Studies on rotational barriers of N-C axially chiral compounds: Increase in the rotational barrier by aromatization

Abstract The rotational barriers in axially chiral quinolin-2-one and quinazolin-2-one possessing N -( ortho - tert -butyl)phenyl group were found to significantly increase in comparison with those of corresponding dihydroquinolin-2-one and dihydroquinazolin-2-one. Analysis of transition state structure during N–Ar bond rotation based on DFT calculation indicates that the increase in the rotational barrier is due to considerable distortion of the nitrogen-containing heterocyclic part.