Chiral isoxazolidine-mediated stereoselective umpolung alpha-phenylation of methyl ketones

An effective asymmetric alpha-phenylation of methyl ketones with tri-phenylaluminium in the presence of (+)-benzopyranoisoxazolidine has been developed. The reaction proceeds via the in situ formation of a chiral N-alkoxyenamine and the subsequent diastereo-selective nucleophilic phenylation to provide alpha-phenylated products in moderate to good yields, with high enantioselectivities.