Enantioselective Synthesis of Atropisomeric Tri-Axis Naphthalenes via Diels–Alder Reaction and Dehydrative Aromatization of Isobenzofurans

Abstract

Atropisomers with multiple stereogenic axes have attracted much attention due to their increasing significance in the fields of natural products, chiral materials, and drug discoveries. However, the catalytic stereoselective construction of axially chiral ring scaffolds with more than two axes on a single benzene ring remains a challenging task. Herein, we present an efficient method for synthesizing triaxially chiral polysubstituted naphthalene scaffolds via sequential Ni(II)-catalyzed Diels–Alder reaction of isobenzofurans and TfOH-promoted dehydrative aromatization reaction. Using 1,3-biarylisobenzofurans and β-aryl-substituted α,β-unsaturated N-acyl pyrazoles as modular reaction partners, a series of naphthalenes with 1,3,4-triaxes were synthesized with excellent enantioselectivities and diastereoselectivities. Furthermore, by attaching two pyrene chromophores to this novel triaxially chiral ring scaffold, a circularly polarized luminescence (CPL)-active dye exhibiting a remarkable luminescence dissymmetry factor (glum = ‒0.019) and high fluorescence quantum efficiency (ØFL = 0.29) was obtained, highlighting the potential applications of atropisomers with multiple stereogenic axes in the design of chiroptical organic materials.