Pyridazines, LIV: On the synthesis of pyridazine-fused S-heterocycles: Thieno[2,3-c]pyridazine, pyrimido[4?,5?:4,5]thieno[2,3-c]pyridazine, and pyridazino[3,4-b][1,4]benzothiazine
摘要:
Starting from 3-chloro-4-pyridazinecarbonitrile (1), the thienopyridazine derivatives 2 and 3 were prepared. Condensation of 3 with triethyl orthoformate afforded the novel tricyclic system 4. Reaction of 1 with 2-aminothiophenol, followed by treatment with NaH/DMSO was found to give the diaza-phenothiazine 6 instead of the expected condensed thiazepine.