Thermal fragmentation and rearrangement of 2-(arylidenehydrazino)-4-(5H)-thiazolone derivatives: synthesis of 1,2,4-triazoles

Thermal fragmentation and rearrangement of 2-arylidenehydrazino-4-(5H)-thiazolone derivatives 1-3 led to the formation of 3-phenyl-1,2,4-triazole derivatives 11-13 as the major products in addition to 1-phenylphthalazine 15, 3-phenyl-2-thiohydantoin 19 and the corresponding nitriles, azines, thioglycolic anilide 16 and thioglycolic acid 14. Thermal fragmentation of 1 in the presence of isoquinoline as a radical trap produced 1-phenylisoquinoline in addition to the previous products. A free radical mechanism has been suggested, involving the homolysis of C-S and C-N bonds to explain the isolated products. (C) 1998 Elsevier Science B.V. All rights reserved.