N-1 substitution of 4-arylamino-3-nitropyridines by a heterocyclic ring-opening reaction

Abstract

The normal substitution of 4-chloro-3-nitropyridine by primary aromatic amines is accompanied by the unexpected formation of 1-aryl-4-arylimino-3-nitropyridines. These products are formed via intermediate 4-arylamino-3-nitro-1-(3-nitro-4-pyridyl)pyridinium chlorides that are substituted by the primary amines by a mechanism involving addition–heterocyclic ring opening, closure, and elimination.