Synthesis and properties of 1,4-dimethylpyridazino[4,5-d] pyridazines

The synthesis and properties of several 1,4-dimethylpyridazino[4,5-d]pyridazines are described. Treatment of diethyl 3,6-dimethylpyridazine-4,5-dicarboxylate ( 1a ) with lithium aluminium hydride and hydrazine did not afford the expected 1,4-dimethylpyridazino[4,5-d]pyridazine ( 21b ) but a mixture of compounds 13, 18, 19 , and 20 , whose structures were deduced from spectroscopic data.