Just a little bit: The 1/FeCl2 complex was activated in the presence of Zn and exhibited catalytic activity for the hydrosilanereduction of ketones to give the S‐configured alcohol. In contrast, the mixed‐catalyst system of 1 and Fe(OAc)2 provides the R enantiomer. This approach provides both enantiomers from a single chiral source by the addition of a small amount of Zn.
Silylation-Based Kinetic Resolution of Monofunctional Secondary Alcohols
作者:Cody I. Sheppard、Jessica L. Taylor、Sheryl L. Wiskur
DOI:10.1021/ol2012617
日期:2011.8.5
The nucleophilic small molecule catalyst (−)-tetramisole was found to catalyze the kineticresolution of monofunctional secondaryalcohols via enantioselective silylation. Optimization of this new methodology allows for selectivity factors up to 25 utilizing commercially available reagents and mild reaction conditions.
The open d-shell enforces the active space in 3d metal catalysis: highly enantioselective chromium(<scp>ii</scp>) pincer catalysed hydrosilylation of ketones
作者:Christian H. Schiwek、Vladislav Vasilenko、Hubert Wadepohl、Lutz H. Gade
DOI:10.1039/c8cc05172k
日期:——
pyrrol (PdmBox) stereodirecting ligands provided the key to the chromium(II)-catalysed highly enantioselectivehydrosilylation of ketones. A rare square planar, chiral chromium(II) alkyl complex was found to serve as a potent precatalyst for the reduction of a broad range of aryl alkyl and dialkyl ketone derivatives. The stereoelectronic preference of the open d4 shell of chromium(II) firmly locks
Third-Generation Amino Acid Furanoside-Based Ligands from <scp>d</scp>
-Mannose for the Asymmetric Transfer Hydrogenation of Ketones: Catalysts with an Exceptionally Wide Substrate Scope
A modular ligand library of α‐amino acid hydroxyamides and thioamides was prepared from 10 different N‐tert‐butyloxycarbonyl‐protected α‐amino acids and three different amino alcohols derived from 2,3‐O‐isopropylidene‐α‐d‐mannofuranoside. The ligand library was evaluated in the half‐sandwich ruthenium‐ and rhodium‐catalyzed asymmetric transfer hydrogenation of a wide array of ketone substrates, including
activities (up to 9800 TON; TON=turnover number), broad substrate scope (81 examples), good functional‐group tolerance, and excellent enantioselectivities (85–98 % ee) in the hydrogenation of various ketones. These aspects are rare in earth‐abundant metal catalyzed hydrogenations. The utility of the protocol have been demonstrated in the asymmetric synthesis of a variety of key intermediates for chiral drugs
已经开发了一系列含有基于核苷的手性钳式配体的Mn I配合物,这些配合物具有模块化和可调的结构。该配合物在各种酮的氢化反应中显示出前所未有的高活性(高达9800 TON; TON =周转数),广泛的底物范围(81个实例),良好的官能团耐受性和出色的对映选择性(85-98%ee)。这些方面在稀土金属催化的氢化反应中很少见。该协议的实用性已在手性药物的多种关键中间体的不对称合成中得到证明。初步的机理研究表明,底物与催化剂相互作用的外层模式可能主导了催化作用。