Enantiomers of sterically hindered n-aryl-4-pyridones: Chromatographic enrichment and thermal interconversion

N-Aryl-4-pyridones 1– 6 were synthesized by condensation of the corresponding 4-pyrone with anilines. The enrichment of the enantiomers was achieved by liquid chromatography on triacctylcellulose, enantiomeric purities of(+)- 1 and (+ )- 2 being measured by 1H-NMR in the presence of an optically active auxiliary. Barriers to partial rotation about the C-N bond in 1- 4 were determined and compared with corresponding biphenyls.