Sterically crowded heterocycles. XIII. An insight into the absolute stereochemistry of atropisomeric (Z)-3-(imidazo[1,2-a]pyridin-3-yl)prop-2-en-1-ones

The absolute configuration of the atropisomeric (Z)-3-(5-methyl-2-phenylimi dazo[1,2-a]pyridin-3-yl)-1,3-diphenylprop-2-en-1-one was evaluated to be R for the dextrorotatory and S for the laevorotatory enantiomers. The assignm ent is based on their two-step syntheses via atropodiastereoisomeric carbam ates prepared from the corresponding atropodiastereoisomeric alcohols with (R)-(+)-alpha -phenylethyl isocyanate and by a complete X-ray space analysi s of the quaternary triiodide obtained from the (R)-(+)-enantiomer. CD spec tra and PM3 calculated heats of formation for selected compounds are discus sed in relation to the found molecular configurations.