D A. Evans Related olefin Addition rxns Chem 206 Olefin Sulfenation follows the preceding stereochemical analogies Halogen-induced heterocyclization in the synthesis of monensin Men A Hg(oAc)2 CH2OH Kishi,JAcs1979,101,259,260,262 I The Kishi Ring D Construction St,JAcS1980,103,21172121 l2, HOAc △Me Rao=98:2(78%) kGaX。一 only one diastereomer Ph H OMe CI Stereocontrol through A(1, 3) Phs-cl Ar Reetz, Angew. Chem. Int Ed. 1987, 26, 1028 DMSO The above stereochemistry is inferred from the following reaction I The Still Ring E Construction D Meo CH2OH Stereocontrol through A(1, 3) Ag2CO3% Me Phs-cI 87% Rato=95:5{59% Me Me Cardillo, Tetrahedron 1990. 46. 3321-3405 Bartlett, Asymmetric Synthesis 1984, 3, Chap 6, 411-454Me HO S Ph C C Et H H HO C C Me Me OH H Ar O O Me H Et H H Me CH2OH HO Me Me O O R R O O Me Me O Me H D O HO Me Me O Me O Me Me Me Me O O Me O Me Me I O n-Bu n-Bu C H C H Me Hg X C I C Me H H H H O Et Ar Me OH Me Me H MeO H C H C H Me S Ph MeO H Me C D D D D D D H Et H Me O O Ar H Br Me Me H Me O Me Me HO OH R + + + E E E E E Me OH n-Bu n-Bu OH Me Hg(OAc)2 HOAc OAc Me I n-Bu OH OH n-Bu HgOAc Me OH D A B O O O O O Me Me HO CH2OH Me Me H Et H HO Me HO O Me MeO Me C NBS D Me OMe Me OMe Me SPh Me Cl Me Et SPh Me MeO Et OMe Me Me Me Me SPh Me SPh Me PhS–Cl Me2Zn TiCl4 Me2Zn TiCl4 PhS–Cl PhS–Cl MeCN DMSO KI3 HCO3 – Ag2CO3 H H -O O Me Me H El(+)-induced heterocyclization Bartlett, Asymmetric Synthesis 1984, 3, Chap 6, 411-454 Cardillo, Tetrahedron 1990, 46, 3321-3408 Ratio = 95 : 5 (59%) Ratio = 99 : 1 (40%) The above stereochemistry is inferred from the following reaction: Reetz, Angew. Chem. Int. Ed. 1987, 26, 1028 + I2 , HOAc Ratio = 98 : 2 (78%) ratio = 80 :20 Olefin Sulfenation follows the preceding stereochemical analogies D. A. Evans Related Olefin Addition Rxns Chem 206 Halogen-induced heterocyclization in the synthesis of monensin Kishi, JACS 1979, 101, 259, 260, 262 Still, JACS 1980, 103, 2117-2121 E ■ The Kishi Ring D Construction: 57% only one diastereomer KO2 _ 47% Stereocontrol through A(1,3) Strain ■ The Still Ring E Construction: 87% 50% I(+) Stereocontrol through A(1,3) Strain