Intramolecular vinylation of carbanions using N-acyl benzomorpholines as masked vinylureas and vinylcarbamates

Treatment of urea or carbamate derived benzomorpholines with lithium diisopropylamide generates N-vinyl ureas or N-vinyl carbamates by elimination of a phenoxide anion, cleaving the benzomorpholine ring. Simultaneous formation of a carbanion α to a stabilising aryl or nitrile group allows migration of the newly formed N-vinyl substituent to the carbanionic centre, in some cases with high enantiospecificity. Mild hydrolysis of the resulting urea or carbamate returns a C-vinylated amine, alcohol or hydantoin, in some cases with high enantiomeric purity. This 'masked' vinylation strategy avoids the need to use the reactive and volatile vinyl isocyanate as a starting material.