1232 J.C.S. Perkin I Vinyl Carbanions. Part 4.t Use of Vinyl Carbanions derived from PP-Diphenylacrylonitrile as Nucleophiles By Uri Melamed and Ben A. Feit," Department of Chemistry, Tel-Avid University, 61390 Ramat-Aviv, Tel- Aviv, Israel Vinyl carbanions of the type Ph,C=euro;.CN (la) were formed by treating PP-diphenylacrylonitrile (1) with BuLi in tetrahydrofuran, at -78 "C. These vinyl carbanions were applied as nucleophiles in addition and S,-type reactions with the f oIIowing e Iectrophi1es : pp-diphe n yI acry Ion it riI e, be n zop he none, trans- a-cya n0stiI be n e, car b on d ioxid e, and alkyl iodides. The addition of (la) to (1) took place at C(E)and afforded the addition product 1.1.4.4-tetra- phenyl-2.3-dicyanobut-1 -ene, and the addition-elimination products 1.1.4.4-tetraphenyl-2-cyanobutadiene and 1,1 ,4,4-tetraphenyl-2-butyl-3-cyanobut-l -ene.With trans-a-cyanostilbene, the Michael addition product was formed. A common by-product in all reactions was 1,l -diphenylhex-1 -ene. ANIONS react with activated olefins having an a-vinyl detected and no other evidence was observed in the hydrogen atom, both as nucleophiles (Michael addition) above mentioned studies for a nucleophilic attack at and as bases, simultaneously: this site. Methoxide ions add to pp-diphenylnitro-I ethylene to give the corresponding P-methyl ether,5 E-C-EH-A indicating that a stronger activating substituent may I compensate for the steric hindrance effect. Anions add to activated double bonds at C(a) if C(p) is sterically hindered.Addition products and/or addition-elimin- ation products are obtained. Ethoxide ions add, A for example, to pp-diphenylfluoroethylene to giveA = electronegative group. Ph,CH*CH(F)OEt and Ph,C=CH*OEt and 1,l-di-A few kinetic studies of reactions of bases with phenylethylene reacts with butyl-lithium followed by pp-disubstituted olefins in which vinyl carbanions an H-elimination (in the presence of an H-acceptor) were involved as intermediates were recently reported. to give 1,l-diphenylhex-l-ene.' Kobrich and his co-The mechanism of alkoxide-cat alysed hydrogen-deuter- workers t~~ studied extensively the reaction of various ium exchange reactions of 2,2,4,6,6-pentamethylcyclo-electrophiles with vinyl carbanions derived from pp-di- hexylideneacetonitrile of the corresponding ketone,2 substituted-a-halogeno-and aa-dihalogeno-ethylenes. of fluorene-9-ylideneacetonitrile,3 and of the alkoxide- The corresponding vinyl carbanions were prepared by catalysed isomerization of cis-arid trans-3-(2-bromo-acid-base type reactions and by metal-halogen ex-were studied kinetically change reactions.Only a few other cases were reported phenyl)-3-phenyla~rylonitrile,~ with regard to the existence of the derived vinyl carb- where activated olefins carrying one typical electro- anions as intermediates and their configurational negative substituent (not halogen) were involved in stability. The pp-disubstitution of these acrylonitrile base-catalysed nucleophilic reactions. Terminally un-derivatives depressed the nucleophilic attack at the saturated dimers of crotonic lo and acrylic l1 esters, p-carbon atom.No Michael addition products were 5 R. Anschiitz and A. Hilbert, Ber., 1924, 57, 1698. t Part 3, ref. 12. E. F. Silversmith and D. Smith, J. Urg. Chem., 1958, 23, H. M. Walborsky and L. M. Turner, J. Amer. Chem. SOC., 427. 1972,94, 2273. M. T. Reetze and D. Schinzer, Angew. Chem. Intewzat. Edn., J. F. Arnett and H. M. Walborsky, J. Org. Chem., 1972, 37, 1977, 16, 44. 3678. 8 G. Kobrich, Angew. Chem. Internat. Edn., 1967, 6, 41. B. A. Feit, L. Bohor, and S. Rubinraut, J.C.S. Perkin IT, G. Kobrich, Angew. Chem. Internat. Edn., 1972, 11,473. 1976, 253. lo J. Shabtai and H. Pines, J. Org. Chem., 1965, 30, 3854. G. Djamal and B.A. Feit, unpublished results. l1 B. A. Feit, European Polymer J., 1967, 3, 523. CH,CH=C(CO,R)*CH(CH,)CH,CO,R and CH2=C(C02R)* CH,CH,CO,R, respectively, were formed by a nucleo-philic addition of the derived vinyl carbanions to the activated olefin. Reactions involving such carbanions Ph,C=C' + BU-Ph,C=C; "CN Ph,C= C; Ph,C=C, CN of these dimers indicates that a fast acid-base type equilibrium is first established, followed by a relatively slow addition of the conjugate base (la) to the double bond of (1). i-BuH CN 9 CN/ CH-CPh,I 3-(6a) CN Ph,C =C NCN -H' 'CH =CPh2(8 1 When equimolar concentrations of BuLi and (1) were allowed to react instead of an excess of (1) being used, addition of (la) to (1) was still the preferred pathway.We suggest, however, that the chemically modified dimer 2-butyl-3-cyano-l , 1,4,4-tetraphenylbut-l-ene(10) obtained in this case is derived from the primarily formed addition product (6a) by an addition-elimination mechanism as follows: Bu Bu as nucleophiles might be of great significance to organic synthesis, by making possible the attachment to a carbon atom of both a double bond and a functional group in one step. RESULTS AN I 1)ISCUSSION Vinyl carbanions of the type Ph,C=c-CN (la) derived from Pp-diplienylacrylonitrile (1) by treating it with (6a) BuLi, were used as nucleophiles in addition and sub- stitution reactions. These vinyl carbanions were treated in THF at low temperature with various electrophiles yielding tlic expected products, along with some by- products.We liavc recently found l2 that when no electrophile was ackled to the (1)-BuLi-tetrahydrofuran (THF) re- action mixture, addition of Bu-at C(a) of (1)took place, followed by elimination of either CN- or H-to yield the olefins (2) and (3)in Scheme 1. A third compound obtained was 3,3-diphenylproyio- nonitrile (4)wliicli resulted from a nucleophilic addition of an hydride ion to (1). Out of these compounds only 1,I-diyhenylhex-1-ene (2) was formed as a by-product in the presently investigated system while the two other expected products (3)and (4) were not detected. A solution of (1) was added to an equimolar mixture of (1) and BuLi (the final ratio of (l): BuLi = 2) at -78 "C.The dimeric addition compound (7) was the main product, while the addition-elimination product (8) was obtained in low yields. The overall high yield l2 U. Melamed and B. A. Feit, preceding paper. Ph,C=C, ,CN + BU Ph2E-C-CN -CNSH; Ph2C=C, / __+ 0 CH-CHPh,,CH -CPh? bsol;,CH--SPhZCN CN CN/ (10) The dimer (8) and the olefin (2) were also formed in low yields. The dimer (8) could be recovered only as a mixture with (7). Subtraction of the absorption bands of (7) from the n.m.r. spectrum of this mixture gave the Ph,C=C, /H + BU' (1) CN I Bu bsol;CN -H-bsol; ,BU Ph2C= "CN(31 SCHEME1 absorption bands of the assigned structure of (8): T(CDCI,) 3.50 (s, 1 H) and 3.20-2.50 (m, 20 H). The vinylic hydrogen atom, being also in an allylic position, gives rise to an absorption band in a relatively low field.Some minor fractions obtained by chromatography had aromatic hydrogens only, as evident from their n.m.r. spectra. It is interesting to note in this regard that heating a mixture of (7) and (8) in ButOH-ButO-K+ under reflux gave an unidentified product containing only aromatic hydrogens (n.m.r. evidence). Such a J.C.S. Perkin I crease in the reaction temperature to 0 "C still gave, in the main, structurally modified addition products (see later). With the much less bulky nucleophile Bu-, the less-stable conformer of the initially formed inter-compound might be 1,1,4,4-tetraphenylbutatriene, mediate carbanion could rotate to the more stable Ph,C=C=C=CPh,, formed by base-catalysed elimination conformers (suitable for elimination of CN-or H-) even phxamp;ph-HH CN ph@ph CN z SCHEME2 of HCN.This compound has been formed under similar conditions from p p-diphen ylnitroet h ylene .13 Two profound differences with respect to the products formed are revealed on comparing the nucleophilic additions of the vinyl carbanion (la) and that of Bu- to the double bond of (1). The reaction of (1)with BuLi afforded the two possible addition-elimination products Scheme lj,12 whereas its reaction with (la) gave mainly the addition product (7) and one addition-elimination product (8) only in a low yield. The con- formational equilibrium (see Scheme 2) for the carb- anionic intermediate (6a) suggests that it should be PhzC=O t---R at a temperature of -78 OC.12 Olefins (8) and (9) can be formed from conformers (6a-11) and (6a-111) re- spectively by elimination of CN-or H-.The olefin (8) /+-amp; (13) was obtained in low yield but the olefin (9) not at all, in spite of the fact that the stability of the two conformers CN/ ,CH-CH Ph zC= C, Ph/ Ph (11 1 'CN CN Ph,C=C/ PhzC=C, / 'C N C02H (151 R = Me (12 1 (16) R = Et SCHEME3 highly populated with the relatively more stable con- formers (6a-11) and (6a-111). However the relatively high yield of the addition product (7), derived from the primarily formed conformer (6a-I) , indicates that the high barrier for rotation around the C(3)-C(4) bond of this conformer, combined with the very low reaction temperature, restricted the conversion of conformer (6a-I) into conformers (6a-11) and (6a-111).An in-l3 W. M. Jones and C. D. Broaddus, .J. Org. Clacm., 1961, 26, 2316. should be about the same. This result might be due to the large differences in the relative nucleophilicities and leaving group abilities of the CN- and H-anions, which lead to the following relation for the rate constants (Scheme 2): k, k,, k-, kPl,k, k-l, and k-, k,. The possible general synthetic application of vinyl carbanions of the type (la) was demonstrated in some nucleophilic addition and substitution reactions in which trans-cr-cyanostilbene, carbon dioxide, benzo-phenone, and alkyl iodides were used as electrophilic substrates (Scheme 3). The expected addition and substitution products were obtained in good yields along with some by-products (see Experimental section).The reaction of (3p-diphenylacrylonitrile (1) with BuLi did not result in formation of the addition product Ph2CH-CH(CN)*(CH,),CH,.12Fluorene-9-ylideneaceto-nitrile (13) on the other hand is more susceptible to this kind of addition due to the possible stabilization of the intermediate carbanion by the fluorene ring system. Fluoren-9-ylidenemalonitrile (17), fgr example, afforded by reaction with BuLi the addition product (18) as the result of such a stabilizing effect : (17 1 ( 18 1 The vinyl carbanion derived from (13) was therefore prepared by treating the olefin with a poor nucleophile, lithium di-isopropylamide. The vinyl carbanion thus prepared was treated with carbon dioxide to give the corresponding carboxylic acid which was further con-verted into the methyl ester derivative.EXPERIMENTAL General.-M.p.s are uncorrected. N.m.r. spectra were taken on JEOL MH60 spectrometer, SiMe, being used as an internal standard. 1.r. spectra were recorded on a Perkin-Elmer model 157 spectrometer. Materials.-Tetrahydrofuran, analytical grade (Merck) was dried by sodionaphthalene, and fractionally distilled under nitrogen into flasks fitted with self-sealing rubber caps. Aliquot portions were removed from the flask with syringes by applying a nitrogen pressure. PP-Diphenyl-acrylonitrile ( 1) was prepared by condensation of benzo- phenone with acetonitrile in the presence of sodamide l4 and dehydration of the resulting alcohol with formic acid.trans-or-Cyanostilbene (5)15 and fluoren-9-ylidenemalonitrile (17) l6 were prepared according to known methods and 1, l-diphenylhex- l-ene (2) was prepared l7 by treating phenylmagnesium bromide with ethyl caproate, followed by dehydration of the alcohol obtained. Fluoren-g-yl-ideneacetonitrile was prepared by hydrolysis of ethyl a-cyano- a-fluoren-9-ylideneacetate. The cyano-ester ( 10 g, 0.04 mol) was refluxed with a solution of sodium ethoxide Na (1.02g, 0.044 mol) in EtOH (150 ml) for 30 h. Kecrystal-lization of the crude product recovered afforded the pure product (7 g, 75), m.p.109 "C (from MeOH). Dimerization of PP-L)iphenylacrylonitriZe( 1) in the Presence of ButyZ-1ithiui.n.-This reaction was carried out under nitrogen in a three-necked flask equipped with a magnetic stirrer and a dropping funnel. The flask and the funnel were fitted with self-sealing rubber caps through which liquids were introduced by syringes. The system was dried, evacuated, and flushed with dry nitrogen prior to the introduction of solvent and solutions of reactants. THF (30 ml) was introduced into the flask and cooled to -78 "C l4 C. Runti and L. Sindellari, Boll. Chem. Farm., 1960, 99,499. E. C. Homing, Org. Synth., 1962, Coll. Vol. 111, p. 715. l6 M. Rabinovitz, I. Agranat, and E. D. Bergmann, J. Chem.SOC.(B),1967, 1281. (acetone-solid CO,). A solution of butyl-lithium (3.3 mmol) in hexane (1.5 ml) was added to the THF. A solution of (1) (0.75 g, 3.3 mmol) in THF (10 ml) was then added dropwise through the funnel. The mixture was stirred for 5 min and a further portion of (1) (0.75 g, 3.3 mmol) dis- solved in THF (10 ml) was added. The reaction mixture was then stirred for 10 min at -78 "C, and then poured into dilute hydrochIoric acid. The aqueous mixture was extracted with ether. The crude residue recovered from the ethereal extracts was chromatographed on a neutral alumina column to *Id the following products: (a) 2,3- dicyano-l,1,4,4-tetraphenylbut-l-ene(7) (0.75 g, 50), m.p. 160 "C (from ethanol), 7(CDCl,) 5.75 (1 H, d, J = 8 Hz, -CHCN), 5.35 (1 H, d, J = 8 Hz, PhZCH), 3.40-2.90 (4 H, m, ArH), and 2.90-2.40 (16 H, m, ArH); (b) 1,l-di-phenylhex-l-ene (2) (0.160 g, lo), 7(CDC13) 9.20 (3 H, t, J = 4 Hz), 8.90-8.30 (4 H, m), 8.15-7.70 (2 H, m, F-C=C-CH,-), 4.00 (1 H, t, J 4 Hz), and 3.00-2.50 (10 H, m, ArH) ; (c) 2-cyano-l,1,4,4-tetraphenylbutadiene (8) (0.15 g, loyo),T(CDC1,) 3.50 (1H, s, C=CH) and 3.20- 2.50 (20H, rn, ArH).The reaction was also carried out at 0 "C. The order of addition of reactants was changed. A solution of butyl-lithium (5.0 mml) in hexane (2.3 ml) was added dropwise to a solution of (1) (1.02 g, 5.0 mmol) dissolved in THF (50 ml) at 0 "C. The reaction mixture was stirred for 5 min at 0 "C and then poured into dilute hydrochloric acid; there was a 60 conversion of (1).The crude mixture of reaction products was chromatographed on a neutral alumina column to yield the following compounds: (a) 1,l- diphenylhex-l-ene (2) (0.12 g, 10); (b) 2-cyano-l,1,4,4-tetraphenylbutadiene (8) (0.19 g, 10); (c) 2-butyl-3-cyano-l,1,4,4-tetraphenylbut-l-ene(10) (1 g, 40), m.p. 120 "C (from EtOH) (Found: C, 89.9; H, 6.9; N, 3.15. C,,H,,N requires C, 89.79; H, 7.05; N, 3.16), r(CDC1,) 9.70-8.50 (7 H, m, CH,CH,CH,), 7.95 (2 H, m, C=C-CH,), 5.70 (1 H, d, J = 7 Hz, CHPh,), 4.45 (1 H, d, J = 7 Hz, C=C-CH-CN), and 3.10-2.30 (20 H, m, ArH) . Reaction of PP-Diphenylacrylonitrile with trans-u-Cyuno- stilbene (5) in the Presence of Butyl-lithium-The experi-mental conditions were the same as those described for the dimerization of (1) at -78 "C.A solution of (5) (0.75 g, 3.3 mmol) dissolved in THF (10 ml) was added to a cooled solution (-78 "C) of butyl-lithium in THF; there was a 76 conversion of (1). The mixture of products was chromatographed to give the addition product 2,4-dicyano- 1,1,3,4-tetraphenylbut-l-ene(11) (0.95g, 630/,), m.p. 130 "C (from EtOH) (Found: C, 87.1; H, 5.7; N, 6.9. C2,H2,N2 requires C, 87.37; H, 5.78; N, 7.05y0), T(CDC1,) 5.90 l H, d, J = 9 Hz, C=C(CN)CH(Ph), 5.35 l H, d, J = 9 Hz, CH(Ph)CN, 3.60-3.20 (2 H, m, ArH), and 3.20-2.10 (18 H, m, ArH); 1,l-diphenylhex-l-ene (2) was obtained as a by-product (0.11 g, 13). 2-Cyano-3,3-diphenyZucrylicAcid ( 12).-The experimental conditions were the same as those described for the dimeriz- ation of (1) at -78 "C.A solution of butyl-lithium (1.1 mol) in hexane (5 ml) was added to THF (40 ml) cooled to -78 "C. A solution of PP-diphenylacrylonitrile (1) (2.05 g, 1.1 mmol) in THF (10 ml) was then added dropwise to the THF-BuLi solution. The dark solution formed was stirred for 2 min at -78 "C and then crushed, solid CO, in ether was added. The pink mixture was stirred for 10 min and then poured into water. The l7 T. K. Serijan and P. H. Wise, J. Amer. Chem. SOC.,1951, 13, 5191. aqueous layer was separated and acidified to pH 3 with hydrochloric acid. The white precipitate formed was separated to give, after crystallization, 2-cyano-3,3-di-phenylacrylic acid (12) (1.8 g, 75), m.p.212 "C l8 (from acetone-benzene); vmax. 2 200 (CN) and 1 710 cm-l (GO). The cyano-acid (12)was converted into the corresponding methyl ester (13) by treatment with diazomethane : 7(CDCl,) 6.35 (3 H, s, OCH,) and 3.00-2.40 (10 H, m, ArH); 1,l-diphenylhex-l-ene (2) was obtained as a by-product (0.24 g, 10). 2-Cyano-l,1,3,3-tetra~henyZ~ro~-2-en-l-ol(14).-The ex-perimental conditions were as described above. A solution of butyl-lithium (3.3 mmol) in hexane (1.5 ml) was added to THF (30 ml) cooled to -78 "C. A solution of @-di- phenylacrylonitrile (1) (1.5 g, 6.6 mmol) in THF (10 ml) was then added dropwise. The resulting mixture was stirred for 2 min and then a solution of benzophenone (0.6 g, 3.3 mmol) in THF (10 ml) was added to it dropwise.After a further period of stirring (30 min) at -78 "C, the reaction mixture was poured into dilute hydrochloric acid (pH 5). Extractions with ether afforded a crude mixture which was separated on a neutral alumina column to give the required product 2-cyano-1,l,3,3-tetraphenylprop-2-en-1-01 (14) (0.68 g, 25) as white needles of m.p. 149 "C (from EtOH), T(CDC1,) 7.35 (1H, s, OH), 3.20-2.00 (20 H, m, ArH), vmRX.(CHCl3) 3 550 (OH) and 2 210 cm-l (CN); m/e = 387 (M+); 1,l-diphenylhex-l-ene (2) (0.09 g, 10) and the dimer 2,3-dicyano-1, 1,4,4-tetraphenylbut-l-ene(7) (0.22 g, 15) were also recovered. 2-Methyl-and 2-Ethyl-3,3-diphenylacryZonitriZe( 15) and (16).-A solution of butyl-lithium (8.8 mniol) in hesane (4 ml) was added to THF (30 ml) at -78 "C.A solution of PP-diplienylacrylonitrile (1) (1.5 g, 7.3 mmol) in THF (10 ml) was then added dropwise. The resulting mixture was stirred for 10 min and then methyl iodide (0.142 g, 0.01 mol) was added to it in one portion. Stirring was con- tinued for 15 niin at -78 "C. The reaction mixture was pourecl into water and extracted with ether. The crude mixture recovered from the ethereal extracts was chromato- graphed to give 2-methyl-3,3-diphenylacrylonitrile(15) (1.25 g, 80), m.p. 60 "C l9 (from EtOH), ~(cDc1,) 8.00 (3 H, s, CH,) and 3.00-2.40 (10 H, m, ArH); 1,l-diphenyl- G. Charles, Bull. SOC.chim.France, 1963, 1566. 19 W. Chodkiewicz, P. Cadiot, A. Willemart, and S. Prevost, Bull. SOC.chim.France, 1958, 1586.J.C.S. Perkin I hex-l-ene (2) was also obtained in a 20 (0.35 g) yield. Using ethyl iodide under the same experimental conditions afforded 2-ethyl-3,3-diphenylacrylonitrile(16) (1.3 g, 75y0), m.p. 75 "C (EtOH) (lit.,l9 76 "C), T(CDCI,) 8.80 (3 H, t, J = 5 Hz, CH2CH,), 7.70 (2 H, q, J = 5 Hz, CH2CH3), and 3.10-2.50 (10 H, in, ArH) ; 1,l-diphenylhex-l-ene (2) was also obtained (0.43 g, 25). l,l-Dicyano-l-jluoren-9-ylpentane( 18) .-The experimental procedure used was as described above for the dimerization of (1). A solution of butyl-lithium (5.0 mmol) in hexane (2.3 ml), and a solution of fluoren-9-ylidenemalonitrile (1.15 g, 5.0 mmol) in THF ( 10 ml) were used. The crude products were chromatographed on a neutral alumina column. An addition product, 1, l-dicyano- l-fluoren-g-yl- pentane (18) was obtained (0.49 g, 30).m.p. 95 "C (from EtOH) (Found: C, 83.0; H, 6.3; N, 9.3. C2,HI8N2 requires C, 82.90; H, 6.30; N, 9.80yo), T(CDCI,) 9.70-8.00 (7 H, m), 7.90-7.40 2 H, m, C(CN),*CH,, 6.00 (1 H, s, fluorenyl Y-H), and 2.80-2.00 (8 H, m, ArH). Several other products which were recovered by the chromato- graphy were impure (t.1.c.) and not identified. Cyano(jlztoran-9-yl)acetic A cid.-The experimental pro-cedure used was as described above. Lithium di-iso-propylamide was first prepared by adding a solution of butyl-lithium (4.4 mmol) in hexane (2 ml) to isopropyl- arnine (0.73 g, 5.2 mmol) at -78 "C. (The isopropylamine was distilled over barium oxide prior to its application.) The resulting solution of lithium di-isopropylamide was diluted by THF (37 ml). A solution of fluoren-9-ylidineaceto-nitrile (0.9g, 4.4 mmol) in THF (10 ml) was added dropwise during 5 niin at -78 "C. After it had been stirred for 5 min crushed dry ice was added to the reaction mixture which after a further period of stirring (10 min) was poured into dilute hydrochloric acid. The red precipitate formed was recovered to give cyano(fluoren-9-y1)aceticacid (0.28 g, 25), m.p. 212 "C (lit.,20 m.p. 212 "C) (from EtOH). Re-action of the acid with diazomethane gave the correspond- ing methyl ester, m.p. 85-87 "C (from EtOH), 7(CDCl,) 6.00 (3 HI s, -OCH,), 2.80-2.30 (6 H, m, ArH), 2.20-1.90 (1 H, m, fluorenyl l-H, cis to CN), and 1.60-1.40 (1 H, m, fluorenyl 8-H, cis to COOCH,). 7/1276 Received, 18th July, 19771 2O E. J. Gragoe, C. M. Robb, and J. M. Sprague, J. Org. Chem., 1950, 15,381.
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