Planar-Chiral Cyclopentadienyl Rhodium Catalysts: Design Concept, Chiral Resolution Strategy, and Applications
Chunhui Zhang, Ji‐Jun Jiang, Xiaoyu Huang, Jun Wang
Abstract
Chiral half-sandwich cyclopentadienyl rhodium(III) (CpRh III ) complexes are potent catalysts for asymmetric C–H activation. They are primarily produced from chiral Cp ligands bearing diverse chiral backbones. However, it remains a big challenge to develop planar-chiral Cp px Rh III catalysts with prochiral Cp ligands (Cp px ) due to the lack of design guidelines and ideal chiral resolution methods. To solve this problem, we present herein a feasible design concept and a robust chiral resolution strategy. Notably, a type of planar-chiral Cp px Rh III catalyst bearing prochiral tetrasubstituted Cp px ligands with the formula C 5 HMe 2 PhAr has been successfully developed by routine silica-gel chromatographic separation of related diastereomeric chiral diene derivatives. This catalyst proved to be highly effective for asymmetric C–H activations, including the reaction of N -methoxybenzamides with 1,4-benzoquinone (up to 92% yield, 96% ee) and the reaction of O -Boc hydroxamates with norbornene (up to 92% yield, 94% ee).