Crossing the ortho-hurdle: Ionic stereocontrol enables atroposelective Suzuki-Miyaura coupling

Abstract

Atropisomerism—a unique stereochemical phenomena arising from a rotationally restricted single bond—is ubiquitous in natural products, functional materials, and pharmaceuticals. As a direct approach to atropoenantiomers of biaryls, catalyst-controlled asymmetric cross-coupling relies exclusively on differentiation between substrates’ ortho-substituents. Here, we describe the development of ionic interaction-directed atroposelective Suzuki-Miyaura coupling. Unprecedented stereocontrol is attainable through catalyst-substrate interactions at not only the ortho- but also the meta-positions. In particular, our study surmounts a formidable hurdle of decoupling the asymmetric induction from the intrinsic influence of proximal ortho-groups and demonstrates that high atroposelectivity is achievable by engaging distal meta-substituents as the dominant stereocontrol elements. The general adaptability of the new ionic catalyst system is attributable to the unconventional approach that engages strong electrostatic steering of substrates by a sterically symmetrical ligand, which could serve as the design principle of novel catalysts to unleash the vast potential of ionic interactions in catalysis.