Controllable Difluorocarbene Elongation via Copper Catalysis

Tetrafluoroethylene (−CF 2 CF 2 −) is a privileged motif in materials and medicinal chemistry. However, a highly modular and synthetically convenient method for constructing the CF 2 CF 2 linkage remains elusive. Here, we report an unprecedented copper-catalyzed, bench-friendly difluorocarbene elongation platform that converts BrCF 2 CO 2 K, silyl enol ethers, and secondary propargyl sulfonates into tetrafluoroalkylated allenes in a single operation. Simply tuning the difluorocarbene stoichiometry switches selectivity to the corresponding monodifluoromethylene (CF 2 ) incorporation products. The method is modular (no preformed fluorinated building blocks are required), operationally simple (all reagents are commercially available or easily prepared), highly selective (controllable formation of bis- or mono-CF 2 -containing products), and tolerant of diverse functional groups, including those found in drug-like scaffolds. The products serve as versatile linchpins for downstream transformations, opening expedient routes to advanced materials and modern drug discovery.