Sterically crowded heterocycles. XII. Atropisomerism of (1-aryl-3,5-diphenyl-1H-pyrrol-2-yl)(phenyl)methanones

摘要

Some 1-(2-substituted phenyl)- and 1-(1-naphthyl)-2,4,6-triphenylpyridinium perchlorates were treated with potassium hexacyano ferrate(III)-potassium hydroxide reagent to give the title pyrroles. Restricted rotation around the C-N bond in the products is demonstrated by NMR experiments with homochiral shift reagents, by semiempirical PM3 calculations as well as using their atropodiastereoselective and enantioselective transformations. Racemisation barriers for the (R)-2-(N-methyl-N-phenylcarbamoyl) derivative were estimated from NMR and polarimetric measurements. [References: 25]