New derivatives of pyridazino[4,5-d]pyridazine

Abstract

1,4,5,8-Tetrahydroxypyridazino[4,5-d]pyridazine (II), obtained by condensation of tetraethyl ethylenetetracarboxylate (I) with hydrazine, gave the 1,4,5,8-tetrachloro-derivative (IV) with PCl₅–POCl₃. The chlorine atoms of compound (IV) could be totally or partially displaced with nucleophiles. Sodium methoxide (2 mol. equiv.) yielded a mixture of two dimethoxy-dichloro-pyridazino[4,5-d]pyridazines from which 1,5-(XI) and 1,8-dihydroxypyridazino[4,5-d]pyridazine (XIII) were obtained by hydrogenation followed by acidic hydrolysis.

The alkaline hydrolysis of compound (IV) yielded a mixture of 1,5-dichloro-4,8-dihydroxy-(XIV) and a little amount of 1,8-dichloro-4,5-dihydroxy-pyridazino[4,5-d]pyridazine (XV).

Compounds (XI) and (XIV) reacted with diazomethane to give mixtures of the corresponding bis-N-methyl-and NO-dimethyl-derivatives, whereas compound (II) yielded 4,8-dimethoxy-2,6-dimethylpyridazino[4,5-d]-pyridazine-1,5(2H,6H)-dione (III).