Synthesis of 3-(N-R)carbamoyl-5-(pyrid-4′-yl)pyridine-2(1H)-thiones and their derivatives

The condensation of salts of amidinium vinylogs with N-R-thiocarbamoylacetamides gave 3-(N-R)carbamoyl-5-(pyrid-4′-yl)pyridine-2(1H)-thiones, which undergo oxidative cyclization in concentrated sulfuric acid with the formation of 3-oxo-5-(pyrid-4′-yl)isothiazolo[5,4-b]pyridines. The oxidation and alkylation of the compounds referred to were investigated.