Pyridazine derivatives and related compounds, Part 9. Tetrazolo{[}1,5-b]pyridazine-8-carbohydrazide synthesis and some reactions

The reaction of the hydrazide of 6,7-diphenyltetrazolo{[}1,5-b]pyridazine-8-carboxylic acid (3) with aromatic aldehydes gave 8-arylidenecarbohydrazide derivatives. The reaction of 3 with methanesulfonyl chloride, benzenesulfonyl chloride, phenyl and benzyl isothiocyanates afforded the corresponding N-substituted derivatives. The reaction of 3 with potassium ethylxanthate gave 5 (6,7-diphenyltetrazolo{[}1,5-b]pyridazin-8-yl)-1,3,4-oxadiazole-2-thione (7). The alkylation of this product in an alkaline medium proceeds at the sulfur atom, while the aminomethylation and acylation proceed at the nitrogen atom. Compound (3) also reacted with N-aminothiosemicarbazide to give 4-amino-5-(6,7-diphenyltetrazolo{[}1,5-b]pyridazin-8-yl)-1,2,4-triazole- 3-thione (11).