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Paper | Regular issue | Vol 43, No. 9, 1996, pp.1863-1871
Published online, 1st January, 1970
DOI: 10.3987/COM-96-7405
A New Synthetic Approach to Fused 1,4-Dihydropyridazines

Tetsuo Yamasaki, Mitsuo Oda, Yoshinari Okamoto, Tadashi Okawara, and Mitsuru Furukawa*

*Faculty of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-hon-machi, Kumamoto 862-0973, Japan


Cyclization of the halohydrazones (3) prepared by the reaction of 5-hydrazinopyridazinones (1) with ethyl bromopyruvate (2a) and phenyl bromide (2b) in EtOH produced pyrrolo[2,3-d]pyridazinones (4). On the other hand, heating of ethyl bromopyruvate pyridazinylhydrazone (3a) in dioxane afforded 1,4-dihydropyridazino[4,5-c]pyridazine (5a) in low yield. Compounds (5) were also obtained in good yields by heating the dihalohydrazones (7), which were synthesized from 4-chloro-5-hydrazinopyridazinones (6) and 2a,b in the presence of An(Cu). Heating of furylhydrazone (9) under similar consitions to those of the cyclization of 7 provides 3,6-provided 3,6-dihydrofuro[3,4-c]pyridazine (10).