Synthesis of Axially Chiral Biaryl-2-amines by PdII -Catalyzed Free-Amine-Directed Atroposelective C-H Olefination

Abstract

A simple and ubiquitously present group, free amine, is used as a directing group to synthesize axially chiral biaryl compounds by Pd^II -catalyzed atroposelective C-H olefination. A broad range of axially chiral biaryl-2-amines can be obtained in good yields with high enantioselectivities (up to 97 % ee). Chiral spiro phosphoric acid (SPA) proved to be an efficient ligand and the loading could be reduced to 1 mol % without erosion of enantiocontrol in gram-scale synthesis. The resulting axially chiral biaryl-2-amines also provide a platform for the synthesis of a set of chiral ligands.

Keywords: C−H olefination; atroposelectivity; biaryl-2-amines; chiral spiro phosphoric acids; palladium.