Pyridazine derivatives and related compounds. Part 13: Synthesis and antimicrobial activity of some pyridazino[3′,4′:3,4]pyrazolo[5,1-c]-1,2,4-triazines

A general method for the preparation of substituted pyridazinopyrazolotriazines is reported. 3-Aminopyrazolo[3,4-d]pyridazine was diazotized and coupled with active methylene reagents to afford the tricyclic pyridazino[3′,4′:3,4]pyrazolo[5,1-c]-1,2,4-triazines with substituents such as methyl, phenyl, ethoxycarbonyl, acetyl or benzoyl, depending on the methylene reagent used. In addition several condensation reactions with hydrazines gave the corresponding acid hydrazide and/or hydrazones. Reactions of 3 with aromatic aldehydes afforded hydrazones. The products were screened for their antimicrobial activity against five microorganisms.