Oxidative Catalytic Spiroketalization Leading to Diastereoselective Synthesis of Spiro[benzofuran-2,1′-isochromene]s

A new one-pot, two-step silver-catalyzed spiroketalization of the in-situ generated quinone imine ketals (QIKs) with β-alkynyl ketones has been established, enabling multiple C−O and C−C bond-forming reactions to access densely functionalized spiro[benzofuran-2,1′-isochromene] derivatives with generally good yields. The use of β-alkynyl ketones bearing alkyl and aryl groups located at the α-position of the carbonyl group could lead to highly diastereoselective spiro[chromane-2,1′-isochromene] derivatives. The reaction features broad substrate scope, mild oxidative catalytic conditions and excellent diastereoselectivity. (Figure presented.).