Enantioselective Synthesis of Axially Chiral Benzothiophene/Benzofuran‐Fused Biaryls via N‐Heterocyclic Carbene Catalyzed Arene Formation

Axially chiral biaryl scaffolds are prevalent in natural products, chiral ligands, and organocatalysts. However, NHC-catalyzed de novo construction of aromatic ring with concomitant axially chiral induction for the synthesis of biaryl atropisomers is far less developed, and the efficient synthesis of axially chiral tetra- ortho -substituted biaryls remains an unsolved problem under NHC catalysis. Herein, we report an NHC-catalyzed de novo synthesis of axially chiral benzothiophene/benzofuran-fused biaryls from enals and 2-benzyl-benzothiophene/benzofuran-3-carbaldehydes through a cascade strategy of [2+4] annulation, decarboxylation, and oxidative aromatization with central-to-axial chirality conversion. The developed method provides an efficient and general access to novel axially chiral benzothiophene/benzofuran-fused biaryls in high enantioselectivities and works well for the synthesis of tetra- ortho -substituted biaryls.