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
Epoxide desymmetrizations by bromide are very rare despite the large synthetic potential of chiral bromohydrins. Herein we present a new concept for epoxide desymmetrizations in which a bifunctional Lewis acid...
The facile synthesis of chiral 1,2-chlorohydrins via the enantioselective ring-opening of meso-epoxides with silicon tetrachloride in the presence of a chiral phosphine oxide was accomplished. The chiral 1,2-chlorohydrins were also obtained from the corresponding cis-alkenes in one-pot without significant loss in the selectivity, thereby permitting easy access to the 1,2-chlorohydrins from cis-alkenes with good yields and enantioselectivities. (C) 2013 Elsevier Ltd. All rights reserved.
Planar-Chiral Pyridine <i>N</i>-Oxides, a New Family of Asymmetric Catalysts: Exploiting an η<sup>5</sup>-C<sub>5</sub>Ar<sub>5</sub> Ligand to Achieve High Enantioselectivity<sup>1</sup>
作者:Beata Tao、Michael M.-C. Lo、Gregory C. Fu
DOI:10.1021/ja003573k
日期:2001.1.1
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