Metal-Free, Brønsted Acid-Catalyzed Formal [3+2] Annulation of Quinone Monoacetals with 2-Naphthols

An operationally simple and metal-free crosscoupling of quinone monoacetals (QMAs) with 2-naphthols catalyzed by triflic acid is reported, This formal [3+2] annulation allowed the synthesis of diverse naphtho[2,1b]benzofuran derivatives in moderate to good yields. Preliminary mechanistic studies reveal the initial nucleophilic substitution of QMAs with 2-naphthols in preference to die mixed acetal formation and subsequent. [3,3] sigmatropic rearrangement.