The rotation-dominated ring inversion/nitrogen inversion/rotation process in N-acyloxy-2,2,6,6-tetramethylpiperidines. A dynamic NMR study

The temperature dependence of the NMR spectra of a series of N-acyloxy-2,2,6,6-tetramethylpiperidines is reported and discussed in terms of a conformational process which involves ring inversion, nitrogen inversion and rotation about the nitrogen–oxygen bond. Nitrogen inversion contributes ca. 11 kcal mol–1 to the observed barriers, so in the compounds with higher barriers, steric interaction of the acyl and methyl groups during rotation determines the barrier height.