A new edition of fluoroalkyl additions

Synthetic organofluorine chemistry has matured by leaps and bounds over the past decade. Yet one limitation has been the lack of basic methods that go beyond adding fluorine and fluoromethyl functional groups to organic compounds to include fluoroethyl groups. A research team led by Jinbo Hu of Shanghai Institute of Organic Chemistry has come up with a convenient and safe solution using tetrafluoroethylene as a reagent (Angew. Chem. Int. Ed. 2017, DOI: 10.1002/anie.201705734). Tetrafluoroethylene, CF₂=CF₂, is one of the most important bulk industrial fluorochemicals. But because of special needs for handling the suspected carcinogen and potentially explosive gas, many academic synthetic organic research groups are not equipped or permitted to use CF₂=CF₂. Hu’s group developed a breakthrough procedure to generate CF₂=CF₂ on the fly by dimerizing difluorocarbene generated under mild conditions from the commonly used fluorinating reagent (trifluoromethyl)trimethylsilane, (CH₃)₃SiCF₃. In a tandem reactor system, the researchers convert (CH₃)₃SiCF₃ to CF₂=CF₂ using sodium iodide as a catalyst in one chamber, then transfer CF₂=CF₂ to an adjacent chamber containing combinations of nucleophilic and electrophilic reagents. With this method, the team carried out pentafluoroethylation of aryl and heteroaryl iodides, (aryloxy)tetrafluoroethylation of an aryl iodide, and addition of tetrafluoroethyl groups to heteroatoms in aryl and alkyl compounds. The new approach promises to complement previous reactions to add fluoroethyl groups and accelerate the use of tetrafluoroethylene as a fluorinated C₂ building block, Hu says.