IMIDAZO[1,2-B]PYRIDAZINES .16. SYNTHESIS AND CENTRAL-NERVOUS-SYSTEM ACTIVITIES OF SOME 6-(CHLORO, ALKYLTHIO, PHENYLTHIO, BENZYLTHIO OR PYRIDINYLMETHYLTHIO)-3-(UNSUBSTITUTED, BENZAMIDOMETHYL OR METHOXY)-2-(STYRYL OR BENZOYL)IMIDAZO[1,2-B]PYRIDAZINES

Some 6-(chloro, alkylthio, phenylthio, benzylthio or pyridinylmethylth io)-3-(unsubstituted, benzamidomethyl or methoxy)-2-styrylimidazo[1,2- b]pyridazines and 6-chloro-3- (unsubstituted and enzamidomethyl)-2-ben zoylimidazo[1,2-b]pyridazines have been prepared and tested for their ability to displace [H-3]diazepam from rat brain plasma membranes. The structures of 6-chloro-2-benzoyl[and 6-fluoro-2-(4'-tolyl)]imidazo[1, 2-b]pyridazine have been confirmed by X-ray analyses. The reactions of 6-methylthio(and 6-phenylthio)pyridazin-3-amines with 3-bromo-1-pheny lpropane-1,2-dione also have been investigated. The 6-substituted 3-un substituted 2-styryl(and benzoyl)imidazo[1,2-b]pyridazines did not bin d strongly to rat brain benzodiazepine receptors; nor did the 3-benzam idomethyl or 3-methoxy derivatives (cf. the 2-phenyl analogues). Howev er, ethyl-6-(pyridin-3-ylmethylthio)-2-styrylimidazo[1 ,2-b]pyridazine was an exception with IC50 68 nM.