IMIDAZO[1,2-B]PYRIDAZINES .21. SYNTHESES OF SOME 3-ACYLAMINOMETHYL-6-(CHLORO AND IODO)-2-(SUBSTITUTED PHENYL)-IMIDAZO[1,2-B]PYRIDAZINES AND-IMIDAZO[1,2-A]PYRIDINES AND THEIR INTERACTION WITH CENTRAL AND MITOCHONDRIAL BENZODIAZEPINE RECEPTORS

A series of 3-acylaminomethyl-6-(chloro, iodo and methyl)-2-(phenyl, 4 '-t-butylphenyl, 4'-cyclohexylphenyl, biphenyl-4'-yl, 4'-chlorophenyl and 4'-iodophenyl)imidazo[1,2-b]pyridazines and imidazo[1,2-a]pyridine s has been prepared and examined for interaction with central and mito chondrial (peripheral-type) benzodiazepine receptors. The imidazo[1:2- b] pyridazines were generally more selective for the mitochondrial rec eptors than the corresponding imidazo[1,2-a]pyridines. Of these compou nds, 2-(biphenyl-4'-yl)-6-chloromidazo[1,2-b]pyridazine (9) proved to be the most selective in studies of the displacement of [H-3]diazepam from peripheral-type and central benzodiazepine receptors (IC50 2.8 nM and 0% displacement at 1000 nM, respectively).