Access to All-Carbon Spirocycles through a Carbene and Thiourea Cocatalytic Desymmetrization Cascade Reaction.

A new catalytic approach for asymmetric quick access to spirocycles is disclosed. The reaction involves a carbene and thiourea co-catalyzed desymmetrization process with simultaneous installation of a spirocyclic core. The use of a thiourea co-catalyst is critical to turn on this reaction, as no product was formed without the presence of the thioureas. Our study constitutes the first success in carbene-catalyzed enantioselective synthesis of all-carbon spirocycles. Products from our reactions can be readily transformed to sophisticated multi-cyclic molecules and chiral ligands.