Visible-light TiO2-catalyzed synthesis of dihydrobenzofurans by oxidative [3 + 2] annulation of phenols with alkenyl phenols

Abstract

An oxidative strategy for the preparation of dihydrobenzofurans via heterogeneous photocatalysis is reported. This method leverages the surface interaction between the alkenyl phenol and the TiO₂ solid surface, which enables direct activation by visible light without the need for pre-functionalization or surface modification. The resulting alkenyl phenoxyl radical is proposed to be selectively captured by a neutral phenol nucleophile, rendering β-5′ coupling with excellent chemo- and regio-selectivity. The reaction proceeds under benign conditions, using an inexpensive, nontoxic, and recyclable photocatalyst under visible light irradiation with air as the terminal oxidant at room temperature.