Stereodivergent Alkyne Hydrofluorination Using Protic Tetrafluoroborates as Tunable Reagents

An inexpensive new reagent enables the development of metal-free protocols for stereodivergent hydrofluorination. Computations and mechanistic data support the intermediacy of vinyl cations, which are trapped to deliver E- and Z-vinyl fluorides under kinetic and thermodynamic control, respectively.