Polyazaheterocyclic compounds: condensation reactions of pyridazine-4,5-dicarboxylic acid derivatives with o-phenylenediamine

Abstract

Diethyl pyridazine-4,5-dicarboxylate (II) and its 3,6-dimethyl derivative (XIV) cyclised with o-phenylenediamine in the presence of sodium hydride to give 6,11-dihydropyridazino[4,5-c][1,6]benzodiazocine-5,12-dione (III) and its 1,4-dimethyl derivative (XV), respectively. By heating under reduced pressure these compounds were dehydrated to the corresponding pyridazino[4′,5′:3,4]pyrrolo[1,2-a]benzimidazol-11-ones (XII) and (XX).

Compound (III) reacted with diazomethane yielding a mixture of di-N-methyl (IV), NO-dimethyl (V), and di-O-methyl (VI) derivatives. Mild alkaline hydrolysis of the dione (III) afforded 5-(o-aminophenylcarbamoyl)-pyridazine-4-carboxylic acid (VII), which cyclised to 5-(benzimidazol-2-yl)pyridazine-4-carboxylic acid (VIII). Heating compound (III) with hexamethylphosphoric triamide gave NN-dimethyl-5-(benzimidazol-2-yl)pyridazine-4-carboxamide (XI).

3,6-Dimethylpyridazine-4,5-dicarboxylic anhydride (XVI) reacted with o-phenylenediamine at room temperature to give 3,6-dimethyl-5-(o-aminophenylcarbamoyl)pyridazine-4-carboxylic acid (XVII), whereas when refluxed with the same reagent in acetic acid it afforded 2-(3,6-dimethylpyridazin-4-yl)benzimidazole (XVIII).