Synthesis of 1,3,4-thiadiazol-2(3H)-one derivatives via an unexpected intramolecular addition-elimination reaction of 1,3,4-thiadiazoles

A new synthesis was developed for 1,3,4-thiadiazol-2(3H)-one derivatives, based on a new arrangement on the thiadiazole ring with an intramolecular addition-elimination reaction. To this end, starting from 5-methyl-1,3,4-thiadiazole-2-thiol (1), derivatives of 3-((un)substituted benzyl)-5-methyl-1,3,4-thiadiazol-2(3H)-one (7a-g) and ((un)substituted phenyl)-2-oxoethyl)-5-methyl,3,4-thiadiazol-2(3H)-one (10-15) were synthesized (in yields of 81-88% and 63-71%, respectively). The structures of all synthesized compounds were characterized using IR, H-1 NMR, and C-13 NMR spectroscopy, and elemental analysis, mass spectroscopy and X-ray diffraction analysis (compounds 3c, 7b-f and 10) techniques. This study presents a new and effective reaction path for the synthesis of 1,3,4-thiadiazol-2(3H)-one derivatives. (C) 2017 Elsevier Ltd. All rights reserved.