Synthesis of Substituted 4H‑Thiochromen-4-imines via Copper-Catalyzed Cyclization Cascades of o‑Bromobenzothioamides with Terminal Alkynes

A series of (E)-N-aryl-4H-thiochromen-4-imines has been conveniently obtained through a cascade reaction between o-bromobenzothioamides and terminal alkynes. This novel approach probably involved an initial generation of benzothietane-2-imine intermidates via an intramolecular Ullmann reaction under CuI/L-proline cocatalysis and alkaline conditions followed by imine alkynylation, ring opening, and cyclization sequences to provide the unexpected 4H-thiochromen-4-imines rather than isothiochromans.本研究通过邻溴代苯硫代酰胺与末端炔烃之间的级联反应，便捷地合成了一系列(E)-N-芳基-4H-硫代色烯-4-亚胺。该新颖合成方法可能经历了如下过程：在碘化亚铜/L-脯氨酸共催化及碱性条件下，首先通过分子内Ullmann反应生成苯硫杂环丁烷-2-亚胺中间体，随后依次经历亚胺炔基化、开环与环化序列，最终得到了意外生成的4H-硫代色烯-4-亚胺产物，而非异硫代色满类化合物。