Dynamic stereochemistry of imines and derivatives. Part 16. Conformation and stereodynamics of oxaziridines, nitrones, and imines containing the N-(1-mesitylethyl) or (1-pentamethylphenylethyl) group; a nuclear magnetic resonance and X-ray crystallographic investigation

Abstract

The ¹H n.m.r. chemical shift nonequivalence of the ortho-methyl groups in eight title compounds observed at or below ambient temperature is assigned to slow rotation about the aryl–CHMe Bond. The rotational barriers(8–17 kcal mol^–1)were evaluated by lineshape analysis and compared with that in 1-mesitylethylamine. The conformation of 3,3-diphenyl-2-(1-mesitylethyl)oxaziridine (1), which shows abnormal ortho-methyl signal positions and a high rotational barrier, has been determined in the solid state by X-ray crystallography.