Magnesium-Catalyzed Electrophilic Trifluoromethylation: Facile Access to All-Carbon Quaternary Centers in Oxindoles.

The first example of a magnesium-catalyzed direct trifluoromethylation of 3-substituted oxindoles using an electrophilic hypervalent iodine reagent is reported. The reaction proceeds under unprecedented mild conditions leading to the formation of an all-carbon quaternary center in oxindoles in high chemical yield and demonstrates excellent functional group tolerance. In addition to trifluoromethyl, other perfluoroalkyl groups can be introduced with similar level of efficacy. Mechanistic investigations are consistent with the involvement of a radical pathway. The chemical versatility of the obtained products is further illustrated through their conversion in situ into valuable organofluorine building blocks, making the protocol more widely applicable.