A. Evans Allylic Strain Enolate Diastereoface Selection Chem 206 OTs NH4CI LiNR OMe diastereoselection 98: 2 n-C4Hg n-C4Hg . Fleming Co-workers, Chem. Commun. 1985, 318. n-C4Hg Y Yamamoto Co-workers. Chem. Commun. 1984. 904 D. Kim Co-workers. Tetrahedron Lett. 1986. 27. Me3SI Bn Me-cHo MesSi OBn diastereoselection 90: 10 at C3 1. Fleming& Co-workers, Chem. Commun. 1986, 1198. G. Stork& Co-workers, Tetrahedron Lett. 1987. 28. 2088 s diastereoselection >95% CH2 TBSOCH2, LiNR2 TBSOCH2 L H T Mukaiyama& Co-workers, Chem. Letters 1986, 637 T Money&Co-workers, Chem. Commun. 1986, 288 Mes Me K Koga& Co-workers, Tetrahedron Letters 1985, 26, 3031 Me R= Me: diastereoselection 99: 1 CO2Et O-t-Bu CO2Et R=Ph: diastereoselection 97- 3 R=H: one isomer KOl-Bu CO2+-Bu R=Me: >15: 1 HF78° Fleming& Co-workers, Chem. Commun. 1984, 28 Y Yamaguchi& Co-workers, Tetrahedon Letters 1985, 26, 1723.CO2Me Me RO2C O O H EtO Me O n-C4H9 OTs H EtO O n-C4H9 H Br LiNR2 LiNR2 MeI LiNR2 H n-C4H9 O Me EtO EtO Me O n-C4H9 H H O O RO2C Me CO2Me H N N Me O Bn S Boc S Me3Si OBn Ph O Ph OM Me3Si OMe R LiNR2 Sn(OTf)2 Me–CHO O Me OMe OLi O-t-Bu R CO2Et I H CH2 TBSOCH2 Me CO2Me CO2Me Me TBSOCH2 H CH2 H Me Me PhMe2Si OEt R OM R O PhMe OEt 2Si (MeS)3C–Li KOt-Bu Me–I R–CHO MeI LiNR2 MeI NH4Cl OMe Me O MeS MeS MeS Me Ph O Me3Si OBn Me H OH H H CO2Et CO2 -t-Bu R S N Boc N S Bn Me O R OH H R Me3Si OMe Ph O D. A. Evans Allylic Strain & Enolate Diastereoface Selection Chem 206 Y. Yamaguchi & Co-workers, Tetrahedron Letters 1985, 26,1723. R = Me: > 15 :1 R = H: one isomer THF -78 °C diastereoselection 90:10 at C3 one isomer at C2 71% yield I. Fleming & Co-workers, Chem. Commun. 1986, 1198. 86% diastereoselection 99:1 K. Koga & Co-workers, Tetrahedron Letters 1985, 26, 3031. T. Mukaiyama & Co-workers, Chem. Letters 1986, 637 diastereoselection >95% 91-95% Y. Yamamoto & Co-workers, Chem. Commun. 1984, 904. major diastereomer opposite to that shown 40:60 80:20 87:13 R = CHMe2 R = Et R = Me R-substituent diastereoselection I. Fleming & Co-workers, Chem. Commun. 1985, 318. R = Ph: diastereoselection 97:3 R = Me: diastereoselection 99:1 I. Fleming & Co-workers, Chem. Commun. 1984, 28. D. Kim & Co-workers, Tetrahedron Lett. 1986, 27, 943. diastereoselection 98:2 G. Stork & Co-workers, Tetrahedron Lett. 1987, 28, 2088. "one isomer" 95% yield "one isomer" T. Money & Co-workers, Chem. Commun. 1986, 288. diastereoselection 89:11