Metal-free diastereoselective construction of bridged ketal spirooxindoles via a Michael addition-inspired sequence

Abstract

A TfOH-catalyzed highly diastereoselective Michael addition/ketalization sequence of 3-hydroxyoxindoles and ortho-hydroxychalcones was developed, leading to biologically important bridged ketal spirooxindoles in moderate to excellent yields. Moreover, some chemical transformations were carried out to further extend the structural complexity and diversity.