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

• Published in: Chemistry : a European journal Vol. 30; no. 14; pp. e202304015 - n/a
• Main Authors: Wenzel, Jonas O., Jester, Fabian, Togni, Antonio, Rombach, David
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 07.03.2024; Wiley Subscription Services, Inc
• Subjects: Acetylene; Cascade chemical reactions; Chemistry; Chemistry, Multidisciplinary; enamines; Functional materials; hydroamination; Isomerization; organofluorine chemistry; pentafluorosulfanyl group; Physical Sciences; Reagents; Science & Technology; Stereoselectivity; Sulfur; Thermal stability; pentafluorosulfanyl group; NEGATIVE HYPERCONJUGATION; MOLECULAR-ORBITAL METHODS; STEREOCHEMISTRY; COMPLEXES; SULFONES; AMINE ADDITIONS; hydroamination; enamines; BASIS-SETS; organofluorine chemistry; acetylene; DERIVATIVES; EFFICIENT
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202304015

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 α‐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≡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 α‐SF5 aldehyde enamines under benchtop conditions. This approach allowed these precious building blocks to be accessed and fully characterized for the first time.