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

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.