title: Generation of chiral boron enolates by rhodium-catalyzed asymmetric 1,4-addition of 9-aryl-9-borabicyclo[3.3.1]nonanes (B-Ar-9BBN) to alpha,beta-unsaturated ketones.
abstract: Asymmetric 1,4-addition of 9-phenyl-9-borabicyclo[3.3.1]nonane (2m) to 2-cyclohexenone (1a) proceeded with high enantioselectivity in toluene at 80 degrees C in the presence of 3 mol % of a rhodium catalyst generated from [Rh(OMe)(cod)]2 and (S)-binap to give a high yield of boron enolate (S)-3am, which is 98% enantiomerically pure. Reaction of the boron enolate 3am with electrophiles, methanol-d, propanal, and allyl bromide, gave the corresponding 2-substituted (3S)-3-phenylcyclohexanones with perfect regio- and diastereoselectivity.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yoshida
authors.forename: Masamichi
authors.initials: M
authors.lastname: Ogasawara
authors.forename: Tamio
authors.initials: T
authors.lastname: Hayashi