Lithium−Sulfoxide−Lithium Exchange for the Asymmetric Synthesis of Atropisomers under Thermodynamic Control
作者:Jonathan Clayden、David Mitjans、Latifa H. Youssef
DOI:10.1021/ja017702o
日期:2002.5.1
introduces a sulfoxide substituent ortho to the stereogenic Ar-CO axis of an aromatic amide. The sulfoxide exerts a powerful conformational bias on the axis, such that after rapid equilibration at ambient temperature essentially only one of two diastereoisomeric Ar-CO atropisomers is populated. Sulfoxide-lithium exchange by treatment with t-BuLi regenerates the ortholithiated amide in an enantiomerically pure
Kinetic and thermodynamic stereocontrol in the atroposelective formation of sulfoxides by oxidation of 2-sulfanyl-1-naphthamides
作者:Mark S. Betson、Jonathan Clayden、Madeleine Helliwell、David Mitjans
DOI:10.1039/b511452g
日期:——
diastereoselectivity. NMR studies and oxidations of chiral benzamides however indicate that the kinetic selectivity of the oxidation is in fact relatively poor, and that the final diastereoisomeric ratio (typically >99:1) is under thermodynamic control, with relatively unhindered Ar-CO rotation readily converting the less stable to the more stable product diastereoisomer. Molecular mechanics indicates that