Sterically Crowded Heterocycles. IX. New α,β-Unsaturated Ketones Containing Imidazo[1,2-a]quinoline, Imidazo[2,1-a]isoquinoline, Benzo[h]imidazo[1,2-a]quinoline and Imidazo[1,2-a]-1,10-phenanthroline Moieties
(Z)-1,3-Diphenyl-3-(2-phenylimidazo[1,2-a]heteroaryl)prop-2-en-1-ones 2-6 and isomeric [1-heteroaryl-3,5-diphenylpyrrol-2-yl]phenylmethanones 17-20 were prepared by the ferricyanide oxidation of quaternary pyridinium salts 12-16. Axial chirality and helicity of the molecules of 4 and 6 are discussed using various energy data obtained by the quantum chemical PM3 method.