D.A. Evans Carbonyl Addition Reactions: Chelate Organization Chem 206 Beta Chelation with Organometals OTBS OTBSOH t isomer Me-M t isomer 78°C BnOCH20 O BnOCH20 Chelate Model R-M M=Mgc70:30 D. A. Evans&E. sjogi Tetrahedron Lett. 1986. 27. 4961 M=znC|97:3 Me2cuLi H Me2 CuLi O stereoselection 78°cEz20 95:5 TBSO R= BOM (CH2OBn) D. A Evans and S L. Bender Bn0c0278℃的 diastereoselection JAm.Chem. Soc.1988 BnOCH20 >95:5 In press M=[cucN1298:2 M=Li 33:67 Chelate Model stereocenters reinforcing OTMS diastereoselection BnoCH20 O -78C Et20 BnOCH20 OH TC4-78°C Chelate Model CH2Cl2 Bno stereocenters non-reinforcing Chelate model M. T. Reetz Co-workers diastereoselection >92 H Me2CuLi Me Me diastereoselection Tetrahedron Lett 1984, 25, 729 BnOCH20 0 -78oC Et20 BnOCH2O OH CO2R Or WC.S圳& Co-workers Me2Zn Me Tetrahedron Lett. 1980. 21. 1035 J. Org. Chem. 1987, 52 diastereoselection 96: 4 Carbonyl Additon: Chelate Control: Evans JACS 2001, ASAP(handout)O Me H BnOCH2O Me H BnOCH2O Me O Me BnOCH2O H Me O O O Me H O Me2CuLi Me2CuLi Me2CuLi Me-M OH Me BnOCH2O Me Me Me BnOCH2O OH Me Me Me OH O O Me BnOCH2O OH Me Me R-M MeMgBr Me2CuLi O H BnO Me Me CHO O OTBS O N O Me2CH Me TBSO H RO Me O Me Ph OTMS M Me Me O O Me Me M Me BnOCH2O H O Me BnOCH2O OH Me H O O CO2R Me H H Me2Zn TiCl4 CH2Cl2 Me2CuLi XV OH O OTBS Me BnO OH Me Ph Me O H H Me CO2R OH Me O OH Me R RO Me Me O O Me Me chelate model diastereoselection 96 : 4 S. W. Baldwin & Co-workers J. Org. Chem. 1987, 52, 320. diastereoselection >92 % Chelate Model M. T. Reetz & Co-workers Tetrahedron Lett. 1984, 25, 729. + isomer TiCl4 -78 °C D. A. Evans & E. Sjogren Tetrahedron Lett. 1986, 27, 4961. Metal Ratio M = MgCl 70 : 30 M = ZnCl 97 : 3 + isomer D. A. Evans and S.L. Bender J. Am. Chem. Soc.. 1988, in press. 33 : 67 98 : 2 M = Li M = [CuCN]1/2 Metal Ratio R = BOM (CH2OBn) W.C. Still & Co-workers, Tetrahedron Lett. 1980, 21, 1035. -78 °C Et2O + isomer diastereoselection 50 : 50 diastereoselection 70 : 30 Chelate Model -78 °C Et2O -78 °C Et2O Chelate Model diastereoselection > 95 : 5 diastereoselection > 95 : 5 Chelate Model -78 °C Et2O -78 °C Chelate Model 97 : 3 50 : 50 Ratio + isomer D. A. Evans Carbonyl Addition Reactions: Chelate Organization Chem 206 Beta Chelation with Organometals Carbonyl Additon: Chelate Control: Evans JACS 2001, ASAP (handout) stereocenters reinforcing stereocenters non-reinforcing