Acid-Catalyzed [4+1]-Dearomatization Spiroannulation of Hydroquinones and Naphthols

Abstract

Acid-catalyzed [4+1] dearomatization spiroannulation reactions of electron-rich hydroquinone and naphthol derivatives were demonstrated as convenient methods to access spiro-cyclic cyclohexadienone derivatives. Lewis acid Bi(OTf)3 exhibit the best catalytic performance when 1,2-dialkynylbenzene was used as the electrophile for the spiroannulation, while Brønsted acid benzene-1,2-disulfonic acid was the best catalyst when 2-ethynylbenzylic esters were used as electrophiles. Most of the reaction conditions are mild, efficient, and simple to operate.