Reaction of 1-acyl-2-phenylacetylenes with thiosemicarbazide

The reaction of 1-acyl-2-phenylacetylenes with thiosemicarbazide in methanol at 60‡C gives 2-amino-7-hydroxy-6,7-dihydro-1,3,4-thiadiazepines which, upon heating in -vacuum fragment with the formation of 3,5-disubstituted pyrazoles.