Ag/Bronsted Acid Co-Catalyzed Spiroketalization of β-Alkynyl Ketones toward Spiro[chromane-2,1'-isochromene] Derivatives

A new Ag/Bronsted acid to-catalyzed spiroketalization of beta-alkynyl ketones with parq-quincine methides (p-QMs) has been: established, enabling multiple C-C and C-O bond-forming events to access densely functionalized spiro[chrcimane-2,1'-isochromene]. derivatives with generally excellent diastereoselectivity and good yields. A reasonable mechanism for forming these 6,6-dibenzannulated spiraetals involving. 6-endo-dig oxo-cyclization and 1,6-addition-cyclization cascades is proposed.