Organocatalytic Activity of N-Heterocyclic Carbenes in the Michael Addition of 1,3-Dicarbonyl Compounds: Application to a Stereoselective Spirocyclization Sequence

An eco-compatible diversity-oriented synthesis of alpha-spirolactones and alpha-spirolactams is described. The overall transformation involves an olefin cross-meta thesis followed by an intramolecular organocatalytic Michael-induced spirocyclization. Under microwave irradiation, the Hoveyda-Grubbs precatalyst can be iteratively used as the source of both the metathesis ruthenium-based catalyst, and the spirocyclization N-heterocyclic carbene catalyst.