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

Synthesis and properties of diaza‐, triaza‐, and tetraazaphenothiazines

“…Only when aminophenyl 4‐cyano‐3‐pyridazinyl sulfide 231 was stirred in DMSO (with sodium hydride) at room temperature 3,4‐diazaphenothiazine 232 was obtained (in 85% yield). Reaction proceeded without the rearrangement (Scheme ) [107].…”

“…10‐Pyrrolidinylethyl and dimethylaminoethyl derivatives 237 exhibited antihistaminic activity [107].…”