Pd(II)-Catalyzed <i>ortho</i>-C–H Olefination/Dearomatization of <i>N</i>‑Aryl Ureas: An Approach to Imine Derivatives

An unprecedented approach for the synthesis of imine derivatives was achieved via a Pd­(II)-catalyzed dearomatization reaction of N-aryl ureas with internal alkynes. The corresponding spirocyclic imine derivatives were obtained with 20 examples in good to excellent yields. Mechanistic investigation indicated that an interesting 1,3-palladium migration process led to the α-regioselective dearomatization when 2-naphthyl ureas were used as the substrates. Fused ring products could also be obtained to further prove this migration process.本研究开发了一种前所未有的亚胺衍生物（imine derivatives）合成策略：通过钯(II)（Pd(II)）催化N-芳基脲（N-aryl ureas）与内炔烃（internal alkynes）的去芳构化反应（dearomatization reaction），成功实现目标产物的构建。该方法共得到20个螺环亚胺衍生物（spirocyclic imine derivatives）实例，产物收率良好至优异。机理研究表明，当以2-萘基脲（2-naphthyl ureas）作为底物（substrates）时，一种独特的1,3-钯迁移（1,3-palladium migration）过程可驱动α区域选择性（α-regioselective）去芳构化反应的发生。稠环产物（fused ring products）的合成亦可进一步验证该迁移过程。