THE BENZOCYCLOBUTENE SYSTEM DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosoph

Home , Cyclobutane, Indane, Phthalaldehyde, Sodium cyanide

THE BENZOCYCLOBUTENE SYSTEM

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

DONALD RAY NAPIER, B. S.

a****** The Ohio State University 1957

Approved hy:

•YU f I J. v f i . Adviser Department of Chemistry ACKNOWLEDGMENT

The author wishes to express his deepest apprecia tion to Dr. Michael P. Cava, who suggested this problem and whose guidance and council were of inestimable value toward its completion. He also wishes to thank fellow graduate students and members of the staff for their co operation.

ii TABLE OP CONTENTS

PAGE

I. INTRODUCTION ...... 1

II. DISCUSSION AND INTERPRETATION OP RESULTS . . 13

III. EXPERIMENTAL ...... 45

Reaction of a,a,a',a'-tetrabromo-o-xylene

(XXXIII) with sodium iodide ...... 45

1.2-Dibromobenzocyclobutene (XXXIV) .... 46

Treatment with maleic anhydride...... 47

Oxidation to phthalic acid ...... 47

Reaction with bromine ...... 48

Treatment with potassium acetate .... 49

1 .2-Diiodobenzocyclobutene (XXXVII) .... 49

Benzocyclobutadiene dimer (XLVI) ...... 50

Aromatization with N-bromosuccinimide . . 52

Behavior with other aromatizing reagents 53

Dibromide of benzocyclobutadiene dimer . . 55

Dehydrobromination to monobromide XLIX . 55

5-Bromobenzo-[a3-biphenylene (XLVII) . . . 56

Zinc dehalogenation of triiodide L . . . . 57

Dehydrohalogenation of triiodide L . . . . 53

Benzocyclobutene (I) 58

Thermal stability and acid sensitivity . 61

Attempted HI reduction of diiodide XXXVII . 62

Action of LiAlH^ on diiodide XXXVII .... 63

1-Bromobenzocyclobutene (LXI) ...... 63 iii iv

PAGE

Reaction with, potassium t-butoxide . . . 64

Reaction with sodium methoxide ...... 65

Reaction with magnesium ...... 65

1-Cyanobenzocyclobutene (LXIII) ...... 66

Oxidation to benzocyclobutene-l-carbox-

amide (LXIV) ...... 67

l=Aminomethyl-benzocyclobutene hydrochlor

ide ...... 68

Benzocyclobutene-l-carboxylic acid (LXYI) . 68

1.2-Bis-(trifluoroacetoxy)-benzocyclobu-

tene (LXIX) ...... 69

Hydrolysis o f ...... 70

Gis and trans esters of 1,2-benzocyclobu-

tenediol (LXXIa and LXXIb) ...... 71

1.2-Diketobenzocyclobutene (LXXII) .... 72

Quinoxaline derivative ...... 73

2,4-Dinitrophenylhydrazone 73

Oxidation to phthalic a c i d ...... 79-

Conversion to phthalaldehydic acid . . . 79-

Reaction with potassium t-butoxide . . . 75

5-t-Butoxyphthalide (LXXXI) ...... 76

Hydrolysis to phthalaldehydic acid . . . 77

APPENDIX I: INFRARED ABSORPTION SPECTRA ...... 79

APPENDIX II: ULTRAVIOLET ABSORPTION SPECTRA . . . 87

AUTOBIOGRAPHY...... 96 LIST OP TABLES

TABLE PAGE

I. Ultraviolet Absorption Maxima for Benzocyclo

butene, Indane, and Tetralin ...... 30

II. Influence of Reaction Variables in tbe Aroma-

tization of Benzocyclobutadiene Dimer

(XLVI) ...... 53

III. Fractional Distillation of Crude Benzocyclo

butene ( I ) ...... 59

LIST OF CHARTS

CHART PAGE

I. Proposed Mechanisms for the Formation of

1,2-Dibromobenzocyclobutene and 1,2-

Diiodobenzocyclobutene ...... 20

II. Proposed Mechanisms for the Formation of

Triiodide (L) ...... 28 THE BENZOCYCLOBUTENE SYSTEM

I. INTRODUCTION

Until recently^" the simplest known alicylic-aromatic system was indane (II). Although the higher homologs of indane such as tetralin (III) are well known, no au thenticated synthesis of even a simple derivative of the 2 lower homolog, Benzocyclobutene (I) , has been previous- lL ly described. As early as 1888, W. H. Perkin, Jr. wrote of unsuccessful attempts to prepare benzocyclobutene der-

I II III ivativas, however, no mention was made of the specific reactions employed. Since that time the problem has been attacked in principally two ways - by the attempted ring contraction of indane derivatives and ring closure of o~ xylene derivatives.

^A part of the work recorded in this dissertation has been published elsewhere. See reference 3« P For the nomenclature of these compounds see refer ence 3»

^M. Cava and D. Napier, J. Am. Chem. Soc., 500 (1956); ibid., Z2, 1701 (1957).

\ . H. Perkin, Jr., J. Chem, Soc., 1 (1888). The lack of any success in these attempts can undoubtably he attributed to the strain existing in a sys

tem such as I. In the absence of any thermochemical data on unsubstituted cyclobutene only a crude approximation can be made as to the magnitude of the strain induced on passing from indane to benzocyclobutene. However, it must be considerably lower than that in the unknown benzo cyclobutadiene (IV) or the known biphenylene (V). Prom heats of combustion data it has been estimated that the latter is strained to the extent of 60 + 5 kcal. with re spect to biphenyl.^ It possesses however, a net stabil ization energy of some 22+5 kcal. On the assumption

IV V that three of the bonds in I are aliphatic and comprable to those of cyclobutane (each with approximately 6 kcal. of strain)^ and the bond common to both rings is similar to the corresponding one in V, then the net strain is

18 + 15 or 33 kcal.

^From thermochemical data it is estimated that the strain in indane is no greater than in unsubstituted cy- clopentane (1.5-2 kcal.). See M. Dolliner, T. Gresham and G. Kistiakowsky, J. Am. Chem. Soc., ^9, 831 (1937)* 6R. Cass, H. Springall and P. Quincy, J. Chem. Soc., 1188, 1955. 7The experimental value for the strain in cyclobutane is 26.2 kcal. as determined by S. Kaarsemaker and J. Coops, Rec. trav. chim., 261, (1952). Although, the assumptions made are perhaps unjust ified, it is to be noted that value of 33 kcal. is less than that of the positive delocalization energy of benzene

(36-40 kcal.), to which must be added a small but not in significant amount of hyperconjugation energy.

Referring to biphenylene as an exception, doubts have been expressed concerning the stability of any other system containing a four membered ring fused to an aroma- 8 tic nucleus. These doubts were based on the nonexis tence of such systems at that time and on the expectation that the resonance stabilization of the aromatic ring would not fully compensate for the instability induced by straining the bond angles through 40 degrees. In regard to bond angles, it has been pointed out that the lines of maximum charge density for the orbitals forming the bonds do not necessarily coincide with the directions of the Q attached atoms. Also, it is to be noted that irrespec tive of the actual magnitude of the strain, unsubstituted cyclobutene is an isolable hydrocarbon."1'0 Referring next to benzocyclobutadiene (IY), the magnitude of the strain in this system - if comparable to that in biphenylene (60

®W. baker, J. Chem. Soc., 258, 1945.

^Cf. C. Coulson and W. Moffitt, Phil. Mag., 40, 26 (1949). 10Por reconfirmations of Willstater and von Schmae- del's original synthesis, see J. Roberts and C. Sauer, J. Am. Chem. Soc., 5925 (1949). kcal.) - is significantly greater than that of its calcu- 11 lated resonance energy 2.38^ (42 kcal.). It might be expected, therefore, that this system would be consider ably less stable than that of benzocyclobutene.

With the object of preparing the bridged tautomer 12 of napthalene, VI, Ingold and Challenor once attempted the synthesis of compounds Vila and Vllb which were to be used as intermediates. Treating the dibromides Villa or

V U I b with a variety of different bases resulted in the isolation of only polymers of compositions approximating to those of the compounds Vila and Vllb. However, in the presence of ethyl sodiomalonate Vllb gave a small amount

vr VIIa, R = VIII *,(?=C04EI V///,

IX XI

^FromFrom simple M.OM.O. Calculations by J. Roberts and A Streitwieser, J. Am. Chem. Soc., 2fh» 9-579 (1954).

12C. Ingold and W. Challenor, J. Chem. Soc., 123, 2066 (1923). of an enolic material (subsequently converted to/^-Uap-

" thol) which, was assigned the structure IX. Since the pro

posed intermediate Vllb was never isolated, the possibil

ity of the product being the ^- N a p thol derivative X(iso-

meric with IX) cannot be excluded. It would then be un

necessary to assume the existence of any four membered

ring intermediates since, for example, X may arise by a

Michael addition of ethyl malonate to an o-methylenequi-

none intermediate XI; the subsequent formation of X in

the basic medium would be unexceptional.

More recently a claim to the effect that deriva

tives of both the unknown systems I and IV are obtained

in the same reaction has been made by the Russian chem- 13 ° ists Logidze and Petrov. Heating a mixture of 1,4-di

ace toxybutyne -2 , benzene and aluminum chloride gave in

addition to other products 20% of a liquid °12H14°

120°/2 mm.) which was assigned the structure XII and 12%

of a solid GqqHqo (m.p. 103°) suggested to be XIII. The

basis for the assignment of structure XII to the compound

C12H14^ Was oxid-a'tiori 'fco hemimellitic acid. On re- o duction with Raney nickel the substance C^H-^q gave G-^^^

the Raman spectra of which indicated a very symmetrical

molecule. Other reactions of XIII included its bromina-

1^R. Logidze and A. Petrov, Doklady Akad. Hauk S.S.S.R., 83, 235 (1952). tion to a monobromide, chromic oxide oxidation to Cn,,Ho0o m- o d and oxonolysis, resulting in the isolation of both formic

and benzoic acids. The formation of benzoic acid on

ozonolysis was cited as evidence that XIII had the pro-Q

perties of a "chemical cliameleon". In the absence of

more definited proof, it would appear that the structures

of XII and XIII have been proposed without adequate ex perimental justification and must therefore be considered 14 untenable. Recent attempts have been made to prepare Ac

■X H

XII XIII these compounds dn order to study them in more detail; o o however, in spite of extensive efforts no materials with physical or chemical properties resembling those ascrib ed to either XII or XIII could be isolated from reaction mixtures of benzene, aluminum chloride and 1,4-diacetoxy- butyne-2.

Still another reference to a possible synthesis of a benzocyclobutene derivative is to be found in the clas sical work of E. Bergman on the addition of alkali metals IS to unsaturated systems. Having observed that sodium

"^Albert Deana, unpublished experiments.

^ y . Schlenk and E. Bergman, Ann. 463, 228 (1928). (or lithium) would add to alkenes only if the double bond ed carbon atoms were phenyl substituted, it was antici pated that two atoms of sodium would react with tetra- o phenylallene (XIV) to form the carbene XlVa. It was found that two atoms of sodium would add to XIV and hydrolysis of the sodio derivative gave l,l,3>3-tetraphenylpropene-l

4 ---CH- ! XIV X l/o. XV

(XV). However, to their expressed surprise the hydrolysis of the corresponding dilithium addition product did not give XV but gave instead an unidentified hydrocarbon of composition authors suggested that this crys talline hydrocarbon (m.p. 184°) might actually be XVI, which could arise via internal condensation of the carbene

XVII. No direct evidence in support of the structure XVI was obtained; however, selective hydrogenation of this compound gave a product, ^2^28^ inciica^inS most the nonequivalence of the aromatic fragments of this compound.

,CHA \j> Reaction with, sodium afforded a monosodio deriva tive which on hydrolysis regenerated the starting mate-o rial. Having previously found that reaction of sodium with compounds containing benzhydryl groups took place only if the benzhydryl was attached to an olefinic carbon atom, the behavior of XYI was explained by assuming that the saturated bonds of the four membered ring had a cer tain degree of olefinic character. Further work on the substance XVI led to nothing more than additional uniden tified products so that its structure remains unsolved.

Attempts to cause certain indene derivatives to undei*go ring contraction by methods successfully employed with higher homologs have not been successful.. Thus, Tif

observed that dihydronapthalene io dohydrin (XVIII), in the presence of silver nitrate, un derwent ring contraction to' yield indanecarboxaldehyde t.

(XIX) whereas a similar treatment of indene iodohydrin

(XX) gave the nitrate ester (XXI) rather than the expect-

KXI 16M. Tiffeneau and A. Orekhoff, Bull, Soc. Chem France, 2£, 782 (1920). 17 18 In the course of his studies ’ on the acid cata- 17 lyzed rearrangement of epoxyketones, House et. al. 1 rein- 19 vestigated the work of Allen ' who earlier had claimed that the epoxyketone XXIIla was isomerized hy a number of different acids to the benzocyclobutenone derivative XXY, whereas XXIIIb gave the lactone XXIVb. The structure of

XXIVb was confirmed; however, the infrared spectrum of the product originating from XXIIIa was in agreement with the 0 lactone structure XXIVa rather than XXV. The acid cata

lyzed rearrangement of either XXIIIa or XXIIIb might have o been expected to give a benzocyclobutenone, since the cy- clohexanone XXVI undergoes contraction to a cyclopentanone

(XXVII). It is significant, however, that the cyclopenta none XXVIII does not give a cyclobutanone under the same conditions, but rather the cyclopentandione XXIX is formed.

House, E. Chandross, and B. Puma, J. Org. Chem., 21, 1526 (1956).

18H. House and E. Wilson, J. Am. Chem. Soc., 29* 1488 (1957).

^ c . Allen and J. Gates, ibid., 65, 1230 (1943). b XXV| r T> XXVII

XXVIII

Assuming the unknown benzocyclobutene (I) to be a stable system, then its formation might be realized by 20 synthesis of the "valence isomer", o-quinodimethane

(XXX). This compound might then isomerize to, or perhaps be in mobile equilibrum with, the system I. As an example of this type of reversable tautomerism, cyclooctatriene

(XXXI) and bicyclo-[4,2,03 - octa-2,4-triene (XXXlI) are 21 interconvertible at temperatures above 40°. It appears,

CH.

XXXI XXXI!

20 J. W. Baker, Tautomerism, George Routledge and Sons, London, 1934, pp. 201-226. ~

21A. Cope, A. Haven, Jr., E. Ramp, and E. Trumbull, J. Am. Chem. Soc., 2ft> 4867 (1952). however, that generation of o-quinodimethane leads only 22 to polymers. No definite conclusions can he drawn with 2d regard to the isomerization of XXX to I, ^ except that o any tendency for this process to occur °is rendered unob

servable by the rapid rate of polymerization of XXX.

Some very interesting unpublished work was carried out almost fifty years ago by H. Finkelstein, working 24- with J. Thiele. During the course of a study of the reactions of a number of halides with iodide ion, Fin kelstein observed that when a,a,a',a'-tetrabromo-o-xylene (XXXIII) was refluxed with ethanolic sodium iodide, a very slow reaction occurred, accompanied by the grad ual liberation of iodine. After two days of refluxing, about 0.8 mole of iodine had been liberated and the reac tion was apparently completed. From the reaction mixture was isolated in 60% yield a crystalline, steam-distillable bromide. This product was contaminated by iodine-contain ing material which could not be removed by crystalliza tion. However, a pure sample of this same bromide was obtained, in very poor yield, by distillation of a,a,a',a'- tetrabromo-o-xylene with silver powder. The pure bromide, m.p. 52.5°, was reported to have the composition CgHgBr2 ,

22F. Mann and F. Stewart, J. Chem. Soc., 2826, 1954-. 2^For further discussion of this point see pp. 19-21. Oh H. Finkelstein, Inaugural Dissertation. Strass- bourg. 1910. 12 as determined by elementary analysis and molecular weight determinations. Oxidation of the dibromide with nitric acid gave phthalic acid, whereas heating with bromine in a sealed tube at 130-165° regenerated XXXIII. On the ba sis of these observations the dibromide was assigned the structure of 1,2-dibromobenzocyclobutene (XXXIV).

ooti ooH

XXXII!

The work described in this thesis is devoted to a reinvestigation and an extension of the observations of

Finkelstein and Thiele.

o (3

11• DISCUSSION AND INTERPRETATION OF RESULTS'

Following the directions given by Finkelstein, the

reaction of sodium iodide and a,a,a',a'-tetrabromo-o-xy-

lene was repeated. Sefluxing an ethanolic solution of the

tetrabromide (50 grams) with excess sodium iodide for 2

days gave, after the removal of solvent and iodine, ca.

25 grams of a steam-distillable product. One recrystal

lization from petroleum ether afforded 14 grams of large

white rhombs, melting 44.5-5-5°. Further recrystalliza- o tion from the same solvent failed to increase the melting o point of this material, the analysis (57% bromine, 7*3%

iodine) of which indicated the presence of one or more

iodine containing products in addition to the dibromide.

As both fractional crystallization and steam distillation

proved ineffective or at most highly inefficient methodg

for resolving the reaction mixture, an alternate procedure

for isolation of the products was adapted. The crude pro

duct from 500 grams of the tetrabromide was subjected to o a series of fractional distillations and resulted in the

isolation of 15 grams of an iodine free material, m.p. o 52.4-52.8°. As determined by elementary analysis and

molecular weight determinations, this substance had the

composition CgHgBr2 and was undoubtably the same dibro

mide, m.p. 52.5°, described by Finkelstein.

13 14

Attempts were made to isolate in pure form the io

dine containing material which underwent extensive decom

position during %he process of isolating the di'bromide.

Chromatographing the residual materials through alumina

gave an iodine rich sample of the di'bromide which after

extensive crystallization afforded 0.5 grams a second pro

duct, m.p. 62.7-62.9°> with the composition CgHglg. Eas

ily separated from the dihalides was a third component of

the reaction mixture. This material, which crystallized

in long white needles, melted at 155-156° and had the

composition

In an effort to isolate additional products, the o residues from which pure samples of the dibromide, diio

dide and essentially all the triiodide had been separated were combined and the resulting material chromatograph- o ed through alumina. This resulted in the isolation of

several fractions with intermediate melting points rang

ing from 42° to 55°. Samples with compositions identical

to those of the unknown mixtures were prepared from the pure dihalides and a comparison made. Both the infrared o and ultraviolet spectra of the various fractions obtained through chromatography were practically identical to those of the corresponding synthetic mixtures. "a Since the reaction of a,a,a 1,a'-tetrabromo-o-xylene with sodium iodide gave the compounds CgHgBr2 and C8HgI2 it is conceivable that a substance of composition CgHgBrl would also be produced. However, in spite of extensive O efforts to isolate an iodobromide from the primary reac

tion mixture no indication of its presence was ever ob

tained. o Subsequent experiments indicated that the diiodide was formed by further reaction of iodide ion with the di bromide, the dibromide being the major and the first iso- 25 lable product in the reaction described above. ^ Reflux-

ing for eight days an ethanolic solution of the dibromide with excess sodium iodide gave a mixture of bromine-free products from which could be isolated, 78% of the pure diiodide and 8.7% of the triiodide. For use in subsequent o investigations, more than two kilograms of .the diiodide was prepared by allowing the reaction of a,a,a!,a’-tetrabromo-o-xylene and iodide ion to go to completion. Un fortunately, no method more efficient than the laborious one described above was ever found for the isolation of pure dibromide. However, investigation of this compound was not hampered by any shortage of material, as more than one-half mole of this substance was made available. o In addition to being similar in solubiliby, the dihalides also appear to be isomorphous compounds. When samples of either of the pure dihalides are melted and

2^The percentage yields, as determined by elementary and infrared analysis, of dibromide, diiodide and triio dide were approximately 85, 13, and 2% respectively. 16 O oallowed to cool slowly, exceptionally large crystals tj (usually 1 or more centimeters on a side) of hexagonal, o pentagonal and cubic symmetry are formed. Mixtures of

the dihalides will also exhibit the same polymorphism,

forming equal large but mixed crystals. Farther, the

o infrared spectra of the two dihalides are practically

identical. The most striking differences in the prop

erties of these two compounds are those of their thermal

and photochemical stabilities. Although both substances

were perfectly stable in polar solvents, e.g. ethanol, a obenzene or petroleum ether solution of the diiodide be

came violet after short exposure to sunlight. Similar

solutions of the dibromide- remained colorless after long

irradiation. In addition, the dibromide can be distil-

ed at 140° (reduced pressure) without decomposition where

as the diiodide undergoes considerable decomposition with

the liberation of iodine.

Confirming the observations of Finkelstein, oxida

tion of the dibromide with nitric acid gave a quantita

tive yield of phthalic acid. Reaction of the dibromide with bromine at 150° for twelve hours gave the original

tetrabromide (XXXIII) in 48% yield. However, a sample

refluxed in pure bromine as solvent for forty-six hours was recovered unchanged.. The possibility that the di bromide might actually possess the isomeric quinonoid

structure XXXV rather than the four-membered ring struc- 17 ture (XXXIV) proposed by Finkelstein is not consistent

with, this observation. In addition, it was found that

no reaction occurred upon heating the dibromide at 100°-

for fifteen hours with maleic anhydride. N-methylisoin-

dole (XXXVI) possesses a quinonoid structure similar to

that of structure XXXV but probably of more stable nature

due to the fused aromatic pyrrole nucleus. This extremely

reactive compound combines readily with maleic anhydride 26 xn ether to give a Diels-Alder adduct.

I 6r

I CHtfr XXXV tl XXXIV XXXV' xxxv

From the evidence cited previously, one might as-

sume that the diiodide is also a 1,2 substituted benzocy

clobutene derivative, namely XXXVII. In addition to being very similar to the dibromide in its physical properties, the diiodide also yields phthalic acid on oxidation. Ad ditional evidence in support of both the structures XXXIV and XXXVII will be cited later. o Unlike those of the open chain analog, a,a'-dibromo-o-xylene, the bromine atoms of 1,2-dibromobenzocyclobutene appear to be rather firmly bound. The former,

26G. Wittig, H. Tenhaeff, V. Schoch and G. Koening, Ann., 672, 1 (1951)♦ 18

as a typical benzyl halide, undergoes solvolysis readily.

Even the considerably less reactive and hindered a,a,a',-

a'-tetrabromo-o-xylene (XXXIII) can be solvolyzed fairly 27 easily to o-phthalaldehyde in the presence of water. '

In contrast, 1 ,2-dibromobenzocyclobutene is completely

stable to boiling aqueous alcohol, no detectable hydro

lysis taking place. In addition, the compound was recov-

,ered unchanged after refluxing for two days with ethanolic potassium acetate, indicating that it must be very resist ant to reaction by either the SN-^ or SNg path. This de creased reactivity cannot be ascribed simply to the struc tural feature of 1,2-dibromocyclobutane system, since the closely related dibromide (XXXVIII) reacts readily with alcoholic potassium acetate to give a good yield of the 28 corresponding diacetate (XXXIX).

.6 r

• Br

XXXVMI

o The inertness of 1,2-dibromobenzocyclobutene to solvolysis must indicate that the carbonium ion XL factors which normally operated to stabilize benzyl carbonium ions

Thiele and 0. Gunther, Ann, 347, 106 (1906).

28W. Reppe, 0. Schlichting, K. Klager and T. Topel, Ann. £60, 1 (1948). 19 are lacking. In other words, the ion XL is not stabi

lized to any appreciable extent by the canonical forms

XL a-c. These forms, which have in common a double bond

exo to the aromatic ring into the four membered ring,

must be sufficiently strained structures so their nega

tive strain energy cancels out the positive resonance

energy which they would normally contribute to the system.

This point of view is consistent with the observation

that the ketone XLI does not readily form an enolate.'29

6r Sr

KL XL* XU

The fact that iodine is a by-product in both the

formation of the dibromide and its subsequent conversion

to the diiodide suggests, in each case, a mechanism in

volving the direct attack of iodide ion on halogen. Ac

cordingly, one may consider the overall reaction as taking place in the step-wise manner outlined in Chart I.

^ A . Cope, S. Shaeren and E. Trumbull, J. Am. Chem. Soc., 76, 1096 (1954). 20

C H A RT I

o 1

■Step a c r CHBr

XXXIII xxxv

Step h-

XXXIV

,rf iSr ;S+ep c p 6r o

XXXIV X Lll\

£tep d

XLII1 XXXVII 21

A process quite analogous to that depicted in

Step a is the reaction a,a'-dibromo-o-xylene (XLII) with 2? magnesium to form o-quinodimethane (XXX).

XLII XXX

As mentioned previously, o-quinodimethane is highly

susceptible to polymerization and does not undergo the

ring closure postulated for the intermediate XXXV in Step b. Although both the ponjugative and steric effects of

the bromine atoms would render the intermediate XXXV less

susceptible to polymerization, the difference in behavior

of the two o-quinoids might be attributed to their rela tive rates of formation. The formation of methylmagnesium halides is, in general, a relatively fast process and it 22 would appear that the conversion of XLII to XXX is no exception. On the other hand, the disappearance of XXXIII

(and subsequently XXXIV), as measured by the amount of io dine formed, was but 80% complete after two days, the re action being carried out in boiling ethanol with excess 24- sodium iodide present. The exclusion of light in this reaction, the presence of iodide ion acting as mild anti oxidant together with the fact that the relatively unsta 22 ble XXXV is generated at a very slow rate may account for the formation of XXXIV rather than polymer as in the case of o-quinodimethane.

Since the dibromide (XXXIV) appears to be essen- 0 tially incapable of either solvolysis or the normal Wal den inversion type of reaction, the most likely remaining o o path is attack by iodide ion (Step c). The reaction of a vicinal dibromide with iodide ion is indeed well known, and occurs with the formation of olefin and the liberation -50 of iodine. In the usual case in which the bromine atoms of a vicinal dibromide can assume a completely transoid configuration to each other, maximum orbital overlap is achieved in the transition state for the elimination and the reaction proceeds readily. If, on the other hand steric factors prevent the complete coplanarity of the atoms in the transition state, theoreaction rate will be 51 considerably decreased.

Although no direct physical proof of the configu ration of 1,2-dibromobenzocyclobutene is yet available, the compound must almost certainly be the trans dibromide.

A cis dibromide of this structure, because of the consid-

^ F o r a recent discussion of the mechanism of this reaction see J. Hine and W. Brader, J. Am. Chem. Soc., 2Z, 561 (1955). ^ F o r a more detailed0 exposition of this principle 0 and a striking application, of it, see D.H.R. Barton and E. Miller, ibid., 72, 1066"' (1950). O 23 erable inflexibility of the cyclobutane ring, would have to possess two bromine atoms directly over each other in such a manner as to create veryogreat repulsion effects.

However, this same rigidity of the cyclobutane ring would prevent the two bromine atoms of the trans dibromide from o being able to assume a position even approaching coplan arity with the carbon atoms bearing them in the transition state for their elimination by iodide ion. It is not sur prising, therefore, that the reaction 1 ,2-dibromobenzoc.y- clobutene with iodide ion requires a number of days to go to completion. The most interesting and curious fact about this particular elimination, however, is that the major reaction product is not the expected olefin, benzocyclobutadiene (XLIII), but rather the diiodide XXXVII which would be formed by the addition of iodine to that olefin (Step d). This situation is just the reverse of that normally encountered, when in the presence of iodine and iodide ion no diiodide can be detected and only olefin can be found. The implication arising from these consid erations is that the 1,2-double bond of benzocyclobutadiene is extremely reactive and undergoes addition reac tions far more easily than a normal double bond. This would mean that not only does benzocyclobutadiene lack the o stability expected of a new non-classical aromatic ring system, but it is more reactive, and therefore less sta ble, than such open chain analogs as styrene and stilbene.

O 24-

The highly reactive character of benzocyclobutadiene was further illustrated by the results of the zinc dust dehalogenation of either the dibromide XXXIV or the diiodide XXXVII. Under ordinary conditions, using moder ate concentrations of dihalide in ethanol and an atmos phere of air over the solution, reaction occurred to give an almost quantitative yield of an amorphous powder, cor responding in composition to a polymer of benzocyclobutadiene containing variable amounts of oxygen. When the dehalogenation was carried out under conditions of high dilution in the presence of hydroquinone as a polymeriza tion inhibitor and under a nitrogen atmosphere, the major reaction product, formed in 70-80% yield., was a colorless crystalline hydrocarbon O-^gH-^? m.p. 74-.5° • This benzocyclobutadiene dimer was dehydrogenated slowly on boiling * ° -52 in benzene with K-bromosuccinimide to a yellow hydrocar bon 0-^gH-^Q, which proved to be identical with benzo-[al~ biphenylene (XLIV).^ The hydrocax*bon C-^gH-^ was, there fore, a dihydro derivative of „ benzo-[a}- biphejiylene. The dimerization of benzocyclobutadiene can be rationalized as involving a Diels-Alder condensation between two molecules

^ The highest yield obtained was 4-9%. A variety of other dehydrogenating reagents were employed without success.

Cava and J. Stucker, J. Am. Chem. Soc., 72? 6022 (1955). 25 of the diene. The initially formed adduct (XLY) has

lost the aromaticity of one of its benzene rings, hut

by a very simple electron shift that ring can rearoma-

tize to give 6a, lOa-dihydrobenzo- a -biphenylene (XLVI).

XLV

x u v

The position of the olefinic double bond was estab

lished as follows. The dimer (XLVI) readily absorbed 1.00

moles of bromine to give a dibromide (m‘P»

111.5-112.2°), isolated in 94-% yield. Dehydrobromination

of this compound by potassium t-butoxide preceeded smooth

ly 1° give, in 84-% yield, a monobromide O^gH^jBr, m.p.

124-.5-124-.60. Dehydrogenation of the monobromide by N- bromosuccinimide in benzene gave as the only isolable product, in 22% of a yellow compound, CjgH^Br, m.p. 126-

126.5°. The identity of this substance with 5-bromoben-

30— [a]-biphenylene54 (XLVII) establishes unambiguously the

Cava and J. Stucker, ibid., 79* 1706 (1957). position of the double bond in the central ring of ben-

zocyclobutadiene dimer. Accordingly the dibromide

^16^12®r2 an(^ mono^romi(3e woul^ bave the struc tures XLVIII and XLIX, respectively.

XLVj PtSuOiC

Jr XL/MI XU*

XL vil

The triiodide, which was the minor product in the reaction of both a,a,a',a'-tetrabromo-o- xylene (XXXIII) and dibromide (XXXIV) with sodium iodide appears to be a derivative (L) of 1,2,4,5-dibenzocycio- octadiene. This was indicated by its reaction with zinc dust to form the now known, 6a, 10a~dihydrobenzo- La] -bi phenylene (XLVI). In addition, dehydrohalogenation with potassium t-butoxide gave a good yield of 5-io

Obtained by a similar treatment of the diiodide (XXXVII); M. Cava and "ty. Ratts, unpublished experiments. See also, reference 34-. 27 metry of the postulated structure L, establishes the po sition of two of the iodine atoms. Although a structure in which two halogens atoms are attached to the same car-°

LIU bon atom cannot be excluded on the basis of the existing evidence, molecular models show such structures to be con siderably more strained than one such as L.

A plausible mechanism for the formation of XLVI is one which involves a concerted process such as that out lined above, the intermediate LI undergoing ring closure to LII in a manner analogous to that of unsubstituted cyclooctatriene (XXXI). A mechanism involving transannular o dehalogenation appears unlikely, especially in view of

o the fact that magnesium reacts with a,a'-dibromo-o-xylene

(XLII) to give o-quinodimethane (XXX) rather than benzocyclobutene (I). Additional evidence against such a mech- 36 anism. will be cited in connection with another problem.-'

56See pp. 32-33. 28

CHARTII

\-l

N . / Since the position of the third iodine atom in the postulated structure L has not "been established, it is not possible to exclude any one of several conceivable mecha nisms for the formation of the triiodide. Three possible paths for the formation of structure L are outlined in Chart II. , ■ In connection with the triiodide it might be mem- tioned that an attempted reduction of the diiodide (XXXVII) with hydriodic acid gave as the only isolable product a very small quantity of material very similar in crystal line form and infrared spectra to the triiodide. This compound melted at 14-4.5-14-5° and had the composition

G16H12I4° Synthesis of the hitherto unknown benzocyclobutene (I) was accomplished with relatively little difficulty by catalytic reduction of the diiodide (XXXVII). Using palladium-charcoal as the catalyst, the hydrogenolysis was carried out in ethanolic solutions containing, in addition to the diiodide, at least two equivalents of a base. The highest yields, ranging from 49-55%> were obtained with sodium ethoxide as the base. Accompanying the formation the hydrocarbon was a polymeric gum with an infrared spec- o trum similar in all respects to the amorphous material ob tained as a by-product in the zinc dehalogenation of the diiodide (XXXVII). Benzocyclobutene, b.p. 150° (748 mm.), is a color

less oil with, a xylene-like odor. The fact that it can

he distilled at atmospheric pressure without decomposi-

o Table I

Ultraviolet Absorption Spectra for Benzocyclobutene, Indane° and Tetralin

COMPOUND Tv max. LOG E

Benzocyclobutene 260 3.09 265.5 5.28 271.5 3.27 Indane 260 3.00 266 3.17 272 3.25

Tetralin 261.5 2.60 267 2.75 274 2.75 tion is proof of its stability® Its mass spectrum (par ent peak at 140 m/e) is very different from that of o- xylene, as is its infrared spectrum. The ultraviolet spectrum of this compound contains three sharp maxima, the position and intensity of which are to be compared

(Table I) with those of indane and tetralin. 37 Although the hydrocarbon is thermally stable, it o is somewhat sensitive to acids, - particularly hydrogen o fluoride. When a weighed sample of the hydrocarbon was

^Additional data on the hydrocarbon is listed in the experimental section. added drop-wise to liquid hydrogen fluoride a vigorous reaction took place, and after allowing the hydrogen flu oride to evaporate, the sample was recovered quantita tively as a highly viscous gum. The infrared spectrum of this material was quite similar to that of polystyrene,

showing, most significantly,' a mono substituted benzene band at 14.2^. However, moderately strong absorption was

shown in the region 12.^, which suggested the presence of some 1,2-disubstituted material. The formation of styrene (LV), and thus polystyrene, could conceivably occur as a result of proton addition to the double bond common to the four and six membered rings, followed by the bond breaking process indicated in LIVa. If breaking

U N/ b XXX of the four membered ring occurs, as indicated in LIVb, o-quinodimethane (XXX) would be formed. The simultaneous occurrence of both of these processes would lead to s. copolymer consisting of units XXX and LV, which might ac count for the observed infrared bands. 32

Although, hydrogenolysis of the readily available

1,2-diiodobenzocyclobutene represents a convenient method for the preparation of the parent hydrocarbon, it would be of interest to find at least one synthesis of benzocy clobutene from intermediates not having the four membered ring initially intact. Unfortunately, attempts at this have been unsuccessful. Of the numerous unsuccessful ex periments carries out, one of these deserves special com ment, namely, the reaction of a,a'-diiodo-o-xylene (LYI) with phenyl lithium. Having noted that the cis-diiodide,

LVII, undergoes an exchange reaction with phenyl lithium to form bicyclo-[4,2,03-octene-2 (LVIII)^, it was of interest to determine whether or not a similar treatment of LVI would lead to benzocyclobutene. The formation of bicyclo- j>,2,03 -octene-2 is thought to occur by"way of the intermediate LIX which, as indicated, undergoes ap 38 internal Vurtz reaction. If the intermediate LX were

CH^I j£h.L i -c* a-r L VI XKX

LVII L I X L VIII

Alder and H, Dortman, Ber., 8£, 1492 (1954-) 33 to behave similarly, the desired product would be formed; however, only polymeric materials could be isolated from a reaction mixture consisting of equimolar quantities of phenyl lithium and LVI. This result suggests that the elimination of lithium iodide from the intermediate LX occurs by a mechanism analogous to that postulated for the dehalogenation of a,a'-dibromo-o-xylene (XLII) with magnesium, the same product being formed, namely, the highly unstable o-quinodimethane (XXX).

Reaction of benzocyclobutene with N-bromosuccinimide gave in 58% yield, 1-bromobenzocyclobutene (LXI), b.p. 90° (10.5 Dim.); accompanying its formation was a considerable amount of an amorphous and undistillable residue. The monobromide, isolated as a colorless oil, possesses anodor which is reminiscent of both benzocyclo butene and 1,2-dibromobenzocyclobutene, and could perhaps be best described as intermediate between the two. The monobromide proved .to°be an important intermediate for

Br " Br KlfiS H 8r H i LX I X X X IV the preparation of additional mono-substituted benzocy clobutene derivatives and it was unfortunate that more satisfactory yields o°f this substance could not be obtained. The failure to isolate more than 58-60% of the

desired product from the above reaction cannot he attri

buted to the instability of the monobromide under the

conditions of the reaction nor to its furthero reaction with IT-bromosuccinimide to form the dibromide XXXIV°, This

was clearly indicated when it was found that the monobro mide could be recovered unchanged "after treatment with

N-bromosuccinimide under conditions comprable to those of

its formation. The source of polymeric material in the

above reaction must then be related to the instability of

the radical LXII, intermediate in the formation of the monobromide from benzocyclobutene.

Like the dibromide XXXIV, 1-bromobenzocyclobutene is quite resistent to both solvolysis and to reactions of the S.^2 type. This was evidenced by the fact that a sam ple was recovered unchanged after heating under reflux with methanolic sodium methoxide (1.0 normal) for three hours. However, on refluxing with one normal potassium t-butoxide, dehydrobromination occurred to give, in 84% yield, benzocyclobutadiene dimer (XLVI). The high yield observed for this reaction would seem to indicate that benzocyclobutadiene (XLIII) - intermediate in the forma tion of XLVI - is relatively stable to polymerization in

strongly basic medium. Similaf evidence for the stabil

ity of the 1-bromo derivative of benzocyclobutadiene in

L t I X LV/I basic medium is indicated by its dimerization (followed

by dehydrobromination) to 5-bromobenzo-[a}-biphenylene

(XLVII) in 86% yield. It may be recalled that in the

preparation of XLVI by zinc dehalogenation of the dihal

ides XXXIV and XXXVII, special reaction conditions were

required to inhibit polymerization of the benzocyclobuta

diene. Since, in this case, the monomer (XLIII) is ac

companied by the formation of a zinc dihalide, the reac

tion solution is necessarily acid and this may in part

account for the formation of polymers.

The reactivity of the monobromide is greatly increased in solvents of higher dielectric than methanol.

Thus, when a dimethyl sulfoxide solution of the monobro mide and sodium cyanide was warmed, reaction occurred rapidly (0.5-1.0 hours) to give, in 93% yield, 1-cyanobenzocyclobutene (LXIII), b.p. 88° (1.3 mm.). However, O when the reaction was carried out in refluxing methanol, the conversion was only 30% complete after eleven hours. 36

-H*0*,NaOU1 l o - ? v % >l

L * l L.X III LXlV

The nitrile (LXIII) was readily oxidized in basic hydrogen peroxide solution to benzocyclobutene-l-carboxamide (LXIV), in yields of 70-80%. Refluxing an ether so lution of the solid amide (m.p. 159«5°) with excess lith ium aluminum hydride for twelve hours resulted in its re duction to the amine (LXV), isolated in 92% yield as the hydrochloride, m.p. 221-222°. Hydrolysis of the amide

(LXIV) in 20% sodium hydroxide occurred readily with the

CHfM; M i O i U - BCL 1 1 5 % V lxvii LX IV l X V formation of an almost quantitative yield of benzocyclobutene-l-carboxylic acid (LXVI). The identity of a sam ple of this acid with one prepared by photolysis of the diazoketone^ (LXVII) constitutes confirmatory evidence of the structure assigned. In an effort to find a more direct synthesis of the acid (LXVI), attempts were made

Little, PhD Dissertation. Ohio State University, 1957. 37 to prepare an ether solution of the Grignard reagent Q (LXVIII) which on carbonation would be expected to give

LXVI. However, reaction of the monobromide (LXI) with

magnesium resulted in the formation of only poisoners.

M 3 6t

LX V lit

Although the reaction of 1-bromobenzocyclobutene

(LXI) and sodium cyanide in dimethyl sulfoxide proceeded

without difficulty to give high yields of the nitrile

(LXIII), similar reactions carried out on the dihalides

XXXIV and XXXVII failed to give any useful products.

Equally unsuccessful were attempts to synthesize the 1,2-

dicyano derivative by treating the diiodide (XXXVII) with

cuprous cyanide in either dimethyl sulfoxide or dimethyl

formanide. In each case the reaction resulted in complete

decomposition of the dihalide and the formation of intrac

table tars. On the other hand, reaction of either dihal

ide with silver salts occurred without complication and

gave the expected oxygenated derivative in satisfactory yield. For example, 1,2-diiodobenzocyclobutene and sil ver trifluoroacetate reacted exothermically in benzene to

give the bis-trifluoroacetate (LXIX), isolated in 68% yield. This compound, m.p. 55*5°* is quite deliquescent and owing to its ease of hydrolysis, slowly decomposes on

standing at room temperature. Attempts to hydrolize the

bis-trifiuoroacetate to the diol (LXX), resulted in the

isolation of only polymers with compositions approximating

to those of LXX.

The reaction of diiodide (XXXVII) with silver ni

trate (carried out most conveniently in acetonitrile) oc

curred at a much slower rate than with silver trifluoro-

acetate and gave a mixture of products. The mixture,

,oocc ,OH cgcoom ^ Po I ij m e H

i 6 t % QOecFz OH XXXVII LXIX LU which was readily resolved by fractional crystallization, yielded two compounds: LXXIa (27%), m.p. 110° and LXXIb

(44-%), m.p. 55»5-56.5° - each with the composition

CgHg^O^. The infrared spectra of these isomers were very

similar, each having bands characteristic of covalent- ni trates. Although these dinitrate esters are undoubtably cis and trans isomers, only a tentative assignment of

LXXU LUU 7>9 40 their configuration (based solely on infrared data) can be made at the present time. For both isomers the asym metric KC>2 frequency occurred at 6.04^_; however, the sym metric NOg vibration, evidenced as a single band at

in isomer b, occurred as a doublet, 7*80^ and 7.9^ , in

isomer a. If this splitting occurs as a result of molec ular symmetry, then compound b (having a singlet at 7.^)

is most probably the trans isomer. Unfortunately, no in

frared data on other cis-trans'dinitrate esters of rigid

systems has, as yet, been published; however, a situation

similar to the above exists with the cis and trans forms of ^-diketones, the cis form being characterized by two 41 carbonyl absorption bands, the trans by one.

Treating either of the dinitrates with a methylene shloride solution of triethylamine gave, in 75% yield, benzocyclobutadienoquinone (LXXII), m.p. 132.5°. This compound, which is pale yellow in color, reacted rapid ly with peracetic acid giving phthalic acid in quantita tive yield. The quinone (LXXII) was further characterized by its reaction with o-phenylenediamine, forming a color less and highly crystalline quinoxaline derivative

^°L. Bellamy, The Infrared Spectra of Complex Mole- cules, John Wiley and Sons, Inc., hew York, N. Y . , 1954, pp. 250-252.

^ R . Rasmussen, D. Tunnicliff and R. Brattain, J. Am. Chem. Soc,, 71i 1068 (1949,) • (LXXIII) of melting point 238-239° <> In addition, it O formed an amorphous and alcohol insoluble bis-dinitrophenylhydrazone, m.p. 268-271°.

! DoU

IdooH

LXXIII Despite the considerable strain that must exist in 4-2 a system such as LXXII, this compound appears to be quite stable. Although the quinone decomposes at a very slow rate when exposed to sunlight, the compound is quite stable thermally, subliming unchanged at 100° (0.2 mm.).

The only other derivative of the unknown cyclobutadieno- 42 quinone (LXXIV) is the 3-phenyl derivative LXXV Like

LXXII, this compound is also quite stable.

d 'Co LXXIV/ LXXV

The strain in LXXIV has been estimated to be ap proximately that which exists in unsubstituted cyclobutadiene. See E. Smutney and J. Roberts, ibid., 77? 3^-20 (1955). o

While the above reactions may be considered as (•7 typical of nearly all -diketones, some contrast is to

be found, particularly among the cyclic diketones, in the

behavior of these compounds with alkali. For example,

phenanthraquinone (LXXVI) undergoes, in the presence of

20% potassium hydroxide, a benzilic acid type rearrange ment to form flourenol-9-carboxylic acid (LXXVII)'^, whereas acenapthenequinone (LXXVIII) gives, under compa-

/ , . !\ 1\ rable conditions, -hydroxy-1,8-napthalide (LXXIX)

The reaction of the diketone (LXXII) is analogous to that of acenapthenequinone, phthaldehydic acid (LXXX) being

formed in 94% yield. This conversion could conceivably occur by the following mechanism.

* LXXX

30% KOH HO COOH LYXV 11 L XXVI

^H. Klinger, Ann., $89< 237 (1912).

^ 0 . Graebe and E. Gfeller, ibid., 276, 1 (1893). 42

When either of the dinitrates (LXXIa or LXXIh) were treated with two equivalents of potassium t-butoxide a vigorous reaction occurred in which nitrite ion (1.92 moles by analysis) was formed. The neutral product of this reaction was not the quinone (LXXII) but rather a compound of melting point 87-88° with the composition

^12^14^3’ as <^e'kcrm^Iie<3- elementary analysis and molec ular weight determinations. Considerable difficulty was encountered in the purification of this substance, conse quently, yields of 10-14% were the best that could be ob tained. The rather high hydrogen content of this compound and the occxirrence of a number of bands in the infrared spectrum of position and relative intensity common to the t-butyl group indicated the presence of a t-butoxy frag ment. -This was confirmed (however, not unequivocally) when it was found that the compound could be converted to phthalaldehydic acid in quantitative yield. On the basis of these observations the unknown substance was assigned the structure of 3-t-butoxyphthalide (LXXXI).

t - g i ^ O K v

o ° L X X X I LXXX 4-3 The preparation and properties of the pseudo-ester

LXXXI were not described until shortly after completion of the above work. Wheeler, Young and Erley 4-5^ prepared a number of the crystalline 3-alkoxyphthalides, including LXXXI, by simply refluxing approximately equimolar quan tities of phthalaldehydic acid and the appropriate alcohol for 2-3 hours. After pouring the reaction mixture into cold water, the product was filtered off and recrystal lized once from petroleum ether or alcohol. By this pro cedure the yield of LXXXI was reported to be 62% and the melting point was given as 77-79° - or approximately 10°

lower than that of the substance described above. At-' tempts were made to verify their findings by repeating the preparation of LXXXI according to the procedure given. The result of a single experiment was a 23% yield of prod uct with melting point 79-81°. The infrared spectrum of a sample of this material was identical to that of a sam ple of the unknown, m.p. 87-88°. In addition, extensive recrystallization from methylene chlorlde-petroleum ether raised the melting point to the constant value of 87-88°. Although the material prepared by Wheeler et.al. was prob- o ably 95% or greater in purity, they apparently failed to observe that this compound possess a rather high melting point depression constant.

^ D . li/heeler, D. Young and D. Erley, J. Org. Chem. , 22, 54-7 (1957). 44

The formation of nitrite ion in the reaction of the dinitrates with potassium t-butoxide implys that the diketone (LXXII) is an intermediate in the formation of

3-t-butoxyphthalide (LXXXI). Since hydroxide ion converts the diketone to phthalaldehydic acid, one might expect the diketone to behave similarly with t-butoxide ion and thus give LXXXI. Although potassium t-butoxide reacted readily with the diketone, no indication of the formation of LXXXI was ever obtained, III. EXPERIMENTAL

All melting points, with the exception of those of

XXXIV and XXXVII, are uncorrected. Elemental analyses

were carried out by Galbraith Laboratories, Knoxville,

Tennessee.

Reaction of a,a,a1,a'-Tetrabromo-o-xylene (XXXIII)

with Sodium Iodide. - To a five 1. 3-necked flask provid

ed with a reflux condenser and an all-glass stirrer was

added a,a,a’,a1-tetrabromo-o-xylene (500 g . , 1,18 mole),

sodium iodide (750 g., 5.0 mole), absolute ethanol (2500

ml.) and water (1 ml.). The mixture was refluxed gently

with stirring for forty-eight hours, during which time

iodine was liberated gradually. The condenser was set

for removal of the solvent and, with stirring, ethanol

(1000 ml.) was distilled out. The mixture was cooled to room temperature and, with good stirring, a stream of

sulfur dioxide was passed through until all of the iodine was reduced. With continued stirring, ice was added to bring the temperature down to 10°. After three hours of

stirring at 10°, the solution was decanted from the oily, granular, dark brown precipitate which was then filtered, washed with ice water (500 ml.), cold 5% sodium bicar bonate (500 ml.) and again with ice water (500 ml.). The

crude moist product (325 g.) was dissolved in Skeelysolve

E and filtered through sodium sulfate. The brown filtrate

45 46 (2000 ml.) was concentrated to 1 liter and passed through alumina (450 g.). The column was eluted with petroleum ether (50-60°) and the eluate collected in two fractions: A (1000 ml.) and B (1500 ml.). Fraction A was evaporated and the residual oil was distilled under reduced pressure. The material boiling at 95-100° (0.6 mm.) was recrystal lized three times from petroleum ether (cool.ing each time to -5°) to yield 124 g. of crystals, m.p.'46-47°. This material on repeated distillation gave a fraction with constant boiling point of 124.5° (9=5 mm.), which was recrystallized from petroleum ether to yield 15 g. of 1,2- dibromobenzocyclobutene (XXXIV), m.p. 52.4-52.8°, not changed by further recrystallization. Anal. Calcd. for CgHgBr^ C, 56.68; H, 2.51; Br, 61.02; mol. wt. 262. Found: C, 56.56, 56.72; H, 2.48, 2.55; Br, 60.87, 60.85; mol. wt. (isothermal distillation in benzene) 258, 259• The residue from the first distillation of A was combined with fraction B, concentrated to 800 ml. and chromatographed through alumina (144 x 2.5 cm.), using 50-60 petroleum ether as eluent. The first 1550 ml. of eluate yielded 150 grams of material on crystallization (m.p. 46-47°); a second fraction (1250 ml.) yielded 15 g. (m.p. 51.6-52.2°) which was recrystallized 20 times from petroleum ether to yield 0.5 g. of pure 1,2-diiodobenzocyclobutene (XXXVII), m.p. 62.7-62.8°. 4-7 Anal. Calcd. for CgHglpi C, 26.99; H, 1.70; I, 71.31; mol. wt. 336. Found: C, 26.84; H, 1.93; I, 71.05; mol. wt. (isothermal distillation in benzene) 350. The alumina column on which the original sodium iodide reaction mixture was chromatographed was eluted with 1:9 benzene-Skellysolve F (1000 ml*). Evaporation

of the eluate left long white needles (15*5 g.) which, after three crystallizations from methylene chloride- Skellysolve F melted at 136-138.° (dec.). „ Anal. Calcd. for C^H^Brl^: C, 28.90; H, 1.82; Br, 12.02; I, 57-26; mol. wt. 664. Found: C, 28.98; H, 1.81; Br, 11.65; I, 57.4-5; mol. wt. (isothermal distil lation in methylene chloride) 664. Treatment of Dibromide XXXIV with Maleic Anhydride. Dibromide XXXIV (1.00 g., 0.0037 mole) and maleic anhy

dride (3.0 g., 0.031 mole) were mixed and heated fifteen hours on the steam bath. Hot water was added to dissolve the unreacted maleic anhydride. The mixture was cooled and the white crystals filtered and dried. Unreacted di bromide (0.975 g«) was recovered, m.p. 51*5°5 not de pressed by a sample of the starting material (m.p. 51*5°)• Oxidation of Dibromide XXXIV. - Dibromide XXXIV (1.00 g., 0.037 mole) and nitric acid (d. 1.42, 20 ml.) were heated together on the steam bath for forty minutes, after which time bromine vapors no longer were evolved. The clear solution was evaporated to dryness, the last 48 traces of nitric acid being removed by adding benzene and evaporating again to dryness. The solid residue of crude phthalic, acid (m.p. 190-210°) weighed 0.650 g. (theoreti cal yield = 0.644 g.). A small portion was sublimed to give phthalic anhydride (m.p. 128-129°). The mixture melting point with an authentic sample (m.p. 152°) was 128-130°, and the infrared spectra of both samples were identical. Reaction of Dibromide XXXIV with. Bromine, (a) A mixture of dibromide XXXIV (1.00 g., 0.0037 mole) and bromine (12 ml., 0.22 mole) was refluxed forty-* six hours. After evaporation of the bromine the residue (1.05 g.) was dissolved in Skellysolve F and filtered through alumina. Evaporation of the solvent and two re crystallizations of the residue from Skellysolve F gave unchanged dibromide, m.p. 49-50°. The infrared spectrum of this material was identical with that of an authentic sample. (b) A solution of dibromide XXXIV (1.00 g., 0.0037- mole) and bromine (2.2 ml., 0.040 mole) in chloroform (12 ml.) was placed in a Carius tube. The tube was sealed and heated at 150° for twelve hours. The tube was cooled and opened and the solution evaporated to dryness. The residue was dissolved in benzene and filtered through alumina. Evaporation of the filtrate left a residue (1.42 g.) which, after one crystallization from methylene 49 chloride - Skellysolve F gave a, a, a1 , a 1 -tetrabromo-o-xylene (0.775 g.» 48%), m.p. 110-115°. A further recrys tallization. from the same solvent gave pure tetrabromide, m.p. 114-115°. The mixed melting point with authentic

material (m.p. 115.5°) was 115.5-115°; in addition, the infrared spectra of both samples were identical. Treatment of Dibromide XXXIV with Potassium Acetate. A mixture of dibromide XXXIV (m.p. 52.1-52.6°; 0.50 g., 0.0018 mole), potassium acetate (2.0 g., 0.020 mole) and ethanol (6 ml.) was refluxed for fifty hours. Gareful addition of water (75 ml.) to the cooled solution gave fine crystals, which were filtered off and dried. The unchanged dibromide (0.45 g.) melted at 52.1-52.6°; the melting point was not depressed by authentic starting material. Reaction of Dibromide XXXIV with Sodium Iodide. A mixture of dibromide XXXIV (46.0 g,, 0.175 mole), sodium

iodide (175 g*i 1.17 mole), iodine (15 g.) and absolute ethanol (500 ml.) was refluxed gently with stirring for eight days. Ethanol (250 ml.) was distilled out, water (700 ml.) was added, and sulfur dioxide was passed through the solution until all of the iodine was reduced. The mixture was extracted twice with 4:1 petroleum ether (50- 60°) - benzene (700 ml. total). The hydrocarbon layer was evaporated under reduced pressure to remove all of the benzene, and the residue dissolved in a minimal volume of petroleum ether (50-60°) and adsorbed on a column of alumina (20 x 5 cm.)* The column was eluted with petro leum ether until evaporation of an eluate sample left no residue. Elution of the column with methylene chloride removed 5*6 g. of triiodide (L), m.p. 155-157°. The pe troleum ether eluate was concentrated to a small volume and rechromatographed on a column of alumina (50 x 4 cm.). The column was eluted first wi'th petroleum ether (50-60°;

5000 ml.) which, on evaporation left 48.7 g. (78%) of 1,2- diiodobenzocyclobutene (XXXVII). After one recrystalli zation from petroleum ether the diiodide melted at 62.7- 62.9°• Elution of the alumina column with methylene chlo ride removed 7*5 g* of triiodide, bringing the total yield of triiodide to 10.1 g. (8.7%). Zinc Dehalogenation of Dibromide XXXIV and Diiodide XXXVII. - Zinc dust (10 g.) was shaken with saturated aqueous ammonium chloride and then washed with water, fol lowed by 95% ethanol. This activated zinc dust (10 g.) and hydroquinone (2 g.) were added to 95% ethanol (200 ml.) in a 500 ml. 3-necked flask equipped with a reflux con denser, nitrogen inlet tube and addition funnel. To the rapidly stirred refluxing mixture there was added slowly over six hours a solution of dibromide XXXIV (3.00 g., 0.0114 mole) in 95% ethanol (150 ml.), nitrogen being constantly passed through the system. After refluxing for an additional thirty hours, the suspension was fil tered, and the filtrate concentrated to 100 ml. Water ° (75 ml.) was added and the milky suspension extracted with Skellysolve F (200 ml.). The extract was concentrated to 100 ml. and poured through a column of alumina (15 x 2 cm.),

the column being eluted with Skellysolve F (500 ml.). Concentration of the eluate and cooling to -50° gave, in two crops, pure benzocyclobutadiene dimer XLVI (0.97 g*, 83%), m.p. 70°. Further recrystallization or sLiblimation at 100° (1 mm.) raised the melting point to 74.7-74-• 9° • Anal. Calcd. for O-^gH-^ 0, 94.07; H, 5*92; mol. wt. 204. Found: C, 93*89; H, 5.93; mol. wt. (isothermal distillation in methylene chloride) 200. Elution of the alumina column with methylene chlo ride and evaporation of the.eluate left a viscous gum. The drop-wise addition of a concentrated solution of the gum in methylene chloride to a large volume of methanol precipitated a white amorphous powder, m.p. 125-145°. Qualitative tests showed this material to be halogen-free, although upon analysis very low carbon values were ob served. The polymer contained, apparently, some oxygen. Anal. Calcd. for (OgHg)x : C, 94.07; H, 5*92.

Found: C, 89*95, 90.15; H, 5*93, 5*96.

The reaction of diiodide XXXVII with zinc dust under similar conditions gave the same mixture of amor phous polymer and benzocyclobutadiene dimer (70%), sep arated as described above. 52 Aromatization of Benzocyclobutadiene Dimer (XLVI) with N-bromosuccinimide. A. Light Catalyzed Reaction. - The dimer (XLVI) (0.400 g., 0.0196 mole) was added to a solution of h- bromosuccinimide (0.400 g., 0.0023 mole) in benzene (50 ml.). The solution was refluxed for thirty-six hours, while illuminated by a 100-W. tungsten bulb. The yellow solution was cooled and filtered through a column of alumina (12 x 0.75 inch), the column being eluted with benzene until the eluate was colorless. The yellow eluate was evaporated on the steam bath to 100 ml. and 2,4,7-trinitroflourenone (0.400 g.) was added. The solution was

concentrated to 75 ml. and methanol (150 ml.) was added. After cooling for one hour at 0° the black complex (299 mg.), m.p. 203-204° was filtered off and washed with pe troleum ether. Concentration of the mother liquor yield ed a second crop of complex (133 mg.), m.p. 204-205° and, after the addition of more 2 ,4,7-trinitroflourenone, a third crop (50 mg.), m.p. 198-202°, was obtained. The total yield was 482 g. (48%). A solution of recrystal

lized complex (0.150 g.) in benzene was filtered through a column of alumina (10 x 0.75 inch) and the yellow eluate was evaporated in a stream of nitrogen. The residue was sublimed at 110-120° (0.5 mm.) to give voluminous yellow yellow needles, m.p. 71.2-72.4° (slow melting point in a preheated bath). The mixed melting point with authentic 53 benzo-[a]-blphenylene^ (m.p. 72-72.8°) was 71*2-72.9°. In addition the infrared and ultraviolet spectra of both sample's were identical. B. Benzoyl Peroxide Catalysis. - The influence of reaction time, catalyst and the variation of quantities of reactants on yield is summarized in Table II, employing in each run, 0.400 g. of dimer and 50 ml. of solvent (ben zene). The reactions were carried out at 80° C. and work ed up as described previously.

Table II

N-bromo succ inimide Benzoyl peroxide Reaction time Yield (mgs.) (mgs.) (hrs.) (%)

600 20 4.5 27 600 20 9.0 27 600 100 5.0 27 1600 100 5.0 9.8 800 40 13 17 400 0* 17 40 400 0* 36 49

*Solution illuminated by tungsten bulb •

Attempted Aromatization of Benzocyclobutene Dimer. A. With Diphenyl Sulfide. - The product would not 45 survive under the conditions described by Makasaki ^ .for o the aromatization of diphenylanthracene, cyclohexene, etc. Alternately, a solution of dimer (0.100 g.) and diphenyl

^ S . Makasaki, J. Chem. Soc. Japan, 74? 403-405 o (1953). o 54- sulfide (0.200 g.) in xylene (b.p. 137-14-0°) was re fluxed 12 hours. The solution was cooled to room temperature and passed through a short column of alumina. The eluate was perfectly colorless^indicating the absence of dehydro genated dimer. With Palladium-Oharcoal. - Dimer (0.100 g.) and 10% Pd-C (0.8 g.) were mixed thoroughly and placed in a sublimer (dia.-2.5 cm.). The mixture was covered with a 2 inch layer of 10% Pd-C. After flushing the system with - nitrogen, the sublimer was immersed in a salt-bath at 250° and the temperature increased slowly (5 mins.) to 350°. At this point the pressure was reduced from 760 to 1 mm. The absence of any yellow colored material on the cold finger indicated that no dehydrogenation occurred. C. With Cuprous Oxide. - Substituting cuprous ox ide for palladium-charcoal, the previous procedure (de scribed in B.) was employed. A few crystals of product sublimed to the cold finger and afforded 20 mg. (0.8%) of TNF complex (crude). D . With 2,3-Dichloro-5 ^ 6-dicyano-l,4-benzoquinone. A solution of dimer (0.100 g.) and the quinone (0.100 g.) in benzene (20 ml.) was refluxed for 1 hour.^ The reac-

^Under comparable conditions tetralin is dehydrogen ated almost quantitatively to napthalene. See E. Braude and P. Linstead, J. Chem. Soc. , 3544-, 1954- 55 tion was worked up as described in A. Although there was no trace of the desired product, the eluate afforded

0.092 g. of pure starting material. With Chloranil. - Substituting chloranil for dichlorodicyanobenzoquinone and employing toluene as sol vent, the experiment was carried out as described in D. No reaction occurred and 95% of starting material was re covered. Reaction of Bromine with Benzocyclobutadiene Dimer XLVI. - To a solution of dimer XLYI (1.03 g-? 0.005 mole) in chloroform (100 ml.), cooled to 0°, there was added drop-wise a solution of bromine (0.808 g., 0.005 mole) in chloroform (50 ml.). After evaporation of the chloroform on the steam bath, the residue was dissolved in Skelly solve F, the solvent was concentrated to a volume of AO ml. and cooled at -5° for fifteen hours. Colorless needles (1.55 g.)» m.p. 104.5-106.5°» separated; concentration of the filtrate gave a further quantity (0.150 g.) of similar material, the total yield being 1.70 g. (94%). After three recrystallizations from petroleum ether analytical ly pure dibbomide (XLVIII) was obtained, m.p. 111.5-112.2°

(dec.). Anal. Calcd. for 016H12Br2 : C, 52.78;°H, 3.52; Br, 43.90. Found C, 52.91; H, 3.46; Br, 43.70. Dehydrobromination of Dimer Dibromide XLVIII. - To a solution of dibromide XLVIII (1.29 g.5 0.0035 mole) in t-butyl alcohol (50 ml.) and. "benzene (15 ml.), was added a 1.15 N solution (20 ml.) of potassium, t-butoxide in t- butyl alcohol. After standing at room temperature for nineteen hours, the solution was diluted with water and extracted with several portions of ether-benzene mixture. The solvent was filtered through sodium sulfate and evap orated to dryness. The solid residue was dissolved in petroleum ether (50-60°), the solvent concentrated to 40 ml. and cooled to -5°• There was obtained, in three crops, 0.840 g. (84%) of dimer monobromide XLIX, m.p. 124°. Recrystallization from petroleum ether (50-60°) gave long needles, m.p. 124.5-124.6°. Anal. Calcd. for. O-^gH-^Br: C, 67.86; H, 5.92; Br, 28.22. Found C, 67.59; H, 4.02; Br, 28.01. Aromatization of Dimer Monobromide (XLIX) to 5" Bromobenzo-Ca]-biphenylene (XLYII). - To a solution of N-bromosuccinimide (0.400 g., 0.0025 mole) in benzene (50 ml.) was addea the monobromide (XLIX) (0.400 g., 0.00196 mole). The solution was refluxed for fifteen hours, while Illuminated by a 100‘V. tungsten bulb. The yellow solution was cooled and filtered through a column of alumina (8 x 0.75 inch), the column being eluted with benzene until the eluate was colorless. The y.ellow eluate was evaporated on the steam bath to .100 ml. and 2,4,7-tri- nitrofluorenone (0.400 g.) was added. The solution was concentrated to 50 ml. and methanol (150 ml.) was added. 57 After cooling for one hour at -5° the fine hrovm crystals (184 mg., 22%) m.p. 202-203° were filtered off and re crystallized from henzene-methanol to give lustrous 'brown- black needles, m.p. 203-204°. A solution of pure complex (100 mg.) in benzene was filtered through a column of alumina and the yellow eluate was evaporated in a stream of nitrogen. Sublimation of the solid residue at 140-150° (0.75 mm.) gave an orange crust (m.p. 125-125.5°) which, after crystallization from aqueous ethanol, afforded volu minous orange-yellow needles, m.p. 126-126.5°. The mixed melting point with an authentic sample of 5-bromobenzo- ta]-biphenylene (m.p. 126-127.5°)^ was 126-127°. In ad dition, the infrared and ultraviolet spectra of both sam ples were identical. Zinc Dehalogenation of Triiodide h. - To boiling absolute ethanol (175 ml.) was added a solution of triio dide L (10.0 g., 0.0151 mole) in benzene (20 ml.) and activated zinc-dust (25 g.). The mixture was refluxed and stirred for 24 hours, filtered and water (300 ml.) added to the filtrate. The milky suspension was extracted twice with petroleum ether (750 ml. portions). The petroleum ether solution was passed through sodium sulfate and evap orated to dryness. Sublimation at 100° (1.0 mm.) gave benzocyclobutadiene dimer XLYI (1.01 g., 35%) m.p. 70- 74.5°. One recrystallization from petroleum ether raised the melting point to 74,5°. The melting point was not de- 58 pressed by an authentic sample and the infrared spectra of both samples were identical. Dehydrohalogenation of Triiodide h. - To a freshly prepared solution of potassium (1.6 g. , 0.04 mole) in t- butyl alcohol (32 ml.) was added triiodide L (2.5 g., 0.0038 mole). After heating the reaction mixture for 30 minutes on the steam plate, water (20 ml.) and dilute ace tic acid (40 ml., IN.) were added. The mixture was cool ed, filtered and the'filtrate evaporated under reduced pressure. The orange colored residue (0.932 g.) obtained was extracted 5 hours with petroleum ether (30-60°). The petroleum ether extract was evaporated to dryness and the residue recrystallized from ethanol-water to yield bright

orange needles (.735 g., 62.6%), m.p. 131-132°. Anal. Calcd. for C^gH^I: C, 58.56; E, 2.76; I, 38.68. Found: C, 58.78; H, 2.92; I, 38.48. A mixed melting point with 5-iod.obenzo-Caj -bipheny-

lene (m.p. 131-132°),"^ was 131-132°. Benzocyclobutene (I). - Palladium-Charcoal (10 g., 10% Pd) was added to a hydrogenation bottle and after flushing the bottle with nitrogen, there was added a solu tion of 1 ,2-diiodobenzocyclobutene (XXXVII) (27.0* g. ,

0.0759 mole) in absolute ethanol (300 ml.) and crude, aged (see below) sodium ethoxide (20 g.). The suspension was

shaken with hydrogen for 19 hours under an initial pressure of 52.0 p.s.i. (capacity of system,A28.0 p.s.i.5 0.10 mole 59 hydrogen). At the end of that time the pressure had drop ped to 29.2 p.s.i. Qi22.3 p.s.i., 0.080 mole). The pres sure was reset to 52.0 p.s.i. and after 48*hours an addi tional 0.0615 mole of hydrogen was taken up. At this stage, fresh catalyst (4.0 g.) was added and after 5 hours shaking the theoretical amount of hydrogen (0.152 mole) had been absorbed. The suspension was filtered through Super*Cell and water (400 ml.) was added to the filtrate. The cloudy solution was extracted twice with 300 ml. por tions of petroleum ether (30-60°). The petroleum ether solution was filtered through anhydrous sodium sulfate and after concentrating to 75 ml., filtered through alumina (4 x % in.). The column was eluted with petroleum ether (350 ml.). The eluate was concentrated carefully to 25 ml. and distilled, under reduced pressure, through a column

(14 x >2 in.) packed with glass beads. The fraction boil

ing at 75-80° (50 mm.) was collected and weighed 3*89 g. (49%). Distillation on a larger scale (5 times the above quantities used) gave a 55% yield, of equally pure materi al 1.5388). A weighed sample was distilled through a Hester spinning band column. The results of that dis tillation are recorded in6Table III. A sample of the combined fractions 4 and. 5 (b.p. 150°/748 mm., d ^ 0.957, m.p. -23 to -24°) was analyzed. Anal. Calcd. for CgHg: C, 92.26; H, 7-74. Pound:

C, 92.33, 92.47; H, 7.74, 7.72. The mass spectrum of I exhibited a parent peak at 104 m./e.; the infrared spectrum contained a band at 47 10.05^ characteristic of a cycloalkane ring. 1

. Table III

Fractional Distillation of Crude Benzocyclobutene (I)

Fract. Pre s s. Boiling range Wt. of fract. 525 (no/) TmmTT (deg. C.) (% total) D

1 141.6-2.0 86.9-90.5° 5.6 1.5278 2 • 142 90.9-93.0° 9.6 1.5348 3 142 93.0-94.2° 21.2 1.5388 4 142.0-2.2 94.2° 32.6 1.5409 5 143 94.2-94.5° 21.5 1.5409 residue -- 9 1.5322

The residue from the first distillation was combined with the material obtained on elution of the alumina column with methylene chloride. The residue [40%, calc, as (CgHg)^, a viscous gum, exhibited an infrared spectrum similar in all respects to the amorphous material obtained as a by-product in the zinc dehalogenation of XXXIV and XXXVII. The degree of purity or (impurity).of the sodium ethoxide employed in these reactions has an appreciable affect on the yield. Freshly prepared sodium ethoxide gave variable yields of 20-38%. The best yields (49-55%) were obtained with sodium ethoxide which had been aged for

^ L . V. Harrison, J. Ghem. Soc. , 1614 (1951)* 61 6 months in a sealed bottle and had become orange and moist during storage. Other bases such as pyridine, so- o dium hydroxide and barium or sodium carbonate gave un- ° satisfactory yields of hydrocarbon (1-20%). Thermal Stability and Acid Sensitivity o,f Benzocy clobutene . - Refluxing the hydrocarbon for 1 hour at nor mal pressures left the boiling point (150°/748 mm.) un- 25 changed; also, the refractive index = 1.54-09) of a sample stored at room temperatures for more than one year remained constant. When 3*0 g. of the hydrocarbon was added dropwise to ca. 50 ml. of hydrogen fluoride a,nd the resulting solu tion allowed to evaporate over a 48 hour peripd, a highly .viscous residue was obtained. Dissolving in methylene chloride and filtering throeigh a small amount of alumina gave, on evaporation of solvent, 3*0 g. of a perfectly transparent glass, - somewhat sticky in texture. The in frared spectrum of a thin film of this material is to be contrasted with that of polystyrene (see Appendix I). The strong bond around 14.4^, (monosubstituted benzene) might

» be interpreted as being indicative of the presence of polystyrene units.^ 0 Benzocyclobutene appears to be stable in the pres ence of dilute mineral acids. For example, a 0.50 g.

u o Bellamy, op. cit», p. 65. O 62 sample was dissolved in methanol (58.5 ml.), 5 ml. of conc. hydrochloric acid added to make the resulting solu tion 1 N in acid and after standing 48 hours, at room tem perature, 0.49 g. of the hydrocarbon was extracted (after adding 200 ml. of water) with 30-60° petroleum ether. The infrared spectrum of the recovered material was identical to that of a pure sample. However, the -refractive index 25 had decreased from 1.5388 to 1.5335 (^p ) due, perhaps, to a trace of methanol. Attempted HI Reduction of 1,2-Diiodobenzocyclobu- tene (XXXVII). - In each of two 100 ml. flasks, labeled A and B respectively, was placed diiodide XXXVII (10.0 g.) adding to A, glacial acetic acid (70 ml.), water (5 ml.) and iodine (3*0 g.)» to B, glacial acetic acid (60 nil.) and 49% hydriodic acid (20 g.) were added. After heating at 100° for 84 hours, considerable decomposition had taken place in both flasks the contents of which were worked up in the following manner. Water (150 ml.) was added and the resulting solutions extracted with 30-60° petroleum ether (200 ml.). The petroleum ether solutions were chro-

> matographed through alumina (15 x % in.) using the same o e solvent (375 ml.) as an eluting agent. The eluates from both columes afforded ca. 0.7 g* each of recovered diio dide, m.p. 60.5-62°. Further elution (400 ml.) of the columns gave on evaporation,0 0.050 g. of white needles, m.p. 144.5-145°, originating from A and 0.170 g. of the Page 63 lacking. Filmed as received from Ohio State University.

UNIVERSITY MICROFILMS mid.e (29.2°g., 0.163 mole) and carbon tetrachloride (75 ml.) was stirred and refluxed for 2.5 hours in the pres ence of a catalytic amount of benzoyl peroxide (10 mg). o After addition of 30-60° petroleum ether (30 ml.) the solution was decanted onto alumina (4 x 1 in.). The alu mina column was eluted with petroleum ether (1000 ml.) and the eluate evaporated to 15 ml. This material was distilled through a Nester spinning band column to yield pure monobromid.e LXI (17*4 g., 58%), b.p.- 90° (10.5 mm.),

1.5907. Anal. Calcd. for CgH^Br: C, 52.49; H, 3.86; Br, 43.66. Found: C, 52.67; H, 4.01; Br, 43.40. Attempted B.romination of 1-Bromobenzocyclobutene (LXI). - A mixture of monobromide LXI (0.64 g., 0.0035 mole), IT-bromosuccinimide (0.7 g.> 0.0392 mole-) and carbon tetrachloride. (10 ml.) was refluxed for 2 hours in the presence of a catalytic amount of benzoyl peroxide (5 mg.). The mixture was cooled and filtered through alumina (3 x

1/2 in.) using 30-60° petroleum ether (150 ml.) as an elut ing agent. Evaporation of the eluate gave 0.62 g. of colorless oil with infrared spectra and refractive index identical to that of the starting material. Reaction of 1-Bromobenzocyclobutene (LXI) with Base. (a). Potassium t-butoxide. - Monobromide (1.00 g.,

0.0055 mole) and 12 ml. of potassium t-butoxide in t-buta- nol (0.98 IT.) was refluxed for 7 hours. Water (40 ml.) was added and the solution extracted twice with 40 ml. portions of petroleum ether (50-60°). After filtering through sodium sulfate, the petroleum ether solution was evaporated to dryness. Sublimation of the residue at 100° (1 mm.) gave 0.475 g. (84%) of benzocyclobutadiene dimer (III), m.p. 68-74.5°. One recrystallization from petro leum ether (50-60°) afforded a sample (m.p. 7^.5°) which was not depressed upon admixture with an authentic sample. In addition, the infrared spectra of both samples were identical. (b). Sodium Methoxide. - Monobromide (0.97 g.» 26 Njj 1.595) was refluxed with 1 IT. sodium methoxide in methanol (10 ml.) for 5 hours. Water (50 ml.) was added and on extraction with petroleum ether (100. ml.) there 26 was obtained, on evaporation, 0.875 §.• of oil (N^ 1.605). The infrared spectrum of this material was identical to that of the starting material. Reaction of 1-Bromobenzocyclobutene (LXI) with Mag nesium. - A solution of the monobromide LXI (1.0 g.) in dry ether (250 ml.).was added dropwise to a 15 x % inch column of dry magnesium turnings (freshly activated by acid followed by mercuric chloride) through which a stream of dry ether continuously poured. When the addition was complete, the reaction solution was evaporated to 100 ml. and then poured on powdered dry ice (ca. 20 g.). After the dry ice had evaporated, the ether solution was ex 66 tracted with 2 IT hydrochloric acid (10 ml.) and then with 5% sodium hydroxide (5 ml.). Evaporation of the ether phase gave 0.522 g. [theory, 0.557 g. calcd. as (C3Hy)xl of a viscous oil with an odor characteristic of the benzocyclobutene polymer obtained by dehplogenation of the dihalides XXXIV and XXXVII. Acidification of the alkaline extract gave ca. 0.050 g. of material (not isolated), the infrared spectrum of which showed, a carboxyl band at 5*8 but the spectrum was different than that of benzocyclobutene-l-carboxylic acid. 1-Cyanobenzocyclobutene (LXIII). (a). - Monobromide LXI (5-00 g., 0.0275 mole) and sodium cyanide (2.0 g., 0.04-1 mode) were dissolved in di methyl sulfoxide (50 ml.), heated at 50° for 50 minutes and finally at 95° for another 50 minutes. Water (150 ml.) was added and the solution was then extracted with 3:1 ether-petroleum ether (150 ml.). The ether solution was washed several times with water and then passed through anhydrous sodium sulfate. The solvent was evaporated and the residue distilled under reduced pressure. Three frac tions, b.p. 88° (1.5 mm.), were obtained: (1) 0.615 g. (N^p 1.5657), (2) 1.4-62 g. (Njp 1.54-92), (5) 1.204 g. (lip 1.5450); yield 5.28 g. (95%). Fraction (2) was an alyzed . Anal. Calcd. foroC^H^N: C, 85.69; II, 5 <>46; IT,

10.85. Found: C, 85.74; H, 5.48; IT, 10.87- 67 (b). A solution of monobromide LXI and. sodium cy anide (excess) in methanol was refluxed for 11 hours and the reaction mixture worked up in the manner described above. A comparison of the infrared spectra of the prod uct with those of the monobromide and nitrile indicated that only 25-30% conversion to l-c7/anobenzocyclobutene° (LXIII) took place under these conditions. Hydrogen Peroxide Oxidation of 1-Cyanobenzocyclo- butene (LXIII). - A mixture of the nitrile LXIII (1.00 g.°, 0.0078 mole), 30% hydrogen peroxide (2 ml., 0.017 mole) and 20% sodium hydroxide (2 ml.) reacted exothermically with evolution of oxygen. After 15 minutes of shaking, methanol was added carefully to sustain the reaction. If the temperature ,of the reaction mixture was allowed to increase above 60°, hydrolysis of the amide occurred as was evidenced by the" evolution of ammonia. In all, 8-10 ml. of methanol was added; the use of less methanol led to incomplete reaction. When the addition of more rneth- « anol failed to increase the rate of evolution of oxygen, the mixture was warmed at 60° for 15 minutes longer. The reaction mixture was then transferred to a separatory funnel diluted with water and extracted with methylene chloride (50 ml.). The methylene chloride solution, after filtration through anhydrous sodium sulfate, was diluted slowly with 30-60° petroleum aether, when benzocyclobutene-

1-carboxamide, LXIV, (0.835 g. , 73%). precipitated in fine °

O 68 white needles, m.p. 158.5-159°. Recrystallisation from methylene chloride - 50-60° petroleum ether raised the melting point to a constant value of 159*5°• Anal. Calcd. for C^H^NO: C, 73.9-5; H, 6.16; N,

9.52. Pound: C, 73.9-4; II, 6 .51; IN, 9.39-. l-Aminomethyl-benzocyclobutene Hydrochloride. - A solution of nitrile LXV (1.15 g., 0.0097 mole) in 50 ml. of dry ether was slowly added to a well stirred suspension of lithium aluminum hydride (1.00 g., 0.026 mole) in ether o (25 ml.). After the addition was complete, the reaction mixture was stirred under gentle reflux for 12 hours, the excess hydride destroyed with saturated sodium sulfate solution and the ether decanted from the inorganic solids. After drying (sodium sulfate), the ether solution was evaporated to 100 ml. and dry hydrogen chloride slowly bubbled through the solution until the addition of more gas failed to cause further precipitation. The white amorphous amine hydrochloride (1.58 g., 92?)) was filtered and washed with liberal portions of ether, m.p.- 208-215°. Several triturations under methylene chloride raised the melting point to 221-222°. Anal. Calcd. for CgH-^HOl: C, 63.71; H, 7-13; N, O 8.26; Cl, 20.89. Pound: C, 63.47; H, 7-H; N, 8 .38; Cl, 20.61. Benzocyclobutene-l-Carboxylic Acid (LXVI). - Amide LXIV (1.00 g.) was dissolved in hot 20% sodium hydroxide (15 ml.) and heated for 5 hours on the steam plate. The solution was then made strongly acid with conc. hydro chloric acid and extracted twice with 5:1 ether - 30-60° petroleum ether (100 ml.). The ether solution was passed through anhydrous sodium sulfate, evaporated to dryness and the residue taken up in a minimun amount of 30-60° petroleum ether. Cooling to -5° gave, in "two crops, 0.975 g. (97.5%) of the acid, m.p. 76.5-78°. Jive recrystal lizations from 30-60° petroleum ether gave material melt

ing at 78.5°• Anal. Calcd. for CgHgO^ C, 72.96; H, 5.4-4-; N.E. 148. Found: C, 72.60; -H, 5-58; N.E. 148. l,2-Bis-(trifluoroacetoxy)-Benzocyclobutene (LXIX). With stirring, and external cooling, a solution of diiodide XXXVII (80.0 g., 0.255 mole) in benzene (250 ml.) was add ed dropwise over a period of 1.5 hours to a solution of silver trifluoroacetate (103 g.» 0.466 mole) in benzene (750 ml.). The temperature was maintained at 13-15° throughout and when the addition was complete, the reac tion mixture was stirred for 1 hour longer at room temper ature. The silver iodide (97*0 g., theory 105*5 g.) was o filtered off and the filtrate evaporated in vacuo (1 mm.) to 70 ml. The solution was then heated at 80° for 1 hour and additional silver iodide (4.0 g.) filtered off. The filtrate was distilled and the fraction (50.2 g., 68/»), b.p. 85-90° (2.0 mm.) was collected. One recrystalliza tion of the solid material (m.p. 40-45°) from petroleum ether (50-60°) raised the melting point to 51-55°, sev eral recrystallizations from the same solvent afforded O an analytical sample of constant melting point, 55»5°*

Anal. Calcd. for C^FgHgO^: C, 45.92; 1 , 54.74;

H, 1.84. Found: C, 44.40, 44.12; F, 55.50, 55.07; H, o I .92, 2.08.

This compound is deliquescent and when exposed to the air, decomposes completely in 2-5 days.to a black, acid smelling tar. It is best stored under nitrogen in the freezer.

Hydrolysis of bis-trifluoroacetate (LXIX). - Bis- trifluoroacetate LXIX (9 g.) was dissolved in alcohol

(55 ml.) and shaken with 5% sodium carbonate solution

(400 ml.) for 16 hours. The solution was then continu ously extracted with ether for 24 hours. The ether ex tract (500 ml.) was passed through anhydrous sodium sul fate and evaporated to dryness-under reduced pressure leaving a white flaky material which could be separated into several amorphous fractions of varying ether solu bility. These fractions gave incongruent melting points

50-60°, 90s-100° , 250-250°, etc., and when dissolved in

50% sodium hydroxide gave a very transcient red color.

A sample of the most ether-soluble material, m.p. 50-60°

(sol. in pyridine, dil. alkoli, warm alcohol; insol. in benzene, methylene chloride) was dissolved in water to 71 give a clear solution from which a colorless amorphous

product separated rapidly after the addition of dilute -

mineral acid. ‘This material was dried and analyzed.

Anal. Calcd. for ( C g H g O ^ : C, 70.57; H, 5-92.

Found: C, 69.22; H, 6.17.

The Dinitrate Bsters of Cis and Trans 1,2-Benzocy-

ciobutenediol (LXXIa and LXXIb). - To a 500 ml. 2-necked

flask provided with stirrer and drying tube (Dehydrite)

were added diiodide XXXVII (46.5 g.» 0.1J0 mole) and sil

ver nitrate (47.6 g., 0.280 mole), each dissolved in ace-

tonitrile (150 ml.). The mixture was stirred at room

temperature and in the dark for 8 days'. At the end of

this time the precipitated silver iodide (58 g.) was fil

tered off and washed with acetonitrile (100 ml.). The

filtrate was concentrated under reduced pressure to ca.

75 ml. whereupon additional (4 g.) silver iodide (total

62 g., 100%) separated. The light yellow filtrate (150 ml. with washings) was again evaporated under reduced pressure to ca. 75 ial. and- water (400 ml.) was added.

The oil which separated from the aqueous phase was ex tracted into methylene chloride (250 ml.). After washing with water (400 ml.), the wet methylene chloride solution was dried thoroughly (sodium sulfate) and evaporated under reduced pressure until nearly all the solvent had been removed. At this point, crystallization of the residue o ° commenced and was essentially complete after cooling at 72

5° for fz houx'. The solid which separated was filtered

off, washed with 1:1 methanol-petroleum ether (15 ml.)

and recrystallized once from methylene chloxtlde-petroleum

ether (50-60°) to yield, in 2 crops, 8.0 g. (27/0 of

colorless needles, m.p. 107-109°. Slow recrystallization

from the same solvents gave LXXIa as colorless rhombs, m.p. 110°.

Anal. Calcd. for CgHgOg^: G, 42.48; H, 2.67;

H, 12.59. Found: C, 42.29, 42.50; H, 2.67, 2.59; N,

12.25, 12.42.

• The filtrate was cooled at -5° for 18 hours during which time the low melting isomer crystallized out. One recrystallization from methylene chloride-petroleum ether gave, in 5 crops, 15.5 g. (44-5%), m.p. 51-55°• Further recrystallizations from the same solvent gave LAXIb as white rhombs, m.p. 55.5-56.5°•

Anal. Calcd. for C g H g O ^ : C, 42.48; H, 2.67;

N, 12.59. Found: C, 42.24; 42.21; H, 2.88, 2.60; I f,

12.29, 12.51. 1,2-Diketobenzocyclobutene (LXXII). - Identical yields of this compound were obtained from either of the dinitrates LZXIa or LXXIb according to the following procedure: a solution of 2.0 g. of the dinitrate in 1:1 triethylamine-methylene chloride (10 ml., excess base) was refluxed 1.0 hours. Complete removal of the solvent at 25° (reduced pressure) left a dry, orange colored residue which, was taken up in methylene chloride. The solu

tion was washed with water (100 ml.), dried (sodium sul

fate) and the solid obtained on evaporation was sublimed

at 100° (0.2 mm.). The crude product thus obtained was

recrystallized from methylene chloride-petroleum ether and on resublimation afforded 0.878 g. (75%) of analyti cally pure product, m.p5. "132.5° • Pale yellow plates were

obtained on recrystallization from methylene chloride- petroleum ether.

Anal. Calcd. for CgH^Og: C, 72.75; H, 3*05.

Pound: C, 72.77; II, 3.08.

Quinoxaline and 2,4-DSPH Derivatives. - The quin oxaline derivative LXXIII liras prepared in 63% yield by combination of equimolar solutions (methanol, 4 ml. per

0.001 mole) of the diketone LXXII and o-phenylenediamines followed by the addition of glacial acetic acid (1 drop). ,

The product, which separated rapidly in long white needlds, was filtered off and washed with liberal portions of meth anol and petroleum ethex1, m.p. 238-239° - unchanged on recrystallization from methylene chloride-petroleum ether.

Anal. Calcd. for C^Hgl^: C, 82.33; H, 3• 95;

13.72. Pound: C, 82.21; H, 3.84;0 K, 13.83.

The amorphous and alcohol insoluble bis-2,4-DNPH derivative, m.p. 268-270° (dec.) did not require further purification when prepared in the absence of excess 2,4-

DHPIi reagent. Anal. Calcd. for C2q H12Nq °8: ^8.78; H, 2.46;

'n , 22.76. Found: C, 48.75; H, 2.69; N, 22.57.

Oxidation of 1 ,2-Diketobenzocyclobutene to Phthal-

ic Acid. - fjb.e diketone LXXII (0.100 g.) dissolved in 2 ml.

of 1:1 glacial acetic acid - 50% hydrogen peroxide (ex

cess) forming a colorless solution which, on evaporation

afforded 0.121 g. (theory 0.126 g.) of pure phthalic acid, O a m.p. 205°. A portion o'f this was sublimed, to give phthal

ic anhydride, m.p. 151-152°, which was undepressed on ad

mixture with an authentic sample. In addition, the infra

red spectra of both samples were identical.

Conversion of l,»2-Diketobenzocyclobutene to Phthal- » aldehydic Acid (LXXX). - To a methanol solution (5 ml.) of

the dilcetone LZXII (0.100 g.) was added 10% sodium hydrox

ide (5 ml.).® The color of the resulting’ solution faded

slowly on standing at room temperature. After 5 hours

(5 ml.) water and conc. hydrochloric acid (10 ml.) were

added to the coiffpletely decolorized solution, which was

then extracted twice with 150 ml. portions of ether. o Evaporation of the combined ether extracts (dried through o o sodium sulfate) gave a solid residhe which on recrystal

lization from methylene chloride-petroleum ether afforded

0.065 g. of phthalaldehydic acid, m.p. 97*5-98.5°, unde- ° 49 pressed by am authentic sample, m.p. 98.5“99*5°. In

^Kindly provided by the National Aniline Division of Allied Chemical and Dye Corp. addition, the infrared spectra of both samples were iden tical. Additional product was isolated conveniently as the 2,4-DEPH derivative, m.p. 2 6 3 ° ^ which with the free phthalaldehydic acid amounted to a composite yield of 94%.

Reaction of 1,2-Diketobenzocyclobutene with Potas sium t-Butoxide. - A small sample of the diketone LXXil

(0.050 g.) was dissolved in 5 ml.=of t-butyl alcohol and after adding 2 drops of 1^37 H potassium t-butoxide the flask was stoppered and allowed to stand overnight. Dur ing that time the color of the solution disappeared and a xtfhite crystalline product formed on the walls of the flask.

After evaporation of the solvent (reduced pressure), wat^r

(2 drops) was added. The residue was dissolved in methyl ene chloride, the solution dried (sodium sulfate) and on evaporation the residue partially sublimed (110°/0.2 mm.) to give ca. 0 .030-0.050 g. of colorless plates, m°.p. 129°

(sharp), which afforded 0.077 g. of a yellow ethanol in soluble 2,4-DITPH derivative, m.p. 247-248°. Ho attempt O was made to identify these products. ° O Reaction of C-is and Trans-1,2-l3enzocyclobutenediol

Dinitrates with t-Butoxide Ion. - A solution of the dini trate LXXIa (1.35 g*» 1.00 mole) in dry t-butyl alcohol

(20 ml.) was placed in a 50 ml. flask provided with reflux condenser. The solution was heated to reflux and 10 ml.

Rowe and ¥. Osborn, J. Ghem. Soc., 829-837 (1947) give 270°. 76

of 1.37 potassium t-butoxide (2.00 mole) added as rap

idly (caution) as possible, otherwise reaction was not

complete. When the vigorous exothermic reaction had sub

sided, the solution was evaporated (reduced pressure) un

til only a trace of solvent remained. The residue, a

light tan powder, was shaken vigorously with 30-60° petro

leum ether (200 ml.) and water (50.0 ml.). The ether

solution was dried (sodium sulfate) and evaporated on the

steam plate. The residue was 0sublimed at, 100° (0.2 mm.)

to give 0.327 g. of an oily sublimate contaminated in part

with t-butyl alcohol and unreacted dinitrate. After sev

eral recrystallizations (methylene chl°oride-petroleum

ether) and sublimations, 0.20 g. (14%) of pure 3-t-butoxy-

phthalide LXXXI was obtained, m.p. 87-88°.

Anal. Calcd. for Gj2^14^3: 69.88; h, 6.84;'

mol. wt., 206. Pound: C, 69*75; H, 6.72; bjoI. wt., 202

0 (isothermal distillation in methylene chloride). Infrared o spectrum (KBr): 3*37 Cm), 5*63 (s), 6.87 (m), 7*25 (m),

7*30 (m), 7.40 (m), 7.85 (m), 10.75 (s), 11.05 (s).

The aqueous phase of the extract was diluted to

250 ml. and an aliquot (10 ml.) ?>f this was added to con

centrated sodium iodide solution (25 ml., 20%). The io

dine liberated on acidification (acetic acid), as deter-0

mined by titration with standardized sodium thiosulfate,

corresponded to 1.92 moles (duplicate runs) of nitrate ion

originating from 1.00 moles of the nitrate ester. Similar yields of LXXXI (10-14%) were obtained by identical treatment of the low melting isomer, LXXIb.

An authentic sample of LXXXI was prepared according to the method of Wheeler et. al. Phthalaldehydic acid

(10 g.) and dry t-butyl alcohol (50 ml.) were refluxed for

5 hours. After cooling, the liquid reaction jnixture was poured into ice water (500 m l 6). The white precipitate which formed was filtered off, washed with ice water (500 o ml.) and dried at 50° (reduced pressure). The product weighed 5-5 g« (25%) and melted 79-81°• The infrared spectrum (methylene chloride soln.) of a sample showed it 0 o to be free of phthalaldehydic acid and was identical in all respects to the material, m.p. 87-88°, described above.

Eight recrystallizations from methylene chloride-petroleum ether afforded ca. 0.2 g. of pure LXXXI, m.p. 87-88°. Un depressed by a sample0 (m.p. 87-88°) of the material de scribed above.

Hydrolysis of LXXXI. - A sample (0.100 g.) of LXXXI was dissolved in hot 5% hydrochloric acid (5 ml.) and on evaporation gave 0.0755 g. (theory 0.0752 g.) of pure phthalaldehydic acid, m.p. 98-99°, identical with an au thentic sample^ (mix m.p. and I.R. spec.). o

APPENDICES o

7 8 APPENDIX I: INFRAHED ABSORPTION SPECTRA

The infrared spectra were obtained with a Baird

Associates Model B spect:eophotometer, employing sodium chloride prisms. Solids were run in carbon disulfide solution; liquids were examined as films. O

to ®

o T ransmission 00 80 - 0 4 80 40 60 60 20 20 2 iue 1,2 Figures _J,2 - D_J,2 i- iodobenzocyclobutene 1,2Di bromobenzocyclobutene - c C iue I Figure iue 2 Figure 4 o 6 O ae length,Wave 8 irn 0 microns © o q O O CQ o Transmission 0 -100 100 80 40 60 80 40 20 60 20 iu^ 3 4 3, Figur^t ezccouoin Dimer Benzocyclobufodiene Benzocyc loBenzocyc butene iue P\ 3 Figure iue 4 Figure ____ o o O o ae egh microns length, Wave O ° ° C- 03 Transmiss ion 0

-100 100 40 80 40 80 60 60 20 20 2 iue 5, Figures iue 6 Figure ezccouain Polymer Benzocyclobutadiene , ) 3 0 ( iue 5 Figure O o 4 rdc fo j J j from Product o oytrn I I I Polystyrene ezccouee t HF -t benzocyclobutene 6 ae egh microns length, Wave 8 o 10 12 14 16 00 ro Transmission 0-100 100 40 20 60 80 80 40 60 20 o iue 7 8 7, Figures Cyanobenzocyclobutene- iue 7 Figure o ezccoueeabxli Acid icBenzocyclobutenecarboxyl CN o e egh microns length, Wove o o CO T T ransmission o-ioo 100 60 - 80 80 20 40 60 40 20 iue 9 10 9. Fiaures Benzocyclobutenedione - Bromobenzocyclobutene - iue 9 Figure J 0 o o ae egh microns length, Wave O T T ransmiss ion 0-100 100 80 60 40 20 60 80 40 20 Figures Benzocyclobutene -I, Dinitrate; m.p. 55.5 - 56 5' 56 - m.p. 55.5 Dinitrate; Benzocyclobutene-1,2 _diol Din it rate iue 11Figure O''W°N02 o 2 0 N ° W rOr' ' F i g 12 u re .ONO. ONO; ono2 d iol o ae egh microns length, Wave % % Transmission o-ioo 100 0 8 0 6 0 4 60 0 8 20 0 4 20 iue !, 4 Q 14 !3, Figures Tetra iodide Tetra Tri Tri iod ide iue 13 Figure gur 14 re u ig F o O ae egh microns length, Wave C o o o o O O o 87

APPENDIX II: ULTRAVIOLET ABSORPTION SPECDBA

The ultraviolet spectra were obtained with a

Beckman Model D.U. spectrophotometer. Grain alcohol was used as the solvent.

o LJ Log 0 0 . 4 0 8 . 3 0 6 . 3 0 2 . 3 0 4 . 3 e r u g i F 220

IS 0 5 2 0 4 2 0 3 2 O o ae Length Wave , - bo obenzocyclobutene ibrom D - 1,2 x m/) o E Log /i) (m ax m A 5 . 3 7 2 2 6 3 0 8 2 6 6 . 3

J U 4.000 3.600

Log 4.400 3.800 3.400 .200- 4 e r u g i f 210 ------218- 0 2 -2 8 1 2 - 1,2 -Diiodobenzocyclobutene a (j. Lg E Log X (mjj.)max 286 - 288 - 286 i(a 220

4.32 3.73 230

3.80-

3.60

3.40 ~XT Tri iod ide

Q 3.20 A max (rryQ Log E 289 3.94

3.00

2.80

2.60- 230 240 250 260 270 280 290 W ave Length ( mju)

F i g u r e . 17 91

3.400

3.200

3.000

2.800

2.600 UJ

2.400

2.200

2.000

Benzocyclobutene .800 AmaxIm/i) Log E 260 3.09 265.5 3.28 .600 271.5 3.27

220 240 250 260 270 280230

_ Wave Length (mjut Figure J9 3.36 t-

3.16 -

2 .9 6-

2.76

UJ 2.56 - o> o

Benzocyclo butadiene Poly me r. X max(mn) Log E

262 3.16

267-268 3.29 274 3.28 l L J L_ 2 50 260 270 280 290 3 0 0 ( 310 320 vO Wave Length tv> Figure 19

o O U) Log 4.60 r 4.60 4.20 4.40 4.00 Figure 3.80 3.40 3.60 210 _ Xmax Xmax _ -Benzocyclobutadiene - 214 72 2 20 - 66 26 O ^ X . 5-273 215.5 Dimer m. Lg E Log (mp.)

4.50 3.96 3.93 32 0240 4 2 230220

o Wave Length Length Wave 250 (m^u) 260 270 280 290 vD \>l 4.6

4.4

4.2

4.0

3.8 liJ

E 3.6

3.4

32 Benzocyclobutenedione

- X max imp) Log E

3.0 224.5 4.59 291. 5 3.73 300 3.75 2.8 220 228 236 244 252 260 268 276 284 292 300 308 vO Wave Length (mp.1 Fiqurc 21 Figure Figure Log 3.6 3.3 3.4 3.5 3.2 2 2 - 2 9 3.0

7 I l i— l l I J 7 .8 3 26 240 236 232

|-Bromobenzocyc!o - |-Bromobenzocyc!o ----- Xmax ZZ 7 338 277 7 3.44 271 mu Lg E Log u) (m butene ^

------

4 252 248 a e egh (m Length Wave 256 260 fj.) Xn 264244 268 272 276 280 AUTOBIOGRAPHY

I, Donald Ray Napier, was born in Cumberland, Ken tucky, on December 16, 1931. My secondary school educa- tion was obtained in the public schools of Mount Dora, Florida, and my undergraduate training at Eastern Kentucky State College, which granted me the Bachelor of Science degree in 1953* In September, 1953 > I enrolled at The Ohio State University, where I acted as an assistant in the Department of Chemistry for the academic yeai's 1953-

1955* During the academic years 1955-1957 I received fel- © lowships from the DuPonteCorporation, the Ethyl Corpora- 0 tion, and the Research. Corporation. o