Catalytic Asymmetric Mannich/Cyclization of 2-Isothiocyanato-1-indanones: An Approach to the Synthesis of Bispirocyclic Indanone-Thioimidazolidine-Oxindoles

This study demonstrates that novel isothiocyanates derived from 1-indanones are useful building blocks in heteroannulation reactions with isatinimines. This convenient Mannich/cyclization cascade reaction serves as a powerful tool for the enantioselective construction of bispirocyclic indanone-thioimidazolidine-oxindoles bearing two adjacent spiro-quaternary stereocenters in good to excellent yields with excellent diastereo- and enantioselectivities. Versatile transformations of the products into other potential bioactive bispirocyclic heterocycles have also been demonstrated.