Axially chiral 2‐(dialkylamino)benzamides. Barriers to rotations, determined by NMR and by racemization (neighboring rotor substituents on arene systems, part 3)

The title compounds (Scheme 1, Y = NMe 2 ) were investigated by variable‐temperature NMR and/or by racemization of enantiomers enriched by liquid chromatography on microcrystalline triacetylcellulose. For several reasons, a dialkylamino and a dimethylcarbamoyl group were used, for the first time, as neighboring rotor substituents on a benzene ring. Barriers to rotations about their aryl‐nitrogen and/or aryl‐carbon bonds were determined and assigned (Table I). Correlated or uncorrelated motions of these groups are possible for amides 11 and 19 bearing in their 3‐positions tert ‐butyl substituents which hinder the aryl‐nitrogen rotation. Uncorrelated rotations have been found for amide 15 (Figure 2) and thioamide 8 which have the less voluminous bromine atom in their 3‐position.