Controllable Single and Double Difluoromethylene Insertions into C-Cu Bonds: Copper-Mediated Tetrafluoroethylation and Hexafluoropropylation of Aryl Iodides with TMSCF 2 H and TMSCF 2 Br.

The selective difluoromethylene insertion into a C-Cu bond is a challenging task and is currently limited to either a single CF 2 insertion into CuCF 3 or double CF 2 insertions into CuC 6 F 5 (or ( Z )-CF 3 CF = CFCu). Achieving both selective single and double CF 2 insertions into the same C-Cu bond is even more difficult. Herein, highly controllable single and double CF 2 insertions into CuCF 2 H species with a TMSCF 2 Br reagent have been described, affording two previously unknown fluoroalkylcopper species "Cu(CF 2 ) n CF 2 H" ( n = 1 and 2) independently under different reaction conditions. This work represents the first example of both single and double CF 2 insertions into the same C-Cu bond in a highly selective manner. The synthetic value of the obtained "Cu(CF 2 ) n CF 2 H" ( n = 1 and 2) species is demonstrated by their reactions with aryl iodides, halogenation agents, and cinnamyl chloride, which enables the direct transfer of HCF 2 CF 2 and HCF 2 CF 2 CF 2 moieties into organic molecules. The key to controllable fluorocarbon chain elongation from C 1 to C 2 and from C 1 to C 3 is presumably attributed to the different reactivities of "Cu(CF 2 ) n CF 2 H" species ( n = 0, 1, 2 and 3) and the loading of the TMSCF 2 Br reagent.