The Effect of Exocyclic Conjugation on the Inversion of a Saturated Six-Membered Ring. A Dynamic NMR Study of N-Substituted Morpholines.

Abstract The effect of exocyclic conjugation on the inversion of a saturated six-membered ring is shown in a dynamic nmr study of a series of N-substituted morpholines where the substituents have similar shapes but different conjugating ability. As conjugation increases the ring inversion barrier decreases in contrast to previous observations of an ring with conjugating substituents. Ring Inversion barriers for N-substituted morpholines are reported and decrease markedly with increasing conjugation along the series - where substituents have similar steric properties.