Gold(III)-Catalyzed Synthesis of 4H-Chromenes

Significance

An efficient and highly selective gold(III)-catalyzed synthesis of functionalized 4H-chromenes has been developed. The reactions of ketones 1 with phenols 2 were investigated and the desired chromenes 3 were isolated in low to excellent yield under optimized conditions. With respect to substrate scope, the reactions ­between electron-deficient aryl methyl ketones (R^¹ = 4-ClC₆H₄, 4-BrC₆H₄, 4-FC₆H₄) and 2 (Ar = 1-Naph) proceeded faster and gave higher yields of target products than the corresponding reactions of electron-rich aryl methyl ketones. With less sterically hindered ketones, the products were obtained in moderate to excellent yields. A possible mechanism concerning the gold(III)-­catalyzed tandem reaction is proposed.