Palladium complexes of abnormal N-heterocyclic carbenes as precatalysts for the much preferred Cu-free and amine-free Sonogashira coupling in air in a mixed-aqueous medium
作者:Alex John、Mobin M. Shaikh、Prasenjit Ghosh
DOI:10.1039/b913068c
日期:——
aqueous medium. Complexes, 1b-4b, were synthesized by the direct reaction of the corresponding imidazo[1,2-a]pyridinium iodide salts, 1a-4a, with PdCl2 in pyridine in the presence of K2CO3 as a base while the imidazo[1,2-a]pyridinium iodide salts, 1a-4a, were in turn synthesized by the alkylation reactions of the respective imidazo[1,2-a]pyridine derivatives with alkyl iodides. The density functional theory
报道了一系列新的PEPPSI(吡啶增强的前催化剂的制备稳定和引发)主题的异常N-杂环卡宾的预催化剂,用于空气中混合水介质中非常需要的无铜和无胺的Sonogashira偶联。具体而言,以PEPPSI为主题的(NHC)PdI2(吡啶)型预催化剂1b-4b在混合水介质中在空气中有效地进行了极为方便的芳基溴化物和碘化物与末端乙炔的无Cu和无胺Sonogashira偶联。配合物1b-4b是通过相应的咪唑并[1,2-a]碘化吡啶鎓盐1a-4a与PdCl2在吡啶中,以K2CO3为碱存在下,而咪唑并[1,2]的直接反应合成的。 -a]碘化吡啶鎓盐1a-4a通过相应的咪唑并[1,2-a]吡啶衍生物与烷基碘。密度泛函理论(DFT)研究表明,这些由咪唑-3-亚基[1,2-a]吡啶衍生的异常碳烯具有强烈的sigma-doning作用,因此会显着削弱1b-4b中具有催化作用的重要的不稳定的反式吡啶配体。