Reactions of sulfur monochloride with some aromatic aldehyde semicarbazones and thiosemicarbazones: New syntheses of substituted 2,4-dihydro-1,2,4-triazol-3-ones, 2,4-dihydro-1,2,4-triazole-3-thiones and 2-amino-1,3,4-oxadiazoles

Treatment of various substituted semicarbazones of aromatic aldehydes with sulfur monochloride yields the corresponding substituted 2,4-dihydro-1,2,4-triazol-3-ones. With thiosemicarbazones, the products are derivatives either of the 2-amino-1,3,4 thiadiazole or of the 2,4-dihydro-1,2,4-triazole-3-thione depending on the experimental conditions.