Conformational study of twisted ethylenes by nuclear magnetic resonance spectroscopy

Abstract

The temperature-dependent n.m.r. spectra of 2-(diacylmethylene)-1,3-dialkylimidazolidines show that the molecules are twisted around the carbon–carbon double bonds and that the planar states represent energy maxima; in the 1,3-dibenzyl derivatives the benzylic protons are non-equivalent at ambient temperature and hindered rotation of the acyl groups is also observed.