Imidazo[1,2-b]pyridazines. XXI. 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

Abstract

A series of 3-acylaminomethyl-6-(chloro, iodo and methyl)-2-(phenyl, 4′-t-butylphenyl, 4′-cyclohexyl- phenyl, biphenyl-4′-yl, 4′-chlorophenyl and 4′-iodophenyl)imidazo[1,2-b]pyridazines and imidazo[1,2- a]pyridines has been prepared and examined for interaction with central and mitochondrial (peripheral- type) benzodiazepine receptors. The imidazo[1,2-b]pyridazines were generally more selective for the mitochondrial receptors than the corresponding imidazo[1,2-a]pyridines. Of these compounds, 3- acetamidomethyl-2-(biphenyl-4′-yl)-6-chloroimidazo[1,2-b]pyridazine (9) proved to be the most selective in studies of the displacement of [³H]diazepam from peripheral-type and central benzodiazepine receptors (IC₅₀ 2·8 nM and 0% displacement at 1000 nM, respectively).