2-Phenylbenzimidazoline as a Reducing Agent in the Preparation of Malononitriles from α,β-Unsaturated Dinitriles

Abstract

The development of methods applicable to the selective reduction of carbon-carbon double bonds conjugated with strong electronwithdrawing group such as cyano, nitro, ester or sulfonate group has been a synthetic subject. Although several procedures¹⁾ have been employed for such selective reduction, virtually no sufficient method is known. Recently we have found²⁾ that benzylmalononitriles and 2-nitroethylbenzenes were obtained in good yields by the reactions of benzylidene-malononitriles and β-nitrostyrenes with a half molar amount of o-phenylenediamine (1), and showed that the products resulted from the reduction of the olefins by 2-phenylbenzimidazolines formed from equimolar amounts of the olefins and diamine (1). However, this reaction mode is not effective as a synthetic procedure for the reduction of the olefins because a half molar amount of the olefins is consumed to form 2-phenylbenzimidazolines.