DMSO-HCl System as an Efficient Oxidant of Thioamides and Selenoamides

(2Е,2\'E)-2,2\'-(1,2,4-Thiadiazole-3,5-diyl)bis(3-arylacrylonitriles) were obtained by short-time heating of 3-aryl-2-cyanoprop-2-enethioamides with DMSO–HCl system. Under the same conditions, cyclic thioamides (2-thioxo-1,2-dihydropyridine-3-carbonitrile and quinoxaline-2(1Н)-thione derivatives) reacted to form bis(hetaryl)disulfides in good yields (65-91%). When treated with DMSO–HCl, ethyl 4-(4-chlorophenyl)-5-cyano-2-phenyl-6-thioxo-1,4,5,6-tetrahydropyridine-3-carboxylate afforded a mixture of products of oxidation at sulfur atom and hetero ring. The oxidation of N-aryl-4,6-dimethyl-2-thioxo-1,2-dihydropyridine-3-carboxamides leads to isothiazolo[5,4-b]pyridines. 3-Aryl-2-cyanoprop-2-eneselenoamides reacted with DMSO–HCl to give (2Е,2\'E)-2,2\'-(1,2,4-selenadiazole-3,5-diyl)bis(3-arylacrylonitriles).