Controlled Synthesis of α‑CF₂H or α‑CF₂Cl Styrenes from the Same Precursors: Dehydrazinative Hydrogenation or Chlorination of 3,3-Difluoroallyl Hydrazines

By carefully choosing the reaction conditions, we have developed the controllable FeCl3- or CuCl2-mediated dehydrazinative hydrogenation or chlorination of 3,3-difluoroallyl hydrazines to access α-CF2H or α-CF2Cl styrenes. The current reaction provides for the first time a facile method for the direct and selective synthesis of α-CF2H and α-CF2Cl styrenes starting from the same precursors, which is easy to scale up and displays a broad substrate scope and good functional group tolerance. Moreover, product derivatization experiments demonstrated that the resulting α-CF2Cl styrenes are practical and versatile building blocks for the diversified synthesis of fluorinated molecules.