Pyridazine derivative and related compound, part 18:: Pyridazino[3′, 4′:3,4]pyrazolo[5,1-c]-1,2,4-triazine-3-carboxylic acid:: Synthesis, reactions, and antimicrobial activity

A series of 3-substituted pyridazino[3',4':3,4]pyrazolo[5,1-c]-1,2,4-triazens have been synthesized starting from the 3-carboxylic acid derivative 2. The reaction of the acid chloride 3 with amines gave the corresponding anilides 4. The reaction of 2 with ethyl chloroformate and sodium azide in the presence of triethyl amine gave the carbonyl azide 5, which underwent a Curtius rearrangement in boiling ethanol to afford the carbamate 6, which converted to the 3-amino derivative 7 upon alkaline hydrolysis, and the reaction with acid chloride resulted in N-substituted products 9. On other hand, the reaction of the carboxylic acid 2 with POCl3 and thiosemicarbazide afforded 2-amino-1,3,4-thiadiazole derivative 13. The condensation of 13 with aldehydes furnished 14 in a good yield. The products were screened for their antimicrobial activity against six microorganisms.