OXIDATION OF THIOAMIDES WITH THE DMSO–HCl SYSTEM: A CONVENIENT AND EFFICIENT METHOD FOR THE SYNTHESIS OF 1,2,4-THIADIAZOLES, ISOTHIAZOLO[5,4- b ]PYRIDINES, AND HETEROCYCLIC DISULFIDES

Abstract

Brief heating of 3-aryl-2-cyanothioacrylamides in the DMSO–HCl system gave (2 E ,2' E )-2,2'-(1,2,4-thiadiazol-3,5-diyl)bis(3-arylacrylonitriles). Under the same conditions, cyclic thioamides (derivatives of 2‑thioxo-1,2-dihydropyridine-3-carbonitrile and quinoxaline-2(1 H )-thione) gave good yields of the bis(hetaryl) disulfides. Ethyl 4-(4-chlorophenyl)-5-cyano-2-phenyl-6-thioxo-1,4,5,6-tetrahydropyridine-3-carboxylate gave a mixture of oxidation products at the sulfur atom and the heterocycle when treated with the DMSO–HCl system. Oxidation of N -aryl-4,6-dimethyl-2-thioxo-1,2-di-hydropyridine-3‑carboxamides gave isothiazolo[5,4- b ]pyridines. Authors: V. V. Dotsenko and S. G. Krivokolysko English Translation in Chemistry of Heterocyclic Compounds , 2013, 49 (4), pp 636-644 http://link.springer.com/article/10.1007/s10593-013-1291-4