Heterocyclization of compounds containing diazo and cyano groups. 2. Synthesis and recyclization of 4-substituted 5-amino-1,2,3-thiadiazoles

The reaction of carbonyl derivatives of diazoacetonitrile with hydrogen sulfide in the presence of triethylamine yields 4-substituted 5-amino-1,2,3-triadiazoles. Under analogous conditions, hydrogen selenide and ethyl mercaptan reduce the starting diazo compounds to hydrazones. Thiadiazoles are recyclized to 4-substituted 5-mercapto-1,2,3-triazoles by the action of bases.