title: Catalytic cycle of rhodium-catalyzed asymmetric 1,4-addition of organoboronic acids. Arylrhodium, oxa-pi-allylrhodium, and hydroxorhodium intermediates.
abstract: The catalytic cycle of asymmetric 1,4-addition of phenylboronic acid to an alpha,beta-unsaturated ketone catalyzed by a rhodium-binap complex was established by use of RhPh(PPh(3))(binap) as a key intermediate. The reaction proceeds through three intermediates, phenylrhodium, oxa-pi-allylrhodium, and hydroxorhodium complexes, all of which were observed in NMR spectroscopic studies. The transformations between the three intermediates, that is, insertion, hydrolysis, and transmetalation, were also observed. On the basis of the catalytic cycle, a more active chiral catalyst, [Rh(OH)(binap)](2), was found and used successfully for the asymmetric 1,4-addition reactions.
authors: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan. thayashi@kuchem.kyoto-u.ac.jp
authors: Tamio
authors: T
authors: Hayashi
authors: Makoto
authors: M
authors: Takahashi
authors: Yoshiaki
authors: Y
authors: Takaya
authors: Masamichi
authors: M
authors: Ogasawara