Coupling reactions of 1-alkylpyridinium salts. Part 1. With phosphite and phosphinite ions

Abstract

Dimerisation of 1-methylpyridinium ion by coupling at the 4-position can be brought about by treatment with diphenylphosphinite, diphenylthiophosphinite, and diethyl or diphenyl phosphite anions in a range of solvents. Evidence is presented for the intermediate formation of 1,1′-dimethyl-4,4′-(1H,1′H)-bipyridylidene via addition of the phosphorus nucleophile at the 4-position of the pyridinium ring.