Asymmetric construction of atropisomeric biaryls via a redox neutral cross-coupling strategy

Abstract

Atropisomerically enriched biaryl frameworks are ubiquitous in many fields of chemistry. Enantioselective aryl–aryl cross-coupling provides the most straightforward entry to atropisomeric biaryls, with remarkable application potential in the field of chemical science. However, their development is hindered due to the lack of convenient and pragmatic protocols. Here, we report a method for the asymmetric synthesis of a myriad of 2-amino-2′-hydroxy-1,1′-binaphthyl (NOBIN) and 1,1’-binaphthyl-2,2’-diamine (BINAM) derivatives in excellent yields and enantioselectivities via a redox-neutral cross-coupling protocol. Two complementary systems were devised employing a chiral phosphoric acid–salt complex or Ni(OTf)2/chiral bis(oxazoline) ligand catalytic system for accessing atropisomeric NOBIN and BINAM derivatives, respectively. This work provides an alternative avenue to enantioenriched biaryls, and provides the capability to explore the synthetic and catalytic potentials of NOBIN- and BINAM-based frameworks. Axially chiral biaryls have proven to have a wide variety of uses—perhaps most importantly as ligands in asymmetric catalysis—but their synthesis remains challenging. Here, Bin Tan and colleagues report a redox-neutral aryl–aryl coupling, providing a direct route to N,N and N,O axially chiral biaryls in high yields and enantioselectivities.