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

Abstract

Reactions of 1,3-disubstituted 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-pyrazolol [4′,3′:5,6]pyrido[2,3-d]pyridazine-5,8(6H,7H)-diones (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-methylsufonyl-1-phenyl-1H-pyrazolo [4′,3′:5,6]pyndo[2,3-d]pyridazine-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