Trifluoromethane (HCF3, HFC-23) is produced on a multi-kilotonne scale during manufacture of poly(tetrafluoroethylene) (PTFE). The process for the synthesis of PTFE relies on first the fluorination of HCCl3 to form HCClF2 then coupling to generate CF2=CF2 which is polymerized. HCF3 forms as a by-product of the fluorination step. While readily separated, HCF3 has limited value. Niche applications include use as a low temperature (-80 °C) refrigerant, a fire suppressant, and as a blanket gas in the semi-conductor industry. The scale of these applications is vastly inferior to the scale of PTFE manufacturing, and so much of the HCF3 generated is either stored or destroyed at the point of production. HCF3 is environmentally damaging. It has a 100-year global warming potential 14,600 times greater than CO2. Despite legislation to phase-down the use of HFCs, atmospheric concentrations of HCF3 are still rising slowly. In recent years, the use of HCF3 as simple and efficient precursor for trifluoromethylation and difluoromethylation reactions have been realised (Figure ). The former transformation occurs with a net loss of a hydrogen atom from HCF3, while the latter requires removal of a single fluorine atom. These processes allow HCF3 to be used as a C1 building block providing access to CF3 and CF2H groups which are attractive motifs in drug-discovery due to their ability to modify lipophilicity, hydrogenbonding properties, and pharmacokinetics. While the CF2H group has emerged as important bioisostere for the hydroxy group, there is increasing concern over use of CF3 groups due to the environmental fate of CF3 containing metabolites. The generation of more complex, longer chain, fluorinated building blocks from HCF3 is incredibly rare, when compared to transformations to C1 building blocks. There are hints, however, that such transformations should be possible. For example, Mikami and coworkers have reported the formation of a fluoroalkene in modest yield from reaction of a lithium fluorenide with HCF3. 1,1-Difluoroalkenes have also be observed as minor side products in the reaction of HCF3 with lithiated carbamates. If a general approach to generate longer chain, complex fluorinated Cn fragments from HCF3 could be achieved it might allow access to new medicinally valuable motifs or bioisosteres, not founded on the CF3 group, and open up new uses for this environmentally damaging waste-product in drug-discovery programs. Fluoroalkenes have been proposed as mimics for amide groups with E or Z isomers acting as surrogates of conformationally locked transoid and cisoid geometries of peptide linkages. Herein, we show that HCF3 reacts with silylated organolithium reagents through an unusual defluoroalkylation reaction. The transformation occurs with the homologation and two-fold defluorination of HCF3 to create a silylated building block that contains a new fluoroalkene motif (Figure ). The defluoroalkylation process is both regiospecific and stereospecific resulting in a single constitutional isomer primarily as the Z-stereoisomer. Investigation of the mechanism by calculations suggests that the key step involves a-elimination of lithium fluoride from an organometallic intermediate with simultaneous 1,2-migration of the silyl group. The new fluoroalkene products were also demonstrated to be competent nucleophiles in the stereospecific fluoroalkenylation of a range of aldehydes. Two a-silylated organolithium reagents (1 and 2) were prepared and their reactions with HCF3 investigated under batch conditions (Figure ). Following optimisation for the concentration, equivalents of HCF3, solvent, temperature, and the nature of the supporting ligand on lithium, it was discovered that 1•PMDETA (PMDETA = pentamethylethylenetriamine) reacts quickly with excess (approx. 16 equiv.) of HCF3 at 25 °C to selectively form CH2=CHF(SiMe2Ph) (3) in 69 % yield as measured by 1 H NMR spectroscopy (Figure ). 3 is characterised by two doublets of doublets in the 1 H NMR spectrum observed at d = 5.28 ppm (dd, J = 32.2, 2.9 Hz) and 4.61 ppm (dd, J = 61.1, 2.9 Hz,), along with a doublet of doublets is observed at d = -103.1 ppm (dd, J = 61.1, 32.2 Hz) in the 19 F NMR spectrum. An HSQC experiment confirmed the proposed connectivity and geminal CH2 group of the terminal alkene. While 3 could be isolated, this compound is volatile, complicating its general utility, hence we sought to prepare an analogue.