Mechanism-Based Enantiodivergence in Manganese Reduction Catalysis: A Chiral Pincer Complex for the Highly Enantioselective Hydroboration of Ketones
作者:Vladislav Vasilenko、Clemens K. Blasius、Hubert Wadepohl、Lutz H. Gade
DOI:10.1002/anie.201704184
日期:2017.7.10
A manganese alkyl complex containing a chiralbis(oxazolinyl‐methylidene)isoindoline pincer ligand is a precatalyst for a catalytic system of unprecedented activity and selectivity in the enantioselective hydroboration of ketones, thus producing preparatively useful chiral alcohols in excellent yields with up to greater than 99 % ee. It is applicable for both aryl alkyl and dialkyl ketone reduction
含有手性双(恶唑啉基-亚甲基)异二氢吲哚钳位配体的锰烷基络合物是酮对映选择性氢硼化反应中空前的活性和选择性的催化体系的预催化剂,从而以高达99的高收率生产了制备有用的手性醇。 %ee。它适用于在温和的反应条件下(TOF> 450 h -1在-40°C下)。富含地球的贱金属催化剂在极低的催化剂负载量(低至0.1 mol%)下运行,并且具有很高的官能团耐受性。有证据表明存在两种不同的锰催化氢化物转移机理,并介绍了它们在选择性确定步骤中对映体控制的作用。
Enantioselective Zinc-Catalyzed Hydrosilylation of Ketones using Pybox or Pybim Ligands
The combination of ZnEt2 and chiral pyridinebisoxazoline (pybox) or pyridinebisimidazoline (pybim) ligands catalyzed the asymmetric hydrosilylation of aryl, alkyl, cyclic, heterocyclic, and aliphatic ketones. Under mild conditions, high yields and good enantioselectivities were achieved. ESI measurements allowed for the characterization of the active catalyst.