Development of Efficient Asymmetric Suzuki-Miyaura Cross-Coupling and Applications in Synthesis

Abstract

A series of structurally rigid, sterically bulky biaryl monophosphorus ligands were designed and synthesized to investigate the reactivity and stereoselectivity of asymmetric Suzuki-Miyaura cross-coupling reaction. High efficiencies were achieved in sterically demanding cross-couplings for the synthesis of tetra-ortho-substituted biaryls with various functional- ities. Sterically demanding aryl-alkyl Suzuki-Miyaura couplings between di-ortho-substituted aryl halides and secondary al- kylboronic acids were also successful. In achieving efficient asymmetric Suzuki-Miyaura coupling, we implemented a new concept by employment of a chiral biaryl monophosphorus ligand developed in the group as well as utilization of a secondary interaction between two coupling partner. Using a π-π interaction of a benzooxazolidinone substituent with one aryl partner, we developed enantioselective biaryl couplings containing ortho-carbonyl substituents. High enantioselectivities were also achieved in biaryl coupling containing ortho-oxy substituents by utilizing a polar-π interaction between a polar bis(2- oxo-3-oxazolidinyl)phosphonic (BOP) substituent and one aryl partner. The methodology enabled us for the first time to im- plement efficient asymmetric Suzuki-Miyaura coupling in total synthesis and accomplish the syntheses of chiral biaryl natural products korupensamines A and B, ultimately a concise and stereoselective synthesis of michellamine B. Keywords monophosphorus ligand; sterically demanding; Suzuki-Miyaura coupling; secondary interaction; total synthesis