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n - (I-Phenylcyclopropy1)alkanoylChlorides J . Org . Chem., Vol .43 , N o . 23 , 1978 4459Lewis Acid Promoted Reactions of n-( -Phenylcyclopropy1)alkanoyl

Chlorides. Ring-Size E ffects in C ompetitive Intram olecular Acylationof Pheny l and Cyclopropyl Substituents

Michael P. Doyle,*a Robert C. Ell iot t, and Joseph F. Dellaria, J r . I bD e p a r t m e n t of C h e m i s t r y , H o p e C o l le g e ,Hol land , Michigan 49423

Received May 4, 1978Exclusive intramolecular acylation of the phenyl ring occurs in aluminum chloride and stannic chloride pro-moted reaction s of 3-(l-phenylcyclopropyl)propanoylhloride (1 , n = 3) . Treatment of 1 ( n = 3) with s tannic chlo-ride in benzene or with aluminum chloride in acetonitrile results in the production of spiro[cyclopropane-l,4-te-tral-l-onel. In methylene chloride aluminum chloride effectively converts 1 ( n= 3 ) to 4-ethyl-1-naphthol,and inbenzene the aluminum chloride promoted reaction results in the production of 4-ethyl-4-phenyl-1-tetralone. ncontra st, aluminum chloride promoted reactions of 4- (1-pheny1cyclopropyl)butanoyl hloride (1 , n = 4) result inexclusive intramolecular acylation of the cyclopropane ring; 4-phenylcycloheptano ne s formed from reactions per -formed in methylene chloride, and both 4-phenylcycloheptanoneand 4,4-diphenylcycloheptanone re producedin benzene. These results indicate that, although the phenyl ring is more susceptible to electrophilic attack thanis the cyclopropyl ring in intermolecular acylation reactions, r ing-size effects dom inate these reactivity differencesin the intramolecularprocess.

We have recently rep orted th at cyclopropylalkanoyl chlo-rides u ndergo Lewis ;acid catalyzed intram olecular a cylationreactions to form five-, six-, and seven-membered ring ke-tones.2 Th e facility of these intramolecular rea rrangem ents,which are analogous to Lewis acid catalyzed cyclizations ofalkenoyl and arylalkanoyl chlorides,3s4has led us to investigatethe reactiv ity of the cyclopropane ring relative to the benzenering in Lewis acid promoted intramolecular cyclizations ofn - (1-phenylcyclopropy1)alkanoyl chlorides (1). AlthoughQ1

intermo lecular acylation of phenylcyclopropane with acetylchloride-aluminum chloride occurs exclusively at th e paraposition of th e benz ene ring,5 ring-size effects in intramolec-ular ac ylation of 1, du e to the positioning of the electrophilicacyl group relative to the phenyl a nd cyclopropyl rings, maybe expected to have a do min ant influence on acylation selec-tivity.3@ Intram olecular acylation of the cyclopropane ringof 1 is expected to occur through an intermediate s tate thatconnects n + 2 carbon atom s, whereas intramolecular acyla-tion of the benzene ring should occur through an in term ediates ta te th a t jo ins n + 3 carbon atoms.Exclusive intram olwu lar acylation of th e phenyl ring occursin alum inum chloride promo ted reactions of 2-phenylcyclo-p ro pa ne ca rb on yl c h l ~ r i d e . ~n addit ion, ( l -phenylcyclopro-py1)acetyl chloride ( 1 , n = 2) has recently been reported tounderg o intramolecular cyclization to form spiro[cyclopro-pane-1,3-indan-l-one] a Although cyclopropane ring openingis observed subsequen t to a cylation of the phenyl ring, reac-tion pro ducts resulting from intramolecular acylation of th ecyclopropyl ring have not been detected. However, ring-sizeeffects are expected ti:, inhibit com petitive acylation in thesesystems.Results and Discussion

Tre atm en t of 3-(1-phenylcyclopropyl)propanoylhloridewith s tannic chloride in benzene at 25 O C resul ts in the pro-duction of spiro[cyclopropane-l,4-tetral-l-one]2, eq I ) ,which was isolate d in B4% yield. Correspon ding products fromintramolecular acylation of the cyclopropane ring are notobserved, nor, surprisingly, are prod ucts resulting from in-

0sOCl? $$ t HC1 (1)0

2termolecular acylation of th e solvent benzene. C onsideringthe reported sensitivity of the cyclopropane ring to ringopening under reaction conditions from which hydrogenchloride is produced,2,8 he formation of 2 in high yield is no-table a nd suggests th at alte ration of the Lewis acid and con-ditions employed with 1 ( n = 3) could effectively lead to d e-signed structur al modifications of the product formed by in-tramolecular a cylation of th e phenyl ring. This expectationis realized in the results from reactions of 1 (n = 3) promotedby the stronger Lewis acid alum inum chloride.Reaction of 3-(1-phenylcyclopropyl)propanoyl chloridewith aluminum chloride (eq 2) in methylene chloride a t 25 C

CH,CHjI

OHproduces 4-ethy l-1-naph thol as the sole identifiable product(59% isolated yield). Under similar conditions in benzene,4-ethyl-1 -phenyl- 1-tetralone s formed (71% isolated yield).The se results are consisten t with a reaction scheme in whichproton addition to th e cyclopropane ring of 2 produces thecorresponding benzylic catio n that undergoes elimination to4-ethyl-1-naphtholor is effectively trapped through e lectro-philic sub stitution with benzene. In acetonitrile, a basic me-dium for aluminum chloride, cyclopropane ring opening thatresults from proton add ition is not observed and 2 is formednearly exclusively.Intram olecular acylation of the phenyl ring of 3-( l-phe n-ylcyclopropy1)propanoyl chloride produces a benzenoniumion interm ediate t ha t possesses an electron-deficient centeradjacent to the cyclopropane ring. Due t o geometrical con-

0022-3263/78/1943-4459$01.00/0@ 1978 Ame rican Chemical Society

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4460 J.Org. Chem. , Vol. 43 , No. 23, 1978 Doyle, Elliott, and D ellariastra ints , this cyclopropylcarbinyl cation is formed in th e bi-sected geometry that is preferred for conjugation with thecyclopropane ring.9 liow ever, th e cyclopropylcarbinyl ringopening process tha t could be expected during intramolecularacylation of n-(1-phenylcyclopropy1)alkanoylhlorides (1, n= 2 ,3 ) is not observed, presumably due to th e stability of thedelocalized benzenonium ion intermediate.In con t ras t t o the intramolecular cyclization reactions re-ported for 3-(l-phenylcyclopropyl)propanoyl chloride, thealum inum chloride promoted reactions of 4-( -phenylcyclo-propy1)butanoyl chloride (1, n = 4) result in exclusive, mo-lecular acylation of th e cyclopropane ring. Pro duct s from in-tramolecular acylation of the phenyl ring tha t correspond tothose observed in reactions of the ne xt lower homologue arenot detected. However, 4-phenylcycloheptanone (3 , eq 3) is

0

IC,H;IJ

the only detectable monomeric substance from react ionsperformed in methylene chloride, and this unexpectedpr odu ct is form ed in relatively low yield (32% sola ted yield).T he residual ma terial is a relatively insoluble, high meltingsubstance th at does not exhibi t lH NMR absorption charac-teristic of either a cyclopropane ring or a benzosuber-1-onestruct ure, and i t was not further characterized. In benzene,however, 4-(l-phenylcyclopropyl)butanoyl chloride formsbo th 3 (26% yield) iind 4,4-diphenylcycloheptanone 48 %yield), indicating th e do min ant preference for intramolecularacylation of t he cyclopropane ring in reac tions of 1( n= 4) withalum inum chloride. F'roducts from intermolecular acylationof th e solvent benzene were not detected. In c ontrast, 4-cy-clopropylbutanoyl chloride has been observed to react w ithalum inum chloride und er similar conditions to form 4-chlo-rocycloheptanone an d 3-chloromethylcyclohexanone;cyclo-hept anon e and 3-met hylcyclohexanone were not detected.*Th e production of 3 is attributab le to hydrogen abstractionby th e carbocat ion formed throu gh intramolecular acylat ionof th e cyclop ropane rnng of 1( n= 4).1 However, att em pts t oincrease th e yield of 3 from reactions performed in methylenechloride through th e addit ion of an equivalent am ount oftriphenylmethane did not result in a substantial improvementin the yield of 4-phenylcycloheptanone (36% solated yield).Since methylene chloride is not an effective hydride donor,the reac tan ts or products from intramolecular cyclizationmu st serve in this capacity for the p roduction of 3. Surpr i s -ingly, 3 is also formed in reactions that occur in benzene;competition with electrophilic substitution apparently doesnot markedly affect the relative rate for hydride abstrac-tion."Th e d ram atic effect. of ring size in intramolecular acylationsof 1 ( n = 3, 4) indicates the substant ial react ivity of the cy-clopropane ring. Although intramolecular acylations with5-phenylalkanoyl chlorides that result in the formation ofseven-membered ring benzosuber-1-ones are well known,3competing intramolecular acylation of the cyclopropane ringin 1 ( n = 4), requiring an intermed iate s tate th at jo ins s ixcarbon atoms, is preferred. Thus, although th e phenyl ring ismore susceptible to electrophilic attack th an is the cyclopropylring in intermolecular acylation reactions,5 ring-size effectsdomina te these react ivi ty differences in the intramolecularprocesses.Aluminum chloride promoted reactions of th e next higherhomologue of 1 ( n = 4) , 5 - (1-phenylcyclopropyl)pentanoylchloride (1,n =: 5 ) ,were investigated in both chloroform an d

benzene. Under conditions identical with those employed forring expansion of 1 ( n= 4), and even with a 10-fold di lut ionof reacta nts, intractab le materials were obtaine d. Althoughas many as seven distinct products were observed by GLCanalysis, none of th e prod ucts was formed in greater tha n 3%yield and the react ion mixtures were not further ana-lyzed.12Experimental Section

Ge ne ral . Instrume ntation has been previously described.13 Massspectra were obtained using a Finnigan M odel 1015 gas chroma to-graph-mass spectrometer operated at 70 eV. For GC analyses use wasmad e of 5 ft columns of 20% SE-30 and 20% Carbowax 20 M and a 6ft column of 10%DEGS, each on Chromosorb P. Th e syntheses of3-(l-phenylcyclopropyl)propanoicacid, 4-(l-phenylcyclopropyl)-butanoic acid, 5-(1-phenylcyclopropy1)pentanoic cid , and thei r re-spective acid chlorides (1, n = 3-5) have been described.14 Finelypowdered aluminum chloride was stored in a desiccator over phos-phorus pentoxide. Stan nic chloride was distilled prior to use. Reagentgrade acetonitri le, benzene, and methylene ch loride were disti l ledfrom calcium hyd ride prior to their use as reaction solvents. Allglassware was oven-dried and assembled in a d ry atmosph ere.Spiro[cyclopropane-l,4'-tetral-l'-one] (2) . 3- ( l -Phenylcyclo-propy1)p ropanoyl chloride (0.209 g, 1.00 mmol) in 2 mL of dry benzenewas adde d to a continuously stirred, ce-ba thcooled solution of stan nicchloride (0.96 g, 3.7 mmol) in 10 mL of anhyd rous benzene. T he rateof addition was sufficiently slow so that the reaction temperature didnot rise above 10 "C. After ad dition was com plete, the l ight yellowreaction solution was allowed to warm to room tem perature . The re-action solution was again cooled in an ice bath a fter a reaction tim eof 12 h, and 20 mL of 6 M hydrochloric acid was slowly add ed to t hehomogeneous reaction medium. Th e acid layer was separated a ndwashed 3 times with 20-mL portions of ether. Th e combin ed ether-benzene so lution was washed successively with 20 -mL portio ns of 6M hydrochloric acid, saturated aqueous sodium bicarbonate, andwater and then dried over anhydrous magnesium sulfate. The organicsolvent was removed un der reduced pressu re, and 0.167 g of a d arkcolored liquid was obtained t ha t, by GC and IH NMR analyses, con-taine d 92% of 2 (0.84 mmol, 84% yield) and 8% of a n u nidentifiedcomponent.15 Purified 2 was obtaine d by GC collection using a 10%DEGS column: mp 51-52 "C ; NM R (CDC13) 6 7.97 (1H, d of d, J , =7 Hz , J , = 2 Hz , H ortho to carbonyl), 7.25 ( 2 H, d of q, J = 7.2 Hz,$ hydrogens), 6.75 (1H, d of d, J , = 7 Hz , J , = 2 Hz, H or tho to cy-clopro pyl), 2.67 (2 H , d i s t t , J = 6.5 Hz) , 1.92 (2 H, dist t, J = 6.5 Hz),and 1.10-0.85 (4 H, m, cyclopropane ring H ); IR (CC14) 1685 cm-l(C=O).Anal. Calcd for C12H120: C, 83.69; H, 7.02. Found : C, 83.54; H,7.06.Similar tre atm ent of 3-(l-phenylcyclopropyl)propanoyl hloride(0.209 g, 1.00 mmol) with an hydro us alu minum chloride (0.44 g, 3.3mmol) in freshly disti lled acetonitri le afforded, after wo rkup, 0.11 gof a light yellow liquid tha t, by GC and 'H NMR analyses, consis tedof 83% of 2 (0.5 3 mmol, 53% yield) and 17% of two un ident ifiedproduct^.'^4 -E thy l -4 -pheny l -1 - t e t r a lone . 3-(l-Phenylcyclopropyl)propa-noyl chloride (2.00 g, 9.6 mmol) in 20 mL of dry benze ne was ad dedto a continuously stirred, ice-bath cooled mixture of aluminumchloride (1.50 g, 11 . 2mmol) in 30 mL of anhydrous benzene. The rateof addition was sufficiently slow so tha t the reaction temperatu re didnot rise above 10 "C . After additio n was complete, the homogeneousreaction solution was allowed to warm to room te mpera ture. Th e re-action so lution was again cooled in an ice ba th afte r a reaction timeof 2 h. Following the wo rkup procedure described for the synthesisof 2, 1.70 g of a white crystalline solid was obtain ed (6.8 mmol, 71%yield): mp 92-93 "C; NMR (CDC13) 6 8.35-8.10 (1H , m , H o r tho t ocarbonyl), 7.85-6.95 (8 H, m ) , 2.80-2.40 (4H, m ) , 2.26 (2 H , q , J = 7Hz), and 0.93 (3H , t, J = 7 Hz); IR (KB r) 1680 cm-1 (C=O).Anal. Calcd for CISH180: C , 86.36; H, 7.24. Found : C , 86.15; H ,7.21.4 -E thy l -1 -naph tho l . 3-(l-Phenylcyclopropyl)propanoylhloride(0.209 g, 1.00 mmol) in 2 mL of dry methylene chloride was added toa continuously stirred, ice-bath cooled m ixture of aluminum chloride(0.33g, 2.5 mmol) in 10 mL of anhydrous methylene chloride. Th e rateof addition was sufficiently slow so tha t the reaction temperature didnot rise above 10 "C . After addition was comp lete, the homogeneousreaction solution was allowed to warm t o room temp erature. T hebrown reaction solu tion was again cooled in an ice bath a fter a reactiontime of 2 h. Following the w orkup procedure described for the syn-thesis of 2,0.12 g of a light green liquid was obtained t ha t, by GC a nd

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Electroreduction of Aryl Ketones J . Org. Chem. , Vol.43, No. 23, 1978 44611H NMR analyses, contained 85% of 4-ethyl-1-naph thol (0.59 mmol,59% yield) a nd 15% of unidentified I ' r n p ~ n e n t s . ~ ~urified 4-ethyl-1-naphthol 'e was obtained following extra ction with 5% aqueo us so-dium hydroxide: NMR ( C C 4 )6 8.3- 7.8 (2 H , m ), 7.6-7.3 (2 H, m ), 7.04(1H , A B d , J = 7.5 Hz),6.61 (1H , A B d , J = 7.5 H z), 6.1-5.6 (1H, br ,phenolic OH ), 3.02 (2 H , q ) , and 1.32 (3 H , t) ; R (CC14)3600 (free0-H) , 3600-3100 (associated 0-H ), 3070,2970,2940,2880,1590,1508 ,1452, 1380 ,127 0,12 58, 1140, 1048, and 880 cm-'.noyl chloride (0.223 , 1.00mmol) in 2 mL of dry methylene chloridewas added to a continuously stirr ed, ice-bath cooled mixture of alu-min um chloride (0.35 g, 2.6 mmo l) in 10 mL of anhydro us methy lenechloride. The rate of addition was sufficiently slow so that the reactiontemper ature did not rise above 10"C. During the a ddition the reactionsolution turned orange and a black solid formed at th e bottom of thereaction flask. After addition was complete, the reaction mixture wasallowed to warn] to room temperature and became progressivelydark er. The d ark brown reaction mixture was again cooled in an icebath after a reaction tirne of 12 h. Following the workup proceduredescribed for th e syn thesis of 2,0.18 g of a dark brown solid was ob-ta ined that , by G C and 1HNM R analyses, contained 0.32 mmol(32%yield) of 3. Purified 3 was obtain ed by GC collection using a 20% SE-30colum n, and its physical and s pectral propertie s were identical withthose repor ted for 3."4,4-Diphenylcycloheptanone. 4-(l-Phenylcyclopropyl)buta-noyl chlorid e (0.223 g, 1.00mmol) in 2 mL of dry benzene was addedto a continuously stirred, ice-bath cooled mixture of aluminumchloride (0.45 g, :3.4 mmol) in 10 mL of anhy dro us benzene. T he ra teof addition was sufficiently slow so tha t the reaction temperatu re didnot rise above 10 "C. During the addition th e reaction solution turnedyellow and a d ark colored solid formed a t th e bottom of the reactionflask. After 1 h th e reaction m ixture was allowed to warm to roomtemperature ,and after a reaction time of 12 h the resulting dark brownreaction mixture was again cooled in an ice bath. Following theworkup p rocedure d escribed for the synth esis of 2,0.32 g of a dark oilwas obtained that, by GC: and 1H NMR analyses, contained 0.26 mmol(26%yield) of 3 and 0.48 mmol (48% yield) of an a ddition al productidentified as 4,4-diphenylcycloheptanone: p 100.5-101.5 "C; NMR(CDC1~)67.27(10H,s),2.8-2.3(2H,m),2.56(4H,s),and2.3-1.5(4H, m ); IR (CC14)183084, 3062 ,3028,29 40,287 2,1702 (C=O), 1597,1492, 1444, 1333, 1060, and 908 cm-';l9 mass spe ctrum, m l e (relativeintensi ty)20264 ((47, ar ent ion), 236 (37, M - CzHd ), 200 (401, 199(28), 194 (43 ), 182 ( 3 7 , 167 (25 ) ,and 91 ( 2 3 ) .Acknowledgment. We wish to thank Peter W. R a y n o l d sfo r the p r e p a r a t i o n o f th e acid c h l o r i d es e m p l o y e d in thisstudy, Thomas R. Bade for his preliminary i n v e s t i g a t i o n s ofth e Lewis acid p r o m o t e d r e a c ti o n s , and Carl C. Druskovichfo r his assistance in p r o d u c t a n a l y s e s.R e g i s t r y No.--1 ( n = 31, 67688-25-9; 1 ( n = 4), 67688-26-0; 2,67688-27-1; 3, 67688-28-2; 4-ethyl-4-phenyl-l-tetralone,7688-29-3;

4 - P h e n y l c y c l o h e p t a n o n e (3) . 4-(1 Phenylcyclopropyl)b u t a -

4-ethyl -1-naphthol , 10240-09-2; 4,4-diphenylcycloheptanone,67688-30-6.References and Notes

(1 ) (a )Camille and Henry Dreyfus Foundation Teacher Scholar Grant Awardee,1973-1978; (b ) National Science Foundation Undergraduate ResearchParticipant, Summer, 1977 .(2 ) M. P. Doyle and T. R . Bade, TetrahedronLett.,3031 (1975).(3) (a)G. A . Olah, "Friedel-Crafts and Related Reac tions", Wiley, New York,N.Y . . 1963;(b ) M. F. Anaell and M. H. Palmer, 0. ev., Chem. Soc., 18,21 I (1964); c)W. S.Johnson, Acc. Chem.Res.,1, 1 (1968); d) A. A. Khalafand R. . oberts, J. Org. Chem., 37,42 27 (1972); e)J.K . Groves, Chem.SOC.ev., 1, 73 (1972).

34, 3679 (1969),and reference s therein.(4) W. S. rahanovsky,M. P. Doyle,P. W. Mullen. and C. C. Ong, J. Org. Chem.,(5)H. Hart, R. H. Schlosberg,and R . K. Murray, J r . , J . Org. Chem., 33, 3800(19681.- - ,(6) W. S. Johnson, Org. React., 2, 114(1944).(7) (a )G. R . Elling, R . C. Hahn, and G. Schwab,J. Am . Chem. SOC.,95 , 5659(1973); b) T. Jacquier and P . Besinet, Bull. SOC.Chim. Fr . ,989 (1957).(8) M. J. Perkins, N. B. Peynircioglu, and 8. . Smith, Tetrahedron Len.,4165(1975).(9) G. A. Olah and G. Liang, J. Am. Chem. SOC.,8, 7026 (1976),and refer-ences therein.(10) (a)C. D. Nenitzescu , Carbonium lons 7970, 2, Chapter 13 (1970); b ) N .C. Deno, H. J. Peterso n, and G. S. Saines, Chem. Rev., 60, 7 (1960).(1 1) Th e corresponding reaction of 1 (n 4)with aluminum chloride in benzenethat contained 1. 2 molar equiv of triphenylmethane produced 3 (34% yield),4,4-diphenylcycloheptanone (31% yield), and triphenylmethanoi (14%yield based on 1) .Thus, hydride transfe r from triphenylmethane, even inthe nucleophilic benzene solvent, occurs at the e xpense of electrophilicsubstitution.These results and the difference in product-forming steps fromaluminum chloride promoted reactions of 4-cyclopropylbutanoyI chloride*and 1 ( n= 4)may reflect the nature of the reaction intermediates involvedin these processes. The results from intramolecular acylation reactionsof 4-cyclopropylbutanoyI ch loride have been interpreted by invoking aprotonated cyclopropane intermediate from which the observed chloroketones could be formed directly. In contrast, he additional stabilizationfrom the phenyl substituen t may promote either direct formation of thestabilized benzyl cation or co llapse of th e protonated cyclopropane in-termediate to the benzyl cation on a time scale in which migration of thetetrachloroaluminate ion to the developing cationic cen ter is slower thanhydride transfer,(12) Similar results were observed during the attempted cyclization of 7-octenoyi~ h l o r i d e . ~(13) M. P. Doyle, B. Siegfried, and J . F. Dellaria,Jr., J. Org.Chem., 42 , 2426(1977).(14) M. . Doyle, P. W. Raynolds. R. A. Barents, T. R Bade, W . C. Danen , andC. T. West, J. Am. Chem. SOC.,95 , 5988 (1973).(15) The characteristic NMR and IR absorptions of 4-phenyl~yclohexanon e'~were absent within the limits of detection ( 5 % ) n the spectra of these re-action mixtures.(16) M . A. lskenderov and V. G. Gyul'mamedov, Uch.Zap. Azerb. Gos. Univ.,Ser. Khim. Nauk, 69 (1965);Chem. Abstr., 65 , 16916c (1966).(17) E. D. Bergmann and S. Yaroslavsky, J. Am. Chem. SOC., 81 , 2772(1959).(18 ) Spectral bands from 4000 to 800 cm-' with intensities 2 20 % that of thecarbonyl stretching frequency are given.(19) Observed spect ral band positions closely match those reported for 3.l'(20 ) Relative intensities of molecular fragments above m /e 91 . relative to basepeak at mle 40.

Influence of Some Metal Sa lts on the Electroreduction of Aryl Ketones'A. Diaz,* , M. Parra, R. Banuelos, and R. C o n t r e r a sIB M Research Labora tory , S an Jos e , Cal i forn ia 95193

Rece ived October 13 ,1977

Th e electrolytic reduction of 2,3:6,7-dibenzotropone was studied in aprotic solvent in the presence of various an-hydro us metal salts. While th e cyclic voltammogram shows this reaction t o be a reversible one-electron reductionin CH3CN and DM F, the presence of sal ts such as CoClz an d Ni(acac)z is found to affect the reversibili ty of the elec-trochemical reaction withou t influencing the redu ction potential .Fe w r e p o r t s appear w h i c h d e s c r i b e the i n f l u e n c e of metal

c a t i o n saltson t h e electrolytic reductions of ketones in a p r o t i cs o l v e n t s . The reduction in these solvents d o e s p r o v i d e somet e c h n i c a l d i s a d v a n t a g e s over the reactions carried out in p r o t i cmedia. Some of the d i f f e r e n c e s are the h i g h e r o v e r p o t e n t i a l s0022-3263/78/1943-4461$01.00/0

required and th e g r e a t e r a m o u n t s of d i m e r i c p r o d u c t f o r m e di n a p r o t i c s o l v e n t s. S i n c e metal c a t i o n s c a n b e q u i t e e f f i ci e n tin p r o m o t i n g th e i on i za t ion r eac t i on s of a lky l halides in a p r o t i csolvents b y a c t i n g as L e w i s a c i d s (eq 1),2t s e e m e d a p p r o p r i a t et o study t h e i r i n f l u e n c e i n th e e l e c t r o r e d u c t i o n r e a c t i o n s o f

0 978A m e r i c a n C h e m i c a l S o c i e t y