Synthesis and chemiluminescence of 1,3-disubstituted pyrazolo[4',3':5,6]pyrido[2,3-d]pyridazine-5,8(6H,7H)-diones and related compounds

Article abstract of DOI:10.1016/0040-4039(95)01862-C

Reactions of 1,3-disubstituted 5-aminopyrazole 5-aminopyrazole-4-carbonitrile derivatives (3a-o) with dimethyl acetylenedicarboxylate in the presence of potassium carbonate in dimethyl sulfoxide gave the corresponding dimethyl 1,3-disubstituted pyrazolo[3,4-b]pyridine-5,6-dicarboxylates (4a-o) which were allowed to react with excess hydrazine hydrate in ethanol under reflux followed by heating at 250-300°C to give 1,3-disubstituted 4-amino-1H-pyrazolo[4',3':5,6]pyrido[2,3-d]pyridazine-5,8(6H,7H)-dione s (7a-s) in good yields. These tricyclic pyridazine derivatives were evaluated for chemiluminescence. Some were found to be more efficient than luminol in light production. 4-Amino-3-methylsulfonyl-1-phenyl-1H-pyrazolo[4',3':5,6]pyrido[2,3-d]p yridazine-5,8(6H,7H)-dione (7r) showed the greatest chemiluminescence intensity derivatives in the presence of H₂O₂, peroxidase, in a solution of phosphate buffer pH 8.0.