Planar Chiral Rhodium Complex Based on the Tetrahydrofluorenyl Core for Enantioselective Catalysis.

ABSTRACT

A simple four-step route to a chiral tetrahydrofluorenyl rhodium catalyst from naturally occurring (-)-α-pinene was developed. Our approach does not use multistep and time-consuming procedures such as chiral HPLC or diastereomeric resolution. The key to success lies in the face-selective coordination of rhodium to the sterically hindered tetrahydrofluorenyl ligand, giving only one diastereomeric complex. This catalyst proved to be highly efficient for asymmetric C-H annulation of aryl hydroxamates with alkenes (yield up to 95%, 91% ee) at low loading (up to 0.4 mol % based on Rh).