Organic Synthesis with Anion-exchange Resins:Reaction of Imines with Active MethyleneCompounds$Dilip Konwar,* Dilip Kumar Dutta and Birendra Nath GoswamiRegional Research Laboratory, Jorhat-785 006, Assam, IndiaImines undergo addition¡Óelimination reaction with active methylene compounds in the presence of Amberlite IRA-400(OH£¾) as catalyst to yield arylidenemalononitrile derivatives.Polymer-supported methods rst developed by Merrield1in polypeptide synthesis have been utilised in many trans-formations in organic chemistry.2 In recent years thecombinatorial chemistry has received much attention inorganic synthesis.3Anion-exchange resins, particularly Amberlite IRA-400,have been shown to be excellent catalysts in various organicreactions, for example aldol condensation,4 Knovenageland Michael condensation,5 cyanohydrin formation,6 etc.Recently, they have been in phenyl sulde formation7 andselective reduction of alkyl halides to alkanes.8 We reporthere an addition¡Óelimination reaction between imines andactive methylene compounds in the presence of AmberliteIRA-400 (OH£¾) as catalyst to give synthetically usefularylidenemalononitrile derivatives9 (Scheme 1).The reaction was carried out by stirring the imines 1a¡Ójand the active methylene compounds 2a¡Óc in the presence ofa molar equivalent of Amberlite IRA-400 (OH£¾) in ethanolunder reux.The product was obtained by simple ltrationevaporation of the solvent under reduced pressure andcrystallisation from appropriate solvents.The results aresummarized in Table 1.In conclusion, we have observed that the anion-exchange resin Amberlite IRA-400 (OH£¾) can rapidlyexchange its labile hydroxide ion with the enolate of theactive methylene compounds in ethanol solution producingAmberlite IRA 400 (HCR0CN£¾) which reacts with theazomethine carbon of the imines and eliminates amines insolution. Work is in progress to understand the mechanismof the reaction.ExperimentalThe mps were measured in a Buchi apparatus and are un-corrected.IR spectra were recorded on a Perkin-Elmer 237B spec-trophotometer, 1H NMR spectra on a Varian T-60 spectrometerwith TMS as internal standard and mass spectra on an AEIMS-30spectrometer The anion-exchange resin Amberlite IRA-400 wasusually purchased from Aldrich as the chloride salt (16¡Ó60 mesh).This conversion into the hydroxide form was accomplished bywashing with 1 M sodium hydroxide until the eluent gave a negativesilver nitrate test for chloride ion.The resin was thoroughly washedwith distilled water, dried for several hours at 40 8C and kept in avacuum desiccator for 24 h. before use. The imines were preparedby the literature method10 or a slight modication thereof.Preparation of Arylidene Malononitrile 3a.In a typical exper-iment, malononitrile (1.32 g, 0.02 mol) in ethanol (25 ml) wasmixed with Amberlite IRA-400 (OH£¾) (7.3 g, 0.02 mol) having acapacity of 2.8 milliequvalent per dry g and benzylideneaniline 1a(3.62 g, 0.02 mol) was stirred for 4 h at the reux temperatureof ethanol.The reaction mixture was ltered through a pad ofCelite and the solvent evaporated under reduced pressure to give aresidue which on crystallation from light petroleum (bp 40¡Ó60 8C)yielded arylidenemalononitrile 3a as white needles, mp 87 8C(lit.,11 87 8C). Yield: 2.5 g (82%). The other nitriles were preparedsimilarly.We wish to express our sincere thanks to Dr N.Borthakur and Dr J.C. S. Kataky, scientists, and Dr J. S.Sandhu, Acting Director, Regional Research Laboratory,Jorhat for their keen interest and help in carrying out thiswork.Received, 3rd February 1998; Accepted, 2nd March 1998Paper E/8/00951AReferences1 R. B. Merried, J. Am. Chem. Soc., 1963, 85, 2194.2 Organic Synthesis, Today and Tomorrow, ed. B. M. Trost andC. R. Hutchison, Pergamon Press, Oxford, 1981, pp. 19¡Ó28 andreferences therein.3 J. S. Fruch and G. Jung, Angew.Chem, Int. Ed. Engl., 1936, 35,2194.4 G. V. Austerwell and R. Palloud, Bull. Soc. Chim. Fr., 1963, 678;P. Mastagi, Z. Zariadis, G. Durr, A. Floch and G. Lagrange,Bull Soc. Chim. Fr. 1953, 693; M. H. Astle and J. A. Zaslowsky,Bull Soc. Chim. Fr. 1952, 2867.5 B. W. Howk and C. M. Langkaminerer, U.S. Pat., 2 579 580,25th December, 1951; E. D. Bergmann and R. Corret, J. Org.Chem., 1956, 21, 107; 1958, 23, 1507.Scheme 1Table 1 Synthesis of arylidenemalononitriles 3a¡ÓjaEntry R R0 t/h Yield (%)1 Ph CN 5 822 p-ClC6H4 CN 4.5 803 p-O2NC6H4 CN 4 754 CN 4.5 705 CN 5 656 Ph CONH2 4 797 Ph CN 5 828 CONH2 5 659 Ph-CH1CH CO2Et 6 6510 Ph CO2Et 6 70aAll the compounds gave satisfactory spectroscopic analyses andwere comparable with authentic samples.J. Chem.Research (S),1998, 342¡Ó343$$This is a Short Paper as dened in the Instructions for Authors,Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there-fore no corresponding material in J. Chem. Research (M).*To receive any correspondence.342 J. CHEM. RESEARCH (S), 19986 C. J. Schmidle and R. C. Mans®eld, Ind. Eng. Chem., 1952, 44, 1388. 7 N. M. Yoon, J. Choi and H. J. Ahn, J. Org. Chem., 1994, 59, 3490. 8 N. M. Yoon, J. H. Lee, H. J. Ahn and J. Choi, J. Org. Chem., 1994, 59, 4687. 9 F. Freeman, Chem. Rev., 1969, 69, 591; 1980, 80, 329; Synthesis, 1981, 925. 10 The Chemistry of Carbon Nitrogen Double Bond, ed. S. Patai, Wiley, New York, 1970. 11 P. J. Bhuyan, R. C. Boruah and J. S. Sandhu, J. Org. Chem., 1990, 55, 568. J. CHEM. RESEARCH (S), 1998 343