Photoredox Catalysis with Visible Light for Synthesis of Thioxanthones Derivatives

A visible-light-promoted and transition-metal-free photoredox-catalysis strategy is developed for the synthesis of thioxanthone derivatives (TXs). The mechanistic study and density functional theory calculations suggest that visible-light-promoted intramolecular cyclization can be divided into hydrogen atom transfer, C–C formation, and oxidative dehydrogenation with high regioselectivity and reactivity. Significantly, this C–C formation strategy can be used in TXs-based commercial photoinitiators and drugs at the gram level.