Taming Radical Intermediates for the Construction of Enantioenriched Trifluoromethylated Quaternary Carbon Centers

Taming the CF₃ radical: A unique single‐electron transfer (SET) induced S_N2‐type reaction enables the construction of enantioenriched trifluoromethylated oxindoles using a hypervalent iodine‐based trifluoromethyl transfer reagent. A combination of magnesium Lewis acid catalysis and PyBOX‐type ligands successfully tames the highly reactive CF₃ radical to achieve excellent enantioselectivities.

Abstract

Demonstrated herein is the construction of trifluoromethylated quaternary carbon centers by an asymmetric radical transformation. Enantioenriched trifluoromethylated oxindoles were accessed using a hypervalent iodine‐based trifluoromethyl transfer reagent in combination with a magnesium Lewis acid catalyst and PyBOX‐type ligands to achieve up to 99 % ee and excellent chemical yields. Mechanistic studies were performed by experimental and computational methods and suggest a single‐electron transfer induced S_N2‐type mechanism. This example is thereby the first report on the construction of enantioenriched trifluoromethylated carbon centers using hypervalent iodine‐based reagents proceeding through such a reaction pathway.

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