A NEW AND SELECTIVE ALPHA'-BROMINATION OF ALPHA,BETA-UNSATURATED KETONES

Alpha'-Bromination of alpha,beta-unsaturated ketones was carried out v ia trialkylsilyl dienol ethers with phenyltrimethylammonium tribromide . This reagent, which has not been previously used to brominate such d erivatives, allows a high degree of selectivity under mild reaction co nditions with the further advantage of not requiring the isolation of the silyl intermediates. The bromination selectivity is dependent on t he trialkylsilyl group present on the dienol ether.