Torsional Strain-Independent Catalytic Enantioselective Synthesis of Biaryl Atropisomers

Abstract

Catalytic asymmetric dynamic kinetic resolution of configurationally labile bridged biaryls is emerging as a powerful strategy for atropisomer synthesis. However, the reported examples suffer from an inherent challenge as the reactivity is highly dependent on the torsional strain of the biaryl substrates, which significantly narrows down the scope and hampers the application. Herein, we report our discovery and development of a torsional strain-independent reaction between biaryl thionolactones and activated isocyanides. By employing auto-tandem silver catalysis, a universal synthesis of both tri- and tetra-ortho-substituted thiazole-containing biaryls was realized in high yields with high enantioselectivities. In addition, these products could be facilely converted to a novel type of bridged biaryls bearing an eight-membered lactone. Mechanistic studies were carried out to elucidate the cause of this unusual torsional strain-independent reactivity.

Keywords: Asymmetric Catalysis; Biaryls; Dynamic Kinetic Resolution; Isocyanides; Silver.