Designing a Planar Chiral Rhodium Indenyl Catalyst for Regio- and Enantioselective Allylic C-H Amidation

Abstract

Chiral variants of group IX Cp and Cp* catalysts are well established and catalyze a broad range of reactions with high levels of enantioselectivity. Enantiocontrol in these systems results from ligand design that focuses on appropriate steric blocking. Herein we report the development of a new planar chiral indenyl rhodium complex for enantioselective C-H functionalization catalysis. The ligand design is based on establishing electronic asymmetry in the catalyst, to control enantioselectivity during the reactions. The complex is easily synthesized from commercially available starting materials and is capable of catalyzing the asymmetric allylic C-H amidation of unactivated olefins, delivering a wide range of high-value enantioenriched allylic amide products in good yields with excellent regio- and enantioselectivity. Computational studies suggest that C-H cleavage is rate- and enantio-determining, while reductive C-N coupling from the Rh^V-nitrenoid intermediate is regio-determining.