A. Evans Enantioselective C=O Addition: Corey-ltsuno Catalyst Chem 115 Discovery of a Catalytic Process Recent Review: Corey, E.J. and C J. Helal (1998) ion of carbonyl The compounds with chiral oxazaborolidine catalysts paradigm for Catalytic cycle =+8 enantioselective catalysis and a powerful new synthetic Angew. Chem. Int. Ed. engl37(15):1987-2012 OBH2 The stoichiometric Process: Itsuno 1983-1985 11=人 Chiral 30°C,10hr Boron Hydride (H-BXc) (H-BXc) R=n-Bu 100 %ee Itsuno. Chem. Commun. 19 itsuno, J. Org. Chem. 1984 Itsuno, J. Chem. Soc. Perkin Trans / 1985. 2615 a The Catalytic Process: Corey, 1987 B JAcs1987,109.5551 Corey,JOc1988,53,2861 Catalyst X-ray, Corey, Tet Let 1992, 33, 3429 athe Joc catalyst prep: Mathre, JOC 1993, 58, 799 lathe JOC 1991. 56 R=t-Bu 97%ee Review)Martens, Tetrahedron Asymmetry 1992, 3, 1475 R=C-C6H11 91%ee But how does it really work? 19A-07-Corey Cat 11/1/00 8:03 AM(Review) Martens, Tertrahedron Asymmetry 1992, 3, 1475 97 % ee 97 % ee 91 % ee But how does it really work ? R = Ph, R = t-Bu, R = c-C6H11 BH3 – + BH3 R = H R = Me ■ The Catalytic Process: Corey, 1987 Itsuno, J. Chem. Soc. Perkin Trans I. 1985, 2615 Itsuno, J. Org. Chem. 1984, 49, 555 Itsuno, Chem. Commun. 1983, 469 ■ The Stoichiometric Process: Itsuno, 1983-1985 ( H –BXC ) 2 equiv BH3 30 °C, 10 hr Chiral Boron Hydride ( H –BXC ) R = Me, 94 % ee R = Et, 94 % ee R = n-Bu 100 % ee D. A. Evans Enantioselective C=O Addition: Corey-Itsuno Catalyst Chem 115 Discovery of a Catalytic Process (0.1 equiv) B B BH3 – + + – + – The Catalytic Cycle + – + Corey, JOC 1988, 53, 2861 Corey, JACS 1987, 109, 5551 Corey, JACS 1987, 109, 7925 Improved version Catalyst X-ray, Corey, Tet. Let 1992, 33, 3429 Mathre, JOC 1993, 58, 2880 catalyst prep: Mathre, JOC 1993, 58, 799 Mathre, JOC 1991, 56, 751 O H2B RL C H RS OBH2 O H2B H N C RL RS N B X Y X O B N O B Y O C RS X RL H2N Ph Ph OH Me2HC R O Ph Ph OH H R H H N N O Ph Ph B R B R O Ph Ph H3B Me O R H R OH Me O Y O X B N Y C RS RL H BH3 N B O Ph B O Me Ph H H H X Ph B Me N O Ph Ph H Recent Review: Corey, E. J. and C. J. Helal (1998). “Reduction of carbonyl compounds with chiral oxazaborolidine catalysts: A new paradigm for enantioselective catalysis and a powerful new synthetic method.” Angew. Chem., Int. Ed. Engl. 37(15): 1987-2012. 19A-07-Corey Cat 11/1/00 8:03 AM