Self-disproportionation of enantiomers via achiral gravity-driven column chromatography: A case study of N-acyl-α-phenylethylamines

- A special new term: “SDE-phoric groups” was introduced.
- New approach for comparison of structural features vs. SDE magnitude based on TLC Rf values was introduced.
- The electronic effects vs. SDE magnitude was demonstrated under the conditions of gravity-driven column chromatography.
- For the first time the SDE via gravity-driven column chromatography of chiral thioamide was studied.
- The replacement of oxygen by sulphur atom in the carbonyl group, drastically changes the magnitude of the observed SDE for chiral amides.

Herein we report a study of the self-disproportionation of enantiomers (SDE) via gravity-driven achiral column chromatography of a series of amides derived from 1-phenylethylamine. We demonstrated that structural and electronic factors of the substituents play an important role in the observed magnitude of the SDE. For the first time, the SDE phenomenon of amides with that of thioamides was compared. We demonstrate that, in sharp contrast to amides, the substitution of the sulphur atom for the oxygen in the acyl group, strongly reduced the observed magnitude of the SDE. These results clearly indicate the importance of the hydrogen bonding for the formation of homo/hetero-chiral association responsible for manifestation of the SDE phenomenon.