研究了吸电子基团的贫电碘代芳烃的Ullmann偶联反应,该反应使用Pd(OAc)2为催化剂,K2CO3为添加剂,以丙酮-水混合液为溶剂,不需要添加额外的还原剂,收率为55-87％.在通过了一系列的试验后,可以认为该反应中的溶剂及碱没有起还原作用,而是碘代芳烃自身作为还原剂,完成整个催化反应的,并首次提出了一种不需要外加还原剂的Pd(Ⅱ)/pd(Ⅳ)/Pd(Ⅱ)的催化循环机理.%The Ullmann homocouplings of electron-deficient aryl iodides were carried out to afford the corresponding biaryls in moderate to good yields(55-87%) in the presence of catalytic Pd(OAc)2 and K2CO3 in acetone/water without additional reducta-nts. After a series of tests, it was also confirmed that aryl iodide itself rather than solvent and base could play the role of reductant to complete the catalytic cycle in this Ullmann reductive coupling. Thus,a Pd(Ⅱ)/Pd(Ⅳ)/Pd(Ⅱ)catalytic cycle was proposed firstly for these couplings without any external reducing agents.
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