Direct Synthesis of α,β-Unsaturated Nitriles Catalyzed by Nonionic Superbases

We report herein the use of 3−30 mol % of a new class of tricyclic strong nonionic Lewis bases P(MeNCH2CH2)3N and P(HNCH2CH2)(i-PrNCH2CH2)2N for the direct catalytic synthesis of a variety of functionalized α,β-unsaturated nitriles in high yields from aldehydes and acetonitrile or benzyl cyanide at 40−50 °C. Evidence for a novel mechanistic pathway proposed for this reaction in a polar protic solvent such as methanol, and a nonpolar aprotic solvent such as benzene is also presented. Under these conditions, primary and secondary aliphatic aldehydes do not condense satisfactorily with acetonitrile to give the α,β-unsaturated nitrile, and ketones do not condense with either benzyl cyanide or acetonitrile.