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

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.