Unexpected Ring Enlargement of 2-Hydrazono-2, 3-dihydro-1, 3-thiazoles to 1, 3, 4-Thiadiazines

…, AS Saghyan, A Villinger, P Langer

Index: Pfeiffer, Wolf-Diethard; Ahlers, Klaus-Dieter; Saghyan, Ashot S.; Villinger, Alexander; Langer, Peter Helvetica Chimica Acta, 2014 , vol. 97, # 1 p. 76 - 87

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Abstract

The cyclization of thiosemicarbazide with a-bromoacetophenone can result in the formation of isomeric 1, 3, 4-thiadiazines and two different thiazoles. We studied the use of 4-methyl- and 4-ethylthiosemicarbazide as dinucleophilic building blocks. In this context, we observed an unprecedented rearrangement of a 2-hydrazono-2, 3-dihydrothiazole to a 1, 3, 4- thiadiazine. While ring contractions of 1, 3, 4-thiadiazines to thiazoles are quite common, ...