作者:Andreas Tschöp、Andreas Marx、Anakallil R. Sreekanth、Christoph Schneider
DOI:10.1002/ejoc.200601101
日期:2007.5
The scandium-bipyridine-catalyzed ring-opening of meso-epoxides with aliphatic alcohols has been studied. Aromatic epoxides were ring-opened with >90 % ee furnishing valuable 1,2-diol monoethers in typically good yields whereas aliphatic epoxides gave rise to moderate enantioselectivities. The catalyst loading may be lowered to 2–5 mol-% with only marginal effects on yield and enantioselectivity. A
Indium-Bipyridine Catalyzed, Enantioselective Aminolysis of <i>meso</i>-Epoxides
作者:Christoph Schneider、Enzo Mai
DOI:10.1055/s-2007-984902
日期:——
The scandium-bipyridine-catalyzedenantioselective addition of anilines and O-alkyl hydroxylamines to meso-epoxides has been optimized and extended to a broad range of epoxides and amines. Whereas aromatic meso-epoxides generally furnished the corresponding 1,2-amino alcohols in excellent enantioselectivities, aliphatic meso-epoxides only gave rise to moderate enantioselectivities in the aminolysis
An efficient and practical synthesis of optically pure β‐pyrazole‐substituted alcohols was achieved by an asymmetric ring‐opening reaction of meso‐epoxides with pyrazole derivatives as the nucleophile. In the presence of 1 mol % of an N,N′‐dioxide–Sc(OTf)3 complex, excellent enantioselectivity and yields were obtained from meso‐epoxides. The process could also be used for a mixture of cis‐ and trans‐stilbene
Allenes in Asymmetric Catalysis: Asymmetric Ring Opening of <i>meso</i>-Epoxides Catalyzed by Allene-Containing Phosphine Oxides
作者:Xiaotao Pu、Xiangbing Qi、Joseph M. Ready
DOI:10.1021/ja9041127
日期:2009.8.5
Unsymmetrically substituted allenes (1,2-dienes) are inherently chiral and can be prepared in optically pure form. Nonetheless, to date the allene framework has not been incorporated into ligands for asymmetric catalysis. Since allenes project functionality differently than either tetrahedral carbon or chiral biaryls, they may create complementary chiral environments. This study demonstrates that optically
A highly enantioselective method for the catalytic cis-stilbene oxide opening reaction with indole derivatives was developed. The scope of the reaction was studied with a selection of aromatic meso-epoxides and various indoles, and the desired 2-(indol-3-yl)ethanol derivatives were obtained in good to excellent yields with excellent enantioselectivities (from 96 to >99% ee).