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>