Hydroamination of Triisopropylsilyl Acetylene Sulfur Pentafluoride - a Bench-top Route to Pentafluorosulfanylated Enamines

Synthetic access to a variety of aliphatic and vinylic pentafluorosulfanylated building blocks remains a major challenge in contemporary organofluorine chemistry hampering its investigation in the context of medicinal chemistry, agrochemistry and functional materials. Herein, we report a bench-top protocol to access the virtually unknown class of alpha-SF5-enamines under mild reaction conditions in good to excellent yields (up to 95 %). This reaction combines the protodesilylation of the commercially available precursor TASP with the in situ hydroamination of HC equivalent to C-SF5. The on-site use of highly toxic gases or corrosive reagents is avoided, making access to this motif applicable to a wide chemical audience. The excellent E-diastereoselectivity of this two-step cascade reaction is suggested to be the result of the convergence of the fast Z-/E- isomerization of a vinyl anion as well as the isomerization of the iminium ion. The remarkable thermal stability of these SF5-enamines encourages further studies of their synthetic utility. The pentafluorosulfanyl group has been proposed as a valuable addition to the toolbox of organofluorine chemistry. Here, we introduce commercially available (triisopropylsilyl)acetylene sulfur pentafluoride (TASP) as a versatile reagent that provides very low-risk access to the elusive class of alpha-SF5 aldehyde enamines under benchtop conditions. This approach allowed these precious building blocks to be accessed and fully characterized for the first time.image