“Sandwich” Diimine‐Copper Catalyzed Trifluoroethylation and Pentafluoropropylation of Unactivated C(sp³)−H Bonds by Carbene Insertion

Abstract

We report here "sandwich"-diimine copper complex-catalyzed trifluoroethylation and pentafluoropropylation of unactivated C(sp 3 )À H bonds in alkyl esters, halides, and protected amines by employing CF 3 CHN 2 and CF 3 CF 2 CHN 2 reagents. Reactions proceed in dichloromethane solvent at room temperature. Identical CÀ H functionalization conditions and stoichiometries are employed for generality and convenience. Selectivities for CÀ H insertions are higher for compounds possessing stronger electron-withdrawing substituents. Preliminary mechanistic studies point to a mechanism involving a pre-equilibrium forming a "sandwich"-diimine copper-CF 3 CHN 2 complex followed by rate-determining loss of nitrogen affording the reactive copper carbene. It reacts with trifluoromethyldiazomethane about 6.5 times faster than with 1-fluoroadamantane explaining the need for slow addition of the diazo compound.