum showed absorptions at 323 mp (E 25,900); 309 mp (E 32,100); 299 mp (E 26,400); 248 mp (10,800); 234 mp (15,300). The N.M.R. spectrum showed signals at "f 5.84 (1H), '"•- 6.91 (2H), 1- 7.76 (2H), 1- 6.22 (2H), 1- 2.11 to 3.02 (n=l3H).

Found C = 80.56%, H = 6.00%, S = 8.84/°. c24H2o0s requires C = 80.88%, H = 5.66%, S = 8.98%. 2-Pheny1-5-benzylthio-3,4,5-trihydronaphtho[4,10,5,bc]- furan (250 mg.) (42) was refluxed in dry benzene (50 ml.) -199- containing Raney-nickel for 5 hours. The reaction mixture was cooled and filtered through celite. Evapor- ation of the solvent gave an oil which was chromatographed on an alumina (Grade III) column in petroleum ether (60-80°C. B.p. range). Removal of solvent from the first fraction gave an oil which crystallised on contact with petroleum ether (30-40°C. B.p. range). M.p. 53-55°C. Yield 117 mg. (71%). Spectral data was identical with authentic 2-pheny1-3,415- trihydronaphtho[4,10,5,bc]furan (31).

Attem ted pzaLmIion of 2- hen 1-3-oxo-9-bent lthio- 2aL8 zIaiEatzimmithihaceno[4,4a15,bc]furan (43) 1) 2-Pheny1-3-oxm-9-hydroxy-2a,8,8a,9-tetrahydronaphthaceno[4,4a,5,bc]furan (50 mg.) was refluxed in dry benzene (20 ml.) containing benzylthiol (0.032 ml.) and p-toluenesulphonic acid (2.3 mg.) in a Dean and Stark apparatus. Two new compounds developed according to T.L.O. and when no further change occurred, the reaction was stopped (20 hours). The cooled solution was poured into sodium bicarbonate solution and extracted with chloroform. The organic extract was washed with water and dried over sodium sulphate. Evaporation of the solvent gave an oil which was placed on a thick layer chromatography silica - 200

plate. After development the main band was removed, extracted with chloroform and on subsequent removal of solvent, an oil was formed. M.p. 197-200°C. 9 mg. The infra-red spectrum showed absorptions at 1656 cm.-1 and 1631 cm.-1. The ultra-violet spectrum showed absorptions at 412 mµ, 317 mµ, 307 m11, 280 mµ and 230 mµ. This compound was subsequently shown to be 272haaar2=oxo- 2a,8:slahalronah- c-furan44a. 2) 2-Phenyl-3-oxo-9-acetoxy-2a,8,8a,9-tetrahydronaphtha, ceno[4,4a,5,bc]furan (100 mg.) in dry benzene (50 ml.) containing benzylthiol (0.143 ml.) and p-toluenesulphonic acid (0.4 mg.) was stirred at room temperature for 18 hours. As only a slow reaction was taking place the mixture was refluxed for a further 15 hours. The mixture was cooled, pouredikbpsodium bicarbonate solution and extracted with chloroform. The organic extract was washed with water and dried over sodium sulphate. The solvent was removed by evaporation to give an orange coloured oil. Chromatography on an alumina (Grade III) column in benzene gave a fraction which deposited a yellow solid on evaporation of the solvent. h.p. 198-201°C. Yield 35 mg. The spectral data was identical to that of the previous experiment. - 201-

2-Phenyl-3-oxo-9-acetoxy-2348,8a19-tetrahydronaphthaceno[4,4a,5,bc]furan (10 mg.) in benzyl thiol (10 ml.) containing p-toluenesulphonic acid (1 crystal) was refluxed under an inert atmosphere of nitrogen for 16 hours. The cooled mixture was poured into sodium bicarbonate solution and extracted with chloroform. The organic extract was washed well with sodium bicarbonate, water, and dried over sodium sulphate. The solvent was removed by evaporation, the last traces of thiol removed on an oil pump. The oil that remained was chromatographed on an alumina (Grade III) column in benzene and the two main fractions collected. (i)Yield 2.5 mg. The infra-red spectrum showed absorptions at 1664 am.-1 and 1634 cm.-1. The ultra-violet spectrum showed absorptions at 412 mg, 276 mg and 262 mg. Spectral data was similar to 2-phenyl-3-oxo-2a,8-dihydronaphthacen0[4,4a,5,bc]- furan (44). (ii)Yield 3.1 mg. The infra-red spectrum showed absorptions at 3440 am.-1 and 1664 cm.-1. The ultra-violet spectrum showed absorptions at 283 mg, 263 mg and 227 mg. Compound (ii) wab-subsequently shown to be ....2-her_p___1,a_-ah.ydro'--1 ...... ,a1...._nonohdro- naPh-la22E2LidalakaLWIla-LA1121. - 202-

2-1)11e4Y173.702-LIaL2=2112=m9111LILAILILIIIfuran (44A.Pad 2.--.10hara-3-4YdroxY-9-monohydronaphthaceno- L414q/5001puran (47b) 2-Pheny1-3-oxo-9-acetoxy-2a,8,8a,9-tetrahydronaphthaceno[4,4a,5,bc]furan (250 mg.) in dry benzene (150 ml.) containing p-toluenesulphonic acid (a few crystals) was refluxed under an aLmosphere of nitrogen for 16 hours. The cold reaction mixture was poured into sodium bicarbonate solution and extracted with chloroform. The chloroform extract was washed with water, and dried over sodium sulphate. Evaporation of the solvent gave an oil which was chromatographed on an alumina (Grade III) column in benzene. Two main fractions were collected which yielded solids on evaporation of the solvent. (i) M.p. 201°C. Yield 158 mg. (73%). The infra-red spectrum showed absorption at 1660 cm.-1, -1 1635 am. , 1608 am.-1, and 1585 cm. -1. The ultra-violet spectrum showed absorptions at 412 mg (4 5,000), 318 mµ (E 5,900), 306 mg (E 7,000), 281 mµ (e 31,000), and 231 mµ (E 34,000). The N.M.R. spectrum showed signals at r 5.56, T 3.29, r 1.91. Molecular formula by mass spectrum

was 025H1602° - 203 -

M.p. 202-204°C. Yield 46 mg. (21%). The infra-red spectrum showed absorptions at 3550 am.-1, -1 -1 1660 cm.-1, 1608 cm. and 1577 cm. . The ultra-violet spectrum showed absorptions at 306 mu, 287 mu, 256 mu, 226 mµ. The N.M.R. spectrum in pyridine showed a signal at ir 5.32.

Reactions with 2- hen l-3-oxo-2a 8-dih drona hthaceno-

LuAaa19:Suran-LILI 1) Calcium in li ammonia To a well stirred mixture of toluene (50 ml.) and liquid ammonia (50 ml.) at -70°C was added excess calcium metal and then 2-pheny1-3-oxo-2a,8-dihydronaphthaceno- [4,4845,bc]furan (45 mg.) in toluene (20 ml.). After 30 minutes,ammonium chloride was added and the solution allowed to rise to room temperature. The mixture was poured into water and the organic layer separated. The organic,: extract was washed with water and dried over sodium sulphate. Evaporation of solvent gave an oil which was chromatographed on an alumina (Grade III) column in chloroform. After removal of solvent from the main fraction an oil was obtained, which could not be crystallised. Yield 12.8 mg. T.L.C. showed oil to be a mixture of two products. 204 rz

The infra-red spectrum showed absorptions at 3650 cm.-1, 1595 cm.-1 and 1471 cm.-1. The ultra-violet spectrum showed absorptions at 282 mp, 275 mp, 268 mµ, 262,mp and 227 mP. 2) E1222A22q1ation reaction 2-Pheny1-3-oxo-2a18-dihydronaphthaceno[4,4a,51 bc]- furan (90 mg.) was heated under reflux with acetic anhydride (9 ml.) containing sodium acetate (520 mg.) for 2 hours. Cooled mixture was poured into water and extracted with chloroform. the chloroform extract was washed with water and dried over sodium sulphate. Evaporation of the solvent gave an oil, which was chromatographed on an alumina (Grade III) column in benzene. The main fraction yielded a solid on removal of the solvent. M.p.221-223°C. Yield 72 mg. (71%). The infra-red spectrum in chloroform showed absorptions at 1764 cm.-1 and 1642 cm.-1. The ultra-violet spectrum showed absorptions at 510 mp (E 470), 477 mp (E 540), 450 mµ (E 300), 403 mp (E 290), 324 mµ ( € 600), 288 mp (E 109,200), 279 (e 74,600), 270 mp (E 451800), 221 mp (. 33,200). Found C = 82.58%; H = 5.02%. C27H1803 requires C = 83.06%; H = 4.65%. Mass spectrum gave molecular weight as 390, and molecular formula 027H1803. - 205-

3) EYPIT2.Eqllation 2-Pheny1-3-oxo-2a18-dihydronaphthaceno[4,4a,5,bc]- furan (20 mg.) in dry benzene (10 ml.) was hydrogenated over a prereduced platinum oxide catalyst. No uptake of hydrogen occurred. After 24 hours the catalyst was filtered off. Evaporation of solvent yielded an oil which gave a solid on treatment with petroleum ether (30-40°C. B.p. range). Yield 16 mg. Spectral data identical with starting material. No reaction also took place with a 10% Pd/C catalyst in benzene. 2-Phenyl-3-oxo-2a,8-dihydronaldhthaceno[4,4a15,bc]- furan (20 mg.) was hydrogenated in glacial acetic acid (10 ml.) over a prereduced Pt02 catalyst. One equivalent of hydrogen was absorbed after 15 minutes. The catalyst was filtered off and washed with benzene. The filtrate was placed on a rotary evaporator under high vacuum, until no acetic acid remained. T.L.C. indicated much starting material and other faster running compounds but no 2-pheny1-3-oxo-2a0,8a,9-tetrahydronaphthaceno[4,4a,5,bc]- furan (36). Chromatography on an alumina (Grade III) column yielded 2-pheny1-3-oxo-2a,8-dihydronaphthaceno[4,4a,5,bc]- furan (44). - 206 -

Yield 8 mg. Spectral data identical with starting material. Hydrogenation in ethyl acetate with a Pt02 catalyst also gave no 2-pheny1-3-oxo-2248,8a,9-tetrahydronaphthaceno[4,4a,5,bc]furan (36).

A221722ion...21212C1=1:21ulzAkaz=llaalama: E.4.244.2 50bolaallL02/ 2-Pheny1-3-hydroxy-9-monohydronaphthaceno[4,4a,5,bc]- furan (40 mg.) in acetic anhydride (8 ml.) and pyridine (10 ml.) was left for 17 hours at room temperature. The mixture was poured into water and extracted with chloroform. The chloroform extract was washed with water and dried over sodium sulphate. Evaporation of solvent gave a solid. M.p. 219-200°C. Yield 37 mg. (Theory 82%). The infra-red spectrum showed absorptions at 1761 cm.-1, 1605 cm.-1 and 1567 cm.-1 . The ultra-violet spectrum showed absorptions at 322 mg (€ 14,000); 285 mg ( E 25,000); 275 mg ( E 26,000); 248 mg ( E 28,000), and 223 mg ( E 42,000). N.M.R. spectrum showed signals at 1- 8.79 (3H); 5.40 (2H). Found C = 83.22%; H = 4.92%. C27111803 requires 0 = 83.06%; H = 4.65%. - 207 -

STUDIES IN TiE ISOLDIN SERIES

Preparation of 2-phenyl7.3_18a-(N-phenyl-isoxazolidine)- 9-ox0-2apteronaplithaceno[404ai5,bc]furan L261_ 1) 2-Pheny1-4-(21-formylbenzy1)-5-oxo-naphtho[4,1015,bc]- furan (6.25 g.) was suspended in absolute ethanol (500 ml.) and treated with phenyl hydroxylamine (3.0 g.) which had been freshly prepared. The mixture was stirred at room temperature under an atmosphere of nitrogen. Purther quantities of phenyl hydroxylamine were added after each period of 24 hours. The pale yellow solid that had formed after 5 days was filtered off and dried. M.p. 178-179°C. Yield 6.82 g. (87% TheorY). The infra-red spectrum in dhloroform showed absorption at 1680 cm.-1. The ultra-violet spectrum showed absorptions at 365 mµ, 299 141, 276 mµ and 243 mµ. The N.M.R. spectrum showed signals at i 6.69, 6.17 (AB system,

JAB 18-19 c.p.s.); rr. 5.56 (1H), 1- 4.65 (1H), T 3.33 to 3.85 (5H).

2) 2-Phenyl-4-(2'-formylbenzy1)-5-oxo-naphtho[4 10,5,bc] furan (1.5 g.) was refluxed with freshly prepared phenyl hydroxylamine (600 mg.) in absolute ethanol (150 ml.) - 208- for 30 hours. A solid was deposited on cooling which was filtered and dried. i)M.p. 178-180°0. Yield 998 mg. (53% Theory). Spectral data identical with authentic 2-pheny1-3,8a-(N- phenyl-isoxazolidine)-9-oxo-2a,3,8,8a-tetrahydronaphtha- cono[4,4a,5,bc]furan (26), isoldin A. The filtrate on concentration gave another solid on cooling. ii)Yield 597 mg. The second crop vas chromatographed on an alumina (Grade III) column in benzene. The first fraction was collected and rotary evaporated at room temperature to give a pale- yellow solid. M.p. 183-184°C. Yield 207 mg. (11% Theory). The infra-red spectrum in chloroform showed absorption -1 at 1680 cm. . The ultra-violet spectrum showed absorptions at 361 mil, 296 mµ, 276 mµ and 235 mµ. The N.M.R. spectrum showed signals at -I- 6.79, 6.57 (AB system, JAB 16 c.p.s.); r 4.48 (1H); -r 3.86 (1H). This compound was later shown to be isoldin B (49). The second fraction contained isoldin A. Yield 132 mg. (7%). Total yield of isoldin A from this reaction was 60%. The filtrate of the second crop deposited an orange-red solid on standing. M.p. 36°C. Yield 153 mg. — 209 —

Mixed m.p. with authentic sample of azoxybenzene showed no depression. The infra-red spectrum showed no carbonyl or hydroxyl absorption. The ultra-violet spectrum showed absorptions at 325 mµ, 263 rap, 239 mil, 233 nall, 227 mµ. The N.M.R. spectrum showed signals at 7- 2.46 to 2.80 (6H) and 1.62 to 1.96 (4H).

Treatment of isoldin A with styrenen...... 1••••••••••••••••••••ha.... monomer

Isoldin A (200 mg.) was refluxed in absolute ethanol (50 ml.) containing monomeric styrene (91 mg.; 2 molar equivalents) under an inert atmosphere of nitrogen. The reaction was followed by T.L.C. and ultra-violet spectra but no reaction occurred after labours. Starting material, contaminated with isoldin B was recovered (115 mg.).

An attempted exchange reaction between isoldin A and ethanol--D

al Pre aration of calcam ethoxide(46) Calcium hydride (13.6 g.) was finely powdered and carefully added to absolute ethanol (50 ml.) containing iodine (one crystal) and mercuric chloride (10 mg.). When the vigorous reaction had subsided, the mixture was refluxed for 19 hours. The excess ethanol was removed - 210 - and the solid formed was heated at 150°C under high vacuum for 37. hour. b) Preparation of ethanol-D Deuterium oxide (6.5 ml.) was added to the cold, dry calcium ethoxide and heated to 8000. Ethanol-D was distilled over slowly. Yield 26 g. The infra-red spectrum showed absorption at 2700 cm.-1 and 2550 cm.-1. The N.M.R. spectrum showed no signal due to the proton on oxygen in ethanol. c) The attempted exchange reaction Isoldin A (100 mg.) was refluxed for 15 hours in ethanol-D (9 ml.) under an atmosphere of nitrogen. A pale-yellow solid was deposited on cooling. Yield 75 mg. T.L.C. indicated that only isoldin A and B were present in approximate ratio 2:1. The N.M.R. spectrum contained all the signals that corresponded to isoldin A and isoldin B.

Preparation of 2- hen 1-4-- 2I-N- •hen lcarboxamidobenzy1)- 5-oxo-naphthp,LAAlaahalfUran (54)

Isoldin A (500 mg.) in acetic anhydride (5 ml.) and pyridine (10 ml.) was heated on a stegm bath for 16 - 211- hoursS 4) The cooled solution was poured into water containing dilute hydrochloric acid and extracted with ether. The organic phase was washed with water, dilute hydrochloric acid and water again. T.L.C. showed three compounds were present, isoldin A, isoldin B and a new component. After drying the organic extract and evaporation of the solvent, the oil formed was chromatographed on an alumina (Grade III) column in benzene. Three main fractions were collected. i) Yield 103 mg. Spectra data identical to Isoldin B. ii) Yield 162 mg. Spectral data identical to Isoldin A. iii) Yield 232 mg. (460 TheorY). M.p. 249-250°C. The infra-red spectrum showed absorptions at 3280 cm.-1, 1650 cm.-1, 1620 an.-1, 1605 -1 cm. - and 1590 am.-1. The ultra-violet spectrum showed absorptions at 406 mµ and 265 12111. The N.M.R. spectrum showed signals at r 5.87 (2H); and 1' -0.51 (1H). The mass spectrum gave 455 as the molecular weight. - 212 -

Reduction of isoldin A

1) EilnaemaaIL11 Formation of 2-phenyl-8a99-dihvdroxy-2a13,8,8a2z 22EITILd2.2allillhacepoi4,4a,5,bc]funom (57) Isoldin A (500 mg.) in absolute ethanol (250 ml.) was hydrogenated over a prereduced 5A Pd/C catalyst. Three molar equivalents of hydrogen were absorbed in ai hours. The catalyst was removed by filtration through celite and the filtrate rotary evaporated to an oil. Chromatography on an alumina (Grade III) column in chloroform gave a fraction which T.L.C. indicated was the new main product. The solvent was removed on a rotary evaporator to give an oil which deposited crystals on contact with petroleum ether. (30-40°C. B.p. range). M.p. 189-190°C. Yield 187 mg. (46;; Theory). The infra-red spectrum showed absorption at 3500 cm.-1. No carbonyl absorption was present. The ultra-violet spectrum showed absorptions at 301 mil (& 17,000); 275 ml_t (E 10,600); 234 mµ (E 121300). The N.M.R. spectrum showed signals at 7.72 (2H); i 6.22 to 7.29 (3H); "r 6.69 (2H); 1- 5.12 (IH). Found C = 81.51%; H = 5.62. No nitrogen.

025H2003 requires C = 81.56%; H = 5.47%. - 213 -

2-Phenyl-8a-11-99t22/7111L38410=122111t14=2:" naphthaceno[4,05,bejfUran (58) 2-Pheny1-8a,9-dihydroxy-2a,3,818a,9-pentahydronaphtha- eeno[4,4045,bc3furan (110 mg.) was dissolved in acetic anhydride (2 ml.) and pyridine (3 ml.) and left for 18 hours at room temperature. The solution was poured into water and extracted with chloroform. The organic extract was washed with dilute hydrochloric acid, water, sodium bicarbonate solution and water again and dried over sodium sulphate. Evaporation of the solvent gave a solid. M.p. 193-194°C. Yield 93 mg. (76% Theory). The infra-red spectrum showed absorptions at 3610 cm.-1 and 1742 em.-1. The ultra-violet spectrum showed absorptions at 298 mµ (€ 21,100); 273 mil (E. 13,400); 232 mµ (E 15,500); 210 mµ (E 29,000). The N.M.R. spectrum showed signals at 7.90 (1H); 1- 7.61 (3H); 1- 6.10 to 7.10 (3H); -I- 6.90 (2H); -r 3.61 (1H). Found C = 79.00%; H =5.40%. C27H2204 requires C = 79.43%; H = 5.67%.

2) Chropous Chloride

2-Pheny1-3-N-phenylamino-8a-hydroxy-9-oxo-2a 3,8 8a- t etrahydronaphthac enoL4_, 4a,r 52 be ]±:uran ( 55) Isoldin A (341 mg.) in glacial acetic acid (25 ml.) containing concentrated hydrochloric acid (0.5 ml.) was -214—

treated at room temperature with 1M. chromous chloride solution (20 cc.) under an atmosphere of nitrogen. After one minute vigorous stirring, the solution was poured into water and extracted with chloroform. The organic extract was washed well with water and dried over sodium sulphate. Evaporation of solvent gave a crystalline solid which was dried at 80°C. for 3 days, as the chloroform solvate had been formed. M.p. 229-230°C. Yield 301 mg. (88% Theory). The infra-red spectrum showed absorptions at 3590 cm.-17 -1 -1 -1 3 450 om. y 3110 cm. and 1690 cm. . The ultra-violet spectrum showed absorptions at 346 mµ, 290 mµ and 250 mµ. The N.M.R. spectrum showed signals at r 6.48, 6.64 (AB system, JAB 19 c.p.s.); 1- 6.02 (2H); 5.90, 4.45 (AB system, JAB 5 c.p.s.); 3.20 to 4.22 (5H).

Treatment of isoldin A with stron acid

Isoldin A (50 mg.) was dissolved in acetic acid ( 5 ml.) and hydrochloric acid (5 ml.) and the solution was stirred at room temperature for 16 hours under an atmosphere of nitrogen. The red solution was poured into water and extracted with chloroform. The chloroform extract was washed with sodium bicarbonate solution, water and dried over sodium uulphate. Evaporation of the solvent gave an - 215 - oil which was chromatographed on an alumina (Grade III) column in benzene. The main fraction on removal of the solvent gave a solid. M.p. 141-142°C. Yield 18 mg. The spectral data was identical to authentic 2-pheny1-4- (2t-formylbenzy1)-5-oxo-naphtho[4,10,5,bc]furan (14). Mixed m.p. with an authentic sample gave no depression.

Reduction of 2 -phenyl-3 -N -phenylamino -8a -hydroxy-9 - etrahydron.aphthac eno [ 4,4a 5, be ]furan ( 55 )

1) 2-Pheny1-3-N-pheny1amino-8a-hydroxy-9-oxo-2a,3,8,8a- tetrahydronaphthaceno[4,4a,5,bc]furan (100 mg.) in glacial acetic acid (30 ml.) and concentrated hydrochloric acid (0.2 ml.) was stirred at room temperature under an atmosphere of nitrogen. Zinc dust (500 mg.) was added and the mixture stirred for one minute. The mixture was filtered quickly through celite into water and extracted with chloroform. The chloroform extract was washed well with water, dried over sodium sulphate and rotary evaporated at room temperature to a foam. Trituration with ethanol gave a pale yellow solid. M.p. 192-194 C. Yield 65 mg. (67% Theory). The infra-red spectrum in chloroform showed absorptions -1 -1 at 3410 am. , 1684 cm. and 1601 cm.`-1 l. The ultra- - 216 -

violet spectrum showed absorptions at.348 mg, 288 mil, 265 mµ and 254 mg. The Y.M.R. spectrum showed signals at T 6.27 to 7.09 (3H); 6.80 (1H); 5.97 (1H); -e 4.59 (1H); r 3.19 to 4.34 (5H). Found C = 81.73%; H = 5.08%; N = 3.40%. C31H2302N requires C = 84.33%; H = 5.25%; N = 3.17%. This compound subsequently was shown to be 2-pheny1-3-N-phenylamino-9-oxo-8a-aL-2a,3,8 8a-tetrahydro- ma.1,...1.11MMLOSE.M.O111011• n...2.1hthao eno C 4 4a1 Aciguran

2-Pheny1-3-N-phenylamino-9-oxo-2a 3,8 8a-tetrahydr - PARAha99122-ALAP5112911121 The above experiment was repeated but the crude oil obtained by removal of solvent was chromatographed on an alumina (Grade III) column in benzene. Evaporation of solvent from the main fraction gave a yellow crystalline solid, which was dried at 50°C for 24 hours. M.p. 224-227°C. Yield 83 mg. (86% Theory). The infra-red spectrum in chloroform showed absorptions -1 at 3440 cm.-1 , 3100 an. and 1685 cm.-1. The ultraviolet spectrum showed absorptions at 348 mg (E 7,700); 295 31111 (E 12,800); .254 mg (E 17,200). The N.M.R. spectrum showed signals at l- 7.13 (1.11); --r- 6.51, 6.60 (AB system, JAB 7.5 c.p.s.); 5.57 to 5.96 (1H); 4.95 (1H); 1- 3.29 to 4.19 (5H). Found C = 84.33%; H = 5.38%; N = 3.27%. 031x2302 Nrequires C = 84.33%; H = 5.25%; N = 3.17%. - 217 -

Deuteration of 2-phany1-3-N-phenylamino-9-oxo- 2a,3,8,8a- 2121/2222IIII/aanaL4 Ean (592 2-Phany1-3-N-phenylamino-9-oxo-2a,3,8,8a-tetrahydro- naphthaeeno[4,4a,5,bc]furan (266 mg.) in dry tetrahydrofuran (40 ml.) was treated with a solution of thionyl chloride (1 ml.) indeuterium oxide (6 ml.). The mixture was refluxed under an atmosphere of nitrogen for 2.i hours. The cold solution was carefully treated with solid sodium carbonate. After filtration, the solvent was removed under high vacuum to give an oil. Treatment with dry chloroform and petroleum ether (30-40°C. B.p. range) gave a solid which was dried at 80°C for 16 hours. 11.p. 230-232°C. The infra-red spectrum in chloroform showed absorptions at 3450 cm.-1, 3100 cm.-1, 2940 cm.-1 and 1684 an.-1. The ultra-violet spectrum showed absorptions at 347 mµ, 295 mµ and 253 mil. The N.M.R. spectrum showed absorptions at 7 7.12 (1H); r 5.79, 6.87 (AB system, JAB 19 c.p.s.); r 5.60 (1H)i. 1- 4.91 (1H); 1. 3.33 (2H). The mass spectrum showed molecular weight to be 445 compared with the undeuterated derivative 441. The deuterated derivative showed fragments of 247 and 195, whereas the undeuterated compound had fragments of 248 and 198 in the mass spectrum. - 218 -

2) 2-Phenyl-3-N-phenylamino-8a-hydroxy-9-oxo-2a,398,8a- tetrahydronaphthaceno[4,4a05,bc]furan (518 mg.) in dimethylformamide (50 ml.) and glacial acetic acid (50 ml.) was stirred at room temperature for 18 hours. The mixture was filtered through celite and poured into water and extracted with chloroform. The organic extract was washed with sodium bicarbonate solution and water and dried over sodium sulphate. Evaporation of the solvent gave an oil which was chromatographed on an alumina (Grade III) column in benzene. The fraction containing the main product was rotary evaporated to an oil which gave a solid on treatment with chloroform and petroleum ether (40-60°C. B.p. range). M.p. 208°-209°C. Yield 147 mg. (28% Theory). The infra-red spectrum showed absorptions at 3550 cm.-1 and 3395 cm.-1. The ultra-violet spectrum showed absorptions at 322 mµ 15,700); 308 mµ (E 23,800); 299 mµ (€ 23,600); 249 mil (E. 21,900); 241 mµ (E 21,400) and 234 mµ (E 20,900). The N.M.R. spectrum showed signals at 7.39 to 7.81 (1H); 1- 7.44 (2H); 6.38 to 7.22 (2H); r 5.79 to 6.09,(1H); 4.80 to 5.12 (2H); 3.18 to 4.18 (511. -219-

This compound was assumed to be 2-pheny1-3-N-phenylamino-9-ell-hydroxy-2a,3,8,8a19-pentahydronaphthaceno[4,- 4a15,bc]furan (64).

Treatment of 2-phenyl-3-1\1-phenylami lam: L43,...02ffi nah,...LL...._tiLiaoeno44a5,bc]furan:i (64) with manganese dioxide 2-Pheny1-3-N-phenylamino-9-92i-hydroxy-2a,3,8 8a,9- pentahydronaphthaceno[4,4a,5,bc]furan (20 mg.) was dissolved in benzene (20 ml.) and treated with manganese dioxide (280 mg.) at room temperature. The' reaction was followed by T.L.C. and after one minute two compounds were present in the ratio of 1:1. These compounds were starting material and 2-pheny1-3-N- phenylaming-9-oxo-2a5,8,4-tetrallydronq01M2a1914,4a/5tbc1 111_4m/ 121i. A complex reaction then took place but amongst the many new products that were formed, there was no trace of 2-pheny1-3-N-phenylamino-9-oxo-8a-zpi-2a,5,8,8a- tetrahydronaphthaceno[4,4a,5,bc]furan (60). After 15 minutes the solution was filtered. Evaporation of the solvent gave an oil. 22 mg. The infra-red spectrum in chloroform showed absorp- -1 -1 tions at 3440 cm.-1, 1685 cm.-1, 1660 cm. y 1640 , 1615 cm. -1 and 1602 am.-1.

-220 -

The ultra-violet spectrum showed absorptions at 339 mil, 307 mil, 296 mil, 265 mµ and 251 mil.

Reduction of 2-phenyl-3-N-phanylamino-9-oxo-2a 3,8 8a- teVallYdronUhtha222224112421122:1aaai221 1) 2-Pheny1-3-N-phanylamino-9-oxo-2a,3,8,8a-tetrahydronaphthaceno[4,4a,5,bc]furan (22 mg.) in ethanol (30 ml.) was treated with sodium borohydride (1.9 mg.). The mixture was stirred at room temperature under an atmosphere of nitrogen and T.L.C. indicated a slow reaction took place. After 24 hours the mixture was poured into water and extracted with ether. The organic phase was washed with water and dried over sodium sulphate. Evaporation of the solvent yielded an oil which was chromatographed on an alumina (Grade III) column in benzene. Two main fractions were collected which on evaporation of solvent gave two solid compounds i) 6 mg. Spectral data identical with starting material. ii) 10 mg. The infra-red spectrum in chloroform showed absorptions at 3590 am.-1 and 3430 cm.-1. The ultra-violet spectrum showed absorptions at 402 mµ, 298 mil, 260 mµ and 235 3114,. - 221 -

Manganese dioxide oxidation of the sodium borohydride zadupt. The sodium borohydride product (8 mg.) derived from the previous experiment, was dissolved in benzene (20 ml.) and treated with manganese dioxide (100 mg.). The mixture was stirred at room temperature and the reaction followed by T.L.C. Formation of 2-pheny1-3-N-phenylamino-9-oxo- 8a-e i-2a,3,8,8a-tetrahydronaphthaceno[4,4a,5,bc]furan (60) was observed. A further slow reaction then took place, but no formation of the 2-pheny1-3-N-phenylamino-9-oxo- 2a,3,8,8a-tetrahydronaphthaceno[4,4a,5,bc]furan (59) resulted. nis reaction indicated that the sodium borohydride product contained the cis-trans fusion of rings B and C, and may have the 9a or 913 structure (62).

2) 2-Pheny1-3-N-phenylamino-9-oxo-2a,3,8,8a-tetrahydronaphthaceno[4,4a9 5,bc]furan (104 mg.) was added in dry ether (40 ml.) to a suspension of lithium aluminium hydride (100 mg.) in dry ether (20 ml.). The mixture was stirred at rocm temperature and shown to be finished in 10 minutes. Ethyl acetate was added dropwise to the reaction mixture until no further reaction occurred. The solution was poured into water and extracted with ether. The organic - 222 -

extract was washed with water and dried outer sodium sulphate. Diaporation of the solvent produced a colourless oil which gave a crystalline solid on contact with petroleum ether (30-40°C. B.p. range). M.p. 207-208°C. Yield 96 mg. (92% Theory). Mixed m.p. with the alcohol (64) showed a 30°C depression. The infra-red spectrum showed absorptions at 3590 cm.-1, 3430 em.-1 and 3380 cm.-1. No carbonyl absorption. The ultra-violet spectrum showed absorptions at 306 mg ( E 31,000); 300 Mµ (E 30,600); 250 mµ (€ 26,600); 244 mg (E 26,100) and 235 mg (E 26,200). The N.M.R. spectrum showed signals at r 7.02 to 7.38 (1H); 1- 6.38 to 6.78 (2H); T 5.87 (2H); r 5.84 (1H); T. 4.87 (1H); q- 3.12 to 4.12 (5H). Found C = 83.78%; H = 5.68%; N = 3.36%. C31H2502N requires C = 83.94%; H = 5.68%; N = 3.16%. The above data was consistent with that expected of 2-phenyl-3-N-phenylamino-9-hydroxy-2a 3,8 8a,9-pentahydr naphthaceno[4,4a,5,be]furan (63).

The T.L.C. Rf values for the alcohols (62), (63) and (64) on silica plates, developed in a mixture of acetone (1 part) and petroleum ether (60-80°C. B.p.range) (4 parts), were as follows: -223-

Alcohol (62) Rf = 0.27 Alcohol (63) Rf = 0.47 Alcohol (64) Rf = 0.32. Treatment of 2-phenyl-3-N-phenylamino-9-hydro4y- 2a,3 82.8a972eEandronaht fu.an63 with man anese dioxide The alcohol (10 mg.) was dissolved in benzene (15 ml.) and stirred at room temperature with manganese dioxide (50 mg.). The reaction was shown by T.L.C. to be rather slow. Formation of 2-pheny1-3-N-phenylamino-9-oxo- 2a388a-tetra hacenoa5bo furan resulted with no trace of its C-8a epimer (60). The reaction was complete in 1 hour.

2-Phenyl-3-N-phenylamino-9-acetoxy-2a 3,8 8a, 9- 2,2ntahydronaphtha9.912144AalalsIllgan101 The alcohol (63) (511 m.g.) was dissolved in pyridine (6 ml.) and acetic anhydride (4 ml.) and heated on a steam bath for 2 hours. The solution was poured into water and extracted with chlorofoxm. The chloroform extract was washed with dilute hydrochloric acid and water, and dried over sodium eulphate. Evaporation of the solvent gave a solid which was crystallisfad from a mixture of ether and petroleum ether (30-40°C. B.p. range). - 224 -

M.p. 176-177°C. Yield 475 mg. (85% Theory). The infra-red spectrum showed absorptions at 3490 cm.-1 and 1742 cm.-1. The ultra-violet spectrum showed absorptions at 324 mg, (E 13,800); 309 mµ (E 21,200); 294 mg (E 18,300)6 281 /41 (E 15,400); 251 mg (E 19,600; 235 mg (E 17,000). The N.M.R. spectrum showed signals at 1- 8.65 (3H); i 7.02 to 7.31 (1H); 6.78 (2H); r 5.82 (1H); 5.61 (1H); 1- 4.72 (1H); -r 3.25 to 4.30 (5H); 3.50 (1H). Found C = 81.62%; H = 5.76%; N = 2.87%. C33H2703N requires C = 81.62%; H = 5.61%; N = 2.88%.

Oxidation of the 3-X-Phenylmino function

1) 2-Pheny1-3-N-phenylamino-9-oxo-2a,3,8,8a-tetrahydronaphthaceno[4,4a,5,bc]furan (10 mg.) in benzene was stirred with manganese dioxide (50 mg.). The reaction was followdby T.L.C. The main product that was soon formed had a greater Rf value than starting material. After 15 minutes the mixture was filtered and the solvent evaporated to give an oil. The infra-red spectrum in chloroform showed absorptions at 1688 cm.-1 1650 cm.-1, 1620 am.-1 1601 cm.-1 and 1585 cm.-1. The ultra-violet spectrum showed absorption at 401' ng, 338 mg, 306 mg, 253 mg and 228 mg. The spectral - 225 -

data and T.L.C. behaviour was consistent with the presence of 2-pheu1-9-oxo-naphthaceno[4,4a,22bo1f'uran (19).

2) 2-Pheny1-3-N-pheaylamino-9-acetoxy-2a13,8,8a,9- pentahydronaphthaceno[4,4a,5,bc]furan (12 mg.) was dissolved in benzene (20 ml.) and treated with manganese dioxide (100 mg.). The stirred solution, under an atmosphere of nitrogen, was examined periodically by T.L.O. No reaction was observed even after 60 hours. The mixture was filtered and the solvent evaporated to give an oil (12 mg.). The spectral data was identicaly to starting material.

3) 2-Pheny1-3-N-phenylamino-9-acetoxy-2a,3,8,8a,9-pentahydronaphthaceno[4,4a,5,bc]furan (27 mg.) was dissolved in dry ether (50 ml.) and treated with t-butyl hypochlorite (1.3 equiv.) at 00C. The mixture was stirred in an atmosphere of nitrogen and the reaction observed by T.L.C. A very slow reaction occurred to give three new compounds. After 18 hours the mixture was poured into water and extracted with chloroform. The organic extract was washed with water and dried over sodium sulphate. Evaporation of the solvent gave a mixture of three un stable compounds, as an oil. Chromatography on an alumina (Grade III) column in benzene/petroleum ether (60-8000. B.p. range) - 226 -

(1:1) gave a fraction which deposited a semi-solid on evaporation of the solvent. Yield 1.2 mg. The infra-red spectrum in chloroform showed absorptions at 3400 cm.-1 and 1733 cm.-1. The ultra-violet spectrum showed absorptions at 325 mil; 310 mil; 273 mµ; 262 mµ; 252 mµ. T.L.C. indicated that this compound was not starting material.

4) 2-Pheny1-3-N-phenylamino-9-acetoxy-2a,30,8a1 9- pentahydronaphthaceno[4,4a1 5,bc]furan (65) was treated with the following reagents: a)Mercuric acetate in glacial acetic acid at room temperature and at 950C. Slight decomposition occurred only with excess reagent. Starting material recovered in 90% yield after 65 hours. b)Peracetic acid in glacial acetic acid containing sodium acetate at room temperature. Traces of other compounds formed with excess reagent after 60 hours and starting material was recovered in high yield. c)m-Chloroperbenzoic acid in benzene at room temperature or toluene at -20°C. Inseparable mixture formed with 1.1 equivalents of reagent. Incorporation of acetic anhydride had very little effect on the course of the reaction. - 227 -

d)Chromium trioxide in glacial acetic acid. Traces of decomposition of starting material after 18 hours with one and ten equivalents of reagent. Starting material recovered in 90% yield. e)Methanesulphonylchloride in pyridine. No reaction with excess reagent after 24 hours at room temperature or at 60°C. Attempted formation of the mesylate via the sodium salt of the amine (65) was likewise not successful. (23) f)Argentic picolinate (prepared as described from picolinic acid, silver nitrate aid potassium per- sulphate). No reaction took place at room temperature or at 50°0 with excess reagent. Starting material was recovered. g)Fremy's salt. No reaction in a one phase system aqueous ethanol, with excess reagent at room temperature. Starting material also recovered in quantitative yield from the two phase systems chloroform/water and ethylacetate/water. h)Oxygen in the presence of 2t02 catalyst. No uptake of oxygen occurred after 18 hours and starting material was isolated quantitatively.

5) 2-Pheny1-3-N-phenylamino-9-acetoxy-2a,318,8a,9- pentahydronaphthaceno[4,4a1 5,bc]furan (25 mg.) was dissolved - 228- in dry benzene (10 ml.) and treated with 2,3-dichloro- 5,6-dicyanoquinone (12 mg.). The mixture was refluxed for 15 hours and poured into water and extracted with chloroform. The chloroform extract was washed with water and dried over sodium sulphate. Evaporation of solvent gave an oil which was chromatographed on an alumina (Grade III) column in benzene. Two fractions containing the two main products were collected. Evapor- ation of solvent gave the two products as oils. i) Yield 8 mg. The infra-red spectrum in chloroform showed absorp- -1 tions at 1733 cm.-1 1665 cm.-1, 1620 cm.-1 and 1600 cm. . The ultra-violet spectrum showed absorptions at 446 mµ, 422 mµ, 361 mµ, 298 mµ and 257 mµ. A solid was isolated on treatment of the oil with petroleum ether (30-40°C. B.p. range). M.p. 298-301°C. Yield 1.5 mg. The infra-red spectrum showed absorptions at 1663 cm.-1, 1620 cm.-1 1600 an.-1 and 1293 cm.-1. The ultra- violet spectrum showed absorptions at 425 mil, 389 m149 353 mil, 299 mµ and 257 mµ. ii) Yield 4 mg. T.L.C. indicated that this fraction was essentially one component but did not solidify on treatment with - 229 - petroleum ether (30-40°C. B.p.range). The infra-red spectrum in chloroform showed absorptions at 3420 cm.-1, -1 -1 -1 -1 1730 am. y 1664 cm. 1640 cm. and 1613 cm. . The ultra-violet spectrum showed absorptions at 299 mµ, 276 mµ, 262 mµ and 228 mil.

6) 2-Pheny1-3-N-phenylamino-9-acetoxy-2a13,8,8a,9- pentahydronaphthaceno[4,4a,5,bc]furan (25 mg.) in dry benzene (20 ml.) was treated with lead tetra acetate (22.8 mg., 1 equiv.). The mixture was stirred at room temperature for 15 hours. The solution was filtered and the filtrate poured into water and extracted with chloroform. The chloroform extract was washed with water and dried over sodium sulphate. Evaporation of the solvent gave an oil which solidified on contact with petroleum ether (30-40°C. B.p. range). Yield 21 mg. Spectral data identical with that of starting material. No reaction could also be effected at 60°C with excess reagent. 2-Pheny1-3-N-phenylamino-9-acetoxy-2a,3,8,8a,9- pentahydronaphthaceno[424a,5,bc]furan (25 mg.) was dissolved in glacial acetic acid (20 ml.) and concentrated hydrochloric acid (0.2 ml.) and treated with lead tetra acetate - 230 -

(22.8 mg.; 1 equiv.). The mixture was stirred at room temperature under an atmosphere of nitrogen. T.L.C. indicated about 95% starting material present after 1 hour. Further lead tetra acetate (100 mg.) was added and after a further hour the solution was poured into water and extracted with chloroform. The organic extract was washed with water and dried over sodium sulphate. Evaporation of solvent give an oil which was chromatographed on an alumina (Grade III) column in a benzene/ petroleum ether (60,80°C. B.p. range) mixture (1:1). One fraction gave a solid on evaporation of the solvent. Yield 3 mg. The infra-red spectrum in chloroform showed absorptions at 3400 cm.-1 1733 cm.-1 and 1604 cm.-1. The ultra- violet spectrum showed absorptions at 332 mil; 313 mil; 274 mll; 254 mil; 216 mi.t. and 208 mp. Mass spectrum gave molecular weight as 592. Lines at 556 and 532 indicated the loss of hydrogen chloride and acetic acid, respectively, in the cracking pattern.

Preparation of 1-N-phenylamino-1 2,3,4-tetrahydro nahIhalene (73) 1,2,3,4-Tetrahydronaphthalene (1.32 g.) in redistilled carbon tetrachloride (50 ml.) was treated with freshly - 231- crystallised N-bromosuccinimide (1.96 g.; 1:1 equiv.) and the mixture was refluxed for -43: hour. The yuccinimide was filtered off (1.08 g.$ 99%) after cooling the reaction mixture. The filtrate was evaporated on a rotary evaporator at room temperature to give an oil which was immediately treated with aniline (4.6 g.) in benzene (40 ml.). The solution was left at room temperature for one hour. Evaporation of the solution to low bulk allowed aniline hydrobromide to separate out (1.75 g., 100%). The filtrate was evaporated further to an orange oil which was ahromatographed on an alumina (Grade III) column in benzene. The first fraction yielded 11, colourlesr oil which crystallised from petroleum ether (30-40°C. B.p. range). M.p. 59-60°C. Yield 888 mg. (38% Theory). -1 The infra-red spectrum showed absorptions at 3390 cm. , -1 -1 -1 -1 1603 am. $ 1510 cm. , 760 cm. and 700 . The ultra-violet spectrum showed absorptions at 299 mµ (€ 2,000); 253 mµ (a 16,400) and 209 mµ (e 24,200). The N.M.R. spectrum showed signals at 1- 8.19 (4H); 1- 7.28 (2H); r 6.30 (1H); 5.44 (1H);7- 3.04 (9H). Found C = 86.04%; H = 7.35%; N = 6.56%. C16H17N requires C = 86.05%; H = 7.67%; N = 6.27%. The second fraction yielded a white crystalline solid. - 232-

N.p. 147-148°C. Yield 399 mg. (13% Theory). The infra-red spectrum showed absorptions at 3410 cm.-1, -1 -1 -1 -1 1605 cm. 1510 am. 1325 cm. 1 1251 cm.-1, 760 cm. and 701 cm,-1. The ultra-violet spectrum showed absorptions at 296 mg (€ 4,700); 253 mp (e 311400) and 209 mp, (E 37,800). The N.H.R. spectrum showed signals at 1- 8.07 (4H); 7- 6.29 (2H); 1- 5.40 (2H); "t- 3.36 (4H); 7-- 2.77 (10H)0 Found C = 83.79%; H = 7.17%; N = 9.13%. 0221122N2 requires C = 84.04%; H = 7.05%; N = 8.91%. This compound must be 1,4-di-N-phenylamino-1,2,3,4-tetra- hydronaphthalen.e (79). The reaction performed on a large scale was more conveniently separated into its components by fractional distillation. Aniline (30°C. at 8 m.m. Hg. pressure) Monoamine (165°C. at 2 m.m. Hg. pressure) Diamine remains in distillation vessel. A yield of 33% of 1-N-phenylamino-1,2,314-tetrahydronaphthalene (73) was obtained in this way.

Formation of the hydrochloride of 1-N-phenylamino- 112014-tetrahydronaphthalene (73) The monoaiine (50 mg.) was dissolved in dry ether (10 ml.) and dry hydrogen chloride was bubbled through -233- the solution for i hour at 0°C. Colourless transparent needles were formed. M.p. 120-135°C. (decomp.). Yield 48 mg. (86% Theory). The infra-red spectrum showed absorptions at 2750 cm.-1, 2650 cm.-1 2520 cm.-1 1580 cm.-1 1500 cm.-1 and 770 am.-1. The ultra-violet spectrum showed absorptions at 297 mµ (& 2,100); 252 mµ (E 14,800) and 208 mµ (€ 25,100). Found C = 74.01%; H = 7.26%; N = 5.23%;

Cl 13.93%. 016H18NC1 requires C = 73.98%; H = 6.97%; N = 5.39%; Cl = 13.68%.

1-N -Nitroso -N-phenylamino -1,213,4 -tetrahydronaphth alene (81) 1-N-phenylamino-1,2,3,4-tetrahydronaphthalene (500 mg.) was dissolved in acetic acid (100 ml.) containing water (11 ml.) and treated with sodium nitrite (235 mg., 1.5 equiv.). The mixture was stirred for 30 minutes at room temperature and then poured into water and extracted with chloroform. The organic extract was washed with sodium bicarbonate solution and water and dried over sodium sulphate. Evaporation of the solvent gave an oil which was converted into a crystalline solid on treatment with petroleum ether (30-40°C. B.p. range). M.p. 65-66°C. Yield 507 mg. (90% Theory). -234-

The infra-red spectrum showed absorptions at 1600 cm.-1 1500 cm.-1 1167 cm.-1 1130 am.-1 and 1092 cm.-1. The ultra-violet spectrum showed absorptions at 273 mp 6,400); 258 mp (€ 7,500) and 210 mp (E. 19,900). The N.M.R. spectrum showed signals at 8.19 (4H); 7.31 (2H); 3.13 (10H).

Pound C = 76.40%; H = 6.24%; N = 11.16%. C16H16N0 requires C = 76.16%; H = 6.39%; N = 11.10%.

1 -N -p -nitrosophenylamino -1 2,3,4 -tetrahydronaphth alene (82) 1-N-nitroso-N-phanylamino-1,2,3,4-tetrahydronaphthalene (23 mg.) was dissolved in absolute ethanol (20 7111.) and dry hydrogen chloride was bubbled through the solution for 1 hour. The solution was poured into water and extracted with chloroform. The chloroform extract was washed with sodium bicarbonate solution and then water and dried aver sodium sulphate. Evaporation of solvent gave an oil which was chramatographed on an alumina (Grade III) column in benzene. The main fraction on evaporation of solvent gave a green solid. Yield 3 mg. The infra-red spectrum in chloroform showed absorptions at 3430 cm.-1, 1603 am.-1, 1510 cm.-1 and 1122 cm.-1. The ultra-violet spectrum showed absorptions at 420 mill 300 mµp 254 mp and 207 mp. -235-

1-N-nitroso-N-phenylamino-1,2,3,4-tetrahydronaphthalene (614 mg.) was dissolved in glacial acetic acid (100 m].) and concentrated hydrochloric acid (2 ml.) and treated with sodium nitrite (289 mg.). The mixture was stirred at room temperature for 5 hours. T.L.C. indicated that the p-nitrosoderivative (82) was formed by way of the N-nitroso derivative (81). The solution was poured into water and extracted with chloroform. The organic phase was washed with sodium bicarbonate solution and then water and dried over sodium sulphate. The solvent was removed using a rotary evaporator, to give an oil. A green crystalline solid was obtained on contact with petroleum ether (30-40°C. B.p. range). N.p. 130-131°C. Yield 145 mg. (21%). The infra-red spectrum showed absorptions at 3300 cm.-1 1603 am.-1 and 1115 cm.-1. The ultra-violet spectrum showed absorptions at 424 lap 34,200); 306 mp (E 1,300); 272 mil (€ 6,500); 237 mµ (€ 9,500) and 207 mµ ( E 16,800). The N.M.R. spectrum showed signals at 8.08 (4H); r 7.22 (2H); "?.' 5.24 (1H); r 4.70 (1H); 1- 3.38 (2H); 2.85 (4H) and r- 2.29 (2H). Found C = 76.33%; H = 6.44%;

N = 10.89%. C16H16N20 required C = 76.16%; H = 6.39%; N = 11.10%. -236 -

Treatment of 1-N-phenylamino-1,2,3:4-tetrahydro- naphthal with nitrosvl chloride 1-N-Phenylamino-1,2,3,4-tdrehydronaphthalene (206 mg.) was dissolved in glacial acetic acid (100 ml.) and nitrosyl chloride was bubbled through the solution at room temperature. T.L.C. showed that the N-nitroso derivative (81) was rapidly formed. A slow conversion to another product was then observed. After 32 hours the solution was pcured into water and extracted with chloroform. The organic extract was washed with sodium bicarbonate solution and then water and dried over sodium sulphate. Dvapor- ation of the solvent gave an oil which was chromatographed on an alumina (Grade III) column in benzene. The main fraction was evaporated to give an oil, which did not crystallise with the usual solvents. Yield 50 mg. The infra-red spectrum in chloroform showed absorptions at 1600 cm.-1 1548 cm.-1 1354 am.-1 cnd 1115 an.-1. The ultra-violet spectrum showed absorptions at 30.9 mµ, 273 251 mp. and 215 mµ.

Photolysis of 1-N-nitroso-N-phenylamino-1 2$3 4- tetrahydx:anath:Lhalent1811(31) 1-N-nitroso-N-phenylamino-1,2,3,4-tetrahydrogaphtha- lene (234 mg.) in dry tetrahydrofUran (200 ml.) containing - 237 - perchloric acid (0.5 ml.) was irradiated with a high pressure lamp in quartz apparatus at roam temperat-uxe. The reaction was followed by T.L.O. which showed that a very slow decomposition to the monoamine (73) was the only reaction taking place. After 32 hours the solution was poured into water and extracted with ether. The organic phase was washed with water and dried over sodium sulphate. Evaporation of the solvent gave an oil which was chromatographed on an alumina (Grade III) column in benzene. The main fraction was evaporated and gave starting material. Yield 180 mg. Spectral data identical with starting material. The blank of this reaction without irradiation also slowly gave the monoamine (73) at room temperature.

Attempted acetylation of 1 -N -nitroso -N -phenylnmino

1 2 3 th al en e (81). The N-nitroso derivative (102 mg.) was dissolved in acetic acid (20 ml.) containing sodium acetate (120 mg.). No reaction occurred at room temperature after 65 haurs. Similarly, no reaction could be effected at 60°0 for 8 hours. On heating the solution at 110-130°C. for 3 hours a complicated reaction ensued. - 238 -

The solution was poured into water and extracted with chloroform. The organic extract was washed with sodium bicarbonate solution and then water and dried over sodium sulphate. Evaporation of the solvent gave an oil which was chromatographed on an alumina (Grade III) column in benzene. One fraction gave a crystalline solid on removal of the solvent. M.p. 162-164°C. Yield 12 mg. The infra-red spectrum showed absorptions at 1653 cm.-1, 1597 cm.-1 and 1503 cm.-1. The ultra-violet spectrum showed absorptions at 274 mil, 265 257 mµ, 219 mµ and 210 mµ.

1-N-ace tyl-N-phenylamino-1 2,3,4-tetrahydronaphthalene (p6) The monoamine (252 mg.) in acetic anhydride (40 ml.) containing sodium acetate (200 mg.) was stirred at roam temperature for 2 hours. T.L.C. indicated that a new product was slowly being formed. Heating on a steam bath at 95°C for a further 1 hour completed the reaction. The solution was poured into water and the precipitate formed was filtered and washed with water. The white solid was dried at 60°C. for 16 hours. M.p. 167°C. Yield 245 mg. (82 Theory). -239-

Mixed m.p. with product from previous experiment, 163-166°C. - i.e. no depression. The infra-red spectrum showed no hydroxyl absorption, but absorptions at 1653 an.-1 and 1595 cm.-1. The ultra- violet spectrum showed absorptions at 275 21111 (E 4,700); 268 mµ (€ 4,800) and 207 mµ (t 29,200). The N.M.R. spectrum showed signals at r 8.39 (4H); 1- 8.04 (3H); -I- 7.46 (2H); 1- 3.83 (1H); 2.63 to 3.26 ( s= 9H). Pound 0 = 81.47%; H = 7.41%; N = 5.25%. C18H19N0 requires C = 81.47%; H = 7.22%; N = 5.280.

1-N-Nitroso-N-phenylamino-1,2,3,4-tetrahydronaphthalene 1.81) was treated with the followin rea ents: 1) Methanepulphonylchloride The N-nitroso derivative (20 mg.) was dissolved in pyridine (10 ml.) and treated with methanesulphonylchloride (0.5 ml.) at room temperature. T.I.C. showed VD reaction occurred even after 15 hours. The solution was poured into water and extracted with chloroform. The chloroform extract was washed with water, dried over sodium sulphate and solvent evaporated to give an oil. The spectral properties were identical to starting material.

2) Hydrogen •eroxide The N-nitroso derivative (50 mg.) in absolute ethanol - 240 -

(40 ml.) was treated withlwdrogan peroxide (0.5 ml., 30%). No reaction occurred at room temperature and starting material was isolated.

3) Chromium trioxide The N-nitroso derivative (20 mg.) was dissolved in chloroform (10 ml.) and treated with chromium trioxide (30 mg.) in water (25 ml.). The mixture was vigorously stirred for 16 hours but T.L.C. showed no reaction took place. Starting material was isolated in high yield.

4) Ferric chloride The N nitroso derivative (20 mg.) in chloroform (10 ml.) was treated with ferric chloride (30 mg.) in water (20 ml.). No reaction occurred after 24 hours of vigorous stirring at room temperature. Starting material was isolated in high yield.

5) lalrazoic acid a) The N-nitroso derivative (106 mg.) was added to a cold solution of sodium azide (218 mg.) in concentrated sulphuric acid (20 ml.). A red colour developed in the well stirred solution and after one hour, T.L.C. indicated no starting material. The solution was carefully poured into ice and extracted with chloroform. The organic extract was washed with water and dried over sodium - 241- sulphate. Evaporation of the solvent gave an oil which contained at least 6 components according to T.L.C. The infra-red spectrum showed absorptions at 3420 cm.-1, 1600 cm.-1 1500 cm.-1 and 1460 am.-1. The ultra-violet spectrum showed absorptions at 351 mil, 289 mµ, 273 mµ, 266 mil, 258 mil, 254 mµ, 227 mµ, 212 mµ. b) Sodium azide (2.5 g.) and water (2.5 ml.) was made into a paste and cooled to 0°C. Chloroform (50 ml.) was added and the solution kept at 0°C during the slow dropwise addition of concentrated sulphuric acid (1.05 ml.). The organic phase was decanted and dried over sodium sulphate. The N-nitroso derivative (200 mg.) in dhloroform was added with stirring to the hydrazoic acid solution. No reaction occurred according to T.L.C. The solution was poured into water and the organic phase separated. Only starting material was present in this solution, and was recovered in high yield. c)The N-nitroso derivative (311 mg.) was dissolved in chloroform (50 ml.) and treated at 0°C with concentrated sulphuric acid (5 ml.). A red colour immediately appeared in the bottom phase. T.L.C. indicated that many components were present in this bottom phase but only one in the top phase. After vigorous stirring for -242-

1 hour the mixture was placed in a separating funnel. The top chloroform phase was separated and washed with concentrated sulphuric acid and then water and dried over sodium sulphate. Evaporation of solvent gave a brown oil which was chromatographed on an alumina (Grade III) column in a mixture of benzene (1 part) and petroleum ether (60-80°C. B.p. range) (2 parts). The first fraction yielded a colourless oil on remove of the solvent. Yield. 60 mg. The infra-red spectrum of a liquid film showed absorp-

tions at 3010 cm.-1, 2920 cm.-1, 2860 cm.-1, 1606 em.-1, 1500 em.-1, 1460 cm.-1 and 755 mµ. The ultra violet spectrum showed absorptions at 273 mµ ( 2,600); 267 mµ (E 2,600); 229 mµ (E 3,900) and 207 mil (E 7,600). The N.M.R. spectrum showed signals at 7- 8.72 (2H); 1- 8.02 (7H)i -r. 7.25 (6H); 1- 6.35 (1H); ?- 5.87 (1H); 1.- 3.80 (1H);

2.91 (9H) . The mass spectrum showed the molecular weight was 260. This data was consistent with a mixture of the hydrocarbons, 1431 -(1',2'-dihydronaphthaleno)]- 1,21314-tetrahydronaphthalene (91) and 1-[21-(1',31 ,4'- trihydronaphthaleno)]-2,3,4-trihydronaphthalene (90) in the ratio 1:3. -243-

Treatment of 1-N-nitroso-N-phenylamino-1,2,3,4- - tetrah drona•hthalene 81) with sodium hydride The N-nitroso derivative (2.0 g.) was dissolved in dry dimethylformamide (200 ml.) and treated with dry benzene washed sodium hydride (455 mg.). According to T.L.C., there was no reaction at room temperature but at 9500 a slow reaction took place. After 5 hours the solution was carefully filtered through celite and poured into water and extracted with chloroform. The chloroform extract was washed with water and dried over sodium sulphate, Evaporation of the solvent gave an oil. Chromatography on an alumina (Grade III) column in benzene gave a fraction which deposited a crystalline solid on evaporation of the solvent. M.p. 72-74°C. Yield 703 mg. (40% Theory). The infra-red spectrum showed absorptions at 1632 am.-1, 1596 am.-1 and 1214 cm.-1. The ultra-violet spectrum showed absorptions at 327 41. (E. 3,000); 296 mil (E 4,000); 255 mµ (E 23,800); 211 mµ (E 34,000). The N.M.R. spectrum showed signals at 1- 8.16 (2H); 'l 7.56 (2H);

9- 7.21 (2H); 7- 3.36 (2H); /- 2.90 (6H); -7- 1.73 (1H).

Found: C = 86.77%; H = 6.86%; N = 6.30%. C 16H15N requires C = 86.84%; H = 6.83%; N = 6.33%. The above data showed this compound was l-N-phenylimino-2,314-trihydro- .04e=1, lem.m naphthalene (74). -244-

T.Then dry dimethylacetamide was used as solvent, the reaction was complete after 6 hours at room temperature. Yield 28.3 mg. from the N-nitroso derivative (51 mg.) (63,; Theory). When dry benzene was used as the solvent, no reaction occurred at room temperature nor at reflux temperatures for 4 days. Starting material was recovered in high yield.

Treatment of 1-N-phenylimino-2 3,4-trihydronaphtha- 1erie_(.4) with dilute acid. 1-N-phenylimino-2,3,4-trihydronaphthalene (50 mg.) was shaken with dilute hydrochloric acid (5 ml.) and ether (10 ml.) for 15 minutes. The organic phase was separated, washed with water and dried over sodium sulphate. Evaporation of the solvent gave an oil. Yield 27 mg. The infra-red spectrum in chloroform showed absorptions at 1687 cm.-1 1679 an.-1 1602 cm.-1 and 1287 an.-1. The ultra--violet spectrum showed absorptions at 294 mils 289 mil, 249 mµ and 211 mil. Spectral data identical with authentic 1-oxo-2,3,4-trihydronaphthalene (a-tetralone). Benzal derivative. M.p. 106°C. Mixed m.p. with authentic sample showed no depression. The infra-red and ultra-violet spectra - 245 - were identical to those of authentic material.

Reduction of 1 -N -phenylimino -2,324 -trihydro- np.Thtkqlvt_1141 l-N -Phenylimino -2,3,4 -trihydronaphthalene (121 mg.) in absolute alcohol (25 ml.) was hydrogenated over a prereduced 1% Pd/C catalyst. One molar equivalent of hydrogen was absorbed in 12 minutes. The solution was filtered through celite and evaporation of the solvent yielded an oil. Chromatography on an alumina (Grade III) column in benzene gave a fraction which gave a crystalline solid on removal of the solvent. M.p. 59-60°C. Yield 100 mg. (82% Theory). Mixed m.p. gave no depression with authentic 1 -N -phenyl - amino-1,2,3,4 -tetrahydronaphthalene (73). The infra- red spectrum showed absorptions at 3380 cm.-1 ; 1603 cm. -1 and 1510 cm.-1. The ultra-violet spectrum showed absorptions at 296 mill 252 mµ and 208 mµ.

Nitrosation of 2-pheny1-3-N-phenylamin.o-9-acetoxy- -thacenol4 iu/._..L6_1f an 5

1) 2-Pheny1-3-p-nitroso-N-phanylamino-9-acetoxy- 2a0221 bandronah furan0 2-Pheny1-3-N-phenylamino-9-acetoxy-2a43,8,8a,9- pentahydronaphthaceno[4,4a,51 bc]furan (52 mg.) was - 246 -

dissolved in acetic acid (45 ml.) containing water (5 ml.) and stirred at room temperature for 1 hour. The mixture was poured into water and extracted with chloroform. The chloroform extract was washed well with water and dried over sodium sulphate. Evaporation of the solvent gave an oil, which yielded a green crystalline solid on treatment with petroleum ether (30-40°C. B.p. range). M.p. 216-219°C. Yield 30.4 mg. (55%). The infra-red spectrum showed absorptions at 3420 cm.-1, 1738 an.-1 1604 an. -1and 1123 an.-1. The ultra-violet spectrum showed absorptions at 417 mp, 325 mp, 312 mp, 297 mp, 281 rap, 251 mp and 235 mp. (N,N-Dimethyl-p-nitrosoaniline absorbs infra-red radiation at 1607 cm.-1 1374 cm.-1 and 1123 cm.-1, and ultra-violet radiation at 420 mµ, 273 mp, 266 mp and 233 mp.) The N.M.R. spectrum showed signals at 1 8.23 (3H); r 7.18 (111); -r 6.85 (2H); 5.75 (1H); 4.70 (1H); "r 4.13 (3H) and "7- 3.44 (2H). Mass spectral molecular weight 514. Cracking pattern showed facile loss of the elements of NO.

2) 2-Pheny1-3-0-nitroso-N-phenylamino-9-acetoxy- 2a0.A8,840-.pentahydronaphthaceno142_0250c1furan (94) 2-Pheny1-3-N-phenylamino-9-acetoxy-2a,3,8,8a,9- pentahydronaphthaceno[4,4a 5,bc]furan (100 mg.) was -247-

dissolved in glacial acetic acid (50 ml.) and treated with sodium nitrite (20 mg.). The mixture was stirred at room temperature for 1 hour and then poured into water. Extraction with chloroform gave an organic phase which was separated and washed well with water and dricd over sodium sulphate. Evaporation of the solvent gave an oil which was chromatographed on an alumina (Grade III) column in benzene. The first main fraction according to T.L.C. contained two compounds i.e. similar

Rf and appearance. Evaporation of solvent gave an oil, which on contact with petroleum ether (30-40°C. B.p. range) yielded a solid. Yield 53 mg. T.L.C. indicated a 1:1 mixture of compounds were present. The infra-red spectrum showed absorptions at 3430 an.-1, 1735 cm.-1 and 1600 cm.-1. The ultra-violet spectrum showed absorptions at 389 mp, 327 imp, 311 mp, 298 mp, 283 mp and 236 mp. Mass spectrum indicated only one molecular ion at 514 units. The cracking pattern was virtually superimposable with the p-nitrosoderivative (70).

3) 2-Pheny1-3-N-nitroso-N-phenylamino-9-acetoxy- 2303,8,8_aI92en.ta_liydro c an.1 2-Pheny1-3-N-phenylamino-9-acetoxy-2a,318,8a,9- pentahydronaphthaceno[4,4a25,bc]furan (676 mg.) in dry - 248- dioxan (100 ml.) and glacial acetic acid (35 ml.) was cooled to 00C. and treated with sodium nitrite (500 mg.). The mixture was stirred for 5 hours and then poured into water. The solid formed was filtered off and crystallised from a chloroform, petroleum ether (40-60°C. B.p. range) mixture. M.p. 183-1850C. Yield 600 mg. (84% Theory). The infra-red spectrum showed absorptions. at 1730 am.-1; 1601 cm.-1; 1502 cm.-1; 1478 cm.-1 and 1455 cm.-1. The ultra-violet spectrum showed absorptions at 383 mg, 326 mg, 311 mg, 298 mg, 282 mg, 275 mg and 251 mg. The N.M.R. spectrum showed signals at i 8.22 (3H); 7-- 7.15 (IH); 6.69 (3H); 1- 6.28 (1H); 7' 5.44 to 5.80 (1H); r 3.05 to 3.91 (5H).

Found C = 69.87%; H = 5.01%; N = 2.740. C33H2604N2 requires C = 77.02%; H = 5.09%; N = 5.44%. Mass spectrum showed molecular weight was 514. The cracking pattern showed the facile loss of the elements of NO. The three nitroso derivatives (71,72,94) could not be nitrosated further with sodium nitrite in acids, nor could the Fischer-Hepp rearrangement be used to form the p--nitroso derivative (72). - 249 -

Sodium hydride treatment of 2-pheny1-3-N-nitroso- N-phenylamino-9-acetoxy-2a 3,8 8a 9-pentahydronaphthaceno- [4,4a~5bcfuran (7l) 2-Pheny1-3-N-nitroso-N-phenylamino-9-acetoxy- 2a,318,8a,9-pentahydronaphthaceno[4,4a,51 bc]furan (50 mg.) was dissolved in redistilled dimethylacetamide (30 ml.), and treated with dry benzene washed sodium hydride (131 mg.). The mixture was stirred at room temperature for 15 minutes and filtered through a pad of celite into wet ether (previously sodium dried) at 0°0. The ethereal solution at 0°C, under an atmosphere of carbon dioxide, was washed with water and dried over sodium sulphate. Evaporation of the solvent at 0°C on a rotary evaporator gave a brown oil, which was extracted with petroleum ether (30-40°0. B.p. range). Evaporation of the solvent at room temperature gave a solid. 1 mg. M.p. 145-155°C., resolidified and final m.p. 174-186°C. The infra-red spectrum gave absorptions at 3390 am.-1 and 1723 cm.-1. The ultra-violet spectrum gave absorptions at 375 mil, 306 mp, 281 mp, 247 mp and 239 mp. The mass spectrum gave 483 as the molecular weight which was consistent with 2-pheny1-3-N-phenylamino-9-acetoxy- 813,a-trihdx_1 _22_, being -250-

this new product. The conditions used in the above reaction were varied, i.e. time, temperature, concentration of reactants and equivalents of reagent. Various work up procedures were also tried. No increase in yield could be obtained in any case even when the reaction was performed under an inert atmosphere. Incorporation of methyl iodide had no effect in the above reaction except for slowing the reaction down slightly. The enamine prepared from cyclohexanone and morpholine(47) when present in the reaction also had no effect on the reaction course.

Treatment of hthaceno

(5 mg. impure) in ether (10 ml.) was treated with concentrated hydrochloric acid (10 ml.). The mixture was stirred vigorously at 0°C under an atmosphere of nitrogen. T.L.C. showed that decomposition occurred rapidly. After 2 hours the mixture was poured into water at 000 and extracted with ether. The ethereal extract was washed with water and dried over sodium sulphate. Evaporation of the solvent gave an oil. The infra-red spectrum showed absorptions at - 251-

-1 -1 -1 -1 3400 cm. y 1703 cm. y 1630 cm. and 1600 am, The ultra-violet spectrum showed absorptions at 301 mµ; 283 mµ; 253 mµ; 247 311i 241 mil; 206 mp. The blank of this reaction without acid present also showed a similar decomposition pattern.

Treatment of 1-N-morpholino-1 2 dehydrocyclohexane romatemailiamom..mos (96) with lead tetra acetate 1-N-Morpholino-1,2-dehydrocyclohexane (1.0 g.) in dry benzene (60 ml.) was treated with lead tetra acetate (2.65 g., 1 equiv.) at room temperature. The mixture was stirred under an atmosphere of nitrogen for 12 hours and the lead diacetate was filtered off (1.93 g., 99% Theory). The filtrate was poured into water (500 ml.) containing dilute hydrochloric acid (10 ml.) and extracted with chloroform. The chloroform extract was washed with water and dried over sodium sulphate. Evaporation of the solvent gave an oil (350 mg.) which was treated with 2,4-dinitrophenylhydrazine reagent in methanol, The crude semi-solid formed was chromatographed on an alumina (Grade III) column in benzene and fractions were collected. On evaporation of the solvent from the first main fraction, a solid was obtained. -252 -

M.p. 160-161°C. Yield 53 mg. Mixed m.p. with authentic 214-dinitrophenylhydrazone derivative of cyolohexanone, showed no depression. The second fraction yielded a solid on evaporation of the solvent. M.p. 153°C. Yield 22 mg. The infra-red spectrum showed an absorption at 1722 cm.-1. The ultra-violet spectrum showed absorptions at 361 mµ, 276 mµ, 260 rap, 230 mµ and 220 mil. This compound may be 2,6-diacetoxycyclohexanono (98). The third fraction gave a solid on evaporation of the solvent. M.p. 169-170°C. Yield 45 mg. -1 The infra-red spectrum showed an absorption at 1735 an. . The ultra-violet spectrum showed absorptions at 358 275 mµ, 260 mil, 239 mµ, 228 mµ and 220 mµ. Literature(34) m.p. of 2-acetoxycyclohexanone is 169.5-170°C. A reaction at -20°C. in chloroform also gave low yields of 2,4-dinitrophenylhydrazone derivatives. With more than one equivalent of lead tetra acetate, the reaction was even more complex. -253-

2-Pheny1-3-N-nitroso-N-phunylamino-9-hydroxy- 2a,3,818a.L.9,dronahthacen04/12 cfuran. 2-Pheny1-3-N-phenylamino-9-hydroxy-2a,318,8a,9- pentahydronaphthaceno[4,4a,51 bc]furan (128 mg.) was dissolved in glacial acetic acid (35 ml.) and water (15 ml.) and treated with sodium nitrite (140 mg.). The solution was stirred at 0°C under an atmosphere of nitrogen. The reaction was followed by T.L.C. and shown to be complete in Ir1 hour. The solution was poured into water and the precipitate formed was filtered off and crystallised from a chloroform, petroleum ether (30-40°C. B.p. range) mixture. M.p. 160-163°C. Yield 128 mg. (80% Theory). The infra-red spectrum showed absorptions at 3440 cm.-1, -1 -1 -1 -1 1596 cm. , 1470 cm. y 1460 cm. and1152 cm.` l. The ultra-violet spectrum showed absorptions at 325 mg, 310 mg, 299 mg, 285 mg, 252 mg and 234 mg. Pound C = 64.98%;

H = 4.41%; N = 4.77%. 031H24N203 requires C = 78.79%; H = 5.12%; N = 5.93'. Mass spectrum showed the molecular weight to be 472 with a facile loss of the elements of NO in the cracking pattern. The N-nitroso derivative (99) eras shown also to be identical to the product formed from 2-pheny1-3-N-nitroso- N-phenylamino-9-acetoxy-2a,3,8,8a,9-pentahydronaphthacano- [4,4a75,bc]furan (71) on sodium hydroxide treatment in -254-

ethanol.

Treatment of 2-pheny1-3-N-nitroso-N-phenylamino-9- hydroNT-2aL3.213 . (99 with sodium hydride The N-nitroso derivative (203 mg.) was dissolved in dry dimethylacetamide (30 ml.) and treated with dry benzene washed sodium hydride (267 mg.). The mixture was stirred at room temperature under an atmosphere of nitrogen for 16 hours. The solution was filtered through celite, poured into water and extracted with ether. The ethereal extract was washed with water and dried over sodium sulphate. The solvent was removed on a rotary evaporator at room temperature, to yield a semi-solid. Crystallisation was achieved with an ether, chloroform mixture. M.p. 280-283°C. Yield 107 mg. (53% Theory). The infra-red spectrum in chloroform showed absorptions at 3300 cm.-1 1614 cm.-1 and 1600 cm.-1. The ultra- violet spectrum showed :absorptions at 325 mg (E 14,900); 310 mµ (E 22,100); 298 mg (E 20,700); 281 mg (E 18,200); 267 mg (E 16,700); 249 mil (E 17,400); 240 mil (E 17,700); 235 mg (E 17,600) and 207 mg (E 30,400). The N.M.R.

spectrum showed signals at 7- 7.13 (11)i 7- 6.98 (1H); -255-

1- 6.46 to 6.21 (2H); 7- 5.28 (1H); r 4.80 (1H); 3.41 to 3.13 (5H). Found C = 78.20%; H = 5,31%; N = 5.92%. C H 0 N 31 24 3 2 requires C = 78.79%; H = 5.12%; N = 5.93%. Mass spectral molecular weight 472. Data consistent with the N-oxideamidine structure (103).

Reactions of the N-oxideamidine derivative (103)

1) Acid Compound (103) (3 mg.) was dissolved in glacial acetic acid (8 ml.) and dilute hydrochloric acid (3 ml.) at room temperature and stirred for 3 hours. T.L.C. showed only starting material present after this time. The solution was heated at 9500. for .1,5- hour and T.L.C. showed that there was no spot corresponding to starting material on the T.L.C. plate. The mixture was poured into water and carefully basified with sodium bicarbonate. Extraction with chloroform gave an organic phase which was washed with water and dried over sodium sulphate. Evaporation of the solvent gave an oil. The infra-red spectrum showed absorptions at 1615 cm.-1 and 1598 cm.. The ultra-violet spectrum showed absorptions at 325 mµ; 310 mp; 299 mi-t4 248 mll; 234 mil and 206 mp. Spectral and T.L.C. data were identical with starting material. - 256 -

2) 492iY12Iion Compound (103) (3.7 mg.) was dissolved in pyridine (5 ml.) and acetic anhydride (2 ml.) and stirred at room temperature under an atmosphere of nitrogen for 18 hours. The solution was poured into water and after leaving for 1 hour was extracted with chloroform. The chloroform extract was washed with water and dried over sodium sulphate. Evaporation of the solvent gave an oil. The infra-red spectrum in chloroform showed absorptions at 1725 cm.-1 1634 cm.-1 and 1598 cm.-l. The ultra-violet spectrum showed absorptions at 325 mil, 311 mil, 300 mµ, 248 mil, 241 mil, 233 mµ and 206 mil. The acetylated derivative (103; 9.H = Ac) was tentatively assumed to be this product.

3) Alkali Compound (103 (1 mg.) in absolute ethanol (5 ml.) containing 4N. sodium hydroxide solution (1 ml.) was refluxed for 16 hours under an atmosphere of nitrogen. T.I.C. indicated no reaction had taken place. Starting material was recovered as an oil. -257-

4) Reduction of the N--oxide amidine derivative (103) (a) Hydrogenation The alcohol (103) (11 mg.) in absolute ethanol (10 ml.) was hydrogenated in the presence of prereduced 5% Pd/C catalyst (13 mg.). No uptake of hydrogen occurred. After 18 hours the solution was filtered through celite and washed with benzene. Evaporation of the solvent gave an oil (10 mg.). The infra-red spectrum showed absorptions at 1614 am.-1 end 1600 cm.-1. The ultra-violet spectrum showed absorptions at 325 mµ, 310 mµ, 298 mµ, 248 mµ, 241 mil, 234 mµ and 210 mµ. The above spectral data was identical with that of starting material. No uptake of hydrogen resulted with a 10% Pd/C catalyst in glacial acetic acid. (b) Zinc in acetic acid The alcohol (103) (55 mg.) in glacial acetic acid (15 ml.) was treated with zinc powder (120 mg.) at room temperature. The mixture was stirred under an atmosphere of nitrogen for 24 hours and then filtered through celite. The residuewas washed with acetio acid and Nester. The filtrate was carefully treated with sodium bicarbonate and extracted with chloroform. The organic extract was washed with sodium bicarbonate, water and dried over sodium sulphate. The solvent was removed on a rotary evaporator - 258 - to give an oil which on treatment with ether, petroleum ether (40-60°C. B.p. range) mixture, gave a crystalline solid. M.p. 255-256°C. Yield 40 mg. (75% Theory). The infra-red spectrum in chloroform showed absorp- -1 tions at 3440 cm.-1; 1623 cm. and 1591 cm.-1. The ultra-violet spectrum showed absorptions at 325 mp (E 15,800); 310 mp ( E 22,300); 298 mp (E 19,200); 282 mp (E 14,200); 246 mp (E 13,600); 240 mp (E 16,300); 234 mp (E 18,900) and 208 mp 38,000). The N.M.R. spectrum showed signals at 7.32 (1H); 1" 7.12 (1H); 1- 6.45 to 6.26 (1H); r 6.06 (2H), 1-' 5.34 (1H) and -r 5.25 (1H). Pound C = 81.45%; H = 5.18%. C311124N202 requires C = 81.55%; H = 5.34%. Mass spectral molecular weight 456. Data consistent with the amidine structure (104).

Treatment of the amidine 104) with acid

The alcohol (104) (117 mg.) was dissolved in glacial acetic acid (15 ml.) and treated with 6N hydrochloric acid (10 ml.) at 95°C. for 3 hours under an atmosphere of nitrogen. The mixture was diluted with water and cautiously treated with solid sodium bicarbonate until the solution -259- was neutral. Extraction with chloroform gave an organic phase which was washed with water and dried over sodium sulphate. Evaporation of the solvent gave a solid which was crystallised from a chloroform, petroleum ether (30-40°C. B.p. range) mixture. N.p. 136-139°C. Yield 95 mg. (56% yield). The infra-red spectrum showed absorptions at 3480 om.- 1. , 3390 am.-1, 1665 cm.-1 1633 cm.-1 end 1599 cm.-1. The ultra-violet spectrum showed absorptions at 332 mµ (E 3,200); 278 mµ (€ 23,100); 243 raP (E 43,400); 213 mµ (E 45,900). The N.M.R. spectrum showed signals at?- 6.06 to 5.89 (2H); 1- 3.97 (3H) and V 3.60 to 2.30 ( 19H). Mass spectral molecular weight 456. Molecular formula C31H24N202° Data consistent with 2-pheny1-3- 17-phenylcarboxamido-4-(2t-aminobenzy1)-2-monohydronaphtho- LA110,5,bcituran (106).

Ace lation of the amine (106)

2-Pheny1-3-N-phenylcarboxamid0-4-(2f-aminobenzy1)- 2-monohydronaphtho[4,10,51 bc]furan (35 mg.) was dissolved in acetic acid (5 ml.) and kept at room temperature for 18 hours. The mixture was poured into water, stirred with solid sodium bicarbonate for 1 hour and extracted with chloroform. The chloroform extract was washed with -260- water and dried over sodium sulphate. Evaporation of the solvent gave a crude solid, (30 mg.), which did not crystallise with any of the common solvents. Chromato- graphy on an alumina (Grade III) column in chloroform gave a fraction containing the main product. Evaporation of the solvent gave a solid. Yield 4 mg. The infra-red spectrum showed absorptions at 3480 cm.-1, 1706 cm.-1 1668 mm.-1 1645 cm.-1 and 1600 cm.-1. The ultra-violet spectrum showed absorptions at 329 mp, 316 mil, 241 mµ, 210 mµ. Mass spectral molecular weight 540. Data consistent with 2-phenyl-3-N-phenylcarboxamido-4-(2t-N,R7diacetylaminobenzy1)- 2-11101121=21U11142LAL1242419.12aa41 (110)

Acetylation of o-toluidine

N,N-Diacetyl-o-toluidine (log) was prepared as directed by Sudborough.(35) o-Toluidine was refluxed for 12 hours in acetic anhydride. Acetic anhydride was distilled off and then the diacetyl derivative came over at 120°C. at 5 mm. Hg. pressure. M.p. 18°C. The infra-red spectrum of a liquid film showed an absorption at 1707 cm.-1. The ultra-violet spectrum -261- showed absorptions at 264 mµ and 218 mil. Treatment of o-toluidine with acetic anhydride at room temperature for 16 hours only gave the monoacetyl derivative (108).

Treatment of 1 -N -nitroso -N-phenylamino-l1 2,3,4 - tetrahydronaphthalene (81) and benzalaniline 118) with sodium hydride 1 -N -Nitroso -N -phenylamino -1,2,3,4 -tetrahydronaphthalene (50 mg.), 1 equiv .) and benzalaniline (107 mg., 3 equivs.) were added to benzene washed sodium hydride (30 mg., 3 equivs.) in dry dimethylacetamide (15 ml.). The mixture was stirred at room temperature for 21 hours under an atmosphere of nitrogen. After filtering the solution through celite, the filtrate was poured into water and extracted with ether. The organic phase was washed well with water and dried over sodium sulphate. Evaporation of the solvent gave a semi-solid, which T.L.C. showed to consist of numerous products. Chromato- graphy on an alumina (Grade III) column in benzene gave two main fractions. Evaporation of solvent from the first fraction gave a red crystalline solid, subsequently shown to be the oxidation product (120). M.p. 179-181°C. Yield 11 mg. - 262 -

The infra-red spectrum in chloroform showed absorp- -1 tions at 3410 cm.-1 and 1599 cm. The ultra-violet spectrum showed absorptions at 386 mil, 298 mil, 250 nl, 242 mil and 207 mil. The second fraction yielded a white crystalline solid on evaporation of the solvent. M.p. 168-172°C. Yield 22 mg. The infra-red spectrum showed absorptions at 3360 am.-1, 1645 an.-1, 1630 em.-1 and 1605 am.-1. The ultra-violet spectrum showed absorptions at 282 mµ, 255 mµ, 224 111, 218 mil and 209 mµ. This compound was identified later as the adduct (119) of dimethylacetamide and benzal aniline.

Treatment of benzal aniline with sodium hydride in di methylacetamide

Benzalaniline (289 mg.) was treated with dry benzene washed sodium hydride (83 mg.) in dry dimethylacetamide (15 ml.). The nixturs'was stirred at room temperature under an atmosphere of nitrogen for 5 hours and then filtered through celite. The filtrate was poured into water and extracted with ether. The organic extract was washed well with water and dried over sodium sulphate. Evaporation of the solvent using a rotary evaporator gave a crystalline solid. - 263 -

H.p. 186-187°C. Yield 351 mg. (82% Theory). The infra-red spectrum in chloroform showed absorptions at 3440 cm.-1, 1650 cm.-1 and 1607 cm.-1. The ultra- violet spectrum showed absorptions at 297 mp (E 1,600); 247 mil (€ 11,900) and 207 mil (E 29,000). The N.M.R. spectrum showed signals at T. 7.27 (4H); 1- 7.14 (4H); "r 5.26 (2H); 1- 2.61 to 3.62 (10H). The N.M.R. spectrum in pyridine showed that the two methylene protons appeared at 7.05, 7.16. This indicated that in the spectrum run in deuteroehloroform, the double doublet produced by the methylene protons was exactly under the doublet due to the two sets of methyl protons. Found C = 75.94%;

H = 7.51%; N = 10.31%. C17H20N20 requires C = 76.08%; H = 7.51%; N = 10.44%. Mass spectral molecular weight 268. _Above data was consistent with the structure (119) assigned to this product.

Treatment- of benzal aniline (118) with 1-N-phenyl- la122=1122AzIsihydronalhthalene 74 with sodium h Bride in dimeth~ylformamide The imine (37 mg., 1 equiv.) and benzal aniline (30 mg., 1 equiv.) were added to a suspension of dry benzene washed sodium hydride (50 mg.) in dry dimethylformamide (10 ml.). The mixture was stirred at room - 264 -

temperature for 16 hours and then filtered through celite. The filtrate was poured into water and extracted with ether. The organic extract was washed with water and dried over sodium sulphate. Evaporation of the solvent gave an oil which was chromatographed on an alumina (Grade III) column in benzene. The first main fraction yielded a red crystalline solid, the previously isolated oxidation product (120). M.p. 183-184°0. Yield 21 mg. (31% Theory). The infra-red spectrum showed absorptions at 3410 cm.-1 and 1599 cm.-1. The ultra-violet spectrum showed absorptions at 392 mia (E 10,000); 250 in (E 50,000) and 206 mp ( E 52,000). A trace of dilute acid when _ added to the ethanolic solution shifted the Amy values'

to 498 mia (E 16,000); 352 mµ (E 19,000); 264 mg (E 42,800) and 207 mg (e 41,500). The N.M.R. spectrum showed signals at -7- 7.75 (2H); 1- 7.32 (2H); 1- 4.90 (1H); 7" 2.56 to 3.49 (19H). Found 0 = 86.57%;

H = 6.21%; N = 7.14%. 0291124N2 requires 0 = 86.96%; H = 6.04%; N = 7.00%. Mass spectral molecular weight 400. - 265 -

Treatment of 2-pheny1-3-N-nitroso-N-phenylamino- eg-id0..••••••11..E•501M-reNst - .1.01.0.11:41.111M"." 4.M..•••••im,....101.1.10 •••• 9-hyaatzzlaallaf212=22111212adEonaphthaceno[4,4a55,be] furan (99) with other bases

1) Potassium t-butoxide The N-nitrosoalcohol (51 mg.) was treated in dry ether (100 ml.) with potassium t-butoxide (149 mg.) at room temperature. The mixture was stirred under an atmosphere of nitrogen for 17 hours, and then poured into water and extracted with ether. The ethereal extract was washed with water and dried over sodium sulphate. Evaporation of the solvent gave an oil which was chromatographed on an alumina (Grade III) column in benzene. The first main fraction yielded a yellow solid on evaporation of the solvent. M.p.246-247°C. Yield 18 mg. The infra-red spectrum showed absorptions at 1664 cm.-1 and 1625 cm.-1, but no hydroxyl or amine absorption. The ultra-violet spectrum showed absorptions at 426 mtly 410 mµ, 339 LI*, 315 mµ, 253 mµ, 226 mµ and 206 mµ. Mass spectral molecular weight 346. The above data was identical to that of an authentic sample of the aromatic ketone (19). The mixed m.p. showed no depression. - 266 -

2) Sodium ethoxide The N-nitrosoalcohol (23 mg.) was dissolved in ethanol (10 ml.) and treated with a sodium ethoxide solution (10 ml. Prepared from sodium (100 mg.) in absolute ethanol (25 ml.)). The solution was stirred at room temperature for 16 hours under an atmosphere of nitrogen. T.L.C. indicated no reaction had taken place. The solution was poured into water and extracted with chloroform. The organic extract was washed with water and dried over sodium sulphate. evaporation of the solvent gave a solid. Yield 21 mg. Spectral data was identical to that of starting material.

3) Sodiumtylp.oxide The N-nitrosoalcohol (10 mg.) in absolute ethanol (10 ml.) was treated with 4N sodium hydroxide solution (0.04 ml.) at room temperature. The solution was stirred for 3 days under an atmosphere of nitrogen, but T.L.C. indicated that no reaction had taken place after this time. The solution was heated at 9500. for 3 hours and T.L.C. then showed that a reaction had taken place giving three new products. The mixture was poured into water and extracted with chloroform. The organic extract -267- was washed with water and dried over sodium sulphate. Evaporation of the solvent gave an oil, which was not separated into its components on an alumina (Grade III) column in benzene. Yield 5 mg. The infra-red spectrum in chloroform showed absorptions at 3600 an.-1, 3400 am.-1 and 1602 cm.-1. The ultra-violet spectrum showed absorptions at 320 mµ, 308 mil, 285 mil, 250 mil, 235 mµ,217 mµ and 212 mµ. T.L.C. indicated that the product with the largest Rf value was the aminoalcohol (65). The blank reaction without sodium hydroxide was performed. The N-nitrosoalcohol (10 mg.) was refluxed in absolute alcohol (10 ml.) for 17 hours under an atmosphere of dry nitrogen. T.I.C. indicated there was complete conversion to the amino alcohol (65). Solution was evaporated to give an oil which had identical spectral data with that of authentic 2-pheny1-3-N-phen lamino-9- hYdr°xY-2a,30222127221 9122ELIUU21L10111a1112- (65).

4) Triethylamine The N-nitrosoalcohol (10 mg.) was stirred at room temperature with triethylamine (1 ml.) in methanol (15 ml.) under an atmosphere of nitrogen. After 18 hours, T.L.C. indicated no reaction had taken place. Starting material was isolated in quantitative yield. -268-

Studies in the rinks A, C and D substituted series

Preparation ILLt2nylchloroformqe Phenyl-chloroformate was pre pared as described, (48) by mixing at 0°C., a solution of phosgene in toluene with phenol dissolved in sodium hydroxide solution. The pure material distilled at 54°C. at 3.5 mm. Hg. pressure. The infra-red spectrum of a liquid film showed no hydroxyl absorption but absorptions at 1781 am.-1 and 1597 am.-1.

Pre aration of anhylrous sodium formate Dry benzene washed sodium hydride was treated with a slight excess of formic acid (> 98%) in dry benzene at 0°C. A white precipitate was formed which was filtered off and dried at 100°C. for 3 days. The infra-red spectrum showed a broad band at 1620 cm.-1 but no hydroxyl absorption.

Treatment of pheuLaloroformate with sodium formate

Phenyl chloroformate (312 mg., 1 equiv.) and sodium formate (136 mg.f 1 equiv.) were stirred in dry tetrahydrofuran (20 ml.) for 18 hours at room temperature under an atmosphere of dry nitrogen. T.L.C. indicated that - 269- there was a slow formation of two products. The solution was transferred directly to a thick layer chromatography silica plate and after development, the two new components were separated. The component with the smaller Rf value was shown to be phenol by its spectral properties. The other component was isolated as an oil. Yield 46 mg. T.L.C. indicated that there was still some phenol present. The infra-red spectrum in chloroform -1. -1 showed absorptions at 3610 cm. p 1736 cm. and 1597 cm.-1. Mass spectral molecular weight 216. Authentic diphenylcarbonate containing phenol gave a broad band in the infra-red spectrum, centred at 1740 -1 cm. •

Gattermann Reactions

Treatment of 2- heal=4:131 .51===a=4?.=aatkl: methoMbeEa11=2:02:22a=1LSLI 10 5.zlaiala3 1L1I1LIELL11 zinc cyanide and hydrOen chloride

The bisphenol (100 mg.) was suspended in redistilled nitrobenzene (50 ml.) and dry hydrogen chloride gas was bubbled through the solution. Zinc cyanide (274 mg.) and then aluminium chloride (156 mg.)were added to the well stirred solution. After 6 hours between 70-90°C., - 270 - the solution was poured into dilute hydrochloric acid, and after stirring for 16 hours was extracted with chloroform. The organic phase was washed well with water and dried over sodium sulphate. Complete evaporation of the solvent was only achieved after heating at 9500. under high vacuum. T.L.C. showed that the oil formed was a complex mixture, and no separation could be brought about by chromatography on a silica column in benzene. The infra-red spectrum in chloroform showed absorptions at 1717 am.-1 1670 cm.-1, 1634 cm.-1 1616 cm.-1 and 1586 am.-1. The ultra-violet spectrum showed absorptions at 405 mµ, 323 mµ, 267 mp, 227 mil and 206 mµ.

Treatment of 2- •hen 1-4-3 5'-dih dro -4'-carbomethoxy ho 4 105aljoo furan 2a11. with DatalL22-zzaaa...2za422 ,T.z1.11=2 chloride.

The bisphenol (100 mg.) in redistilled nitrobenzene (50 ml.) was treated with liquid hydrogen cyanide (1.0 mi.) and aluminium chloride (156 mg.). Dry hydrogen chloride gas was bubbled through the stirred solution. After 6 hours at 9000., the solution was poured into water and extracted with chloroform. The organic extract was washed well with water and dried over sodium sulphate. -271-

Evaporation of the solvent under high vacuum gave an oil, which on treatment with chloroform, petroleum ether (40-60°C. B.p. range) mixture, deposited a yellow solid. Yield 62 mg. T.L.C. indicated two compounds were present. A slow running component and a material which was non running on a silica T.L.C. plate. The infra-red spectrum showed absorptions at 3370 cm.-1 1665 cm.-1, 1638 cm.-1 1617 cm.-1, 1587 cm.-1 and 1570 cm.-1. The ultra-violet spectrum showed absorptions at 408 mµ, 337 mµ, 294 mµ, 267 mil, 250 mµ, 218 mµ and 206 mµ.

Treatment of 2- henla±32252 -carbo- noxpo-nahti.....,..h anwith the nGattermann complex." (42'43) The bisphenol (500 mg.) was added to a preheated (100°C.) solution of aluminium chloride (1.5 g., 10 equiv.) in redistilled nitrobenzene (30 ml.). The Gattermann complex (1.9 g., 10 equiv.) was immediately added and the solution vigorously stirred at 95°C. for 20 minutes. The rapidly cooled solution was poured into excess dilute hydrochloric acid and stirred at room temperature for 16 hours. Extraction of the mixture with chloroform gave an organic phase as an emulsion. Addition of excess - 272 sodium chloride broke the_emulsion down slowly. The organic phase was then washed well with water and the solvent removed under high vacuum at 95°C. The oil formed was chromatographed twice on a silica column in chloroform. The main fraction on evaporation of solvent at room temperature, gave an oil, which deposited a solid on treatment with an ether, chloroform mixture. M.p. 228-229°C. Yield 181 mg. (34% Theory). The infra-red spectrum showed absorptions at 3370 cm. -1 -1 1665 cm. 1638 cm.-1 1617 cm.-12_1587 -1, and 1570 cm.-1. The ultra-violet spectrum showed absorptions at 405 mµ (E 28,800); 340 mµ (6 19,100); 264 mµ (E 27,600); 248 mµ (E_29,100) and 206 mµ (& 38,700). The N.M.R. spectrum showed signals at T' 5.99 (3H); /- 5.79 (2H); r 3.54 (1H);7 1.88 to 2.63 (n, 10H) and 7- -0.15 (1H). Found C = 71.31%; H = 4.09%. C27H1807 requires C = 71.36%; H = 3.99%. Mass spectral molecular weight 454. Data indicated that this compound was 2-t21224tIl4z(2l= for -4e-carbometho htho- L4J1212/111=al-L1I2l. When the above reaction was treated with ethanolic hydrochloric acid in the work up, a new compound was formed and identified as 2-j22 - .42.::.C...a.X1--°°lneth°x1-- 'oxahthalene138)'-L.-- - 273 -

N.p. 177-8°C. partially. Final m.p.181-185°C. (decomp.). The infra-red spectrum in chloroform showed absorptions -1 -1 -1 -1 at 3420 am. , 3230 an. 1663 am. 1632 cm. 1593 all.-1 and 1573 cm.-1. The ultra-violet spectrum showed absorptions at 429 mil (E 15,900); 337 mµ (E. 31,200); 289 mµ (a 31,300); 247 mil (E, 76,300); 231 mµ (E, 95,900); 210 mil(S 70,500). Found C = 68.97%; H = 4.49%.

027H2008 requires C = 68.64%; H = 4.27%. Mass spectral molecular weight 472.

Treatment of 2-2Ual=2=li21712124221L5, kalsama with acid 2-Phenyl-5-oxo-naphtho[4,10,5,bc]furan (100 mg.) was dissolved in dioxan (30 ml.) and treated with dilute hydrochloric acid (10 ml.). The mixture wts stirred at room temperature for 3 hours, poured into water and extracted with chloroform. The organic extract was washed with water and dried over sodium sulphate. Evaporation of solvent gave a crystalline solid. N.p. 182°C. Yield 107 mg. (100% Theory). The infra-red spectrum showed absorptions at 3290 cm.-1, -1 2515 am. 1595 cm.-1 and 1530 cm.-1. The ultra-violet spectrum showed absorptions at 334 mtlf 321 mil, 305 mµ, 291 mµ, 247 mµ and 227 mµ. This compound was shown to be -274-

1-benzoy1-4122:21h=92amaIhalene (137). Treatment of 2-phenyl-5-oxo-naphtho[4,10,5,bc]furan (3) in a two phase system (nitrobenzene/water) with dilute hydrochloric acid, resulted in no reaction taking place. Starting material was isolated quantitatively.

benallZzac27112aILISILA112LakIla-M1- 21-LIII12. The Gattermann reaction, using the vGattermann com- plexv as previously described, was performed with chlorobenzene as solvent in9tead of nitrobenzene. The usual work up gave a crystalline compound, non-running on a T.L.C. silica plate. M.p. 204-208°0. The infra-red spectrum showed -1 -1 -1 absorptions at 3400 cm. 3220 cm. 1713 cm. 1659 -1 -1 -1 -1 an. 1630 cm. , 1610 cm. and 1591 an. . The ultra- violet spectrum in chloroform gave absorptions at 405 mµ, 308 m42 267 riaµ, 254 mµ, and 243 mµ. The N.M.R. spectrum in dimethylsulphoxide gave signals at 1- 5.91;

1- 5.75; 1" 4.00; 'r 3.70; 1.93 to 2.87; 1- 1.68; -I- -0.40 and r -4.17. Pound C = 67.73%; H = 4.18%; N = 4.11%. Mass spectral molecular weight 440. A facile loss of 44 units was observed to give a line at 396 units. - 275 -

Chromatography of 2-phenyl-4,3'1217111LIMELAL carlalalia2=12 1'311I1121_[09.1,59bc]furan (131) on an alumina_iGrade III column The bisphenol (500 mg.) was dissolved in ethanol and passed down an alumina (Grade III) column made up in ethanol. The first main fraction was collected and evaporation of solvent gave a yellow crystalline solid. Yield 41 mg. The infra-red spectrum showed absorptions at 3390 cm. 3250 cm.-1, 1683 cm. 1643 cm. -1and 1579 cm.-1. The ultra-violet spectrum showed absorptions at 400 mil, 263 mµ, 222 mµ and 207 mµ. The N.M.R. spectrum showed signals at -r 8.56 (3H); "r 6.10 (2H); -r 5.47 (2H); r 3.51 (2H); r 1.90 to 2.58 (.26 9H) and 7- 0.26 (2H). Mass spectral molecular weight 468. Data consistent with 2-phen71-4-(31 ,54-dihydroxY-4'- carboethoxybenzyl fuan139).

2-Phenyl-4-(31 ,5!-diacetoxy-41 -carboothoxyben.v1)- 5-oploco-nalth oc faran140 2-Pheny1-4-(3',51 -dihydroxy-4'-carboethoxybanzy1)- 5-oxo-naphtho[4,10,5,bc]fUran (25 mg.) was treated with acetic anhydride (10 ml.) containing sodium acetate (50 mg.). The mixture was heated for 15 minutes on a steam bath and then poured into water and extracted with -276-

chloroform. The chloroform extract was washed with water and dried over sodium sulphate. , Evaporation of the solvent gave an oil which crystallised on contact with ether. _Yield 23 mg. The infra-red spectrum showed absorp- -1 -1 -1 -1 tions at 1772 cm. y 1722 an. , 1641 am. 1623 cm. , 1591 cm.-1 and 1573 am.-1. The ultra-violet spectrum showed absorptions at 400 mil, 264 mil and 206 mil. The N.M.R. spectrum showed signals at 7- 8.69 (3H); 7.73 (6H); 1- 6.00 (2H); r5.70 (2H); "r 2.96 (2H) and 7- 1.90 to 2.57 (8H).

22s2019112a1212m1)-5-oxo-naphthoL4,10,5,bc3furan (142) 2-Phenyl-4-(21-formy1-31,5'-dihydroxy-41-carbomethoxy- ben.zy1)-5-oxo-naphtho[4,10,5,bc]furan (50 mg.) was dissolved in dry benzene (50 ml.) containing 2-butanone ethylene ketal (1.0 ml.) and p-toluenesulphonic acid (1 crystal). The mixture was refluxed for 24 hours and after cooling, was treated with triethylamine (1 ml.). The solution was then poured into sodium bicarbonate solution and extracted with chloroform. The chloroform extract was washed with water and dried over sodium sulphate. The solvent was_removed on a rotary evaporator, to give an oil which was converted into a solid on treatment with a chloroform, petroleum ether (40-6000. B.p. range) mixture. - 277 -

Yield 41.9 mg. (76% Theory). The infra-red spect,um showed absorptions at 3410 am.-1, -1 -1 -1 -1 1663 cm. , 1641 cm. 1617 cm. and 1574 cm. • The ultra-violet spectrum showed absorptions at 405 mpg, 262 mµ, 253 mµ, 227 mµ and 207 mµ. Mass spectral molecular weight 498. Molecular formula by mass spectrum, a29H22°8' 2-Phenyl-4-(2t-ethyleneaceta_ carbomethoxybenwl)-5-oxo-n _25bcfanl 2-Pheny1-4-(21 -ethyleneacetal-31,51 -dihydroxy-0- carbomethoxybenzy1)-5-oxo-naphtho[4,10,5,bc]furan (22 mg.) was treated with acetic anhydride (10 mi.) containing sodium acetate (90 mg.). The mixture was heated at 9500. for 16 hours and after cooling, was poured into a sodium bicarbonate solution and extracted with chloroform. Me organic extract was washed with water and dried over sodium sulphate, Evaporation of the solvent gave an oil, which on contact with ether, gave a yellow crystalline solid. M.p. 194-195°0. partially. Final m.p. 200-201°C. Yield 20.6 mg. (80% Theory). The infra-red spectrum showed absorptions 1769 cm.-1, -1 -1 -1 -1 1728 cm. y 1642 cm. 1623 am. and 1590 am. . The - 278 - ultra-violet spectrum showed absorptions at 400 mil, (E 29,500); 268 ma. (E 25,900); 253 mil (E 20,900); 245 in (€ 20,500) and 236 mil (E 13,800). The N.M.R. spectrum showed signals at r 7.76 (3H); 1- 7.71 (3H); 7.16 (3H); er- 5.93 to 6.11 (4H); 'e 5.78 (2H); 'r 4.09 (1H); 'r 3.03 (1H) and 'e 1.86 to 2.64 (,L1:10H). Found C = 67.77%; H = 4.56%. 033H26010 requires C = 68.03%; H = 4.50%. Mass spectral molecular weight 582. 33 Molecular formula C H0'ell' 10 6 2-Phenv1-4-(2,-formyldiacetoxy-31_,P-diacetoxv-4t- carbomethox2,....benzyl-5-w) cfuran14 2-Pheny1-4-(21 -formy1-3',51 -dihydroxy-41 -carbomethoxy- benzy1)-5-oxo-naphtho[4,10,5,bc]furan (188 mg.) was treated with acetic anhydride (15 ml.) containing sodium acetate (500 mg.). The mixture was heated at 950. for 16 hours and then after cooling, was toured into a mixture of dilute hydrochloric acid and chloroform. Extraction with chloroform gave an organic phase which was washed well with water and dried over sodium sulphate. Evapor- ation of the solvent gave an oil, which on'treatment with a chloroform, ether mixture, deposited a yellow crystalline solid. o M.p. 150-160 C. partially. Final m.p.181-184°C. Yield 188 mg. (72% Theory). -279-

The infra-red spectrum showed absorptions at 1772 cm.-1, -1 -1 -1 -1 1729 cm. , 1642 an. y 1621 cm. , 1589 cm. and 1571 cm.-1 . The ultra-violet spectrum showed absorptions at 403 mg, 266 mg, 249 mg, 238 mg, 234 mg and 208 mg. The N.M.R. spectrum showed signals at 8.10 (6H); '- 7.76 (3H); 7.62 (3H); 7- 6.15 (3H); 5.62 (2H); -7- 2.98 (1H); T 1.94 to 2.62 (9H) and T 1.85 (1H). Found C = 64.76%;

H = 4.50%. 035H28012 requires C = 69.07%; H = 4.64%. Mass spectral molecular weight 608.

2-Ph2m1-4a2lzformy1-31-hydroxv-51-acetoxy-41- carbom2a2alala1la2=120thaL4a0a111121EaaLI42/(6) The formyldiacetate derivative (50 mg.) was dissolved in ethanol (50 ml.) and stirred with sodium bicarbonate solution for 2 hours. The mixture was poured into water and extracted with chloroform. The chloroform extract was washed with water and dried over sodium sulphate. Evaporation of the solvent gave an oil, which was converted into a crystalline solid on treatment with a chloroform, ether mixture. Yield 33 mg. (81%) Theory). The infra-red spectrum showed absorptions at 1775 am.-1, 1684 cm. , 1663 cm.-1, 1639 cm.-1, 1619 an.-1, 1590 cm.-1 and 1572 cm.-1 . The ultra-violet spectrum showed - 280-

a'osorptions at 405 mµ, 340 mµ, 267 mµ, 250 mµ, 230 mµp 226 mµ and 207 mµ. The N.M.R. spectrum showed signals at '1' 7.75 (3H); 1- 5.67 (2H); 1- 6.10 (3H); -e 3.31 (1H); 1.89 to 2.54 (9H); 1- -0.48 (1H) and 1- -2.51 (1H). Mass spectral molecular weight 496.

2-Pheny1-4-(2'-formy1-31,5t-diacetoxy-4'-carbo- methobenz1-5-wa na tho 10 5 be furan13 The bisphenolaldehyde (56 mg.) in acetic anhydride (8 ml.) containing sodium acetate (200 mg.) was stirred at room temperature for 5 days. The yellow solid formed was filtered off and washed with sodium bicarbonate solution and water. The solid was recrystallised from a chloroform, ether mixture. M.p. 178-179°C. partially. Finatm.p. 192-193°C. Yield 37.2 mg. (56% Theory). The infra-red spectrum showed absorptions at 1765 cm.-1, 1716 an.-1 1688 mm.-1 1632 cm.-1 and 1613 cm.-1. The ultra-violet spectrum showed absorptions at 403 mµ (E 27,000); 264 mµ (€ 15,900) and 220 mµ (E 14,000). The N.M.R. spectrum showed signals at ?- 7.76 (3H); 1- 7.63 (3H); D 6.13 (3H); 1- 5.60 (2H); 1' 2.82 (1H); 1' 1.88 to 2.59 (9H) and 1- -0.32 (1H). Found C = 68.85%; H = 4.02%.

031112209 requires C = 69.14%; H = 4.12%. Mass spectral molecular weight 538. - 281-

Treatmant of 2-pheny1-4-(26-formy1-31 15/_-diacetoxy- ALcarbomethoxybenzy1)-5-oxo-naphtho[4,109 5 be-furan (1411_with 2-butanone ethyleneketal. The diacetatealdehyde (10 mg.) in dry benzene (15 ml.) was treated with 2-butanone ethyleneketal (1 ml.) and boron trifluoride etherate (2 drops). An immediate colour change resulted. After 10 minutes, the solution was poured into water and extracted with chloroform. The chloroform extract was washed well with water and dried over sodium sulphate. Evaporation of solvent gave an oil which yielded a solid on treatment with ether. Yield 8 mg. The spectral data was identical with authentic

methoxylzaw cfarllan. pati2z1=2,..1§za=2ac z2r24.2/22 -thi- haumaala1 Methyl-2,6-dihydroxy-3-formyl-4-methylbensoate (1.0 g.) was dissolved in methanol (40 ml.) and refluxed with aniline (0.490 ml., 1.1 equiv.) for 30 minutes. The orange solution was evaporated until two thirds of the solvent had been removed and cooled at 000. Pale yellow crystals then separated out. - 282 -

M.p. 144-145°C. Yield 1.332 g. (98% Theory). -1 The infra-red spectrum showed absorptions 1640 cm. and -1 1595 0]m. . The ultra-violet spectrum Flowed absorptions at 412 mp (€ 19,400); 328 in (E 12,400); 296 mp (E 6,700); 2.85 mp (e 6.500); 25o mµ (E 16,700); 228 mp (e 16,500); 224 mp (t 17,200) and 203 mp (E 18,400). The N.M.R. spectrum showed signals at 7.66 (3H); 6.00 (3H); 3.87 (1H); T 2.56 to 2.84 (5H); -r 1.57 ( 1H); ' -2.98 (1H) and 1- -6.18 (1H). Found 0 = 67.60%; H = 5.43%; N = C H 0 16 15 4N requires C = 67.36%; H = 5.30%; N = 4.91%.

Methyl-2 6-21hyslma.:3-Z-PhariN1111MaaIML:1112 methy1122nzoate (151) Methy1-2,6-dihydroxy-3-phenyliminoformy1-4-methyl- benzoate (1.20 g.) in dry benzene (100 ml.) was hydrogenated over a 5% Pd/C catalyst. After 30 minutes, when there was no further uptake of hydrogen the solution was filtered through celite. Evaporation of the solvent gave an oil which yielded a crystalline solid on trituration with ether. M.p. 116-117°C. Yield 1.08 g. (88% Theory).

The infra-red spectrum showed absorptions at 3430 cm.-1 , -1 3170 cm.-1 , 1671 cm.-1, 1635 cm.-1, 1609 cm. and 1583 -1 cm. . The ultra-violet spectrum showed absorptions at - 283-

325 MP, ( E 3,500); 286 mµ (E 5,900); 253 mil 25,400); 223 mµ (E 25,300) and 206 mµ (E 28,100). The N.M.R. spectrum showed signals at 'r 7.67 (311); 1- 5.97 (3H); T. 5.79 (2H); 1- 3.64 (1H) and r 2.70 to 3.50 (5H). Found 0 = 66.970; H = 5.81%; N = 5.00%. C16H1704N requires C = 66.88%; H = 5.96%; N = 4.88%. Mass spectral molecular weight 287.

Treatment of the amine 151 with Fremvis salt Fremy2s salt was prepared in the usual way.(49) The amine (200 mg.) was dissolved in dimethylformnmide (40 ml.) and treated with Fremy's salt (2.0 g.), dissolved in dilute aqueous sodium hydroxide solution (5 ml. 4N. NaOH solution in 60 /11. water). The reaction was stirred, with cooling, for 10 minutes. T.L.C. indicated there was then no starting material present. The solution was poured into dilute hydrochloric acid and extracted with chloroform. The organic extract was washed with water and dried over sodium sulphate. Evaporation of the solvent gave a brown oil which on treatment with an ether/petroleum ether (30-400C. B.p. range) mixture, gave a brown solid. Yield 12 mg. T.L.C. showed essentially one spot on the origin of a T.L.C. plate. The infra-red spectrum -1 showed absorptions at 1665 cm.-1, 1643 cm.-11 1635 cm. - 284 - and 1602 cm.-1. The ultra-violet spectrum showed absorptions at 339 mµ9 261 mµ, 251 mµ and 208 mµ. The N.M.R. spectrum showed signals at -r 7.49 to 7.91; 1- 6.77 to

7.10; ?- 5.91 to 6.23; -r 2.59 to 3.34 in the ratio of 1:1:2:4. The mass spectrum showed weak lines at 287 and 267 units, and the strongest lines in the cracking pattern were at 135, 119 and 93 units. The presence of the line at 93 units suggested that the aniline residue was still present in this compound.

Treatment of Fremy's salt product with zinc in acetic acid The product (5 mg.) from the previous reaction was dissolved in dimethylformamide (2 ml.) containing acetic acid (0.2 ml.) and treated with zinc powder (20 mg.). After stirring at room temperature for 15 hours the mixture was filtered through °elite. The filtrate was poured into water and extracted with chloroform. The organic extract was washed with sodium bicarbonate and water and dried over sodium sulphate. Evaporation of the solvent gave a brown oil which deposited a solid on contact with petroleum ether (30-40°C. B.p. range). Yield 1 mg. T.I.C. showed that there was still essentially one product present which was non-running on - 285 - a T.L.C. plate. The infra-red spectrum showed absorptions at 3480 an.-1, 1665 am.-1 and 1590 am.-1. On treatment of this product with acetic anhydride in pyridine at 95°C. for 2 hour a very dark brown coloured solution was formed. T.L.C. indicated a very complex mixture of products. The infra-red spectrum of the oil, obtained by working up the mixture, showed absorptions at 1750 cm.-1„ 1679 an.-1 1638 an.-1 and 1607 am.-1. Reactions between Fremyls salt and the amine (151) in the one phase systems; ethanol/water/sodium acetate, dimethylformamide/Water/sodium acetate, ethanol/water, dimethylformamide/water, resulted in complex reaction mixtures from which no better yields of products could be isolated.

Treatment of 2-pheny1-3-N-phenylamino-9-hydroxy- 3,8 aLV22a2112k2a2iAaA12111221LUMILEI1 with Fremvls salt The ominoalcohol (24 mg.) was dissolved in ethanol (15 ml.) and stirred with Fremy's salt (500 mg.) suspended in dilute sodium hydroxide solution (0.5 ml., 4N. NaOH in 15 ml. water). The mixture was stirred at room temperature for 17 hours and then poured into dilute acid and extracted with chloroform. The organic extract was - 286 - washed with water and dried over sodium sulphate. Evap- oration of the solvent gave an oil which was converted into a crystalline solid on treatment with ether. M.p. 206-208°C. Yield 22 mg. Mixed m.p. with starting material showed no depression. The spectral data was also identical with starting material.

2-Phenyl-3,8a-(N-phenyl isoxazolidine)-4,6-dihydroxy- 5-carbometlaU7172PIZZaLlat2amIa=21=11111:

2-Pheny1-4-(21 -formy1-3 ,5°-dihydroxy-4t-carbomethoxy- banzy1)-5-oxo-naphtho[440,51 bc]furan (100 mg.) was suspended in absolute ethanol (20 ml.) containing phenyl hydroxylamine (200 mg.). The mixture was heated to 95°C. for 2 hour and then stirred at room temperature under an atmosphere of nitrogen. T.L.C. showed the slow formation of a new compound with a greater Rf value than starting material. Further quantities of phenyl hydroxylamine (100 mg.) were added after 2 and 4 days. The reaction was stopped after 8 days whCn T.L.C. had shown there was about an 80% conversion. The solid was filtered off and crystallised from ether/chloroform. Hip. 217-218°C. Yield 73 mg. (61% Theory). The infra-red spectrum showed absorptions at 3440 cm.-1, -287-

1681 cm.-1 1643 cm.-1 and 1580 cm.-1. The ultra-violet spectrum showed absorptions at 361 mil (E 12,400); 336 mµ (E 10,700); 295 mµ (E 17,900); 278 mµ (E 25,300) and 263 mµ (E 35,000). The N.M.R. spectrum showed signals at 1- 6.26, 6.72 (AB system, JAB 18-19 c.p.s.); 5.91 (3H); 3.90 (1H);,1- 3.34 to 3.82 (5H); -r 2.40 to 2.67 (8H); -r 0.04 (1H).

Pound C = 67.87%; H = 4.20%. 33H2307N requires C = 72.65%; H = 4.25%. Mass spectral molecular weight 545. Molecular formula calculation gave 033H2307N.

Treatment of 2-pheny1-4-(21-formy1-3',5f-diacetoxy-

4'-carbme11222 911121225,ldaMI (141).-w1411—Phe122-2 lagzamlaatla1222111111. The diacetatealdehyde (128 mg.) was suspended in absolute ethanol (20 ml.) and treated with phenyl hydroxylamine (300 mg.). The mixture was stirred at room temperature under an atmosphere of nitrogen and there was no starting material present after 2 days, according to T.L.C. After cooling to 0°C, the solid was filtered off. Yield 110 mg. The infra-red spectrum showed -1 absorptions at 3410 cm.-1, 1766 cm. 1728 cm.-1, 1688 -1 cm. , 1628 cm.-1 and 1575 cm.-1 . The ultra-violet spectrum showed absorptions at 365 mµ, 338 mµ, 297 mµ, - 288-

and 270 mil. The N.M.R. spectrum showed signals at T 7.70; '7' 6.75 to 6.18; r 6.07; .r 5.94; 7- 5.72; y 5.62;

7- 3.95 to 3.29 and '1' 2.64 to 2.00. The integration of this spectrum indicated that a mixture of the dihydroxy- isoldin (155) and the monoacetoxyisoldin (159) were present, in a ratio of 1:2. T.L.C. examination of this mixture showed only one spot on the T.L.C. plate.

Treatment of 2-pheny1-3 8a-(N-phenyl isoxazolidine)- 4.•••••••• •••••111.1••••••• 4 6-dihydroxv-5-carbomethoxy-9-oxo-2ap3,8 8a-tetrahvdro- naphthacenoL4,4a9 5,bc]furan (155) with Fremy's salt The substituted isoldin (12 mg.) was suspended in ethanol (15 ml.) and treated with Fremy's salt (50 mg.) in sodium hydroxide solution (3.5 ml. 4N. NaOH in 15 ml. water). The solution was stirred under an atmosphere of nitrogen at room temperature. The reaction was followed by T.L.C., and no starting material was observed after 15 minutes. The solution was poured into dilute hydrochloric acid and extracted with chloroform. The chloroform extract was washed with water and dried over sodium gulphate. Evaporation of the solvent at room temperature via a rotary evaporator, gave a brown oil. Addition of petroleum ether (30-40°0. B.p. range) to the oil afforded a brown solid. Yield 7 mg. T.L.C. indicated one spot, - 289 - non-running on a silica T.Z.C. plate. The infra-red spectrum showed absorptions at 3420 -1 -1 cm.-1, 1682 mn.-1, 1660 cm.-11 1639 cm. and 1584 cm. . The ultra-violet spectrum showed absorptions at 405 mg, 342 mµ, 264 mil and 239 mµ. The mass spectrum showed three weak lines at 545, 513 and 454 which may possibly be due to starting material. The most intense lines in the cracking pattern were at 337, 262, 198 and 182 units. - 290 -

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