Photoinduced Radical Selective O-Alkenylation of Phenols and Naphthols with Terminal Alkynes

Abstract

Visible light-promoted O-alkenylation of phenols and naphthols with terminal alkynes is achieved using 2,4,6-tris(4-fluorophenyl)pyrylium tetrafluoroborate (T(p-F)PPT) as photocatalyst at room temperature without the need of any external ligand or additive. Apart from its excellent functional group tolerance, the protocol described herein represents an appealing alternative strategy to the classical transition-metal catalysed hydroarylation reactions. The mechanistic investigations revealed that the reaction involves the radical pathway. The synthetic utility of hydroarylated products to fused benzofurans via a one-pot annulation was also demonstrated. Therefore, herein, we are reporting the first intermolecular radical hydroarylation of alkynes.