Stereospecific syntheses of (Z)- and (E)-4-bromomethylene-5,5-dimethyl-3-phenyloxazolidin-2-one
Abstract
3-Bromo-1,1-dimethylprop-2-ynyl carbanilate undergoes base-catalysed cyclisation to give (Z)-4-bromomethylene-5,5-dimethyl-3-phenyloxazolidin-2-one. Bromination of 5,5-dimethyl-4-methylene-3-phenyloxazolidin-2-one, followed by dehydrobromination, gives the E-isomer. The stereoisomers have been characterised by n.m.r. spectroscopy. The stereospecificity of each reaction is rationalised in mechanistic terms.