Controllable Single and Double Difluoromethylene Insertions into C–Cu Bonds: Copper-Mediated Tetrafluoroethylation and Hexafluoropropylation of Aryl Iodides with TMSCF₂H and TMSCF₂Br

Abstract

The selective difluoromethylene insertion into a C-Cu bond is a challenging task and is currently limited to either a single CF₂ insertion into CuCF₃ or double CF₂ insertions into CuC₆F₅ (or (<i>Z</i>)-CF₃CF = CFCu). Achieving both selective single and double CF₂ insertions into the same C-Cu bond is even more difficult. Herein, highly controllable single and double CF₂ insertions into CuCF₂H species with a TMSCF₂Br reagent have been described, affording two previously unknown fluoroalkylcopper species "Cu(CF₂)_nCF₂H" (<i>n</i> = 1 and 2) independently under different reaction conditions. This work represents the first example of both single and double CF₂ insertions into the same C-Cu bond in a highly selective manner. The synthetic value of the obtained "Cu(CF₂)<i>_n</i>CF₂H" (<i>n</i> = 1 and 2) species is demonstrated by their reactions with aryl iodides, halogenation agents, and cinnamyl chloride, which enables the direct transfer of HCF₂CF₂ and HCF₂CF₂CF₂ moieties into organic molecules. The key to controllable fluorocarbon chain elongation from C₁ to C₂ and from C₁ to C₃ is presumably attributed to the different reactivities of "Cu(CF₂)<i>_n</i>CF₂H" species (<i>n</i> = 0, 1, 2 and 3) and the loading of the TMSCF₂Br reagent.