Wang Chuanyong, Chen Liang-An, Huo Haohua, Shen Xiaodong, Harms Klaus, Gong Lei, Meggers Eric
Fachbereich Chemie , Philipps-Universität Marburg , Hans-Meerwein-Straße , 35043 Marburg , Germany . Email:
Department of Chemical Biology and Key Laboratory for Chemical Biology of Fujian Province , College of Chemistry and Chemical Engineering , Xiamen University , Xiamen 361005 , People's Republic of China.
Chem Sci. 2015 Feb 1;6(2):1094-1100. doi: 10.1039/c4sc03101f. Epub 2014 Nov 10.
A rhodium-based asymmetric catalyst is introduced which derives its optical activity from octahedral centrochirality. Besides providing the exclusive source of chirality, the rhodium center serves as a Lewis acid by activating 2-acyl imidazoles through two point binding and enabling a very effective asymmetric induction mediated by the propeller-like -symmetrical ligand sphere. Applications to asymmetric Michael additions (electrophile activation) as well as asymmetric α-aminations (nucleophile activation) are disclosed, for which the rhodium catalyst is found to be overall superior to its iridium congener. Due to its straightforward proline-mediated synthesis, high catalytic activity (catalyst loadings down to 0.1 mol%), and tolerance towards moisture and air, this novel class of chiral-at-rhodium catalysts will likely to become of widespread use as chiral Lewis acid catalysts for a large variety of asymmetric transformations.
引入了一种基于铑的不对称催化剂，其光学活性源自八面体中心手性。除了提供手性的唯一来源外，铑中心还作为路易斯酸，通过两点结合活化2-酰基咪唑，并实现由螺旋状对称配体球介导的非常有效的不对称诱导。公开了该催化剂在不对称迈克尔加成反应（亲电试剂活化）以及不对称α-胺化反应（亲核试剂活化）中的应用，发现铑催化剂总体上优于其铱同类物。由于其通过脯氨酸介导的直接合成方法、高催化活性（催化剂负载量低至0.1 mol%）以及对湿气和空气的耐受性，这类新型的铑手性催化剂很可能会作为手性路易斯酸催化剂广泛用于各种不对称转化反应。
