Re-examination of the Anodic Dimerization of Enamines, 2-Cyano-2-phenylvinylamines, Using the Austin Model 1 Method

Dimerization of cation redicals derived from 2-cyano-2-phenylvinylamines (1) to produce diphenylmethane derivatives (Ph-CH(CN)-C6H4-C(CN)=CH-NR2R3, 2) was re-examined by the AM1 (Austin model 1) method.However, dimerization of cation radicals derived from 1 was forbidden by calculation of the total energies of the dimers. An alternative reaction mechanism for the formation of 2 was proposed. Hydrolysis of cation radical (A) derived from N, N-dimethyl-2-cyano-2-phenylvinylamine (1a) gives a cyanophenylmethyl radical (F), which attacks at 1a to give a redical (G). Following anodic oxidation of G, deprotonation gives phenyl-[4-(1-cyano-2-dimethylaminovinyl)phenyl]acetonitrile (2a) as the final product.