Scandium-Catalyzed Phenol-Directed Construction of 5-Carbonyl-4-hydroxybenzofurans via Intramolecular Friedel-Crafts Reaction.

Herein we report a scandium-catalyzed regioselective synthesis of 5-carbonyl-4-hydroxybenzofurans via a phenol-directed intramolecular Friedel-Crafts reaction. This synthetic method was applied for the total synthesis of furanoflavones. Experimental studies and density functional theory calculations suggest that hydrogen bond interactions between the phenolic hydroxy group and the scandium complex realize regioselective intramolecular cyclization.