Planar-Chiral Cyclopentadienyl Rhodium Catalysts: Design Concept, Chiral Resolution Strategy, and Applications

Chiralhalf-sandwich cyclopentadienyl rhodium(III) (CpRhIII) complexesare potent catalysts for asymmetric C-H activation.They are primarily produced from chiral Cp ligands bearing diversechiral backbones. However, it remains a big challenge to develop planar-chiralCp(px)Rh(III) catalysts with prochiral Cp ligands(Cp-px) due to the lack of design guidelines and ideal chiralresolution methods. To solve this problem, we present herein a feasibledesign concept and a robust chiral resolution strategy. Notably, atype of planar-chiral (CpRhIII)-Rh-px catalyst bearingprochiral tetrasubstituted Cp-px ligands with the formulaC(5)HMe(2)PhAr has been successfully developed byroutine silica-gel chromatographic separation of related diastereomericchiral diene derivatives. This catalyst proved to be highly effectivefor 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 withnorbornene (up to 92% yield, 94% ee).

Automated summary

A new type of CpRh(III) catalyst has been successfully designed and synthesized for asymmetric C-H activation. The catalyst, with prochiral tetrasubstituted Cp-px ligands, showed high catalytic activity in various reactions, achieving high yields and enantiomeric excesses.