REACTIONS of HALOCYCLOPROPANES. The

Home , Cyclopropenone, Cyclopropenylidene, Favorskii reaction, Sodium trichloroacetate

This dissertation has been microfilmed exactly as received 69-11,652

HOUSER, Charles W., 1934- REACTIONS OF HALOCYCLOPROPANES.

The Ohio State University, Ph.D., 1968 Chemistry, organic

University Microfilms, Inc., Ann Arbor, Michigan REACTIONS OF HALOCYCLOPROPANES

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School o f The Ohio State U niversity

Charles W. Houser, B.A.

********

The Ohio State U niversity 1968

Approved hy

/Adviser Department of Chemistry Dedicated to

Jane and Brian

i l ACKNOWLEDGMENTS

The author wishes to express sincere appreciation to Professor

Harold Shechter for the inception of this problem and for his helpful

discussions throughout the course of this research. His editorial

guidance during preparation of this manuscript is also gratefully

acknowledged. National Science Foundation and Petroleum Research Fund

are thanked for their financial assistance to this research.

The author owes a special debt of gratitude to his wife, Jane,

for her patience and encouragement during completion of this work.

i i i VITA

October 20, 1934 Born - Parkersburg, West Virginia

1954-1958 U. S. Marine Corps

1962 B.A., David Lipscomb College, Nashville, Tennessee

1962-1965 Teaching Assistant, The Ohio State University, Columbus, Ohio

I965-I968 Research Associate, The Ohio State University, Columbus, Ohio

iv CONTENTS

Page

ACKNOWLEDGMENTS...... i i i

VITA ...... iv

TABLES ......

STATEMENT OF PROBLEM ...... 1

PART I

INTRODUCTION...... 7

DISCUSSION...... 19

Syntheses of polyhalogenated cyclopropanes ...... 19 Thermal reaction s o f halocyclopropanes ...... 22 Electrophilic reactions of halocyclopropanes with metal acetates ...... 27 Reactions of halocyclopropanes with bases ...... 28

PART II

INTRODUCTION ...... 46

Displacement reactions of 2,2-dichlorocyclopropylmethyl derivatives ...... 46

DISCUSSION...... 60

Displacement reactions of electronegatively substituted cyclopropylmethyl derivatives ...... 60

EXPERIMENTAL...... • 77

Preparation of 3-bromo-l,l-dichloro-2,2-dimethylcyclopropane . j8 Preparation of l,l,3-trichloro-2,2-dimethylcyclopropane . . . 79 Preparation of l,l-dibromo-2,2-dichloro-3,3-diraethyl- cyclopropane ...... 79 Preparation of l,l,2,2-tetrachloro-3-phenylcyclopropane. . . . 80 Preparation of methyl 2,2-dichloro-trans-3-phenylcyclopropanecarboxylate ...... 8l

v CONTENTS (Contd.)

Page Preparation of 2-(bromomethyl)-l,l-dichlorocyclopropane . . . 8l Preparation of l,l,2-trichloro-2-(chloromethyl)- cyclopropane ...... 82 Preparation of (2,2-dichlorocyclopropyl)methyl acetate .... 82 Preparation of (2,2-dichlorocyclopropyl)methanol ...... 83 Preparation of (2,2-dichlorocyclopropyl)methyl p-toluene- s u lf o n a t e ...... T ...... 83 Attempted preparation of (2,2-dichlorocyclopropyl)- metbylamine ...... 84 Preparation of (2,2-dichlorocyclopropyl)methylamine ...... 85 Preparation of 2,2,3,3-tetrachlorospiro(cyclopropane-l,9'- f lu o r e n e ) ...... 85 Preparation of methyl 2,2-dichlorocyclopropanecarboxylate . . 86 Preparation of l,l-dichloro-2-cyanocyclopropane ...... 87 Preparation of l,l,2,3-tetrachloro-2-(chloromethyl)cyclo- p ro p a n e ...... 87 Preparation of 2,2-dichlorocyclopropanecarboxaldehyde d ie th y l a c e ta l ...... 88 Preparation of 2,2-dichlorocyclopropanecarboxaldehyde 2,4-dinitrophenylhydrazone ...... 88 Thermal reaction of 3-kromo-l,l-dichloro-2,2-dimethylcyclopropane ...... 89 Thermal reaction of l,l,3" ‘trichloro-2,2-dimethylcyclopropane . 89 Thermal reaction of l,l,2,2-tetrachloro-3-phenylcyclopropane . 89 Thermal reaction of 2,2,3j3-tetrachlorospiro(cyclopropane- l ,9'-fluorene) ...... 90 Attempted thermal reaction of 2-(bromomethyl)-l,l- dichlorocyclopropane ...... 90 Attempted thermal reaction of l,l,2-trichloro-2-(chloro- me thy l) cyclopropane ...... 90 Reaction of l,l,3-trichloro-2,2-dimethylcyclopropane vith alcoholic potassium hydroxide ...... 91- Reaction of l,l,3-trichloro-2,2-dimethylcyclopropane vith lithium piperidide ...... 92 Reaction of 1,1,3-trichloro-2,2-dimethylcyclopropane vith potassium jt-butoxide ...... 93 Reaction of 3"’bromo-l,l-dichloro-2,2-dimethylcyclopropane vith n-butyllithium ...... 93 Attempted reaction of l,l,3-trichloro-2,2-dimethylcyclopropane with sodium h yd rid e ...... 94 Reaction of l,l,2,2-tetrachloro-3_phenylcyclopropane vith sodium h yd rid e ...... 94 Hydrolysis of 2,3j3-trichloro-l-phenylcyclopropene ...... 95 Reaction of 2,3>3“trichloro-l-phenylcyclopropene vith toluene catalyzed by aluminum chloride ...... 96

vi CONTENTS (Contd.)

Page

Reaction of methyl 2,2-dichloro-trans-3-phenylcyclopropanecarboxylate with methanolic potassium hydroxide . . 96 Reaction of l,l,3-trichloro-2,2-dimethylcyclopropane vith sodium ...... 97 Reaction of l,l,3~trichloro-2,2-dimethylcyclopropane with magnesium and methyl iodide ...... 98 Attempted reaction of l,l,3 -trichloro-2,2-dimethylcyclopropane and l,l-dichioro-3-bromo-2,2-dimethylcyclopropane vith zinc in a lco h o l ...... 99 Reaction of 3-hromo-l>-dichloro-2,2-dimethylcyclopropane vith silver acetate ...... 100 Reaction of 2-(bromomethyl)-l,l-dichlorocyclopropane with sodium methoxide ...... 100 Reaction of 2-(bromomethyl)-l,l-dichlorocyclopropane with potassium t-butoxide ...... 101 Attempted reaction of 2 -(bromomethyl)-l,l-dichlorocyclopropane with sodium hydride ...... 101 Reactions of 2-(bromomethyl)-l,l-dichlorocyclopropane with sodium cyanide ...... 102 Reaction of 2-(bromomethyl)-l,l-dichlorocyclopropane vith piperidine ...... 102 Reaction of 2-(bromoraethyl)-l,l-dichlorocyclopropane with triphenylphosphine ...... 103 Attempted oxidation of 2-(bromomethyl)-l,l-dichlorocyclopropane with dimethyl sulfoxide ...... 10*i- Reaction of 2-(bromomethyl)-l,l-dichlorocyclopropane with benzene and aluminum chloride ...... 10^ Reaction of 2-(bromomethyl)-l,l-dichlorocyclopropane with silver acetate ...... 106 Solvolysis of (2,2-dichlorocyclopropyl)methyl £-toluenesulfonate in acetic a c id ...... 106 Reaction of (2,2-dichlorocyclopropyl)methylamine with aqueous nitrous a c id ...... 107 Reaction of (2,2-dichlorocyclopropyl)methylamine- and nitrous acid in acetic a cid ...... 108 Attempted reaction of l,l,2-trichloro-2-(chloromethyl)- cyclopropane vith silver acetate ...... 108 Attempted reaction of l,l,2-trichloro-2-(chloromethyl)- cyclopropane with z in c ...... 109 Reaction of tetrachlorocyclopropene with phenyl(trichlorome thyl)m ercury ...... 109 Diels-Alder reaction of tetrachlorocyclopropene and cyclopentadiene ...... 110

v ii TABLES

Table Page

1. Reactions of Haloolefins with Phenyl(trichloromethyl)mercuiy ...... 21

2. Nuclear J-fegnetic Resonance Spectra of Cyclopropyl- carbonium Io n s ...... $2

3* Relative First-order Rate Constants for Solvolysis of Substituted Cyclopropylmethyl Arylsulfonates...... 58

Bimolecular Displacement Reactions of (2,2-Dichloro- cyclopropyl)msthyl Systems...... 62

5. Unimolecular Displacement Reactions of (2,2-Dichloro- cyclopropyl)methyl System s ...... 69

v i i i STATEMENT OF PROBLEM

1,1-Dihalocyclopropanes are readily prepared from olefins and dihalomethylenes or appropriate dihalomethylens transfer reagents.

Reactions of 1,1-dihalocyclopropanes vith metals or alkyllithium reagents result in 1,1-elimination to yield allenes (Equation l).

R R

R Metals + or *> RgCsC-CRg (1) RLi

1,1-Dihalocyclopropanes do undergo 1,2-elimination with strong bases such as potassium t-butoxide or potassium isopropoxide in dimethyl

sulfoxide (Equation 2); but this is usually a poor method for synthesis

R + Strong DM50 base > (2 )

of cyclopropenes because the intermediates readily undergo isomerization

to methylenecyclopropanes or addition of nucleophiles to yield cyclo

propane derivatives. Only highly-stabilized or sterically-hindered

cyclopropenes have been isolated using previous dehydrohalogenation methods. An in itial objective of this research vas to study dehydrohalogenation or dehalogenation of 1,1,2-trihalo- and 1,1,2,2-tetrahalocyclopropanes to determine if these polyhalocyclopropanes react by 1,1- or

1,2-elimination mechanism to give allenes or cyclopropenes advantageously

(Equation 3)*

•*- R2 c=c—CX^ H X

R R

Eliminations vith many different reagents under a vide variety of conditions were investigated. Initially, a study vas made of thermal reactions of l ,l ,3-trichloro-2,2-aimethylcyclopropane, 3-brono-l,l- dichloro-2,2-dimethylcyclopropane, 1,1,2,2-tetrachloro-3-phenylcyclopropane, and 2,2,3,3"tetrachlorospiro[cyclopropane-1,9'-fluorene]. This

study vas then modified to include metal-ion-assisted dehydrohalogenation of 3“t>ro:r‘0-l,l-d ichloro-2,2-diinethylcyclapropane and 1,1,3-

trichloro-2,2-dimethylcyclopropane.

Subsequently, an investigation vas made of the base-catalyzed dehydrohalogenation of 1,1,3-trichloro-2,2-dimethyIcyclopropane,

3-bromo-l,l-dichloro-2,2-dimethylcyclopropane, l ,l ,2,2-tetrachloro-3- phenylcyclopropane, and methyl 2,2-dichloro-tr£ns-3-phenylc.yclopropane-

carboxylate. A final elimination study was carried out on the behavior of

1.1.2-trihalo- and 1,1,2,2-tetrahalocyclopropanes with active metals.

An investigation was made of the reactions of 3-bromo-l,l-dichloro-2,2- dimethylcyclopropane, 1,1,3-trichloro-2,2-dimethylcyclopropane, and

1.1.2.2-tetra-3-phenylcyclopropane with sodium, magnesium, and zinc.

The need for developing a method of trapping cyclopropenes having halogen at olefinic positions led to a study of Diels-Alder reaction of tetrachlorocyclopropene with cyclopentadiene.

Synthesis of cyclopropenyl derivatives has stimulated much research into the practical aspects of their chemistry and into the theoretical interpretations of their behavior. The cyclopropenyl cation is the simplest system obeying the "Huckel Rule," which predicts special stability for cyclic and planar electron systems containing + 2

(N = 0) electrons.

After the first cyclopropenyl cation, triphenylcyclopropenium ion, had been synthesized, subsequent calculations were made which indi cated that there would be substantial delocalization and stability in cyclopropenones, methylenecyclopropenes, hydroxycyclopropenones, and benzocyclopropenium ions. Cyclopropenones and 3-hydroxy-2-phenylcyclopropenone were subsequently synthesized; but, benzocyclopropenium derivatives and 2,3-dihydroxycyclopropenone have not been prepared as y e t.

A second objective of this research was to develop an improved and v e r sa tile method fo r synthesis o f cyclopropenones, 2-hydroxycyclo propenones, and 9,10-phenanthr.ocyclopropenium derivatives. A study was made of the formation and reaction of the 2,3-dichloro-l-phenylcyclopropenium ion. Electrophilic substitution of aromatic nuclei with this ion might give diarylcyclopropeniura intermediates that are hydrolyzable to unsymmetrical diarylcyclopropenones (Equation 4).

Cl Cl Ar

Aid® + ArH -M l* 4 00

The study of the 2,3-dichloro-l-phenylcyclopropenium ion was extended to systems that might allow intramolecular Friedel-Crafts reactions to yield benzocyclopropene derivatives. An investigation was thus made of reactions of this ion at the 0,0'- positions of biphenyl and 3,3' ,5,5'-hexamethoxybiphenyl to yield 9*10-phenanthrocyclopropenium ions (Equation 5)*

/ (5)

A sa tisfacto ry- method is needed for preparing 2-aryl-3-hydroxy-

cyclopropenones; these cyclopropenolones are possibly convertible to

2-alkoxy-3-sryl-l-diazocyclopropenes. A study was then made of the

hydrolysis of 2,3>3-trichloro-l-phenylcyclopropane to 3-hydroxy-2-

phenylcyclopropenone (Equation 6). 5

Displacement reactions of cyclopropylmethyl derivatives occur at an unusually fast rate and frequently are accompanied by extensive rearrangement. A further objective of this research was to study bimolecular and unimolecular substitution reactions of (2,2-dichlorocyclopropyl)methyl and related derivatives. An investigation was sub sequently made of the synthetic utility of Sn2 reactions of

2-(broaomethyl)-l,l-dichlorocyclopropane with nucleophiles to prepare other (2,2-dichlorocyclopropyl)methyl derivatives as indicated in

Equation J.

6 Q CHgBr + X CH2X + Br (?) Cl Cl Cl

Of far greater importance, however, are reactions of (2,2- dichlorocyclopropyl)methyl derivatives by Snl processes. A study vas

thus made of the effects of chlorine on the extent of rearrangement of

the 2,2-dichlorocyclopropyl carbonium ion as generated unimolecularly

(Equation 8). Electron-withdrawing substituents in cyclopropyl , cups 6

,6 CH^X CHg c i V© Cl Cl Cl (8)

Cl C1v c h 2y + Y + ^ + CHg= CH-CHgCHgY \ \ Cl" Cl Cl Cl might favor formation of unrearranged products; v’nereaselectron- releasing groups do lead to increased amounts of ring-opened products.

An investigation vas thus made of solvolysis of 2-(bromomethyl)-l,l- dichlorocyclopropane and (2,2-dichlorocyclopropyl)methyl p-toluenesulfonate and deamination of (2,2-dichlorocyclopropyl)methylamine. PART I

INTRODUCTION

Dehydrohalogenation and dehalogenation reactions are of great importance in preparative and theoretical organic chemistry. Alpha or

1. 1-dehydrohalogenations and dehalogenations have been greatly over shadowed by the more familiar beta or 1.,2-eliminations. Eliminations of

1.1-dihaloeyelopropanes take place, however, by both mechanisms. Com plete dehalogenation of 1,1-dihalocyclopropanes occurs with active metals or organoraetallic reagents to yield allenes, nonhalogenated cyclopropanes, or in sertio n products. Magnesium, sodium on alumina, and alkyllithiums react with 1,1-dibromocyclcpropanes to produce allenes

(Equation 9)-^’^

R Metals + or ------9* R2C=C=C=R2 (9) RLi .

Br Br

(1) (a) W. von E. Doering and P. M. LaFlamme, Tetrahedron, 2, 75(1958); (b) P. D. G ardner and M. Narayana, J. Org. Chem., 26, 3158(1961).

(2) V/. R. Moore and H. R. Vara, J. Org. Chem., 25, 207 3 (i960); (b) W. J. Ball and S. R. Landor, Proc. Chem. Soc., 1^3(1961); (c) L. Skattebol, Tetrahedron Let., j>, 167(1961); (d) S. Ranganathan, Ph.D. Dissertation, The Ohio State University, 1962; (e) L. Skattebol, J. Org. Chem., 31, 2789(1966).

7 8

Allenes and cyclopropanes result from reaction of 2-alkyl-l,l-dichlorocyclopropanes with magnesium and an alkyl or aryl halide (Equation 10).

+ + RX RCH»C=CH2 + H ( 1 0 )

R = decyl

(3) T. J. Logan, Tetrahedron Let., £, 173(1961).

Reactions of such 1,1-dihalocyclopropanes take different courses when allene formation is suppressed. Thus, 9>9-3ibromobicyclo-

[6.1.0]non-2-ene and methyllithium give tricyclo[6.1.0.0^9]non-2-ene and tricyclo[6.1.0.Q'*,9]non-2-ene (Equation ll)A Treatment of

(k) C. C. Gsrdenas, B. A. Shoulders, and P. D. Gardner, J . Org. Chem., 32, 1222(1967). 7,7-dibromobicyclo[^.1.0]heptane -with methyllithium yields tricyclo- heptanes resulting from intramolecular carbon-hydrogen insertion

(Equation 12).^

CH^Li (1 2 )

( 5 ) W. R. Moore, H. R. Ward and R. F. M erritt, J . Am. Chem. S o c ., 83, 2019(1961).

With alkoxiae bases in dimethyl sulfoxide or alcohols,

1. 1-dihalocyclopropar.es undergo facile dehydrohaloger.ation via 1,2- elimination mechanisms. Isolation of cyclopropenes thus generated is extremely difficult because the intermediates are readily converted

(1) to me thylene- or vinylcyclopropanes by base-catalyzed isomerization o f the unsaturated intermediates or (2) to other cyclopropane deriva tives by addition of nucleophiles.

Recently, synthesis of cyclopropenes^ has been attempted by

1.2-eliminations of cyclopropanes. Dehydrobromination of ethyl trans-

(6) Cyclopropenes have been reviewed recently by (a) G. L. Closs in "Advances in Alicyclic Chemistry," H. Kart and G. J. Kara’oatsos, Eds., Academic Press, New York, N.Y., 1966, and (b) F. L. Carter and V. H. Frampton, Chem. Rev., 6h, i)-97(l96J0 •

2-bromocyclopropanecarboxylate with potassium t-bufcoxide gives only ethyl trans-2-"butoxycyclopropanecarboxylate. Using t-butanol-OD as solvent, it was shown that ethyl eyelopropenecarboxylate is the initial product; however, rapid addition of t-butanol prevented its isolation

(Equation 13)*^

co2c2h5 t-BuOD COgCgHj exchange t-BuOK Br V V

t-BuO ’2C2H5 / (13) “A co2c2h5 S = - - / 0; t-BuOD V

(7) K. B. Wiberg, R. K. Barnes and J. Albin, J. Am. Chem. Soc., 22, 1^ ( 1957).

Elimination of hydrogen bromide and isomerization to bicyclo-

[Jj-.1.0]hept-2-ene occurs when cis-7-brom obicyclo.1.0jheptane reacts Q vith potassium t-butoxide in dimethyl sulfoxide (Equation 1^). Under 11

(8) C. L. Osborn, T. C. Shields, B. A. Shoulders, J. F. Krause, H. V. Cortez, and P. D. Gardner, J . Am. Chem. S oc., 87 > 3158(1965)*

conditions l,l-dichloro-2-ethyl-3-methylcyclopropane yields vinylmethyl

enecyclopropane (Equation 15)

CH3 CH2CH3 CHg

DMSO + t-BuOK A i i " ch=ch2 Cl Cl

(9) T. C. Shields, W. E. Billups and A. R. Lepley, J. Am. Chem. Soc., OO, ^9(1968).

Elimination of a halocyclopropane to a cyclopropene is fre

quently accompanied by rearrangement and then addition of a nucleophile.

Thus, l,l-dichloro-_cis-2,3-dimethylcyclopropsne reacts with potassium

isopropoxide in dimethyl sulfoxide to give trans-2-isopropoxy-3-methyl-

methylenecyclopropane and 2-isopropoxy-2-methylmethylenecyclopropane

(Equation 16).^

CHg :CH2 CH CH 3 i-PrOK + DMSO ' / \ / \ CH3C H -) L \ L------1------pi.

O-i-Pr Cl Cl O-i-Pr 12

(10) T. C. Shields and P. D. Gardner, J. Am. Chem. S o c ., 89, 5425(1967).

Base-catalyzed isomerization of a double bond to a position external to the three-merabered ring generally occurs faster than nucleophilic addition to the intermediate cyclopropene except in systems where the rearranged product is very strained. Because the steric requirements for isomerization cannot be met easily, reaction of

7,7~dichlorobicyclo[4.1.0]heptane with potassium isopropoxide in dimethyl sulfoxide yields cis-l-isopropoxy-7-chlorobicyclo[4.1.0]heptane and cis-l,6-diisopropoxybicyclo[4.1.0]heptane (Equation 17). The product ratio depends upon the mole ratio of reagents.^

O-i-Pr O -i-Pr Cl .Cl i-PrOK + ^C 1 DMSO

Blocking of isomerization pathways and steric inhibition to . .

nucleophilic addition and to polymerization have made possible isolation

of two cyclopropenes prepared by dehydrochlorination. Thus, 1,1-

dichloro-2,2-dimethyl-3.-t-butylcyclopropane and 3-chloro-l,l-dimethyl-

-2-t-butylcyclopropane are converted to 2-chloro-3,3"^iciathyl-l-t-butyl-

cyclopropene and 3,3-dimethyl-1-t-butylcyclopropene respectively by

potassium t-butoxide in dimethyl sulfoxide (Equations l8, 19).^ *5

H Cl t-Bu Cl t-B u — Cl (1 8 ) + t-BuOK DMSO,

H H t-B u H Bu Cl

+ t-BuOK - 2 S 2 * (19)

H3C CH3 CH

( l l ) T. C. S h ield s, B. A. Loving, and P. D. Gardner, Chem. Comm., 556(1967).

Similarly, the 1,2-elimination route has been used successfully to prepare tetrachlorocyclopropene in high yield from pentachlorocyclopro- 12 pane and 18M potassium hydroxide (Equation 20).

H Cl CL Cl Cl Cl (20) + KOH

Cl Cl Cl Cl Ik

(12) (a) S. W. Tobey and R. West, Tetrahedron L e t., 1179(1963); (b) S. W. Tobey and R. West, J. Am. Chem. Soc., 88, 2^78(1966).

1,2-Dehydrohalogenations of cyclopropane derivatives have provided elegant syntheses of cyclopropenones. 13 Breslow and co-workers

(13) For reviews of cyclopropenones see: G. L. Closs, Ref. 6a; and A. W. Krebs, Angew. Chem., Intern. Ed. E n g l., k, 10( 1965). obtained diphenylcyclopropenone by reaction of phenylketene dimethyl acetal, benzal chloride and potassium t-butoxide. 2-Chloro-l,l- dimethoxy-2,3-

Hydrolysis then yields diphenylcyclopropenone (Equation 2 l).^

OH OCH 0CHC12 + t-BuOK + jZ/CH = C(OCH3)2

H3CO OCH3 (21)

OCH

(1*0 R. Breslow, R. Haynie and J. Mirra, J. Am. Chem. Soc., 8l, 2^7(1959).

Reactions of cL, -dihalo ketones with tertiary amines provide a more general cycloprooenone sy n th e sis. This method in volves a 15 modified Favorskii reaction in which the cyclopropanone in itially formed undergoes 1,2-dehydrohalogenation as indicated in Equation 22.^

0 II R-CH-C-CH-R (OaHsh” . I I Br Br Br

(2 2 )

R = alkyl or aryl

(15) (a) R. Breslow., T. Eieher, A. Krebs, R. A. Peterson and J. Posner, J. Am. Chem. £oc., 87, 1320(1965); (b) R. Breslow, L. J. Altman, A. Krebs, E. Mohacsi, I. Murata, R. A. Peterson and J. Posner, J. Am. Chem. Soc., 87, 1326(1965).

Cyclopropenones have also been prepared by hydrolysis of 3>3~

dihalocyclopropenes. Thus, diphenylacetylene reacts vith dichloro-

carbene, as derived from chloroform and potassium t-butoxideor

phenyl(bromodichloromethyl)mercury,^ to yield 3>3~dichloro-l,2-

diphenylcyclopropene which hydrolyzes rapidly to diphenylcyclopropenone

(Equation 23). Cyclopropenone can be generated in solution by 1 6

(16 ) (a) M. E. Volpin, Yu. D. Koreshkov, and D. N. Kursanov, Iz v . Akad. Nauk SSSR, Otd. Khira. Nauk, Ji, 56o(l959)j fa) D. N. Kursanov, M. E. Volpin, and Yu. D. Koreshkov, J. Gen. Chem. USSR, 30, 2855(l°6o).

(17) D. Seyferth and R. Damrauer, J. Org. Chem., _^1, 1660(1966). hydrolysis of 3}3-^ichlorocyclopropene; however, as yet the unsaturated l 8 ketone has not "been isolated (Equation 24).

( l 8 ) R. Breslow and G. Ryan, J. Am. Chem. S oc., 89, 3073(1967)*

A fourth method for preparing cyclopropenones utilizes reactions of the trichlorocyclopropenium ion. Careful hydrolysis of trichloro- cyclopropanium tetrschloroalu/ninate yields dichlorocyclopropenone

(Equation 25), a dangerously explosive liquid.^

\ 17 Cl

slow A1C1; hyd. / (25) Cl Cl ^ C 1

(19) R. West, J. Chickos, E. Osaws, J. An. Chem. Soc., 90, 3885(1968).

Electrophilic substitution on aromatic compounds by trichlorocyclopropenium tetrachloroaluminate gives diarylcyclopropenones upon hydrolysis (Equation 26).“® This method is limited to benzenoid

hyd. A1C1 * ( 26 ) Cl Ar Ar

Ar = phenyl p -to ly l p-chlorophenyl p-fluorophenyl

(20) S. W. Tobey and R. West, J. Am. Chem. £ o e ., 86, ^215 (196*0 •

derivatives as reactive aS halobenzenes. More electronegatively-

substituted benzenes do not undergo Friedel-Crafts reactions with

trichlorocyclopropenium tetrachloroaluminate. 18

Hydroxycyclopropenones are predicted to be strong acids because pi of the large resonance energies of their anions. x Much experimental

(21) (a) E. J. Smutny, C. Caserio, and J, D. Roberts, J. Am. Chem. Soc., §2, 1793(1960); (b) R. West and D. L. Powell, J. Am. Chem. Soc., 81, 2577(1963). activity has been directed toward preparation of hydroxy- and dihydroxy- cyclopropenones; however, 3-hydroxy-2-phenylcyclopropenone (pK a^2) is the only member of the series to be synthesized as yet. 3-Hydroxy-2- phenylcyclopropenone has been prepared by reaction of 2,3>3-trichloro-

-1-phenylcyclopropene or l , l , 3,3-tetrachloro-2-phenylpropene with 22 potassium t-butoxide and subsequent acidification (Equation 27).

0 Cl

KOt-Bu 1) KOt-Bu ClpC=C-CKClP 2 ) H3O0 0I Cl Cl

(27)

(22) D. G. Farnum, J. Chickos, and P. E. Thurston, J. Am. Chem. Soc., 86, 4206(196^). DISCUSSION

Syntheses of polyhalogenated cyclopropanes

A series of di-, tri-, and tetrahalocyclopropanes are needed for the elimination and substitution studies proposed. Prior to the discovery of reaction of phenyl(trihalomethyl)mercury reagents^ vith

(2 3 ) (a) 0. A. Reutov and A. N. Lovtsova, Dakl. Akad. Nauk SSSR, 139, 622(1961); (b) D. Seyferth and J. M. Burlitch, J. Organometal. Chem., 4, 127(1965)j (c) E. E. Senweizer and G. J. O'Neill, J. Org. Chem., 28, 851(1963); (d) T. J. Logan, Org. Syn., k6, 98 (1966).

pk olefins, polyhalogenated cyclopropanes could be synthesized only in

(2*0 The preparation and reactions of helocyclopropanes have been reviewed by V7. E. Parham and E. E. Schweizer, Org. Reactions, 13, 55(1963). poor yields. Using these mercurials, Seyferth et al. prepared a variety of dichlorocyclopropanes in high efficiency ^ This method has been

(25) D. Seyferth, J. M. Burlitch, R. J. Minasz, J. Y-. P. Mui, H. D. Simmons, J r ., A. J. H. Treiber, and S. Dowd, J. Am. Chem. S oc., 87, ^259(1965). presently extended to various olefins containing electron-releasing and electron-withdrawing groups.

19 20

The nev cyclopropanes vere prepared by reactions of the appropriately substituted olefins vith phenyl(trichloromethyl)mercury

(26) Tne preparation of phenyl(trichloromethyl)mercury by thermal decomposition sodium trichloroacetate in the presence of phenylmercuric chloride -was found to be advantageous. See Ref. 23d.

(Equation 2 8 ) and are summarized in Table 1. Reaction o f the d ich loro- methylene transfer reagent vith tetrachlorocyclopropene to yield hexachloro-1,3-butadiene is also included.

RX R RgC =CX2 + 0HgCCl3 + 0HgCL (28)

Reaction of phenyl(trichloromethyl)mercury vith acrolein diethyl acetal to yield 2,2-dichlorocyclopropanecarboxaldehyde diethyl acetal demonstrates that an acetal function is unaffected by phenyl(trichloro~ methyl)mercury, an acidic reagent. It is notevorthy too that the highly-strained haloolefin, tetrachlorocyclopropene, and phenyl(trichloromethyl)mercury gives hexachloro-l,3~hutadiene (Equation 29)* The

Cl Cl

C Cl

+ 0HgCCl- Cl Cl \ /

Cl Cl Cl Cl ci2 c=cci-cci=cci2 (2 9 ) 21 TABLE 1

Reactions of Haloolefins with Phenyl(trichloromethyl)mercury

Olefin Product ($ yield) B .P. (mm.) o r m .p. l-Bromo-2 -me th y l - 3-Bromo-l,l-dichloro-2,2- 78 -80 ° (15) propene dime thy Icy clopropane 72 ( ) 1 , 1-Dibromo-2 -me th y l 1,l-Dibromo-2,2-dichloro- 90-91° propene 3 , 3-dimethylcyclopropane (47) 1- C hloro-2 -methy1- 1 , 1, 3-Trichloro-2 , 2 -dim ethy1- 66- 68 ° (15) propene cyclopropane 62 ( )

9-Di chloromethylene- 2 ,2 , 3, 3“Tetrachlorospiro- 179-180° flu o ren e [cyclopropane-1, 9-fluorene](37 ) 2 , 3-Dichloropropene l,l,2-Trichloro-2-(chloro 90-92° (15) me thyl)cyclopropane 75 ( ) 6 , # -Dichloro- 1,1,2,3- Te tra chloro-3-pheny1- 63-64° sty re n e cyclopropane 60 ( )

1 , 2 , 3-Trichloro- ,1,1,2,3-Tetrachloro-2- 80 -84 ° ( 5 ) propene (chloromethyl)cyclopropane (54)

Tetrachlorocyclo- Hexachloro-1,3-butadiene propene Methyl trans- Methyl 2,2-dichloro-3-phenyl- 56-57° P7 cinnam ate cyclopropane carboxylate l i t . 65- 66° r

Acrolein diethyl 2,2-Dichlorocyclopropane- 103-105° (15) a c e ta l carboxaldehyde diethyl a c e ta l (60) Acrylonitrile l,l-Dichloro-2-cyano- 78-79° (15) 25 cyclopropane 23 ( ) lit. 78-79°(15) Allyl acetate 2,2-Dichlorocyclopropyl- 88 - 90° (15) methyl acetate (68 ) Allyl bromide 2- ( Bromome th y1)- 1 , 1- d i ch lo ro - 73-75° (15) p 5 cyclopropane (51) lit. 77-78° ( 2 3 )"

Methyl acrylate Nfcthyl2 ,2-dichlorocyclo- 69-71° (15) propanecarboxylate 36 ( )

27 British Drug Houses Ltd., Neth. Appl. 6 , 506, 88 l, Dec. 2, 1965; see Chem. A h str. 64: 17445f. 22

reaction probably proceeds via perchlorobicyclobutane which undergoes

valence isomerization to perchloro-1,3-butadiene. Isolation of per-

chlorobicycylobutane might be possible by use of milder conditions and

the more reactive mercurial, phenyl(bromodichloromethyl)mercury.

Thermal reactions of halocyclo pro pa ne s

A study vas made of pyrolysis of 3_,bromo-l,l-dichloro-2,2-

dime thyIcyclopropane,1 , 1, 3-trichloro-2 , 2-d ime thyIcyclopropane, and

l , l , 2 , 2 -tetrachloro-3-phenylcyclopropane to determine if they (l) lose

hydrogen halide or halogen via a 1, 2-mechanism to yield cyclopropenes or

a 1 , 1-mechanism to give allenes or 2 ( ) rearrange by rupture of the

"three-membered ring to form isomeric products. It was thus found that

when 3-bromo-l,l-dichloro-2 , 2-dimethylcyclopropane is heated to150 °,

evolution of hydrogen bromide begins and l,l-dichloro-3-m e th y l-l,3-

butadiene (Equation 30) is formed in 40$ yield along with a polymer

■3 CH3 Br -L5Q?------> CHg= t -CH=*CCl 2 + HBr (30)

Cl Cl

presumably the corresponding polyisoprene. Neither l,2-dichloro-3,3-

dimethylcyclopropene nor l,l-dichloro-3-methyl-l,2-butadiene was found.

The structure of l,l-dichloro-3-methyl-l,3-butadiene was deter

mined from its analytical and spectral properties. Its infrared

spectrum shows absorption for a carbon-carbon double bond (6 .2 u) and for hydrogen on terminal methylene (ll.O u), and trisubstituted ethylene

(11.9 u) groups; n.m.r. signals are at t (singlet, 1H ), t k-.'f

( q u a rte t, 2H), and t 7.9 (triplet, 3*0.

A possible mechanism of decomposition of3 "br°mo-l,l-dichloro-

2 , 2 -dimethylcyclopropane involves homolytic scission of the carbon- bromine bond to give the cyclopropyl radical (i). Collapse of I to the

(31)

highly-stabilized allylie radical (il) and hydrogen abstraction by bromine atoms can give l,l-dichloro-3-methy1- 1 , 3-butadiene and hydrogen bromide as indicated in Equation 31• Alternately, elimination of

hydrogen bromide from 3-bromo-l,l-dichloro-2 , 2-dimethylcyclopropane might occur by a cis-concerted process (Equation 32). 2k

The thermal elimination of 3-bromo-1,1-di chloro-2,2-dimethy 1- cyclopropane is analogous to pyrolytic conversion of l,l-dichloro-la,6a- 28 dihydrocycloprop[V,]indene to 2-chloronaphthalene (Equation 33).

Cl h eat (33) Cl

(28) W. E. Parham, H. E. Reiff, and P. Swartzentruber, J. Am. Chem. S o c., J8 , 1^37(1956).

Presumably, strain relief and delocalization in the transition state leading to the allylic radical (II) are driving forces in pyrolysis of

3-bromo-l,l-dichloro-2 , 2-dime thylcyclopropane.

The study was continued with l,l,3-trichloro-2,2-dim ethylcyclo- propane. When this trichlorocyclopropane is heated at l60-l6l°, its atmospheric boiling point, only slight decomposition occurs. The greater thermal reactivity of 3"bromo-l,l-dichloro-2 , 2-dimethylcyclopropane than of l,l,3-trichloro-2 , 2-dimethylcyclopropane must be due primarily to the relative weakness of the carbon-bromine bond.

l,l,2,2-Tetrachloro-3-phenylcyclopropane was pyrolyzed to deter mine if the phenyl group would alter the reaction so that cyclopropenes and/or allenes might be formed. At 200° for 0.5 hr., 1,1,2,2-tetra- c h lo ro3 - -phenylcyclopropane rearranges quantitatively to2 , 3 , 3j 3- t e t r a - chloro-l-pkenylpropene (Equation 3*0. Dehydrochlorination does not 25

Cl H Cl h e a t -> 0CH=CC1CC13 m

Cl Cl

occur upon thermolysis of l,l,2 , 2-tetrachloro-3-phenylcyclopropane, and

other possible products such as IH , IV, and V were not formed.

III - IV V

Structural assignment of 2,3,3>3-tetrachloro-l-phenylpropene was based on its analysis and spectral properties. The infrared spectrum

exhibits absorptions at 6.2 (olefin), 12.2 (hydrogen on trisubstituted

olefin), 13*0 and 1^.3 (monoaromatic substitution) u. The n.m.r.

spectrum has absorptions at t 2 .6 (multiplet, 5*0 and t 3*5 (singlet,

1H). The isolated proton signal is shifted downfield extensively by its olefinic and benzylic environment. The ultraviolet spectrum of the prod-

u c t (Xmax 232, E 16, 000) indicates a conjugating chromophore of the

styrene type.

Pyrolysis of l,l,2,2-tetrachloro-3-phenylcyclopropane may be

explained by cleavage of either cyclopropyl bond at the benzylic posi

tion to give the intermediate diradical (Vi) and simultaneous or subse

quent intramolecular migration of chlorine to the terminal position

yielding 2,3,3j3-tetrachloro-l-phenylpropene (Equation 35)* Similar

transformations are postulated when pentachlorocyclopropane and 2 6

H Cl ^CH-CClg-CClg * ------> (35)

0CH=CC1-CC13

l,l-dibromo-cis- 2 , 3-dime thy lcyclopropane thermolyze to1 , 1, 3, 3 , 3-p e n ta - 12 29 chloropropene and 3 ,h-dibromo-2 -pentene respectively.

(29) D. C. Duffey, J. P. Minyard and R. H. Lane, J. Org. Chem. 3 1 , 3865 ( 1966).

To study further the pyrolytic behavior of tetrachlorocyclo-

propane derivatives, 2 , 2 , 3 , 3*tetrachlorospiro[cyclopropane-1, 9 '-

fluorene] was thermolyzed. It was found that isomerization occurs to

give 9-(tetrachloroethylidene)fluorene (Equation36 ).

h eat (36)

Cl Cl C1 CC13 The structure of 9-(tetrachloroethylidene)fluorene was based on

its analysis and its infrared and ultraviolet absorptions. The infrared

spectrum exhibits bands at 6 .3 (olefin) and 13.2 (ortho-diaromatic

substitution) u. The ultraviolet absorptions ( Amax 21^, € 25,000;

^max ^ 7 , € 27 , 000; 277, € 19, 000) closely resemble values 27 reported for 9-ethylidenefluorene, 9-chloromethylenefluorene, and

(30) E. J. Greenhov, A. S. Harris, and E. N. White, J. Chem. Soc., 3116(195*0.

Electrophillc reactions of halocyclopropanes vith metal acetates

Displacement and elimination reactions of l,l,3-trichloro-2,2 dimethylcyclopropane and 3-bromo-l,l-dichloro-2,2-dimethylcyclopropane vith heavy metal acetates were then investigated. In refluxing acetic acid, 1,1,3-trichloro-2,2-dimethylcyclopropane and 3-bromo-l,1-dichloro-

2,2-dimethylcyclopropane react vith silver acetate or mercuric acetate to yield l,l-dichloro-3-methyl-l,3-butadiene (Equation 37) and polymers thereof. There was no evidence for formation of l,2-dichloro-3>3-

+ M(OAc)

C1 Cl

X = B r, Cl M = Ag, Hg dimethylcyclopropene or l,l-dichloro-3-methyl-l,3-butadiene in these experiments. The elimination product was identified by comparison of

its retention time and spectral properties to that of l,l-dichloro-3- methy1-1,3-butadiene obtained by thermal decomposition of 3-bromo-l,1- dichloro-2,2-dimethylcyclopropane. Reaction of 1,1,3-trihalo-2,2-dimethylcyclopropanes vith metal acetates is similar to conversion of l,l-dibromo-2 , 2 , 3 , 3-tetramethyl- 31 cyclopropane by silver acetate to 3-bromo-2,3-dimethyl-l,3-pentadiene.

(31) S. R. Sandler, J. Org. Chem., 3 2 , 3876 ( 1967 ).

Formation of l,l-dichloro-3-m ethyl-l,3-butadiene possibly occurs by metal-assisted removal of halide, ring collapse, and loss of a proton as indicated in Equation 3 8 .

H H H

Cl Cl Cl Cl (38)

X = B r, Cl M = Ag, Hg

0 •H CH3-C-CH=CCl2 HgCsC-CH^CClg

CH- CH- 3 3

These present results indicate that thermolysis and metal-ion catalyzed dehydrohalogenations of tri- and tetrahalocyclopropanes are not suitable for synthesis of cyclopropanes or allenes.

Reactions of halocyclopropsnss v it h bases

An investigation was then made of base-catalyzed elimination of hydrogen halide from 1,1,3-trichloro-2,2-diuethylcyclopropane, 3-bromo-l,l-dichloro-2,2-dimethylcyclopropane, and 1,1,2,2-tetrachloro-

-1-phenylcyclopropane.

Dehydrochlorination of l,l,3-trichloro-2,2-dimethylcyclopropane vas explored vith a number of bases for possible synthesis of 1,2- dichloro-3,3-dimethylcyclopropene, l,l-dichloro-3-metby1-1,2-butadiene, or products thereof (Equation 39)• It vas thus found that vhen an

(39) Cl

ethanolic solution of potassium hydroxide and l,l,3-trichloro-2,2- dimethylcyclopropane is refluxed, ethyl 3-methylcrotonate (42$), ethyl

3-methyl-3-butenoate (11$), and 3“Chloro-3-methyl-l-butynyl ethyl ether

(47$) are formed (Equation 40).

H3C H

h 3c - X KOH

Cl Cl The initial structural assignments to the two olefinic esters in the reaction mixture were based on the ethylenic substitution patterns of their infrared absorptions. The absorption at 11.8 u indicates the presence of hydrogen on the trisubstituted double bond in ethyl 3* methylcrotonate; absorption at 11.1 u is indicative of the terminal methylene (C=CHg) in ethyl 3“methyl-3-butenoate. The esters are separ able by gas chromatography, and the ethyl 3-niethylcrotonate was identi fied by comparison of its retention time with an authentic sample and by its n.m.r. signals at t ^-.5 (septuplet, 1H), t 6.0 (quartet, 2H), t 7*9

(doublet, 3H), t 8.2 (doublet, 3H) and 8.8 (triplet, 3H). Final con firmation of the structure of ethyl 3-niethyl-3-butenoate came from its n.m.r. spectrum which shows signals at t 5*2 (multiplet, 2H), t 5*9

(quartet, 2H), t 7*1 (singlet, 2H), t 8.2 (doublet, 3H) and t 8.7

(triplet, 3H).

3-Chloro-3-methyl-l-butynyl ethyl ether was separated by gas chromatography. The structure of the ether was derived from its analyt ical and spectral properties. The presence of a disubstituted acetylene group in the ether is indicated by-the infrared absorption at 4A u and the absence of acetylenic C-H absorption at 3*3 u; proton resonance is exhibited at t 6A (quartet, 2H), t 8.6 (singlet, 6H) and t 8.9

(triplet, 3H). Mass spectral peaks at ll/e 131 and 133 (M-15) in a 3:1 isotopic ratio confirm the presence of chlorine and the molecular weight of the ether.

The reactions of l,l,3-trichloro-2,2-dimethylcyclopropane with the hydroxide-ethoxide bases proceed by dehydrohalogenation of the 31 cyclopropane followed by addition of ethanol and hydrolysis. Mechanisms for the formation of ethyl 3-methylcrotonate can be envisaged utilizing either alpha or beta elimination pathways. Since none of the reaction intermediates could be isolated, the mode of elimination of VI is not known.

In a beta elimination sequence, ethyl 3-methylcrotonate is derivable by dehydrochlorination of l,l,3 -trichloro-2,2-dimethylcyclopropane to l,2-dichloro-3>3~dimethylcyclopropene (VII), base-catalyzed addition-elimination to cyclopropanone (VIII), and cleavage by alkoxide with loss of chloride ion (Equation 21). The latter reaction is part of the Favorskii system.

HoC Cl Cl

Cl Cl H^C CH3 (in) VII H3C Cl H3C —\ ------H e EtO > (CH3)2C=CHC02Et -Cl 0 VIII 32 Algha elimination of hydrogen chloride from l,l,3-trichloro-2,2- dimethylcyclopropane can also give l,l-dichloro-3-metby1-1,2-butadiene

(IX) as an intermediate which undergoes "base-catalyzed addition of ethanol and controlled hydrolysis to yield ethyl 3-methylcrotonate

(E quation 1+2).

Cl ©OH , , EtOH . ------» (CH3 )2C=C=CCl2 ------*> (1+2)

Cl Cl

(CH^J^CH-CClg-OSt ------> (CH3 )2 C=CHC02E t ^

Bie small amount of ethyl 3-ðyl-3-butenoate can arise from

base-catalyzed equilibration of its isomeric olefinic ester, ethyl

3-methylcrotonate (Equation 1+3)* Isomerizations of this type are quite 32 videly known.

CHg = C - CHgCOgCgH^ ~ > (CH3 )2 C=CHC02 C2 H 5 (1+3)

CH^

(32) C. D. Broaddus, Accounts Chem. Res., 1, 231(19^8).

Formation of 3-chloro-3-c:ethyl-l-butynyl ethyl ether can be

explained allylic rearrangement of l,l-dichloro-3-methyl-l-butenyl ethyl

ether (x) to l,3-dichloro-3-iaethyl-l-butenyl ethyl ether (XI) and base-

catalyzed elimination of hydrogen chloride (Equation 1+4). 3*Chloro-3- 33

:h3 ^C 1 NaCC2Hq (CH3 )§=CH-CCl20C2H5 J* Cl-C-CH=C

X XI JH3 m ci-c-cac-o-CgHj •a 3 methyl-l-butynyl ethyl ether can possibly be formed from 1,1,3-trichloro-

-2,2-dimethylcyclopropane by other mechanisms which cannot be ruled out at present.

Lithium piperidide in hot excess piperidine reacts with 1,1,3- trichloro-2,2-dimethylcyclopropane to give l-(3-methylcrotonyl)piperidine Equation ^5)* ®ae structure of the amide is based on its

h 3c h 0

Cl Cl chemical analysis and infrared and n.m.r. properties. Infrared absorp tion reveals the presence of strong amide carbonyl (6.0 u) and hydrogen on a trisubstituted ethylene (11.7 u). The n.m.r. absorptions at t **.3

(septuplet, 1H), t 6.7 (unresolved multiplet, Uh), t 8.2 (doublet, 3H), t 8 .3 (doublet, 3H), and t 8 .5 (unresolved multiplet, 6H) confirm the structure assigned. 1-(3-lfethylcrotonyl)piperidine may be formed from l,l,3-trichloro-2,2-dimethylcyclopropane by a mechanism similar to its ester analog (Equations 4l, 42).

Eae study of possible elimination of l,l,3-trichloro-2,2- dimethylcyclopropane and 3-bromo-l,l-dichloro-2,2-dimethylcyclopropane to l,2-dichloro-3,3-

-2,2-dimethylcyclopropane and l,l,3-trichloro-2,2-dimethylcycylpropane are unchanged by potassium t-butoxide in the above inert solvents.

Dehydrohalogenations of l,l,3-trichloro-2,2-dimethylcyclopropane and 3-bromo-l,l-dichloro-2,2-dimethylcyclopropane were then attempted in dimethyl sulfoxide, a polar solvent in which the previous bases are soluble. Reaction of the trihalodimethylcyclopropanes vith alkoxide bases in dimethyl sulfoxide is uncontrollable at 5° and yields polymeric m a te r ia ls .

Dehydrohalogenations of 3-bromo-l,l-dichloro-2,2-dimethylcyclopropane and 1,1,3-trichloro-2,2-dimethylcyclopropane vith sodium hydride and with sodiup^amide were then investigated in benzene, hexane and mineral oil. Elimination of these halides is impractical under the conditions because of their unreactivity and because the surface of each heterogenous base becomes coated vith impervious m aterials.

n-Butyllithium, a strong soluble base, reacts vith 3-bromo-l,1- dichloro-2,2-dimethylcyclopropane at ca. 25 - ° yielding n-butyl bromide and an intractable solid. In the same basic environment, 1,1,3- trichloro-2,2-dimethylcyclopropane gives n-butyl chloride and polymeric materials. The predominant reaction of these trihalodimethylcyclopropanes with alkyllithiums must be halogen exchange, and halocyclopropenes, if formed, probably undergo additional exchange reactions, thus destroying the product.

From the present study, it became apparent that unactivated cyclopropanes, such as 1,1,3-trichloro-2,2-dimetbylcyclopropane and

3-bromo-l,l-dichloro-2,2-dimethylcyclopropane, do not undergo elimina tion readily. An obvious factor is the strain involved in generation of a cyclopropene. In general, beta eliminations occur most rapidly when the departing groups are coplanar (dihedral angle is 0* or 180 ° ) .

(33) J. McLennan, Quart, Rev., 21, ^90(1967 )*

In a cyclopropane the rigidity of the ring prohibits coplanarity of the trans leaving groups, thereby, greatly retarding the trans elimination process, cis-1,2-Departing groups are coplanar in cyclopropanesj how ever, transition states resulting from their eliminations are consider ably less favorable stereoelectronically than are trans coplanar a n a lo g s.

A further difficulty in isolating l,2-dichloro-3j3-dimethylcyclopropene if formed by dehydrochlorination of l,l,3-trichloro-2,2- dimethylcyclopropane in polar solvents is that cyclopropenes are highly 34 susceptible to nucleophilic attack. 36

(3*1-) While the present work was in progress, Gardner and Shields successfully prepared l-chloro-3>3-diniethyl-2-t-butylcyclopropene by dehydrochlorination of 1,l-dichloro-2,2-dimethyl-3-t-butylcyclopro pane (Ref. ll). Generation of cyclopropenes in dehydrohalogenation of other halocyclopropanes was also demonstrated by effecting their trap ping with suitable nucleophiles. Tnus, reaction of 2,2-dichloro-3- methylvinylcyclopropane with potassium methoxide yields 2,2-dimethoxy-3- methylvinylcyclopropane (Ref.10). As a result of the work of Gardner and Shields, the present effort was restricted to development of methods for isolation and then for trapping of the intermediate cyclopropenes by reagents other than nucleophiles.

From the results of attempted dehydrohalogenation of 1,1,3-

trichloro-2,2-dimethylcyclopropane and 3-bromo-l,l-dichloro-2,2-

dimethylcyclopropane, it was apparent that halocyclopropenes, such as

l,2-dichloro-3,3-diniethylcyclopropene, if generated are highly unstable

and do not survive the experimental conditions. It was then decided to

investigate methods for trapping chlorocyclopropenes with conjugated oc ■ diolefins by reactions of th e Diels-Alder type as in Equation 46.

Cl Cl Cl

" Cl <*6 ) I

(35) Cyclopropenes react readily with dienes. Adducts o f cy clo - propene, 3-aethylcyclopropene, and 1,2-diphenylcyclopropene with cyclopentadiene have been reported previously. 3>3-Disubstituted cyclopro penes do not react with dienes. See G. L. Closs, Ref. 6a . A study vas then made of reaction of tetrachlorocyclopropene vith cyclopentadiene. Addition occurred readily at room temperature to give 2,2,3>**-tetrachlorobicyclo[3*2 .l]octa-2,6-diene (Equation Vf).

Cl Cl Cl

Cl Cl Cl XI (*7)

Cl Cl Cl Cl XII.

The adduct vas identified by its infrared and n.m.r. spectra. Strong double bond absorption appears at 6.2 u (-CC1=CC1-); n.m.r. signals are at t 3*3 (quartet, 1H), t 3*8 (quartet, 1H), t 6.2 (triplet, 1H),

t 6.8 (triplet, 1H) and a multiplet from t 7*3 to 7*9 (2H).

The product 2,2,3A-tetrachlorobicyclo[3.2 .l]octa-2,6-diene,

probably arises by initial formation of the bicyclic adduct XI, vhich

rearranges spontaneously via the ion XII to give the observed product

(Equation lt-7)* Further investigation in this promising area vas terminated when a paper appeared fully describing Diels-Alder reactions of halocyclopropenes withd ie n e s.36

(36) D. C. P. Law and S. W. Tobey, J. Am. Chem. Soc., 90/ 2376(1968).

It was then decided to determine the influence of groups that could activate elimination of halocyclopropanes and possibly stabilize cyclopropenes. Dehydrohalogenation of l,l,2,2-tetrachloro-3-phenylcyclopropane and methyl 2,2-di chlo ro-1ra ns-3-phenyIcyclopropanecar- boxylate, derivatives containing-strong conjugating groups, was studied in attempts to synthesize stable cyclopropenes. Hydrogen evolution begins immediately when 1,1,2,2-tetrachloro-3-phenylcyclopropane is added to a suspension of sodium hydride in benzene, and 2,3,3-trichloro-

-1-phenylcyclopropene^® is isolated in87 $ yield (Equation hQ),

f Cl H Cl Na H V / W /H------> . \/ + Hg

Cl Cl Cl Cl

(3-Elimination of 1,1,2,2-tetrachloro-3-phenylcyclopropane thus occurs efficiently.

The product was identified by its chemical and spectral analysis. The cyclopropene exhibits weak infrared absorption at 5*5 u

(cyclopropene ring); its n.m.r. spectrum reveals only an aromatic multiplet. Mass spectral analysis shows an isotopic cluster at m/e183 , 185 > and 187 (M-Cl); the fragments are attributed to the 2,3-dichloro-

-1-phenylcyclopropenlum ion (XIV). Subsequent reactions (see page ^-2)

Cl Cl

XIV provide additional evidence for the structure of 2 , 3, 3”trichloro-l- phenylcyclopropene.

Little reaction occurs, though, when methyl 2,2-dichloro-trans-

- 3-phenylcyclopropanecarboxylate is treated sim ilarly with sodium hydride. The ester reacts readily, however, with methanolic potassium hydroxide, but an intermediate cyclopropene could not be isolated;

3-carbomethoxy-3-phenylpropionic acid was obtained in 88 $ yield after hydrolysis (Equation M?)*

H 0CH-CH2CO2H

COoCHq Cl Cl

The structure of 3-carbomethoxy-3-phenylpropionic acid is based on the following evidence. Broad infrared absorption bands at 2.9

(hydrogen bonded 0-H) and 5*8 (hydrogen bonded carbonyl) indicate the

presence of a carboxyl group. The n.m.r. spectrum contains signals at

t 2 .9 (aromatic m ultiplet, 51l), t 6.0 (quartet, 1H), t 6 A (singlet, 3H) ho and a multiplet from t 6 .8 to 7-7 (2H). Basic hydrolysis of this half ester yields phenylsuccinic acid (m.p. 167 - 168 * ) . ^

(37) R. Auschutz, Ann., 117 (1907 ).

A possible mechanism for the formation of the monomethyl ester of phenylsuccinic acid is elimination of methyl 2,2-dichloro-trans-3- phenylcyclopropanecarboxylate to cyclopropene XV, base-catalyzed con version to eyelopropanone XVI, and cleavage by alkoxide to give the dimethyl ester (XVII, Equation $0)•

Cl H C02CH3 h 2 o 'OH e,OH

Cl Cl (50) XV 0 H

H e CHoO 3~ 0CH-CH2CO2CH3 0ch-ch2co2h I H20 I C02CH3 C02CH3

XVI XVII

The lesser hindered ester group is preferentially hydrolyzed during work-up, and 3“carbomethoxy-3-phenylpropionic acid is isolated.38

(38) H. L, Moal, A. Foucaud, R. Carrie, D. Danion and C. Fayat, Bull. Soc. Chim. France, 828, 196^ .

It has been found that phenyl and ester groups facilitate elimination of hydrogen halide from halocyclopropanes; however, the 1*1 ester group accelerates competitive Michael addition so that the inter mediate cyclopropene could not he isolated from the nucleophilic environment.

In order to overcome many of the problems encountered in base- catalyzed generation of cyclopropenes or allenes, a study was made of dehydrohalogenation or dehalogenation of halocyclopropanes with active metals (Equation 5l)* l,l,3-Trichloro-2,2-dimethylcyclopropane

-> (CH_ )_C=C=CXC1 Cl H3' Na (51)

1 ,2 -e lim .

X = H, Cl CK

3-bromo-l,l-dichloro-2,2-dimethylcyclopropane and 1,1,2,2-tetrachloro-

-3-phenylcyclopropane react with high-surface sodium or with magnesium and methyl iodide, but the reactions are uncontrollable and intractable materials (see Experimental section for details) are formed. It appears that the halogen-containing reaction products (see Equation 51) undergo rapid reaction with sodium and magnesium.•

Further investigation of methods of preparing cyclopropenes by dehydrohalogenation was then terminated, and a study of the chemistry of 2,3;3-trichloro-l-phenylcyclopropene was begun. Reactions of this 42 cyclopropene could provide (l) final proof of its structure, (2) a convenient synthesis of unsymmetrical diarylcyclopropenones or 9,10“ phenanthrocyclopropenium derivatives on reaction with appropriate aromatic compounds, and (3 ) an improved method for preparing 3-bydroxy-

-2-phenylcyclopropenone.

It was thus observed that 2,3,3-trichloro-l-phenylcyclopropene reacts readily with toluene when catalyzed by aluminum chloride yielding phenyl-£-tolylcyclopropenone after hydrolysis (45$, Equation 52).

f Cl Cl 1) 0CHc> A i d :— 2 ) HgO

XIV (52)

0 -P-CH3

Structural determination of the product was made by comparison of the

infrared spectrum (cyclopropenone bands, 5*4 and 6.2 u) and melting

p o in t (128 - 1290) with that reported for phenyl-£-tolylcyclopropenone as

prepared from phenyl(bromodichloromethyl)mercury and phenyl-p-tolyl-

acetylene and hydrolysis of the intermediate dichlorocyclopropene.17

The reaction probably proceeds by electrophilic attack on toluene by the 2,3-dichloro-l-phenylcyclopropenium ion (XIV) and hydrolysis of the

intermediate yielding phenyl-p-tolylcyclopropenone.

This reaction will probably be general and is of primary

synthetic value because it provides a method for introducing phenyl

groups bearing electron-withdrawing and electron-releasing substituents

on a cyclopropenone.

Generation of the 2,3-dichloro-l-phenylcyclopropenium ion (XIV)

in the presence of a biphenyl derivative might give a 9>10-phenanthro-

cyclopropenium ion. A mutual investigation was carried out with T. D.

Roberts in this laboratory of reactions of 2,3*dichloro-l-phenylcyclo-

propenium tetrachloroaluminate with biphenyl and with 3j3 ,>1S^ % 5 j5 i“

hexamethoxybiphenyl; however, all attempts to effect the desired reac

tion have failed thus far (Equation 53)*^

(53)

(39) R* West and D. C. Zecher, J. Am. Chem. S o c., 2K?, 152( 1967)*

A study was then made of a b e tter method of preparation of

2-hydroxy-3-phenylcyclopropenone. 2,3>3-Trichloro-l-phenylcyclopropene

is hydrolyzed by aqueous potassium hydroxide and subsequent acidification k k to 2 -hydroxy-3-phenyIcyclopropenone (7***5$> Equation 5*0• This product

1) Aq KOH

vas identified by comparison of its infrared spectrum and melting point 22 (100-101*) to that reported. This method is also adaptable for synthesis of cyclopropenolone analogs having variously substituted phenyl groups.

Like other c*--hydroxy- ot, ? -unsaturated ketones, 2-hydroxy-3- phenylcyclopropenone is alkylated readily yielding 2-alkoxy-3-phenyl- cyclopropenones (XVIIl). Thus arylation of 2,3>3-trichloro-l-phenyl-

0-R

XVIII cyclopropenone and alkylation of 2-hydroxy-3-phenylcyclopropenone provide practical routes to unsymmetrical diaryl- and arylalkoxycyclo- propenones.

A versatile synthesis of cyclopropenone derivatives vas desired for subsequent research efforts will be made to convert these ketones to ^5 diazocyclopropene precursors. A goal of that research, if successful, vill be the generation of cyclopropenylidene derivatives (Equation 55)•

N-NHTs

Base + TsNHNH„ ■TsH

(55)

n 2

- No

Ar Ar PART II

INTRODUCTION

Displacement reactions of 2,2- dichlorocyclopropylmethyl derivatives

Bie cyclopropylmethyl system has been of interest because of the rapidity vith which it undergoes displacement and the mechanistic challenge it presents. Bimolecular displacements occur at accelerated rates, and the cyclopropylmethyl carbon skeleton is maintained. Thus cyclopropylacetonitrile is formed from reaction of cyclopropylmethyl bromide and potassium cyanide (Equation 56).^® Triphenylphosphine also

(40) M. Hanack and H. M. Em sslin, Ann. Chem., 697 > 100(1966). effects nucleophilic displacement of bromide ion from cyclopropylmethyl bromide (Equation 57)^ Such bimolecular reactions of cyclopropylmethyl (4 l) (a) E. E. Schweizer, J. G. Thompson, and T. A. Ulrich, J . Org. Chem., 33> 3082(1968); (b) A. Jfeercker, Angew. Chem., 79 » 576(1967). derivatives have had limited use for synthetic purposes.

Unimolecular displacements, however, have received by far the most attention. The search for the reasons for the extensive inter

conversion of cyclopropylmethyl- and cyclobutyl derivatives and for the

structures of the intermediate cations has engendered much experimental 42 a c t iv it y .

(42) Reviews: (a) M. Hanack and H.-J. Schneider, Fortsch. Chem. Forsch., 8, 554(1967); (b) G. A. Olah and P. v. R. Schleyer, Ed., "Carbonium Ion s,*1 John Wiley & Sons, New York, N. Y. (1968); (c) H. G. RLtchey, p rivate communication; (d) N. C. Deno, Progr. Phys. Org. Chem., 2, 129(1964); (e) R. Breslow in ’’Molecular Rearrangements," Vol. I, P. de J-hyo, Ed., Interscience Publishers, Inc., New York, N. Y., 1963; (f) A. Streitweiser, Jr., Solvolytic Displacement Reactions, McGraw- H ill Book Co., Inc., New York, N. Y., 1962.

Cyclopropylmethyl and cyclobutyl derivatives are solvolyzed at

enhanced rates compared to th e ir saturated or a l l y l i c analogs and give

similar product ratios. For example, the solvolysis rate in aqueous

ethanol of cyclopropylmethyl chloride exceeds that of 3 -methallyl

chloride by a factor of 40;^^ cyclopropylmethyl benzenesulfonate

(43) J. D* Roberts and R. H. Mazur, J. Am. Chem. S o c., 73 > 2509(1951).

undergoes ethanolysis 500 times more rapidly than does ethyl benzene

sulfonate. Almost identical mixtures of cyclopropylmethyl, cyclobutyl

and 3~butenyl derivatives are obtained in deaminations of 48 cyclopropylmethylamine and cyclobutylamine at 0* (Equation 58)^3 with

CHgOH + OH

o r HNOc (58)

NHg> CH2=CH-CH2-CH20H

5* nitrous acid. Acetolysis of cyclobutanol p-toluenesulfonate also occurs with rearrangement to cyclopropylmethyl acetate (65$), cyclobutyl 44 acetate (22$) and 3-buten-l-yl acetate (13$) as shown in Equation 59*

0 II :2-oc-ch3+ OC-CH: CH3CO2H OSOgCyHY — u------=> 22$ (59)

CHg* ch-ch2-ch2-oac

13$

(44) J . D. Roberts and V. C. Chambers, J. Am. Chem. S o c ., 73 5034(1951).

In order to explain the enhanced reactivities and the similar '

product ratios resulting from reactions of cyclopropylmethyl or cyclo

butyl compounds, Roberts suggested that a ll products resulted from the

same intermediate, a symmetrical tricyclobutonium ion of pyramidal

structure, XVIII.^ +J / I \ +‘d - - - O f e

XVIII

(*5) (a) J . D. Roberts and V. C. Chambers, J . Am. Chem. S o c., 73j 503Ml95l); (b) J* D* Roberts, C. C. Lee, and W. H. Saunders, Jr., J. Am. Chem. Soc., J7, 303^(1955)•

Later experiments necessitated a change in the proposed struc- 1^ ture, I. Nitrous acid deamination of cyclopropylmethylamine-1- C gives products showing redistribution of activity; the label, however,

is not statistically distributed among the three methylenes as indicated

in Equation 60.^

27# 36# 1*5$ HNOr ch2oh + 28# — OH

(6 0 ) 27# 36# CHg-CH-CHg-'CHg-OH

33# 1# 66# 50

(1^) M. C. C aserio, W. H. Graham, and J . D. Roberts, Tetra hedron, 11, 171(1960).

Since a symmetrical tricyclobutonium ion should give equal isotopic distributions at C-2, C-3, and C-U in cyclobutanol and cyclopropyl- methanol, the experimental results were better rationalized by invoking rapid but not instantaneous equilibration of three pyramidal unsymmetrical bicyclobutonium ions (XIX, XX, and XXI). Substitution on

XIX XX XXI

Cg and then gives cyclobutyl, cyclopropylmethyl and homoallyl products respectively.^

A different and highly rewarding approach to the study of cyclo propylmethyl cations has involved nuclear magnetic resonance spectros copy. From analysis of n.m.r. spectra, information can be gained regard ing charge distributions in the ions, the effectiveness of cyclopropyl relative to other groups in delocalizing positive charge, and the geom etries of the ions.

The first cyclopropyl cation to be studied by the n.m.r. method was the tricyclopropylcarboniura ion. This ion is prepared by dissolving tricyclopropylmethanol in'concentrated sulfuric acid. The resulting solution exhibits an i-factor of k as required by the following balanced equation for ionization of an alcohol to a carbonium ion (Equation 6l).

G COH + 2HgS0^ ^ + H30 + 2HS0J| (61)

The presence of a new species in the solution is evident from the intense ultraviolet absorption ( ^max 270mu> £ = 22,000). Recovery of the parent alcohol by careful addition of the sulfuric acid solution to aqueous base indicates that the absorbing species can hardly be-polymeric or have a structure greatly different from that of the alcohol.

The n.m.r. spectrum of the solution consists of a single absorption at

2.26 ppm.^ The position of this absorption, downfield from the complex

(kj) N. C. Deno, H. G. Richey, J r ., J. S. Liv, D. N. Lincoln, and J. 0. Turner, J. Am. Chem. Soc., 8j> ^533(1965)* multiplet observed for the cyclopropyl hydrogens of tricyclopropylmethanol, is consistent with the influence of the positive charge in the io n .

Existence of other cyclopropylcarbonium ions as stable particles is based principally on the mode of preparation and on the n.m.r. spectra of their solutions (Table 2). Convincing evidence for the presence of most of the proposed cyclopropylmethyl cations is provided by their hydrogens as uniquely determined by n.m.r. spectroscopy. 52 TABLE 2 f Nuclear Magnetic Resonance Spectra of Cyclopropyl- carbonium Ions

Ion -H's -H's Other H Ref

^>-C® 7-7^(s) 1*7 3

| 0 4 6.5-7*1 7.2-7.7 1.8 (t) 1*7 L J2

ch3 7.00(m) 7.!*0(m) 7-72(s) 1*8

-0 6.7-7-0 7.15-7*55 1.90-2.1*5 a r y l H 1*9

6.72-7-11* 7.38-7.67 1.58-2.85 aryl H 1*9 H C+H is buried under aryl H's

6.10-6.1*1* 7 . 02- 7.18 7 . 1 * 8 ( s ) CH3 1*9 ch31 1.73-2.66 a r y l H's

!2 6 . 0 5 - 6 . 6 0 7 . 26 - 7.65 2.15-2.70 a r y l H's

w 0>_C-CH3 6.05-6.56 7.1*0(s) CH. 1*9 ^ CH3 6.86(s) CH3 53

(U8) N. C. Deno, J. S. Liv, J. 0. Turner, D. N. Lincoln, and R. E. Fruit, Jr., J. Am. Chem. Soc., 8j, 3000(1965).

(49) C. U. Pittman, Jr., and G. A. Olah, J. Am. Chem. Soc., Qj, 2998 (1965).

The absorptions of the cyclopropyl hydrogens of these cations

appear strikingly downfield from that at t 9*78 for cyclopropane.**® It

(50) K. B. Wiberg and B. J . N ist, J . Am. Chem. S o c., 8 3 , 1226(1961).

expected that the hydrogen absorption w ill be shifted downfield by the

presence of a positive charge and that the magnitude of the shift w ill

be proportional to the amount of charge on the carbon to which the

hydrogen.is attached. The large downfield shift of the beta-hydrogens

must be due to conjugation which places considerable positive charge on

the beta-carbons. The shift of the beta-hydrogen absorptions cannot be

caused only by the inductive effect of the positive charge because the

beta-hydrogens then would be affected much less than the alpha-

hydrogens. Resonance of the beta-hydrogens of the cyclopropyl group is

found to shift downfield with decreasing ability of other substituents

of the carbonium ion to delocalize positive charge (see Table 4). This

downfield shift reflects greater positive charge on the beta-carbons as

a result of increasing conjugation by the cyclopropyl group. For exam

ple, the cyclopropyl-

absorption unusually far downfield. The n.m.r. spectrum of the cyclopropyldimethylcarbonium ion is of further interest because of its structural implication. The spectrum o f th is ion in SOg-SOClF-SbF^ a t - 7 5 * shows that the methyl groups are chemically nonequivalent (singlets separated by 0.5^ ppm), but lie in a plane perpendicular to the plane of the three-membered ring. This orientation ("bisected” structure) is only reconcilable with the bicyclobutonium ion structure if it assumed that interconversion of the bicyclobutonium ions is fast compared to the n.m.r. time-scale.

Spectral studies of cyclopropylmethyl cations have supplemented the investigations. Intense ultraviolet absorption of such systems shows the strong conjugating effect of the three-membered ring. Consequently, tricyclopropylmethyl- and , £--dimethylcyclopropylmethyl cations give

A max ^ 0 mu (E 22,000) and 289 mu (E 10,800) respectively^ as com pared to that of the t-butyl cation (\max> 200 mu, E 500).-^ The

(51) (a) A. Olah, E. B. Baker, J. C. Evans, W. S. Tolgyesi, J. S. McIntyre, and I. J. Bastien, J. Am. Chem. Soc., 86, 1360(196^)] (b) G. A. Olah, C. U. Pittman, Jr., R. Waack and M. Doran, J. Am. Chem. S o c ., 88 , 1U88(1966). ultraviolet absorptions of cyclopropylmethyl cations do not, however, give much specific structural information.

As shown by n.m.r. methods, delocalization in cyclopropylmethyl cations relays positive charge to beta-ring carbons. Beta-ring substituents that can stabilize this charge should favor formation of ring-opened and/or ring-isomerized products at the expense of unre arranged products. Indeed, reaction of (2-methylcyclopropyl)methylamine vith nitrous acid gives l-penten-4-ol (35$)> 1-cyclopropylethanol51 ($), and (2-methylcyclopropyl)methanol (13$) (Equation 62)j ring opening in

CH OH HNO, I ch2= ch - ch2- ch - ch3 CH-CH 35$

CH-

deamination of cyclopropylmethylamine occurs only to an extent of 5$-^

(52) M. S. Silver, M. C. Caserio, H. E. Rice, and J. D. Roberts, J. Am. Chem. Soc., 8^., 3^71(19^1).

Reaction of (2-phenylcyclopropyl)methanol vith potassium hydrogen sulfate to give 1-phenyl-l,3-butadiene (Equation 63) as the

CH20H r /CH=CH-CH=CHg ^

sole product reflects the ability of a phenyl group to delocalize c h a r g e . 53 Similarly, the strongly electron-releasing phenoxy group

(53) H. M. Walborsky and J. F. Pendeton, J. Am. Chem. Soc., 82, 1^05(1959). promotes ring opening in reaction of (3-phenoxycyclopropyl)pentan-3-ol with sulfuric acid in that 4-ethyl-3-hexenal is formed (Equation 6 k ) . ^

0-0

C-OH HgSO^ 0 -0 -CH CH=C-(C2H c )2 1/ CH q

(6k) ?2H5 HgO CH3-CHg-C=CH-CHg-CHO -H®, -0OH

In contrast, 1-alkyl or aryl-substituted cyclopropylmethyl

derivatives yield 1-substituted cyclobutanols on solvolysis or deamina

tion. Thus (l-methylcyclopropyl)methylamine gives 1-methylcyclobutanol

upon diazotization with nitrous acid as shown by Equation (65)-^2

CH- CH- HNO2 (65) OH

Similarly, 1-phenylcyclobutanol acetate is the sole product from

acetolysis of (l-phenylcyclopropyl)methyl p-toluenesulfonate (Equa

tio n 66. 55

0 (66) CH^COgH \ 0 CHgOSOgCyHy II OC-CH. (55) D. D. Roberts, J. Org. Chem., 2712(1968).

The influences of electron donor ring substituents on the rates of solvolysis of substituted cyclopropylmethyl arylsulfonates have been determined and are summarized in Table 3* The rate enhancements produced by methyl substituents have a remarkably constant multiplica-

( c is - 2 ) (trans-2) ^

( tr a n s -3 ) (c is -3 )

tive effect; each additional methyl group accelerates the rate inde pendent of the number and location of its neighbors. The nearly identical rate increases by the methyl substituents in the 2 and 3 positions indicate that the beta-carbons participate to similar extents in the rate determining transition states possibly as in XXII-XXV; Schleyer and Van Dine suggest that the resulting intermediates have cis-

"bisected" structures (see page 5^ also). 58 TABLE 3 Relative First-order Rate Constants for Solvolysis of Substituted Cyclopropylmethyl Arylsulfonates

Cyclopropyl Substituents Relative Rate Ref

None 1

1-methyl 4 .0 56 cls-2-methyl 8.2 56 trans-2-methyl 11.0 56 cis-2-cis-3-dimethyl 82 56 cis-2-trans-31-dimethyl 80 56 trans-2-trans-3-dimethyl 124 56

2,2-dimethyl 92 56 trans-2,2,3-trimethyl 490 56

2,2,3,3-tetramethyl 1570 56 trans-2-ethoxy 940 56

1-phenyl 1.3 57 cis-2-phenyl 0.62 58 trans-2-phenyl 2.19 58 trans-2-trans-3-diphenyl 0.37 59

(56) P. v. R. Schleyer and G. W. Van Dine, J. Am. Chem. Soc., 88, 2321(1966).

(57) J* W. W ilt and D. D. Roberts, J . Org. Chem., 2 7 , 3^30(1962).

(58) R. A. Sneen, K. W. Lewandowski, I. A. I. Taha, and B. R. Smith, J. Am. Chem. Soc., 83, 4843(1961).

(59) (a ) R. Breslow, J. Lockhart, and A. Small, J. Am. Chem. S o c ., 84 2793(1962). (b) D. D. Roberts, J. Crg. Chem., 29, 294(1965). Phenyl substituents, however, have little effect on the solvolysis rates of cyclopropylmethyl derivatives (see Table 5). The explanation has been advanced that (l) the geometry of the interacting orbitals is unfavorable to maximization of the conjugative effect of the phenyl ring, (2) the inductive effect of the phenyl group is independent of its stereochemistry, and (3) the orbitals in the cationic portion of the transition state promote bonding intermediate between <7- and i r types thus resulting in near balance of the electron-donating (conjuga- tively via 7 T interaction) and electron-withdrawing effects (inductively via o- interaction) of the phenyl group.^

(60) D. D. Roberts, J. Org. Chem., ^3, 2712( 1968) and reference therein; see also M. Nikoletic, S. Borcic and D. E. Sunko, Tetrahedron, 21, 6^9(1967).

An examination of the literature showed that the unimolecular displacement reactions of electronegatively substituted cyclopropyl methyl derivatives have not been investigated. It seems possible that electron-withdrawing substituents w ill suppress unimolecular ring open ing or ring isomerization of cyclopropylmethyl cationic intermediates.

Cyclopropylmethyl derivatives containing beta-chlorine substituents have been synthesized and subjected to solvolysis and deamination. The results of this study are presented in the next section. DISCUSSION

Displacement reactions of electronegatively substituted cyclo propylmethyl derivatives

3he present investigation primarily involves study of (l) possi ble bimolecular displacement reactions of 2-(bromomethyl)-l,l-dichlorocyclopropane and related (2,2-dichlorocyclopropyl)methyl derivatives with various nucleophiles, (2) unimolecular solvolysis of (2,2-dichlorocyclopropyl)methyl p-toluenesulfonate in acetic acid and of deamination of (2,2-dichlorocyclopropyl)methylamine with nitrous acid in different environments, and (3) reaction of 2-(bromomethyl)-l,l-dichlorocyclo-

C1 Cl X = Br, 0S02C7H7, MHg propane with benzene in the presence of aluminum chloride. The princi

ple purposes of this study are to determine whether 2-(bromomethyl)-l,l- dichlorocyclopropane undergoes non-rearrangement displacement reactions of the Sn2 type which w ill be of value for studies projected for the future, whether the (2,2-dichlorocyclopropyl)methyl cationic system

involves isomerization of the cyclopropylmethyl-cyclobutyl-homoallyl

type (Equation 67), and whether further study of electronegatively

60 substituted cyclopropylmethyl and cyclobutyl derivatives might be of promise in developing the chemistry and mechanistic details of this controversial area. The structures of the products of reaction of

2-(bromomethyl)-l,l-dichlorocyclopropane, benzene and aluminum chloride vere established because they vere incident to study of the behavior of the (2,2-dichlorocyclopropyl)methyl cation in potential trapping

Friedel-Crafts systems.

A study has been made of reaction of nucleophiles such as sodium, methoxide, p ip erid in e, ammonia, triphenylphosphine and sodium cyanide- dimethyl sulfoxide with 2-(bromomethyl)-l,l-dichlorocyclopropane

(Table ^-). Sodium methoxide in methanol reacts readily with 2-(bromomethyl)-l,l-dichlorocyclopropane at 50° to give (2,2-dichlorocyclopropyl)methyl methyl ether (Equation 68). The displacement occurs

CH2Br + liaOi'

Cl Cl Cl Cl without structural alteration of the parent (2,2-dichlorocyclopropyl)- methyl system and on the basis of acceleration of reaction by sodium 62 methoxide is presumably of the Sn2 type. The identity of (2,2-dichlorocyclopropyl)methyl methyl ether is based on its analytical and spectral properties. Proton resonance signals which confirm the structure assigned are at t 6.52 (doublet, 1H), t 6.68 (singlet, total 3H) and t 8 .0-9.0 (complex multiplet, 3H). Infrared absorptions occur at 9«0 u

(C-O-C) and I3A u (CClg). The gas chromatographic retention time of

(2,2-dichlorocyclopropyl)methyl methyl ether is identical with that prepared from a lly l methyl ether and phenyl(trichloromethyl)mercury.

TABLE b

Bimolecular Displacement Reactions of (2,2-Dichloro- cyclopropyl)methyl Systems

Compound Reactant Temp. Product(s)

2 -(Bromomethyl)-l,l- CHgONa 50* (2,2-Dichlorocyclopropyl)- dichlorocyclopropane methyl methyl ether

2 - ( Bromome thy1 ) - 1,1 - 500 1-[(2,2-Dichlorocyclopropyl)- C5H10M dichlorocyclopropane methylJpiperidine

2- ( Bromomethy1) - 1 , 1- nh 3 50° (2,2-Dichlorocyclopropyl)- dichlorocyclopropane methylamine

2 -(Bromomethyl)-1,1- NaCN 25° (2,2-Dichlorocyclopropyl)- dichlorocyclopropane acetonitrile

2 - (Bromomethy1 )-1 ,1 - 03P 8o° [(2,2-Dichlorocyclopropyl)- dichlorocyclopropane methyl]triphenylphosphonium bromide)

Piperidine effects selective displacement of bromine from

2-(bromomethyl)-l,l-dichlorocyclopropane at 50° to yield l-[(2,2- dichlorocyclopropyl)methyl]piperidine and piperidine hydrobromide

(Equation 69). The substitution reaction parallels that of sodium C1 Cl methoxide and 2- (bromomethyl)-l,l-dichlorocyclopropane in that the carhon skeleton of the cyclopropylmethyl system is not isomerized. The structure of 1- [(2,2-dichlorocyclopropyl)methyl]piperidine is assigned from its elemental analysis, its infrared spectrum and its nuclear magnetic resonance. The product exhibits structurally significant infrared absorptions a t 8 .9 ; 9-6 (C-N o f t-amine) and 13 .4 u (CClg) and n.m.r. signals at t 7*4 (unresolved multiplet 6H) and t 8.4 (multiplet) vith a superimposed multiplet of cyclopropyl hydrogens from t 8 .0-9*0

(total 9*0. That this amine has the cyclopropylmethyl skeleton is demonstrated as follows. Ring opened products are excluded by the lack of infrared double bond or n.m.r. vinyl proton absorptions. Cyclobutyl derivatives are eliminated by the position and integration of the t 7'-^ signal of the n.m.r. spectrum of the product. The absorption at t 7*4 is due to the protons adjacent to the nitrogen atom. A total of six protons occupy such a position in 1- [(2,2-dichlorocyclopropyl)methyljpiperidine; integration of the spectra expected from the cyclobutyl derivatives derived from rearrangement would give only five such protons.

Similarly, ammonia and 2 -(bromomethyl)-l,l-dichlorocyclopropane in methanol at 50° give (2,2-dichlorocyclopropyl)methylamine 6k

(Equation 70)* (2,2-Dichlorocyclopropyl)raethylamine is of interest for studies to be described subsequently.

CI^Br + 2NH3 CH2NH2+ m ^ B r (70)

Cl Cl Cl Cl

The amine vas identified by its chemical and spectral proper ties. The product gives a Hinsberg test for a primary amine. Infrared absorptions characteristic of a primary amine appear at 2.8 (N-H stretch), 6.2 (broad, -EHg in plane bend) and 11.7 (very broad, -NH2 out of plane bend) u, along with C-Cl absorption at 13*^ u; proton resonance signals are at t 7-2 (triplet, 2H), t 8.55 (singlet) and t 8.0-9*0

(complex multiplet, total 5H)* Since the double bond region for infra red absorption i s masked by th at o f the amino group, the ring opened product, 2,2-dichloro-3-butenylamine, is excluded by the absence of nuclear magnetic resonance for vinyl protons. Cyclobutane derivatives are ruled out by the n.m.r. absorption at t 7*2. This resonance arises from protons on carbon adjacent to nitrogen and integrates as two protons. The triplet multiplicity of this resonance is due to addi

tional couplings resulting' from the asymmetric center.

Triphenylphosphine is also an effective nucleophile for displacement of bromine in 2-(bromomethyl)-l,l-dichlorocyclopropane in that [(2,2-dichlorocyclopropyl)methyl]triphenylphosphonium bromide

(Equation 7l) is formed in 6l$ yield at 80°. 65

(71)

c i c i Cl Cl

Kie product gives an immediate bromide test with silver nitrate and exhibits strong and very sharp infrated absorptions at 6.9 and 8.9 u.

2-(Bromomethyl)-l,l-dichlorocyclopropane reacts with sodium cyanide at 25* in dimethyl sulfoxide, yielding (2,2-dichlorocyclopro- pyljacetonitrile (Equation 72).^ The structure of the nitrile is

CHgCN (72)

Cl Cl indicated from its spectral properties. The product shows strong infrared absorption at U.5 (nitrile) u; n.m.r. signals are at t 7*9

(doublet, 2H) and t 8.0-9.0 (complex multiplet, 3H). The product must have the cyclopropylmethyl carbon skeleton (l) because it does not exhibit infrared double bond absorption or vinyl proton resonance and

(2) because of the signal position (t 7*9) and the integration (2H) of

its external methylene protons. This displacement with cyanide ion is noteworthy in that competitive oxidation of 2- (bromomethyl)-l,l- dichlorocyclopropane by dimethyl sulfoxide is not serious and there are no structural complications in the displacement reaction arising from

dimethyl sulfoxide functioning as an ionizing solvent. 66

Oxidation of activated halides hy dimethyl sulfoxide results in rapid formation of aldehydes and ketonesO xidation of 2-(bromo-

(6 l ) N. Kornblum, W. J . Jones and G. J. Anderson, J . Am. Chem. Soc., 8l, 4113(1959) and A. P. Johnson and A. Pelter, J. Chem. Soc., 520(1954). methyl)-l,l-dichlorocyclopropane by dimethyl sulfoxide does occur rapidly (see Experimental); however, 2,2-dichlorocyclopropanecarboxaldehyde (see below) could not be prepared effectively by this method.

2,2-Dichlorocyclopropanecarboxaldehyde diethyl acetal has been obtained

(see Experimental) by reaction of acrolein diethyl acetal with phenyl-

(trichloromethyl)mercury and converted to 2,2-dichlorocyclopropanecar- boxaldebyde 2,4-dinitrophenylhydrazone. 2,2-Dichlorocyclopropanecar- boxaldehyde is of interest as an intermediate for generation of

(2,2-dichlorocyclopropyl)methylene.

Upon finding that bimolecular displacements on 2 -(bromomethyl)-

1,1-dichlorocyclopropane could be effected satisfactorily and without apparent isomerization, a study was initiated of the products formed in unimolecular electrophilic reactions of (2,2-dichlorocyclopropyl)methyl and related cationic systems. The objectives of this effort were to determine the effects of the electron-withdrawing chlorine substituents on the possible cyclobutyl and the homoallyl cationic interrelationship of this cyclopropylmethyl process. It is possible that the electro negative chlorine atoms might repress or eliminate rearrangement in these cyclopropylmethyl carbonium ion processes. A study was then made of solvolysis of (2,2-dichlorocyclopropyl)methyl p-toluenesulfonate prepared in pyridine from p-toluenesulfonyl chloride and (2,2-dichlorocyclopropyl)methanol as derived from saponification of

(2,2-dichlorocyclopropyl)methyl acetate (Equation 73; see Experimental).

NaOH CHgOH C7H7SO2CI

Cl Cl Cl Cl (73)

Cl Cl

Acetolysis of (2,2-dichlorocyclopropyl)methyl p-toluenesulfonate at 100° in acetic acid containing one equivalent of sodium acetate^

(62) The acetolysis conditions are similar to those used for unimolecular reaction of a variety, of substituted cyclopropylmethyl t o s y la te s . yields only (2,2-dichlorocyclopropyl)raethyl acetate (Equation 7*0 and

CH2-OSO2C7H7 CH3C02H CHgOCCH^ (7*1-) CH^COjNa C1‘ Cl recovered (2,2-dichlorocyclopropyl)methyl p-toluenesulfonate. The important feature of the displacement process is that reaction takes place vithout formation of isomerization products of the cyclobutyl and homoallyl types or derivatives thereof. It is also apparent that acetolysis takes more slowly than those reported for cyclopropylmethyl p-toluenesulfonate and its derivatives containing electron-donating substituents in the 2-position of the cyclopropyl group.5^ The structure of the (2,2-dichlorocyclopropyl)methyl acetate was established by direct comparison (infrared and n.m.r. absorption and chromatographic properties) with the acetate as prepared previously from allyl acetate and phenyl(trichloromethyl)mercury.

In an effort to-generate the (2,2-dichlorocyclopropyl)methyl cation as a more discreet and perhaps a more energetic and thus rearranging cation than that from acetolysis of (2,2-dichlorocyclopropyl)raethyl p-toluenesulfonate, the reaction of 2-(bromoraethyl)-l,l- dichlorocyclopropane and silver acetate was investigated. The function of the silver acetate was to effect nucleophilic catalysis on (pseudo) unimolecular electrophilic displacement of the dichlorocyclopropylmethyl bromide. Reaction of 2-(bromomethyl)-l,l-dichlorocyclopropane and silver acetate at 120°^ Was found to occur readily with formation of

(63) The relatively high temperature (120°) was used to enhance possible rearrangement processes. silver bromide. The only product of displacement, however, is (2,2- dichlorocyclopropyl)methyl acetate (Equation 75 > Table 5)* There was no evidence for formation of cyclobutyl or homoallyl products in this experiment.

ch3co2h 69

TABLE 5

Unimolecular Displacement Reactions of (2,2-DichlorO' eyelopropy1)me thy1 Systems

Compound Reactant Temp. Product

2-(Bromomethyl)-l,l- AgOAc 120# (2,2-Dichlorocyclopropyl)- dichlorocyclopropane methyl acetate

(2,2-Dichlorocyclopro- HOAc/ 100* (2,2-Dichlorocyclopropyl)- pyl)methyl p-toluene- NaOAc methyl acetate sulfonate *“

(2,2-Dichlorocyclopropyl)- NaNO 25* (2,2-Dichlorocyclopropyl)- methylamine HOAc2 methyl a ceta te (82$) and unidentified product (l8$)

(2,2-Dichlorocyclopropyl- NaNo2 18* (2,2-D ich lorocyclopropyl)- methylamine HOAc methyl acetate (92.5$) and unidentified product (7*5$)

(2,2-Dichlorocyclopropyl)- NaN02 25° (2,2-Dichlorocyclopropyl)- methylamine HC1 methanol (89$) and uni dentified product (11$)

(2,2-Dichlorocyclopropyl)- NaN02 0* (2,2-Dichlorocyclopropyl)- methylamine HC1 methanol (9 6 .5^) and unidentified product (^•5$) TO

The study of the (2,2-dichlorocyclopropyl)methyl cation as a reaction intermediate was then extended to deamination of (2,2-dichlorocyclopropyl)methylaraine by nitrous acid at various temperatures and in different acidic environments. Diazotative-decomposition of amines is a widely used method for effecting generation of high-energy carbonium ion intermediates -which may undergo isomerization and/or / fragmentation. 6k

(64) A. S tr eitw e iser , J r ., J . Org. Chem., 22, 861(1957)-

Indeed, as has been indicated previously, cyclopropylraethylamine under goes deep-seated rearrangement and isomerization upon reaction with nitrous acid . ^

(2,2-Dichlorocyclopropyl)methylamine reacts with sodium nitrite in glacial acetic acid at 25* to give (2,2-dichlorocyclopropyl)methyl acetate (82$) and an unidentified product (l8$) of higher gas chromato graphic retention time (Equation 76). Upon lowering the reaction

NaNOo ------£-----5> CK^OgCC^ (76 ) CH3C02H Cl Cl Cl Cl 25°, 82$; 0°, 9 2 .5$ temperature to l8c, conversion to (2,2-dichlorocyclopropyl)methyl acetate by nitrous acid in glacial acetic acid is increased to 92.5$ £ud that to unidentified product is lowered to 7-5$- It is clear that the principal reaction of nitrous acid and (2,2-dichlorocyclopropyl)methylamine occurs without structural alteration to yield (2,2-dichlorocyclopropyl)methyl acetate (Equation 76). 71

In an effort to minimize formation of the unidentified product from diazotization of (2,2-dichlorocyclopropyl)methylamine in acetic acid and also to determine if the nucleophilicity of the solvent might affect the reaction processes, diazotization of (2,2-dichlorocyclopropyl)methylamine was effected with sodium nitrite and hydrochloric acid in aqueous solution. At 25" deamination yields (2,2-dichloro- cyclorpopyl)methanol (8950) and an unidentified higher boiling product

(Equation j j ) . Lowering reaction temperature increases the amount o f

(77 )

25°, 89 $; 0°, 9 6.5# unrearranged alcohol to 96*5$• Diazotative-decomposition of (2,2- dichlorocyclopropyl)methylamine is thus more selective in water and at

lower temperatures. The greater selectivity of the deamination process in water than in acetic acid might stem from the greater nucleophilicity of water than of acetic acid.

The results of the present investigation of unimolecular reac

tions of (2,2-dichlorocyclopropyl)methyl systems do not allow final

conclusion relative to the structure or structures of the carbonium ion

intermediate(s) generated (such as XXVI-XXXI ) prior to capture by the

environment. It is clear, however, that the 2,2-dichloro substituents greatly retard formation and minimize net homoallyl and cyclobutyl

structural isomerization of the 2,2-dichlorocyclopropylmethyl cationic 72

CHg

.Cl Cl Cl XXVI CL XXVII XXVIII Cl Cl Cl

Cl V-3 2 \ 3 + Cl XXIX XXX XXXI intermediate(s) or derivative(s) apparently generated. The dominant effect of the chlorine substituents likely stems from their electron withdrawing demands functioning through the intracyclic partial p bonds of the cyclopropyl group. Thus it is probable that the resistance to formation and to isomerization of the (2,2-dichlorocyclopropyl)methyl cation as compared to the cyclopropylmethyl cation arises simply from the fact that a 2,2-dichlorocyclopropyl group is more electron deficient than is a cyclopropyl group.^

(65) It has been observed that 1,l,2-trichloro-2-(chloromethyl)cyclopropane is essentially unchanged by silver acetate in refluxing glacial acetic acid in 36 hours (see Experimental).

It w ill be of interest to examine the (2,2-dichlorocyclopropyl)- methyl cation in greater detail. Of particular value will be study of unimolecular displacement of (2,2-dichlorocyclopropyl)- -dideutero- methyl systems to determine whether the carbinyl and the 3~cyclopropane methylene group become (p a rtly ) equivalent during rea ctio n . D irect Cl Cl observation of the cation or related electronegatively-substituted cations might be possible using n.m.r. methods. Since the methylene groups in the 2- and the 3-positions in cyclopropylmethylamine are considerably less than statistically scrambled in deamination to cyclo- propylmethanol, it may veil turn out that there w ill not be any struc tural alteration involving interchange of the C-l and the C-3 methylene groups. What is indeed now obvious from the present work is that synthesis and study of a variety of electronegatively-substituted cyclopropylmethyl intermediates are very feasible at present and offer real opportunity for determining structural and electronic transmission effects in such systems.

A study was also made of reactions of 2-(bromomethyl)-l,l- dichlorocyclopropane with Lewis acids in attempts to generate the

(2,2-dichlorocyclopropyl)methyl cation. Intractable materials result from 2 -(bromomethyl)-l,l-dichlorocyclopropane and Lewis acids in non reactive solvents. However, 2- (bromomethyl)-l,1-dichlorocyclopropane i s converted by aluminum chloride in the presence o f benzene to

3-methyl-2-phenylindene^ along with 2,3-diphenyl-l,3-butadiene

(66) W. Hausraan and A. E. W. Smith, J. Chem. Soc., 1030(19^9)• (Equation 78). The system provides no real information relative to

r + '0 P P

Cl CH the stability of the (2,2-dichlorocyclopropyl)methyl cation; but, it leads to an efficient synthesis of 3-methyl-2-phenylindene (8l$ ).

The structures of the products were determined from their analyt ical and spectral properties. Mass spectral analysis of the mixture gives a molecular ion at M/e 206 (calcd. 206); then, the components were separated by preparative gas chromatography. 3-Msthyl-2-phenylindene

shows aromatic monosubstitution and ortho-disubstitution infrared bands at 13.2, 13*7> and 14.3 u, and n.m.r. absorptions are at t 3*3 (multiplet, 10H), t 6.3 (quartet, 1H, J = 7 c p s), and t 8 .8 (doublet, 3H,

J = 7 cps). The identical coupling constant indicates that the hydrogen and the methyl group are attached to the same carbon atom.

2 ,3-Diphenyl-1,3-butadiene exhibits diagnostic infrared absorp

tions at 6.2 (olefin), 11.1 (hydrogen on terminal methylene), 12.8 and

14.3 (monoaromatic substitution) u; proton resonance signals appear at

t 3«2 (rau ltip let, 10H)and 5*12 ( s in g le t, 4ll).

One possible mechanism for formation of 3-methyl-2-phenylindene

and 2,3-diphenyl-1,3-butadiene involves initial generation of the

cyclopropylm ethyl ca tio n , XXXII, rearrangement to XXXIII, and e le c tr o -

philic attack on benzene to give XXXIV; the reaction continues by

removal of chlorine and electrophilic attack yielding the diphenylated specie, XXXV; and the transformation is completed by removal of residual chlorine, cyclization of the ion, XXXVI, and isomerization to give

3-methyl-2-phenylindene. Loss of a proton from XXXVI gives 2,3- diphenyl-1,3-butadiene as indicated in Equation 79*

-CHg CH

Cl Cl Cl Cl Cl

XXXII XXXIII

XXXVXXIV

XXXVI 76

CH CH

XXXVI ---- =H?------^ CH2=C-C=CH2

The cyclization of 2 ,3~diphenyl-l,3-butadiene to 3-methy1-2- phenylindene by dry hydrogen chloride in acetic anhydride has been observed previously.^ EXPERIMENTAL

Melting points.--A ll melting points were taken in open capillaries in a Hirshberg or a Thomas Hoover melting point apparatus and are uncorrected.

Elemental analyses.--Elemental analyses were performed by

Galbraith Laboratories, Inc., Knoxville, Tennessee, or by Microanalysis,

Inc., Wilmington, Delaware.

Infra red s pe c tra.—All Infrared spectra were obtained with a

Perkin-Elmer Infracord recording spectrophotometer. The spectra of liquid samples were recorded neat; solid samples were recorded as KBr w afers.

Nuclear magnetic resonance spectra.--A ll nuclear magnetic resonance spectra were determined in carbon tetrachloride or chloroform-d using tetramethylsilane as an internal standard with a Varian

Associates nuclear magnetic resonance spectrophotometer, Model A-60.

Ga s chroma tog ra phy.- -Ga s chromatographic analyses were carried out on ( l ) an Aerograph instrum ent, Model A-90, connected to a 1.0 m illivolt full-scale deflection Sargent recorder and (2) an F and M u n it, Model 720, equipped with a 1 .0 m illiv o lt f u ll- s c a le d e fle c tio n

Honeywell Electronic 15 recorder. Helium was used as the carrier gas.

The Aerograph, Model A-90, was equipped with a column (10' x l/V ) o f SE-30 (15^) on Chromosorb W; the F and M, Model 720, was

77 78 equipped w ith a column (10' x 3 /8 ”) of SE-30 (20$) on Chromosorb W unless specified otherwise.

Preparation of 3-bromo-l.l-dlchloro- 2 ,2-dimethylcyclopropane

Under nitrogen phenyl(trichloromethyl)mercury^ (309 g ., O.78

(66) Prepared from phenylmercuric chloride and sodium trichloroacetate by the method of T. J. Logan. Ref. 23d. mole was added to freshly distilled l-bromo-2-methylpropene^ (500 ml.,

(6 7 ) Prepared by the method of E. A. Braude and E. A. Evans, J. Chem. Soc., 332^(1955). b.p. 92*). The stirred mixture was refluxed overnight during which time the starting mercurial dissolved and phenylmercuric chloride precipi tated. The cooled mixture was filtered and most of the excess starting olefin was removed by distillation. Treatment of the remaining solution with pentane precipitated additional phenylmercuric chloride (22^ g., total 91$) • After removal of the pentane, distillation of the residue yielded 3-bromo-l,l-dichloro-2,2-dimethylcyclopropane (122.5 g., 72$, b.p. 78-80° at 15 mm.).

Calcd. for CjH^BrClg: C, 2J.J0; H, 3.21; Br, 36.82; Cl, 32.^5.

Found: C, 27-76; H, 3 .28; Br, 37-00; Cl, 32.22.

The cyclopropane exhibits infrared bands at 3*5, 6 .9, 7*3 (doublet),

8.0, 9-1, 10.0 (doublet), 10.U, 11.6, 12.0, 13.9, and 1I+.3 u. The n.m.r. spectrum consists of three singlets: t 6 .J (lH ), t 8 .6 (3H) and t 8.8 (3H). 79 Preparation of l,l,3-trichloro-2,2- dimethylcyclopropane

l-Chloro-2-methylpropene (500 ml., b.p.,68°) vas distilled directly into a flask previously purged with nitrogen. After addition of phenyl(trichloromethyl)mercury (297 g., 0.75 mole), the stirred mixture was refluxed for 60-72 hr. After cooling, the mixture was filtered and the excess olefin distilled. Addition of pentane pre c ip ita te d more phenylmercuric chloride (2l8 g ., to ta l 93$)* Removal o f the pentane and distillation of the residue afforded 1,1,3-trichloro-

2.2-dimethylcyclopropane (80.5 g., 62$, b.p. 66-68° at 15 mm.).

Calcd. for C^HjCl^: C, 34.78; H, 4.03; Cl, 6l.l8.

Found: C, 34.82; H, 3-96; Cl, 61.10.

The infrared spectrum of the product consists of major bands at 3*5*

6.9* 7*3 (doublet), 8.0, 9.1, 10.0 (doublet), 10.5, 11.3* IT.9 and

13.1 u. S in g lets a t t 6.8 (lH ), t 8.6 (3H) and t 8 .7 (3H) make up the n.m.r. spectrum.

Preparation of 1 ,l-dibromo-2,2-dichloro- 3 .3-d.imethy lcyclopropane

Phenyl(trichloromethyl)mercury (10 g., 0.025 mole) was mixed with freshly distilled 1,l-dibromo-2-raethylpropene^® (100 ml., b.p.

(68) Prepared by the method of L. M. Norton and H. J. Williams, Am. Chem. J ., % 87 (1887).

152-154°) under nitrogen. The mixture was heated overnight at 100°.

Filtration of the cooled mixture gave phenylmercuric chloride (7*0 g.,

8 7 $ ). The excess o le fin was d is t ille d o ff under vacuum, and the residue was stirred with petroleum ether. The product dissolved leaving behind 8o phenylmercuric chloride. The hydrocarbon solution was cooled in Dry

Ice-acetone, and the solid collected. Recrystallization from methanol- vater yielded 1,l-dibromo-2,2-dichloro-3,3-diniethylcyclopropane (3.5 g-,

47$, white crystals, m.p. 90_91*)-

Calcd. for C^HgBrgCl^: C, 20.26; H, 2.02; Br, 53.6U; Cl, 24.08.

Found: C, 20.05; H, 2.03; Br, 53-64; Cl, 23.89.

Absorptions at 3.If, 6.9, 7-3 (doublet), 8.3, 9-1, 10.4, 11.2, 11.7,

12.3 and 12.6 u make up the infrared spectrum; only a singlet at t 9*0

is present in the n.m.r.

Preparation of 1,1,2,2-tetrachloro-3- phenylcyclopropane A mixture o f p , ’3 -dichlorostyrene^ (258 g., 1.5 mole)and

(6 9 ) Prepared by the method o f R. Rabinowitz and R. I*hrcus, J. Am. Chem. Soc., 84, 1312(1962).

phenyl(trichloromethyl)mercury (200 g., 0.51 mole) in dry heptane was

refluxed overnight. After filtration of the cooled mixture from phenyl

mercuric chloride (136 g., 88$), the heptane and excess olefin were

removed by distillation . The residue was chromatographed on alumina

(act. grade I, 1" x 6") and eluted with petroleum ether. Concentration

of the hydrocarbon solution to ca. 150 ml., cooling to room temperature

and then in a freezer overnight afforded 1,1,2,2-tetrachloro-3-phenyl-

cyclopropane (78 g., 60$; white crystals, m.p. 63-64°).

Calcd. for C9H6CI4.: C, 42.22; H, 2.34; Cl, 55.32

Found: C, 4l.94; H, 2.27; Cl, 55-35- 81

The product shows infrared absorptions at 3*3; 6.2, 6.7, J.O, 9*8, 10.0,

10.7; 10.8, 11.3^ 12.9; 13*7; and 1^4-.5 u and proton resonance signals at

t 2.6 (multiplet, 5H) and t 6.7 (singlet, 1H).

Preparation of methyl 2,2-dichloro-trans- ,3-phenylcyclopropanecar'boxylate

A dry heptane solution of methyl trans-clnnamate (1.84 g., 1.12 mole) and phenyl(trichloromethyl)mercury (222 g ., O.56 mole) was

refluxed overnight under nitrogen. The cooled solution was filtered

(phenylmercuric chloride, 149 g., 85$); and the filtrate was vacuum

d is t ille d to remove heptane and excess methyl trans-cinnam ate.

Chromatography of the residue on alumina (act. grade I, 1” x 6"),

elution with petroleum ether, and recrystallization from the same

solvent afforded methyl 2,2-dichloro-trans-3-phenylcyclopropanecar-

boxylate (53*5 g»; 54$; white needles, m.p. 58-57°; lit. m.p. 65-66°).^

The infrared spectrum of the ester consists of major bands at 3*4, 5*8,

7.0, 7.6, 7-7; 8.1 to 8.6 (four bands), 9.2, 9.4, 9.9, 10.8 to 11.4

(four bands), 13*1; 13*6, and 14.4 u; n.m.r. signals are at t 2.9

(multiplet) (5H), t 6.3 (singlet, 3H), t 6.6 (doublet, 1H) and t 7*2

(doublet, 1H).

Preparation of 2-(bromomethyl)- 1,1-dichlorocyclopropane

To freshly distilled allyl bromide (500 ml., b.p. 71°) vas

added phenyl(trichloromethyl)mercury (232 g ., O.58 mole), and the

stirred mixture was heated to reflux. Phenylmercuric chloride began to

precipitate slowly; heating was continued for 60 hr. Filtration of the 82 cooled solution, removal of the excess allyl bromide, and reprecipita tio n v ith pentane gave phenylmercuric chloride (170 g ., 92$)* Removal of the pentane and distillation of the residue yielded 2-(bromomethyl)-

1,1-dichlorocyclopropane (59*5 g*> 50$; b.p. 73-75* at 15 mm., lit. b.p. 77“78# at 23 mm. ) . ^ The bromide has infrared absorption bands at

3.3 (broad), 6.9, 7.3* 8.1 to 8.4 (three bands), 8.9, 9.5, 9.8, 10.5,

13.0 and 13.2 u. The n.m.r. spectrum has a doublet at t 4.5 (2H) and a complex multiplet at t 7*7 to 8.9 (3H).

Preparation of 1,1,2-trichloro- 2-(chloromethyl)cyclopropane

Phenyl(trichloromethyl)mercury (175 g*> 0.44 mole) vas added to freshly distilled 2,3-dichloropropene (500 ml., b.p. 94°) in a nitrogen atmosphere. Stirring was begun and the mixture vas heated to reflux overnight. The mixture was cooled, filtered and excess olefin removed by distillation. Fractionation was continued to yield 1,1,2-trichloro-

2-(chloromethyl)cyclopropane (64 g., 75$, b.p. 88-90° at 18 mm.). The cyclopropane exhibits infrared bands at 3*3> 3*4, 7«1 (doublet), 7*8,

8.0, 8.4, 9*8 (doublet), 10.2 (doublet), 11.3* 13*0, and 13.6 u; the n.m.r. spectrum possesses sharp singlets of equal intensity at t 5*9 and t 8 . 0 .

Preparation of (2 ^-dichlorocyclo- propyljmethyl acetate

Allyl acetate (150 g., 0.82 mole) and phenyl(trichloromethyl)- mercury (246 g ., 0.62 mole) were added to dry heptane under nitrogen.

Refluxing the stirred mixture resulted in precipitation of phenyl mercuric chloride (170 g . , 90$) which was removed by f ilt r a t io n . Fractionation of the filtrate afforded (2,2-dlchlorocyclopropyl)methyl acetate (76 g . , 68 $, b .p . 88 -90° a t 15 mm.)* The infrared spectrum of the ester shows absorptions at 3 *^> 5 *7 , 6 .9 # 7 *3 ; 8 .0 , 8 .9* 9*5, and

13.2 u. The n.m.r. spectrum consists of a multiplet at t 5*9 (2H) and a singlet at t 8.0 which overlaps a complex multiplet (total 6H) from t 7*9 to t 8 .9 .

Preparation of (2,2-dichlorocyclo propyl ( me tha nol

Sodium hydroxide (8 g ., 0.2 mole) was dissolved in water (10 m l.). The aqueous solution was diluted with methanol (100 ml.) and cooled in ice. (2,2-Dichlorocyclopropyl)methyl acetate (182. g., 0.1 mole) in methanol (25 ml.) was added dropwise while the stirred solution was maintained at 0°. After two hours, the solution was poured into an equal volume of water and extracted with methylene chloride. The com bined extracts were washed with water, dried and the solvent removed.

Vacuum distillation of the residue yielded (2,2-dichlorocyclopropyl)- methanol (11.5 82$;,b.p. 93-9^° at 15 mm., lit. b.p. 82-85° at

10 mm.^). Infrared absorptions of the'alcohol are at 2.8, 3*3? 6.8-7.3

(three bands), 8.1, 8.9, 9*5, and 13.3 u. The n.m.r. spectrum has signals at t 5*2 (singlet, 1H), t 6.2 (multiplet, 2H) and t 7*9 to 8.9

(complex m ultiplet, 3H).

Preparation of (2,2-dichlorocyclopro- pyljmethyl p-toluenesulfonate

Into a flask flushed with nitrogen, pyridine (200 ml.) was dis

tilled (from BaO) and cooled to 0°. After addition of p-toluenesulfonyl

chloride (30 g., 0.l6 mole), a solution of 2,2-dichlorocyclopropyl- 8U methanol (ll.O g ., O.O78 mole) in dry pyridine (50 ml.) was added dropwise. The stirred solution was maintained at 0° overnight; then water

(lO ml.) was added dropwise to. destroy the excess p-toluenesulfonyl chloride. After pouring the reaction mixture into an equal volume of water and acidifying with hydrochloric acid, the aqueous solution was extracted with methylene chloride. The combined extracts were washed with water, sodium bicarbonate, saturated sodium chloride and dried.

Removal o f the solven t and r e c r y sta lliz a tio n of the r esu ltin g so lid from petroleum ether afforded (2,2-dichlorocyclopropyl)methyl p-toluene sulfonate (18 g., ^9$; white needles, m.p. 83-8^°). Caution: Excessive heating during recrystallization causes precipitation of p-toluene- sulfonic acid. Principal infrared absorptions of the product are at

7.3, 8A, 10.5 (doublet, 12.0 to 12.6 (four bands) and 13-3 u. The n.m.r. shows a characteristic AgBg pattern at t 2.0 to 2.7 (^H) along with absorptions at t 5*8 (multiplet, 2H), t 7*5 (singlet, 3H)'and a complex multiplet from t J .8 to 8.9 (3H).

Attempted preparation of (2,2-dichloro cyclopropyl )meth.ylamine

To a solution of N-allylformamide^ in dry benzene was added

(70) Prepared by addition of methyl formate to allylamine at room temperature. phenyl(trichloromethyl)mercury (kO g., 0.1 mole) under nitrogen. The stirred mixture was refluxed for W3 hr. The cooled mixture was filtered and the benzene removed. Treatment of the reaction mixture with 10$ aqueous potassium hydroxide overnight and subsequent distillation afforded no (2,2-dichlorocyclopropyl)methylamine.

i Preparation of (2,2-dichlorocyclopro- pyljmethylamine

Concentrated ammonium hydroxide (200 m l.) was added to methanol

(300 m l.), and a solution of 2-(bromomethyl)-l,l-dichlorocyclopropane

(37 g., 0 .18 mole) in methanol (50 ml.) was added dropwise. When the addition was complete, the reaction mixture was heated at 5°° overnight.

After cooling, the contents of the flask were added to an equal volume of water and acidified with hydrochloric acid. Extraction of the acidic

solution with ether afforded no unreacted bromide after work up in the

usual way. The acidic solution was made basic and extracted with ether again. After washing with water, sodium bicarbonate, saturated sodium

chloride and drying, the ether was removed. D istillation of the remain

ing material yielded (2,2-dichlorocyclopropyl)methylamine (12.7 'jVfc,

b .p . 73-75° a t 18 mm.). The amine shows infrared absorptions a t 2.9*

3.3> 6.2 (broad), 6. 9 , 7*2, 8.1, 8.9, 9*5> H «2 (very broad), 12.6

and 13.^ u. The n.m.r. consists of multiplets at t 7*2 (2H) and 7.9 to

9.0 (complex, 5H).

Calcd. for. C^HjClgN: C, 3^-26; H, 5.00; Cl, 50.7^; N, 10.00.

Found: C, 3^.11; H, 5 .11; Cl, 5O.9O; N, 10.16.

Preparation of 2,2,3,3-tetrachlorospiro(cyclopropane-1,9*-fluorene)

9-Dichloromethylenefluorene^ (8.0 g., 0.03 mole) and phenyl-

(71) Prepared by the method of Rabinovitz and tiarcus, Ref. 6 9 . 86

(trichloromethyl)mercury (10 g ., 0.025 mole) in dry benzene were refluxed under nitrogen for *+8 hr. Filtration of the cooled mixture gave phenylmercuric chloride (6.3 g., 80$). The filtrate was concen trated to ca. 20 ml. and chromatographed on alumina (act. grade I, l" x 8"). Petroleum ether was used as the eluent. Recrystallization from petroleum ether afforded 2,2,3,3-tetrachlorospiro(cyclopropane- l,9'-fluorene) (3.1 g., 37$; faint yellow crystals, m.p. 179-180°).

Calcd. for C^HgCty: C, 5^-92; H, 2.kb; C l, k2.rfk.

Found: C, $k.Qk; H, 2.1+9; C l, 1+2.87.

Kie product exhibits infrared bands at 6.8, 6.9, 10.6, 11.9 to 12.2

(three bands) and 13.7 u; ultraviolet absorptions are at X max 216

E 25,800, >>max 230 E 27,700, X m ax 239 E 30,000, X 276 E ll+,300, and X max 286 E 13,500.

Preparation of methyl 2 ,2-dichlorocyclopropanecarboxylate

Phenyl(trichloromethyl)mercury (1+6 g., 0.12 mole) was added to a dry heptane solution (200 ml.) of methyl acrylate (25 g., 0.29 mole) under nitrogen. The stirred mixture was refluxed for 2l+ hr., cooled and filtered. Due to extensive polymerization of the acrylate, no attempt was made to recover phenylmercuric chloride. After removal of

solvent and excess of olefinic ester, distillation gave methyl

2,2-dichlorocyclopropanecarboxylate (7*0, 36$) whose properties are

identical with those reported earlier 87

Preparation of l,l-dichloro-2- cyanocyclopropane

To dry acrylonitrile (250 ml;) vas added phenyl (trichlorome thy l)- mercury (64 g., 0.16 mole) under nitrogen. While stirring, the mixture vas refluxed for 38 hr. After cooling the darkened mixture, the solid, which vas composed of phenylmercuric chloride and acrylonitrile polymer, vas filtered. Fractionation of the filtrate yielded l,l-dichloro-2- cyanocyclopropane (5*0 g., 23$). The properties of the product have been described p r e v i o u s l y.25

Preparation of 1,1,2,3-tetrachloro- 2 -(chloromethyl)cyclopropane

To dry 1,2,3-trichloropropene (150 ml.) vas added phenyl(trichloromethyl)mercury (50 g., 0.12 mole) in a nitrogen atmosphere. The stirred mixture vas heated to 100® for 12 hr. Filtration of the cooled material gave phenylmercuric chloride (30 g., 75$). Distillation of the filtrate yielded 1,1,2,3-tetrachloro-2-(chloromethyl)cyclopropane

(15 g‘, 54$, b.p. 80-84° at 5-6 mm.).

Calcd. for C^Clj: C, 21.18; H, 1.32; Cl, 77-50.

Found: C, 21.24; H, 1.40; Cl, 77-61.

The product is a mixture of geometrical isomers and exhibits infrared absorptions at 3-3; 3.4, 6 .9 , 7*5; 7*7; 8.3; 9*7; 10.0, 10.2, 11.0,

12.5, 13-0, and 13.6 u. The n.m.r. spectrum consists of a doublet at t 5*9 (2H) and two sin g le ts a t t 4 .1 and 4.25 (to ta l 1H). 88

Preparation of 2 ,2-dichlorocyclopropanecarboxaldehyde diethyl acetal

Acrolein diethyl acetal (35 g., 0.27 mole), freshly distilled from sodium carbonate, was added to dry heptane under nitrogen along with phenyl(trichloromethyl)mercury (39*5 $•> 0,1 mole). After refluxing the stirred mixture overnight and cooling, the solid was f ilt e r e d (phenylmercuric ch lorid e, 27 g -j 87$ ) . Removal of the solven t and starting acetal and distillation of the remaining material afforded

2,2-dichlorocyclopropanecarboxaldehyde diethyl acetal (13.0 g ., 60$, clear liquid, b.p. IO3-IO50 at 15 mm.).

The product shows infrared absorptions at 3*3, 3-*4, 6.8, 7*2,

8 .9 , 9-*S and 13.2 u; proton resonance signals are at t 5*6 (doublet,

1H), t 6.3 (multiplet, *4H) and t 7-8 to 6 9*0 (complex multiplet, 9*0•

Preparation of 2 ,2-dlchlorocyclopropane- carboxaldehyde 2,*4-dinitrophenylhydrazone

2,2-Dichlorocyclopropanecarboxaldehyde diethyl acetal (0.7 g->

0«003 mole) was dissolved in 80$ aqueous ethanol and treated with an alcoholic solution of 2,*4-dinitrophenylhydrazine. The solution was warmed slightly, and a solid began to form. Moderate heating was continued for 15 min. When the reaction mixture had cooled to room temperature, the precipitate was collected. Recrystallization from ethanol gave 2,2-dichlorocyclopropanecarboxaldehyde 2,U-dinitrophenyl hydrazone (0 .9 g ., 87$ , red-orange c r y sta ls, m.p. 1*41-1*42°).

Calcd. for C^qHqCI^Nj^O^:

C, 37-88; H, 2.5*4; Cl, 2 2 .16; N, 17.66; 0, 19.8 6 .

Found: C, 37-8*4; H, 2.60; Cl, 22.27; N, 17.60; 0, 19.6 9 .

(by difference). > 89

Thermal reaction o f 3-B rom o-l,l- d i chlo ro -2 ,2 - d i me thyIcy clo pro pa ne

3-Bromo-l,l-dichloro-2,2-dimethylcyclopropane (3.0 g ., 0.014 mole) was added dropwise to a flask equipped with a short path distilling head and heated to 150°. Evolution of hydrogen "bromide began almost immediately and a liquid distilled which analyzed as l,l-dichloro-3- methyl-1,3-Butadiene (0.7 £•, 40$, B.p. 32-34° at 12 mm.). The infrared spectrum of the product contains strong absorptions at 6.2 (double bond), 11,0 (terminal methylene) and 11.9 (tri-substituted ethylene) u; proton resonance signals appear at t 3*^ (singlet, 1H), t 4.7 (quartet,

2H) and t 7-9 ( t r ip le t , 3H).

Thermal reaction o f 1 ,1 ,3 -tr ic h lo r o - 2 ,2-djmethylcyclopropane

Using the apparatus described above, l,l,3-trichloro-2,2- dimethylcyclopropane was heated at its atmospheric boiling point (l60-

l6l°) for 0.5 hr. The recovered cyclopropane shoved a very weak infra

red absorption at 6.2 u (double bond) which indicates that only a slight amount o f decomposition had taken p lace.

Thermal reaction of 1 ,1 ,2 ,2 -tetra ch lo ro - 3-phenylcyclopropane

l,l,2,2-Tetrachloro-3-phenylcyclopropane (4.0 g., 0.016 mole)

was heated to 200° for 0.5 hr. Distillation of the material gave the

faintly yellow liquid, (2,3>3>3-tetrachloro-l-phenylpropene (3*5

87$, b.p. 99-100° at 1 mm.).

Calcd. for C^Cl^: C, 42.22; H, 2.34; Cl, 55.32-

Found: C, 42.55; H, 2.46; Cl, 55-51. . 90

The product shows infrared absorption at 6.2 u (double bond), n.m.r. signals at t 2.6 (multiplet, 5H) and t 3*5 (singlet, 1H), and ultra v io le t absorption a t Xjnax 232, E 16,000.

Thermal reaction o f 2 ,2 ,3 ,3 -te tr a - chlo ro s pi r o (cy c lo pro pa ne -1 , 9 1 ~ fluoren e)

Heating of 2,2,3*3-tetrachlorospiro[cyclopropane-l,9'-fluorene]

(0.5 g., 0.015 mole) at 200° for 0.5 hr. and chromatography (alumina, eluent: pet. ether) of the darkened material afforded 9~(tetrachloroethylidene)fluorene (0.35 6 ** 70$;. faint yellow prisms, m.p. 85-86°).

Calcd. for C^HqCI^: C, 5^-92* H, 2M ; Cl, k2.7k.

Found: C, 5^.69; H, 2.1+3* Cl, 4 2 -Oh-.

The product exhibits major infrared bands at 6.3* 6 .7* 10.1+, 10.6, 11.7*

13.2 , 13.6 , and l k .6 u; ultraviolet absorptions are at 21*+,

E 25*000, ;imax 2^7, E 27*000, X n a x 277* E 19,000.

Attempted thermal reaction of 2- (bromomethylj-l^-dichloro- . cyclopropane

A sample of 2-(bromomethyl)-l,l-dichlorocyclopropane was heated

at its atmospheric boiling point (165°) for 0.5 hr. Infrared and gas

chromatographic analyses indicated that no change had taken place.

Attempted thermal reaction of i ,l ,2-trichloro-2~- (chloro- m ethyl)eyelopropa ne

After heating a sample of l,l,2-trichloro-2-(chloromethyl)cyclo-

propane to 190° for 0.5 hr., the material was recovered unchanged. 91

Reaction of l,l,3-trichloro-2,2- dimethylcyclopropane with alco holic potassium hydroxide

Potassium hydroxide (10 g., 0.18 mole) was dissolved in ethanol

(100 m l.), and l ,l ,3-trichloro-2,2-dimethylcyclopropane (8.0 g., 0.04 mole) was added. While the mixture refluxed, potassium chloride pre

cipitated, and the solution turned slightly yellow. After refluxing 12

hr., the cooled solution was poured into water and neutralized with

hydrochloric acid. The aqueous layer was extracted with methylene

chloride; the combined organic extracts were washed, dried, and the

solvent evaporated. The residue was distilled (b.p. 50-70° at 18 mm.),

and the distillate was composed of three components. Preparative gas

chromatography (3/8" x 8 ’ silicone rubber UC-W98 column) separated the

compounds which were found to be 3-chloro-3-methyl-l-butynyl ethyl ether

(47*), ethyl 3-^sthylcrotonate (42*) and ethyl 3-methyl-3-butenoate

(ii* )• Based on ethyl 3-oethylcrotonate, the overall yield is 53*.

3-Chloro-3-methyl-l-butynyl ethyl ether shows infrared absorp

tions at 4.4 (internal acetylene), 7*3 (gem-dimethyl doublet), 8.1 and

9.3 (ether bands) u along with n.m.r. absorptions at t 6.5 (quartet,

2H), t 8.6 (singlet, 6h), and t 8.9 (triplet, 3H).

Calcd. fo r CyH^ClO: C, 57-72; H, 7 -5 4 .-

Found: C, 57-98; H, 7 .72 .

The presence of chlorine was demonstrated mass spectrally by peaks at

M/e 131 (M-15) and M/e 133 in a 3:1 intensity ratio.

Ethyl 3-^ethylcrotonate exhibits infrared absorptions at 5-8

(carbonyl), 6.1 (double bond), 8.7, 9-3 (ester C-O-C) and 11.7

(trisubstituted double bond) u, and n.m.r. signals at t 4.4 (septet, IK), t 6.0 (quartet, 2H), t 7*9 (doublet, 3H), t 8.2 (doublet, 3H), and t 8.8

(triplet, 3H). Its retention time is identical with that of an authentic sample.

Ethyl 3-methyl-3-butenoate has infrared absorptions at 5-7

(carbonyl), 6.0 (double bond), 8.6, 9.6 (ester C-O-C) and 11.1 (terminal

methylene) u; n.m.r. signals are at t 5*2 (multiplet, 2H), t 5*9

(quartet, 2H), t 7-1 (singlet, 2H), t 8.2 (singlet, 3H) and t 8.8

(triplet, 3H).

Reaction of 1,1,3-trichloro-2,2- dime thy ley clo pro pane v ith lithium plperidlde

Dry piperidine (100 ml.) was placed in a flask previously purged

with nitrogen. While the piperidine was cooled in ice, n-butyllithium

in pentane (100 ml., 0.13 mole) was added carefully. 1,1,3-Trichloro-

2,2-dimethylcyclopropane (l4.0 g., 0.08 mole) was then added dropwisej

gradual heating of the stirred solution drove off the hydrocarbons.

Then, the reaction mixture was refluxed overnight. The cooled solution

was poured into an equal volume of water and acidified with hydrochloric

acid. The aqueous solution was extracted with ether; the combined

extracts were washed, dried and the ether removed. Vacuum distillation

of the remaining material yielded l-(3-methylcrotonyl)piperidine (6.5 g*>

48$, b.p. 130-134° at 12 mm.). The aqueous solution was made basic and

extracted again. The ex tra cts yield ed a sm all amount o f the su b sti

tuted piperidine. The product exhibits structurally significant infra

red absorptions at 6.1 (amide band), 7*9 (C-N) and 11.6 (trisubstituted

double bond) u; proton resonance signals appear at t 4.3 (septet, 1H), 93 t 6.6 (multiplet, 4h ), t 8.6 (multiplet, 6 h) and doublets a t t 8 .2 and

8.3 (total 6H).

Reaction of l.l.S-trichloro^^- dlmethylcyclopropane with potassium t-butoxide

To a solution of potassium t-butoxide (2.0 g., 0.18 mole) in dry dimethyl sulfoxide (50 ml.) was added 3-bromo-l,l-dichloro-2,2- dimethylcyclopropane (1.5 g •, 0.07 mole) dropwise. Immediately, the reaction mixture turned very dark, and gas chromatographic analysis of the reaction mixture showed only t-b u ty l alcoh ol and dimethyl su lfo x id e.

After stirring two hours, the dark solution was poured into water, neutralized with hydrochloric acid, and extracted with ether. The combined ether layers were washed and d ried . Only a dark polymeric residue remained after removal of the ether.

Reaction of 3~bromo-l,1-dichloro- 2 ,2-dimethylcyclopropane with n-butyllithi urn

Under nitrogen, 3-bromo-l,l-dichloro-2,2-dimethylcyclopropane

(3*0 g., 0.014 mole) was added to dry pentane (100 m l.). The solution was cooled to -50°, and n-butyllithiura in pentane (25 ml., 0.032 mole) was admitted carefully. Since no reaction occurred, the solution was warmed up slowly. At ca. -25° lithium halide began to precipitate.

After the mixture had warmed to room temperature, the solid was f il

tered, and the pentane solution was poured into water, washed and dried.

Fractionation of the pentane solution afforded a clear liquid (b.p.

100-101°). Tne infrared spectrum and retention time are identical with that of n-butyl bromide. The solid isolated above was examined further to see if the lithium salt of the starting cyclopropane had been formed.

The slightly yellow, salt-like material gives a positive flame test for lithium and shows C-H absorption in the infrared. One gram of the solid was placed in a flask fitted with a short path distilling head and heated to 200° under reduced pressure (15 mm.). No volatile organic material distilled.

Attempted reaction of 1,1,3-trichloro- 2 ,2-dimethylcyclopropane with sodium hydride

A dispersion of sodium hydride (2 .b g., 0.1 mole) in mineral o il (100 ml.) was prepared in a flask equipped with a short path dis tilling head. l,l,3-Trichloro-2,2-dimethylcyclopropane (3*0 g., 0.017 mole) was added, but no reaction occurred. The mixture was heated at reduced pressure (l8 mm.) and continued to 100° whereupon the cyclo propane distilled unchanged. Other attempts to react this cyclopropane with sodium hydride in inert solvents failed likewise.

Reaction of 1,1,2,2-tetrachloro-3- phenylcyclopropane with sodium hydride

Under nitrogen, sodium hydride (5*0 g. of a 53$ dispersion in mineral o il, 0.1 mole) was added to dry benzene (100 m l.). A benzene solution of l,l,2,2-tetrachloro-3-phenylcyclopropane (12.7 g •, 0.05 mole) was added dropwise. Almost immediately hydrogen evolution began.

The reaction mixture was stirred at room temperature until gas evolution nearly ceased. Then, slight warming ensured complete reaction. The solution was filtered and solvent evaporated. From the residue a clear liquid distilled which was identified as 2,3jS-trichloro-l-phenylcyclopropene (9*5 g-, 87 $ , b .p . 72 - 7 ^° a t 1 mm.)*

This cyclopropene has been prepared earlier by reaction of trichlorocyclopropenium tetrachloroaluminate with benzene at 0° for

30 sec.; 20 however, its properties were not described. This present product exhibits infrared absorption at 3-3, 5-5 (double bond, weak),

8.0, 8.7, 9-7, 9-9, 10.1, 13.1, 13-9, and 1^.6 u. Only an aromatic multiplet at t 2.6 appears in its n.m.r. spectrum. The phenyldichloro- cyclopropenium ion accounts for the major fragment at M/e 183 (M-Cl) in the mass spectrum; the isotopic cluster is characteristic of a dichloro compound. Subsequent reaction s provide ad d ition al evidence fo r the structure of the cyclopropene.

Hydrolysis of 2,3,3-trichloro-l- phenylcyclopropene

Potassium hydroxide (5-0 g., 0.09 mole) was dissolved in water

(lOO m l.). At room temperature, 2,3,3-trichloro-1-phenylcyclopropene

(3.0 g ., O.Ollj- mole) was added and the heterogeneous mixture stirred vigorously. After three hours, the cyclopropene had dissolved. As the solution was acidified with hydrochloric acid, a precipitate formed.

The solid was collected and recrystallized from acetonitrile to give hydroxyphenylcyclopropenone (1.5 g., 7^-5$)- The melting point (100-

101°) and infrared spectrum, are identical to that reported Reaction of 2,3>3-trichloro-l- phenylcyclopropene with toluene catalyzed by aluminum chloride

To dry toluene (100 ml.) was added 2,3>3-trichloro-l-phenylcyclopropene (2.0 g., 0.009 mole). While stirring, aluminum chloride

(3.0 g., 0.022 mole) was added in four equal portions over a period of

15 min. After an additional 15 min., the dark red solution was poured into water and stirred until the dark color dissipated. The toluene layer was separated, and the aqueous layer was extracted with ether.

The combined organic layer was washed with water, sodium bicarbonate, saturated sodium chloride and dried. The solvents were evaporated, and the residue was recrystallized from cyclohexane to give phenyl-p- tolylcyclopropenone (0.9 g-, ^5dp) • The melting point (128-129°) and infrared spectrum (5*^ and 6.2 u, cyclopropenone bands) are identical to that reported for this cyclopropenone as prepared by the reaction of phenyl(bromodichloromethyl)mercury and phenyl p-tolylacetylene and hydrolysis of the intermediate dichlorocyclopropene.^

Reaction of methyl 2 ,2-dichloro-trans- 3-phenylcyclopropanecarboxylate with methanolic potassium hydroxide

Potassium hydroxide (8.0 g ., 0.1^ mole) was dissolved in methanol

(100 m l.), and methyl 2 ,2-dichloro-trans-3-phenylcyclopropanecarboxylate

(3.0 g., 0.012 mole) was added. The solution was refluxed for k- h r. during which time potassium chloride precipitated. The cooled solution was poured into water, acidified with hydrochloric acid and extracted with ether. The combined extracts were washed, dried and the ether 97 removed. Recrystallization yielded a white solid which was found to be

3-carbomethoxy-3-phenylpropionic acid (2.2 g., 88$, m.p. 102°).

Calcd. for C, 63-52; H, 5-78; 0, 30-70.

Found: C, 63.63; H, 5-86; 0, 30.51 (by difference).

The product shows broad infrared absorption bands at 2.9 and 5*8 u characteristic of a carboxylic acid. The n.m.r. spectrum contains signals at t 2.9 (multiplet, 5H), t 6.0 (quartet, 1H), t 6 .h ( s in g le t,

3H) and a multiplet from t 6.8 to 7*7 (2H).

The half ester (l g., 0.005 mole) was dissolved in aqueous potassium hydroxide and allowed to stand overnight. After acidification with hydrochloric acid, the aqueous solution was extracted with ether.

The combined ether layers were washed, dried and the ether removed; the remaining material was recrystallized from water to give phenylsuccinic acid (0.7 78$; white solid, m.p.' I67-I680, lit. m.p. 167°^).

Reaction of l,l,3-trlchloro-2,2- dimethylcyclopropane with sodium

Under n itrogen , a d isp ersion o f sodium (10 g . , 0.43 g-atom .) on diy alumina (100 g.) was prepared as described..W hen the dispersion had cooled to room temperature, anhydrous ether (100 ml.) was added.

While the stirred mixture was cooled in ice, l,l,3-trichloro-2,2- dimethylcyclopropane (l^.O g., 0.08 mole) was added dropvise. After an hour, the ether was decanted, washed, dried and evaporated. The residue was a complex mixture (8$) containing six components. Anhydrous ether

(lOO ml.) was added to the dispersion, and the excess sodium was destroyed by careful addition of methanol. An equal volume of water was added, and the mixture was acidified with hydrochloric acid. The ether layer vas separated, and the aqueous solution extracted with ether. The

t combined ether portions were washed, dried and the ether removed. The residue was a small amount of a mixture similar to that obtained above.

Ho attempt was made to separate the components.

In a similar experiment, l,l,3-trichloro-2,2-dimethylcyclopropane (5*0 g ., 0.03 mole) was added dropwise to high surface sodium at reduced pressure (15 mm.). Bubbling and a dark color indicated that the cyclopropane was reacting when it contacted the reagent; however, no volatile material collected in a trap at -78°. After completion of the reaction, anhydrous ether was added. Decantation and evaporation of the ether yielded no residue. A second portion of ether was added and the sodium was hydrolyzed with methanol. This ether layer did not yield a residue after washing, drying, and evaporation.

Reaction of l,l,3-trlchloro-2,2- dimethylcyclonropane with mag nesium and methyl iodide

Under n itrogen , anhydrous ether (15 m l.) and a few drops o f methyl iodide were added to magnesium shavings (h.8 g., 0.2 mole). As

soon as the ether became cloudy, anhydrous ether (100 ml.) and 1,1,3-

trichloro-2,2-dimethylcyclopropane (17-2 g., 0.1 mole) were added.

Methyl iodide (28 g., 0.2 mole) in anhydrous ether (50 ml.) was added

at a rate to maintain gentle reflux. Stirring was continued for 2 hr.;

then, the reaction mixture was cooled in ice and hydrolyzed by dropwise

addition of 5$ hydrochloric acid. After pouring the mixture into an

equal volume of water, the ether layer was separated, washed, dried and

evaporated. Distillation of the residue yielded only a small amount 99

(c a . 20$) o f sta r tin g cyclopropane; a large amount o f polymeric m aterial remained.

Attempted reaction of 1,1,3-trichloro- 2 .2-dimethylcyclopropane and 1,1- dichloro-3-bromo-2 ,2-dimethylcyclopropane vlth zinc in alcohol

In three flasks were placed zinc (0.5 g*> 0.07 mole), pre viously cleaned with dilute hydrochloric acid and dried, and absolute ethanol (5 m l.). l ,l ,3-Trichloro-2,2-dimethylcyclopropane (0.5 g.,

0.03 mole), l,l-dichloro-3-bromo-2,2-dimethylcyclopropane (0.5 g*, 0.023 mole) and hexachlorocyclopropane (0.5 g ., 0.02 mole) were added to separate flasks and warmed moderately. Under conditions that hexa chlorocyclopropane reacts,*^ the trihalocyclopropanes do not. Analysis

(72) S. Tobey and R. West, J . Am. Chern. S o c., 86, 56(196*0* was carried out by gas chromatography.

Reaction of S-bromo-l^-dichloro- 2 .2-dimethylcyclopropane with silver acetate

3-Bromo-l,l-dichloro-2,2-dimethylcyclopropane (21.7 g*> 0.1 mole) and silver acetate (25.0 g., 0.15 mole) were added to dry acetic acid (200 m l.). The stirred mixture was refluxed until gas chromatog raphy indicated th at the cyclopropane had been consumed (ca . 48 h r .) .

The cooled mixture was diluted with ether (200 ml.) and filtered. The ethereal solution was washed with water, sodium bicarbonate, and saturated sodium chloride and dried. Fractionation of the ether 100 solution yielded l,l-dichloro-3-methy 1-1,3-butadiene (l.O g., 7*4$) and a large amount o f a polymeric m aterial.

Reaction of 3-bromo-l,l-dichloro- 2 .2-dimethylcyclopropane with mercuric acetate

Under conditions described in the previous experiment, mercuric acetate (24.0 g., 0.075 mole) was reacted with 3-bromo-l,l-dichloro-

2.2-dimethylcyclopropane (10.8 g., 0.05 mole). After work up in the same manner, l,l-dichloro-3-methyl-l,3-butadiene (1.3 g.> 19*5$) ‘was obtained. Only low yields of this highly reactive monomer can be isolated under the conditions employed; the major product is the corresponding polyisoprene.

Reaction of 2-(bromomethyl)-!,!- dlchlorocyclopropane with sodium methoxide

To a solution of sodium methoxide (5-4 g., 0.1 mole) in methanol

(150 ml.) was added 2-(bromomethyl)-l,l-dichlorocyclopropane (5*0 g.,

0.025 mole). The stirred solution was warmed to 50° for two hr. After cooling the solution was poured into water, neutralized with hydro chloric acid and extracted with ether. The combined extracts were washed, dried and the ether removed. Distillation of the residue gave material (2.3 g*, 66$) composed ot (2,2-dichlorocyclopropyl)methyl methyl ether and an unidentified carbonyl component (8$). Preparative gas chromatography (3/ 8" x 8 1 silicone rubber UC W-98 column) provided an analytical sample of the ether. 101

Calcd. for CjHqC^O: C, 38.72; H, 5.65; Cl, 45.68; 0, 10.20.

Found: c, 38.95; h, 5 .67; Cl, 45-91; 0, 9-57

— (by difference).

The infrared spectrum of the product shows diagnostic bands at 9-0

(C-O-C) and 13-4 (CClg) u; proton resonance signals are a t't 6.52

(doublet, 1H), t 6.68 (singlet, 3*0, and t 8.0 to 9*0 (complex multi p le t , 3H).

Reaction of 2-(bromomethyl)-!,!- djchloroc.ycloprooane with potassium j.-butoxide

To a solution of potassium t-butoxide (5.0 g., 0.04 mole) in dimethyl sulfoxide (100 ml.) was added 2-(bromomethyl)-l,l-dichlorocyclopropane (5*0 g., 0.025 mole). Immediately, the reaction turned very dark; gas chromatographic analysis of the mixture indicated the presence of t-butyl alcohol and dimethyl sulfoxide. Work up in the usual way afforded no residue after removal of the extracting solvent.

Attempted reaction of 2 -(bromomethyl)-!,!- dichlorocyclopropane with sodium hydride

To a suspension of sodium hydride (5*0 g. of 53$ dispersion in mineral o il, 0.1 mole) in dry benzene was added 2 -(bromomethyl)-1,1- dichlorocyclopropane (5-0 g., 0.025 mole). Within a short time, the

surface of the sodium hydride became light brown. The mixture was

refluxed overnight; sampling by gas chromatography indicated only

starting cyclopropane was present. On work-up 2 -(bromomethyl)-l,l-

dichlorocyclopropane (3-6 g., 72$) was recovered. 102 Reactions of 2-(bromomethyl)-!,!- dlchlorocyclopropane with sodium cyanide

2-(Bromomethyl)-l,l-dichlorocyclopropane (3-0 g ., 0.014 mole) was added to a solution of sodium cyanide (4.5 g., 0.09 mole) in dimethyl sulfoxide (75 ml.) at room temperature. After stirring two hours, the dark mixture was poured into water and extracted with ether

(3 x 25 m l.). The combined ether layers were washed, dried and evaporated. The product, (2,2-dichlorocyclopropyl)acetonitrile^

(73) Reported b.p. 100-104° at 10 mra.^

(1.7 g*i 80$) was isolated by preparative gas chromatography (3/8" x 8* silicone rubber UC W-98 column). The product exhibits significant infrared absorption at 4.5 (nitrile) and 13*2 (C-Cl) u; proton resonance signals are at t 7*3 (doublet, 2H) and t 7*7 to 8.8 (complex multiplet,

3H).

Reaction of 2-(bromomethyl)-l,1- dichlorocyclopropane with piperidine

While stirring, 2 -(bromomethyl)-l,l-dichlorocyclopropane was added to piperidine (50 m l.). The solution was warmed to 50 °> ar*d a white so lid separated from so lu tio n . S lig h t warming was continued for one hr. Filtration of the cooled solution and recrystallization of the precipitate from dimethylforraamide gave a material which analyzed as piperidine hydrobromide (2.0 g., 70$)* The piperidine solution was diluted with water, acidified with hydrochloric acid, and extracted with eth er. Removal o f the ether yield ed no sig n ific a n t resid u e. The 103 aqueous layer was made basic and extracted again with ether. After washing and drying, this extraction yielded 1-[(2,2-dichlorocyclopropyl)methyl]piperidlne (2.6 g., 73$; clear liquid, b.p. 78-79° a-t

2 mm.).

Calcd. fo r C^H^NCl^: C, $2.02; H, 7*20; N, 6.72; C l, 3^.10.

Found: C, 52.09; H, 7.^1; N, 6.72; C l, 33.80.

This amine has structurally significant infrared absorptions at 8.9,

9.6 (C-N of t-amine) and 13 (C-Cl) u; n.m.r. absorptions appear at t 7.^ (unresolved multiplet, 6 h) and t 8.U (multiplet with a super imposed multiplet from t 8.0-9*0 (total, 9H).

Reaction of 2-(bromomethyl)-1,1- dichlorocyclopropane with tr i phenylphos ohine

To dry benzene (100 ml.) was added triphenylphosphine (10 g.,

0.0^ mole) and 2 -(bromomethyl)-l,l-dichlorocyclopropane (3*5 g«> 0.017 mole), and the stirred mixture was refluxed overnight during which time a white solid precipitated. The cooled solution was filtered, and the solid recrystallized from dimethyIformamide-benzene to yield (2,2- dichlorocyclopropyl)methyltriphenylphosphonium bromide (3*1 g«* 6l$, m.p. 218-219°).

Calcd. for Cg^QBrC^P: C, 56.72; H, Br, 1?.2^;

Cl, 15.20; P, 6.50.

Found: c , 56.75; H, k .35; Br, 17-17;

Cl, 15.50; 6.65 (by difference). ic k

The product exhibits infrared bands at 3»3> 3*5* 6.9> 8.9, 10.0,

10.6, 12.2, 12.8, 12.9, 13.2, 13.4, 13.8, 1*4.3, and l*4-.*4 u. The n.m.r. spectrum was determined in deuterium oxide using external tetramethylsilane and shows signals at t 2.9 (aromatic multiplet) and t 5*2

(external methylene). Hie cyclopropyl multiplet is not clearly dis tinguished because of the low solubility of (2,2-dichlorocyclopropyl)- methyltriphenylphosphonium bromide in deuterium oxide.

Attempted oxidation of 2 -(bromomethyl)- 1,1-dichlorocyclopropane with dimethyl sulfoxide

To dimethyl sulfoxide (200 ml.) and sodium bicarbonate (10 g.) was added 2 -(bromomethyl)-l,l-dichlorocyclopropane (8.0 g ., 0.0*4- mole).

The stirred mixture was heated to 100° to initiate reaction. The solution darkened slowly while being heated overnight. After cooling, the mixture was poured into water and methylene chloride was added. The mixture had to be filtered before extraction could be effected. A dark polymeric residue was collected. Extraction of the filtrate with methylene chloride was continued. , After washing and drying the combined extracts, the methylene chloride was evaporated. Very little residue remained.

Reaction of 2-(bromomethyl)-l>l- dichloroc.yclopropane with ben zene and aluminum chloride

Aluminum chloride ( l g .) was added to a so lu tio n o f 2 - (bromo methyl)-!, 1-dichlorocyclopropane (8.0 g ., 0.0*4- mole) and dry benzene

(200 m l.). The stirred mixture was warmed on a steam bath until gas evolution began. Intermittent vanning was continued over a period of two hours. During th is tim e, two a d d ition al portions o f aluminum chloride (l g.) were added. When gas evolution had ceased, the dark solution was cooled and poured into ice water. On stirring, the dark color dissipated. The benzene layer was separated and washed with water, sodium bicarbonate, saturated sodium chloride and dried. The benzene solution was concentrated to ca. 15 ml. and on chromatography

(l” x 6" alumina, act. grade I; eluent, petroleum ether) gave a highly fluorescent material (6.5 g-> 8l$). This material was a mixture of

2-phenyl-3-methylindene (82$) and 2,3-diphenyl-1,3-butadiene (l8$).

The mixture gave the following analysis:

Calcd. for C^H^s C, 93-20; H, 6.80.

Found: C, 92.52; H, 7-35-

A molecular weight of 206 (theo. M.W. = 206) was obtained mass spectrally.

The mixture was separated by preparative gas chromatography

( l / V x 10* column o f 5$ FFAP on Chromosorb W); 2-phenyl-3-m ethylindene was elu ted f i r s t . This indene was obtained as an o i l , and a l l attempts

to obtain a crystalline product failed. The infrared spectrum of

2-phenyl-3~methylindene exhibits absorptions at 3-3 (doublet), 6.2, 6.7*

6 .9 ) 9 -1) 1 2 .7 ) 13-2, 1 3 .7 ) and lU.3 u; the fingerprint region indicates both monosubstituted and ortho-disubstituted phenyl rings. Proton

resonance signals appear at t 3-3 (multiplet, 10H), t 6.3 (quartet,

1H, J = 7 cps) and t 8.8 (doublet, 3H, J = 7 cps). 106

The infrared spectrum of 2 ,3-diphenyl-l,3-butadiene shows

characteristic monoaromatic absorptions at 12.8 and 1^.3 u along with

terminal methylene absorption at 11.1 microns; n.m.r. signals appear at

t 3*25 (multiplet, 10H) and 5*12 t (singlet, ta).

Reaction of 2 -(bromomethyl)-!»!- dichlorocyclopropane with silver acetate

2-(Bromomethyl)-l,l-dichlorocyclopropane (6.2 g., 0.03 mole) was added to a mixture of silver acetate (T*5 0.0^5 mole) in dry acetic acid (100 m l.). The stirred mixture was refluxed overnight and after

cooling an equal volume of ether was added. The mixture was filtered.

The filtrate was washed with water (2 x 100 m l.), sodium bicarbonate,

saturated sodium chloride and dried. Fractionation of the ether solu

tion yielded (2,2-dichlorocyclopropyl)methyl acetate (3.8 g., 75$) as

the sole product. The infrared and n.m.r. spectra and retention time of

the product are identical to that of 2,2-dichlorocyclopropanemethanol

acetate prepared earlier in this research. Gas chromatographic analysis

of the crude reaction mixture showed that there were no products that were lost during work-up of the reaction. Examination of the acetate on

a number of columns gave only one peak. Infrared spectrum shows no

double bond absorptions arising from ring opened products. Integration

(2H) of the t 5*9 (methylene group) signal excludes a cyclobutyl ester.

Solvol.ysis of (2,2-dichlorocycloprop.yl)- methyl d - toluenesulfonate in acetic acid

To dry acetic acid (100 ml.) was added sodium acetate (2.0 g.,

0.025 mole) and (2,2-dichlorocyclopropyl)raethyl p-toluenesulfonate 107

(7.0 g., 0 .024 mole) prepared earlier, and the stirred solution was heated at 100° overnight. The cooled reaction mixture was poured into water and extracted with methylene chloride. Hie combined extracts were washed with water, sodium bicarbonate, saturated sodium chloride and dried. After removal of the methylene chloride, vacuum distillation afforded (2,2-dichlorocyclopropyl)methyl acetate (2.1 g., based on material reacted). The remaining material on recrystallization yielded

1.5 g. of (2,2-dichlorocyclopropyl)methyl p-toluenesulfonate. The acetate was subjected to the same analysis as the product of the pre

ceding experiment and found to be identical.

Reaction of (2,2-dichloroc.yclo- propyl)methylamine with aqueous nitrous acid

To a solution of hydrochloric acid (l ml.) in water (100 ml.)

was added (2,2-dichlorocyclopropyl)methylamine (1.4 g ., 0.01 mole)

prepared previously. While the stirred solution was cooled in ice, an

aqueous solution of sodium nitrite (2.5 O.036 mole) was added drop-

wise. After maintaining the reaction mixture at 0° overnight, the

aqueous solution was extracted with methylene chloride. The combined

extracts were washed, dried, and solvent evaporated. By comparison of

retention time to that of an authentic sample, the residue was found to

be (2,2-dichlorocyclopropyl)methanol (96.5$) an& an unidentified

product (4.5$); the latter material had a slightly longer retention

time. The overall yield was 40.5$ using (2,2-dichlorocyclopropyl)methyl

acetate as an internal standard. Variation of reaction conditions gave

slightly different product ratios; room temperature and higher acid 108 concentration gave the unidentified product (ll$) and (2,2-dichloro- eyelopropyl)methanol (89$). By comparison of retention times the unidentified material was not 3“butenoic acid or cyclopropanecarboxylic a c id .

Reaction of (2,2-dichlorocyclopropyl)methylamine and nitrous acid in acetic acid

To a stirred solution of (2,2-dichlorocyclopropyl)methylamine

(lA g ., 0.01 mole) in acetic acid at 20° was added sodium nitrite

(2.0 g. total) in four equal portions at approximately 10 min. inter v a ls . After k hr., the reaction mixture was poured into water and extracted with ether. The combined extracts were washed with water, sodium bicarbonate, and saturated sodium chloride. After drying and removal of the ether, the residue was analyzed as (2,2-dichlorocyclopropyl)methyl acetate (92*5$) an(* an unidentified material (?*5$) hy retention times and infrared spectra. The overall yield was 58$ using bromobenzene as internal standard. Acidification and extraction of the basic wash yielded no residue. A similar experiment conducted at room temperature gave (2,2-dichlorocyclopropyl)methyl acetate (82$) and unidentified material (18$).

Attempted reaction of 1,1,2-trichloro- 2 -(chloromethyl^cyclopropane with silver acetate

l,l,2-Trichloro-2-(chloromethyl)cyclopropane ( l.9 g*> 0.01 mole) was added to a mixture of silver acetate (2.0 g., 0.012 mole) in dry acetic acid. The stirred mixture was refluxed for 36 hr., cooled and poured into water. The aqueous solution was extracted with methylene chloride; the combined extracts were washed with water, sodium bicarbon ate, saturated sodium chloride and dried. Gas chromatographic analysis of the residue after the solvent had been evaporated indicated that no reaction had taken place and l,l,2-trichloro-2-(chloromethyl)cyclopropane (l.4 g., 7^$) v&s recovered.

Attempted reaction of 1,1,2-trichloro- 2 -(chloromethyl)cyclopropane with zinc

To freshly cleaned zinc (5*0 g., 0.075 mole) in dry bis (2- methoxyethyl) ether was added l,l,2-trichloro-2-(chloromethylJcyclopro- pane (5*0 g., 0.025 mole). The stirred mixture was heated to 150° for one hr. The cooled solution was decanted, poured into water and extracted with ether. The ether was washed, dried and evaporated. The residue was distilled to give unreacted 1,1,2-trichloro-2-(chloromethyl)- cyclopropane (4.1 g., 82$).

Reaction of tetrachlorocyclopropene with phenyl(trichloromethyl)mercury

While stirring under nitrogen tetrachlorocyclopropene^ (50 ml.) and phenyl(trichloromethyl)mercury (20.0 g., 0.05 mole) was heated to

100° overnight. After filtration of the cooled mixture, fractionation of the filtrate yielded hexachloro-1,3-butadiene (6.0 g., 46ji). The product was identified by comparison of its infrared spectrum and

retention time to that of an authentic sample. 110

Dlels-Alder reaction of tetrachlorocyclopropene and cyclopentadiene

Tetrachlorocyclopropene (8.0 g., 0.045 mole) and freshly dis

tilled cyclopentadiene (25 ml.) were stirred overnight at room temper

ature. Then, the mixture was poured into water and extracted with

ether. The combined ether layers were washed, dried and evaporated.

The remaining cyclopentadiene and i t s dimer were removed by vacuum

distillation. The residue was chromatographed (alumina, act. grade Ij

eluent, petroleum ether) to yield 2,3>4,4~tetrachlorobicyclo[3.2.l]octa-

2 , 6 -diene (7*5 g«> 79 dp> white crystals, m.p. 91-92°, lit. m.p. 90°).

The infrared spectrum of the product shows sharp absorptions at 3»3>

6.2, 6.9, 7.6, 7.8, 8.1, 8.4, 8.8, 9.6, 10.2, 10.5, 10.7, 11-3, 12.2,

12.8, 13*4, 13.8, and 14,3 u. Proton resonance signals at t 3*3

(quartet, 1H), t 3*8 (quartet, 1H), t 6.2 (triplet, 1H), t 6.8 (triplet,

III) and a m u ltip let from t 7-3 to 7*9 (2H) and correspond to those

r e p o r te d .^