Coupling reactions of 1-alkylpyridinium salts. Part 2. Reaction of 1-methylpyridinium-4-carboxylate with cyanide and diphenylphosphinite ions

Abstract

A novel reaction between 1-methylpyridinium-4-carboxylate and cyanide ion in dipolar aprotic solvents leading to high yields of 1,1′-dimethyl-4,4′(1H,1′H)-bipyridylidene (4) is described. Coupling is also brought about by diphenylphosphinite ion. N-Methylpyridinium-2-carboxylate on heating in dimethylformamide also surprisingly affords some 4,4′-coupled product, as does 1-methylpyridinium ion when heated with carbonate or fluoride ion in non-protic media.