D. A. Evans Oxymercuration EXamples Chem 206 Diastereoselective ring closures via oxymercuration I Acyclic ally lic alcohols R ROH Et HoH 65% Mukaiyama, Chem Lett. 1981, 683 ese. Tet lett. 1985. 26. 1197 t MeoH93:0772% HOH88:1266 AcHr OTFAh - tBu HoH98:0270% AcNH CO2 Me "one isomer" OBn Sinay, Tet. Lett. 1984, 25, 3071 X Hg(OAc)2 H Hg(OAc)2 RL Isobe. Tet. Lett. 1985. 26. 5199 syn. anti=80: 20 Kinetic vs Thermodynamic control Chamberlin, Tetrahedron 1984, 40, 2297 H H O-acetate participation will tum over the stereochemical course of the n NaBH Bnoc BnOc H BnOc erythro Harding, JOC 1984, 49, 2838 Hg(OAC)2: short rXn times: 40: 60 Hg(OTFA)2: longer rxn times: 2: 98 With more electrophilic Hg() salt, more polar solvents, and COOMe BnO COOMe longer xn times, the rxn may be rendered reversible Seebach JACS 1983. 105 7407HO HO RL RL C Hg X C H H H C H C H Me Hg X H H H OBn H OC6H11 BnO BnO H OH Hg(OTFA)2 OH H AcNHR' H OBn CO2Me OR H O OR HO Me H OBn H N Me BnO2C H H H NaBH4 Ph3SiH Hg(OTFA)2 NaBH4 Hg(OAc)2 Hg(OAc)2 NaBH4 XHg–HgCH2 H N BnO2C H Me H O H BnOBnO H H OC6H11 OBn O OR CO2Me OBn H R' AcNH H H OBn Me H HO O OR HO H N Me BnO2C H CH2–HgX H OAc Et n-Bu OH Me R OH OH RL HOH NaBH4 Hg(OAc)2 Me BnO O COOMe Hg(OAc)2 Hg(OAc)2 Hg(OAc)2 OH Et Me OAc OH R OR' HgOAc BnOH NaBH4 Hg(OAc)2 R OH Me Et OAc NaBH4 HOH HOH HOH MeOH COOMe BnO O Me OBn OR' R Me OH OH RL HgOAc Me OH HgOAc OR' RL OH With more electrophilic Hg(II) salt, more polar solvents, and longer rxn times, the rxn may be rendered reversible. D. A. Evans Oxymercuration Examples Chem 206 Diastereoselective ring closures via oxymercuration a:b = 96 : 4 Mukaiyama, Chem. Lett. 1981, 683 Sinay, Tet. Lett. 1984, 25, 3071 "one isomer" Isobe, Tet. Lett. 1985, 26, 5199 ■ Kinetic vs Thermodynamic control: Hg(OAc)2 : short rxn times : 40 : 60 Hg(OTFA)2: longer rxn times : 2 : 98 Harding, JOC 1984, 49, 2838 syn:anti = 80 :20 Chamberlin, Tetrahedron 1984, 40, 2297 R'OH ■ Acyclic allylic alcohols: R'OH Ratio -Et 76 : 24 yield 65% -Et 93 : 07 72% -Ph 88 : 12 66% -tBu 98 : 02 70% Giese, Tet. Lett. 1985, 26, 1197 erythro 77 : 23 O-acetate participation will turn over the stereochemical course of the rxn Seebach, JACS 1983, 105, 7407 diastereoselection = 83 : 17 (79%)