Substituted thiosemicarbazides react with dimethyl acetylenedicarboxylate to give 3-amino- 2, 3-dihydrothiazin-4-ones. Confirmation of the structures is provided by catalytic hydrogenation and by characteristic mass spectral fragmentations. 4-Substituted thiosemicarbazides react with methyl propiolate in the same way as monosubstituted hydrazines and hydrazides to give hydrazones, whereas 1-substituted thiosemicarbazides ...
