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.