Probing Into Asymmetric Dearomatizing Photocycloadditions of 2‐Naphthalene Derivatives With Alkenes: [2 + 2] and [4 + 2] Pathways

Abstract

ABSTRACT Catalytic dearomative photocycloaddition stands as one of the most powerful strategies for constructing highly complex, three‐dimensional polycyclic scaffolds from readily accessible planar aromatic precursors. However, achieving asymmetric variants of these transformations with simple alkenes remains a formidable challenge, as it demands precise control over regio‐, diastereo‐, and enantioselectivity. Herein, we report asymmetric dearomatizing [2 + 2] and [4 + 2] photocycloadditions of 2‐naphthalene derivatives by chiral terbium(III)/ N,N' ‐dioxide complexes, wherein a pronounced ligand‐acceleration effect is operative. The selectivity between the two pathways is governed by reaction temperature, alkene stoichiometry, and reaction time, thereby enabling the divergent synthesis of chiral cyclobutane‐fused adducts (46 examples, up to 99% yield, > 19:1 dr, 99% ee) and bridged adducts (41 examples, up to 99% yield, up to 12:1 dr, 99% ee) with high efficiency. Notably, both cycloaddition manifolds accommodate terminal and internal olefins. Mechanistic investigations elucidate the origin of the ligand‐acceleration effect and establish a kinetic basis for ortho ‐selectivity in the [2 + 2] pathway and a thermodynamic basis for para ‐selectivity in the [4 + 2] pathway. Density functional theory calculations further rationalize the competitive interplay between [2 + 2] and [4 + 2] cycloadditions and provide insight into the stereochemical outcome.