Synthesis of Chiral Bispirotetrahydrofuran Oxindoles by Cooperative Bimetallic-Catalyzed Asymmetric Cascade Reaction.

A new, efficient route for the enantioselective construction of bispirotetrahydrofuran oxindoles is described via the cooperative dinuclear zinc-AzePhenol catalyst. Under mild conditions, a broad range of bispirotetrahydrofuran oxindoles have been synthesized with excellent stereoselectivities through the cascade Michael/hemiketalization/Friedel-Crafts reaction of β,γ-unsaturated α-ketoamide and 2-hydroxy-1-indanone. The reaction can be performed on a gram scale with low catalyst loading (2 mol %) without impacting its efficiency.