The synthesis of pyrazino[2,3-d]pyridazine and some of its derivatives

Pyrazino2,3-d]pyridazine (I) was synthesized by two different routes. 5, 8-Dihydroxy-pyrazino2, 3-d]pyridazine (IV) was converted to 5, 8-dichloropyrazino2, 3-d]pyridazine (V) and 5, 8-dibromopyrazino2, 3-d]pyridazine (Va). When V was treated with various benzyl mercaptans and alkoxides the corresponding disubstituted derivatives were obtained. Compound V when allowed to react with aromatic amines gave 5, 8-bisamino-pyrazino2,3-d]pyridazines, however, with aliphatic amines only mono substituted products were obtained substituted in the 8-position. The reaction of pyrazine-2, 3-dinitrile with hydrazine gave 5, 8-diaminopyrazino2, 3-d]pyridazine (X).