Visible-Light-Induced Intramolecular Double Dearomative Cycloaddition of Arenes.

Herein we report visible-light-induced intramolecular double dearomative cycloaddition of arenes. Compared with the well-known photodimerization of arenes under ultraviolet irradiation, the current reactions are carried out under mild conditions and feature wide substrate scope. A large array of structurally-diverse polycyclic indoline derivatives is afforded in high yields (up to 98 %) with exclusive diastereoselectivity (>20:1 dr) via dearomative [4+2] or [2+2] pathway.