N-Heterocyclic Carbene Catalytic [4 + 2] Cyclization of 3-Alkylenyloxindoles with Enals: γ-Carbon Activation for Enantioselective Assembly of Spirocarbocyclic Oxindoles.


The ubiquitous structure of all-carbospirocyclic oxindoles makes the development of new methods for their enantioselective and stereoselective synthesis a significant ongoing challenge. Herein, we disclose a formal [4 + 2] annulation through N-heterocyclic carbene (NHC) catalysis for highly enantioselective synthesis of intriguing spirocarbocyclic oxindoles… (More)