Enantioselective Assembly of Ferrocenes with Axial and Planar Chiralities via Palladium/Chiral Norbornene Cooperative Catalysis.

Abstract

The preparation of ferrocenes with both axial and planar chiralities poses a considerable challenge. Herein, we report a strategy for the construction of both axial and planar chiralities in a ferrocene system via palladium/chiral norbornene (Pd/NBE*) cooperative catalysis. In this domino reaction, the first established axial chirality is dictated by Pd/NBE* cooperative catalysis, while the latter planar chirality is controlled by the preinstalled axial chirality through a unique axial-to-planar diastereoinduction process. This method exploits readily available ortho-ferrocene-tethered aryl iodides (16 examples) and the bulky 2,6-disubstituted aryl bromides (14 examples) as the starting materials. Five- to seven-membered benzo-fused ferrocenes with both axial and planar chiralities (32 examples) are obtained in one step with constantly high enantioselectivities (>99% e.e.) and diastereoselectivities (>19:1 d.r.).