Synthesis and Biological Activities of Novel 1,2,3,5-Tetrahydroimidazo[2,1-b]quinazoline Derivatives

A series of variously substituted 1,2,3,5-tetrahydroimidazo[2,1-b]quinazoline derivatives 3-4 and 6-7 were prepared by the reactions of 2-chloro-4,5-dihydroimidazole (1) with the appropriate 2-aminophenyl ketones 2 and 5. The structures of the new compounds obtained were determined by elemental analysis as well as IR and NMR spectroscopic data. Biological activities of the compounds 3 and 6 was examined on P2 membrane preparations obtained from rat whole brains and rat tail artery. Among the compounds tested, 5-methylidene-1,2,3,5-tetrahydroimidazo[2,1-b]quinazoline (6a) showed high and moderate binding affinities to I2 imidazoline (Ki = 5.2 nM) and alfa2-adrenergic (Ki = 149 nM) receptors, respectively.