Synthesis of Tetrahydropyridine Derivatives through a Reaction of 1,6-Enynes, Sulfur Dioxide, and Aryldiazonium Tetrafluoroborates

Sulfonated tetrahydropyridine derivatives are accessed through a radical reaction of 1,6-enynes, sulfur dioxide, and aryldiazonium tetrafluoroborates under mild conditions. Sulfonated pyrrolidine can be generated when terminal alkyne is used as the substrate. This reaction proceeds efficiently in dichloroethane without the addition of any catalysts or additives, providing sulfonated tetrahydropyridine derivatives in moderate to good yields. During this transformation, aryldiazonium tetrafluoroborates cooperate with DABCO·(SO2)2 leading to sulfonyl radicals, which initiate the radical cyclization process. Two molecules of aryldiazonium tetrafluoroborates are involved in the reaction.磺化四氢吡啶衍生物（Sulfonated tetrahydropyridine derivatives）可通过1,6-烯炔（1,6-enynes）、二氧化硫与四氟硼酸芳基重氮盐（aryldiazonium tetrafluoroborates）在温和条件下的自由基反应（radical reaction）合成。当以末端炔烃为底物时，可生成磺化吡咯烷（Sulfonated pyrrolidine）。该反应可在二氯乙烷中高效进行，无需添加任何催化剂或添加剂，以中等至良好的收率得到磺化四氢吡啶衍生物。在此转化过程中，四氟硼酸芳基重氮盐与DABCO·(SO2)2作用生成磺酰自由基（sulfonyl radicals），进而引发自由基环化过程（radical cyclization process）。该反应共涉及两分子四氟硼酸芳基重氮盐。