A reinvestigation of the cyclodesulfurization of thiosemicarbazides

A recent report describing the preparation of 2-(substituted-amino)-3,4-dihydro-5H-1,3,4-benzotriazepin-5-ones (3), by the cyclodesulfurization of hydrazides prepared from o-aminobenzoylhydrazine ( 1 ) and isothiocyanates, is erroneus. The products resulting from this reaction sequence are, instead, 2-(substituted-amino)-5-(o-aminophenyl)-1,3,4-oxadiazoles ( 4 ). Alternate syntheses of the oxadiazoles led to the correct structural assignments.