Nucleophilic displacements of N-aryl and heteroaryl groups. Part 4. Pyrylium-mediated transformations of heteroarylamines into pyridinium salts and their inter- and intra-molecular displacement

Abstract

Heteroarylamines and the appropriate pyrylium salts give 1-heteroaryl-2-ethoxycarbonyl-4,6-diphenylpyridinium, and 1-(2-pyridyl)-2,6-diethoxycarbonyl-4-phenylpyridinium salts. Hydrolysis and decarboxylation afford 1-(2-pyridyl)-2,4-diphenyl- and 1-(2-pyridyl)-4-phenyl-pyridinium salts. Neither these, nor their 2,4,6-triphenyl analogues underwent smooth nucleophilic substitution.

1-Pyrimidin-2-yl- and 1-(4,6-dimethylpyridimidin-2-yl)-2-ethoxycarbonyl-4,6-diphenylpyridinium with ethanolic NaOEt smoothly formed the corresponding pyrimidin-2-ones via intramolecular attack.