Owing to their importance in organic synthesis, transition metal catalyzed cross-coupling reactions have been the focus of many studies. Recently, it was recognized that merged transition metal and photoredox catalysis is a powerful strategy for the design of challenging Csp3–Csp2 bond forming cross coupling reactions. However, these reactions require metals (e.g., Ni) to activate Csp2-halogen bonds. In the current investigation, we developed a new, photocatalysis based, metal free approach to accomplish Csp3–Csp2 bond formation between an alkyl fragment, derived from a carboxylic acid, and a vinyl moiety of a,β-aryl-substituted vinyl halide. The cross coupling process, which is activated by using the simple organic dye 4CzIPN, acting as a single electron transfer type photocatalyst, and visible light, is chemoselective, E-stereoselective and efficient. Moreover, upon prolonged irradiation of the reaction mixture, 4CzIPN serving as an energy transfer photocatalyst, promotes isomerization of the initially formed alkenes into mixtures enriched in the Z-isomers.

中文翻译：

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有机光催化的E和Z立体选择性Csp3-Csp2键形成羧酸与β-芳基乙烯基卤化物的交叉偶联反应

由于其在有机合成中的重要性，过渡金属催化的交叉偶联反应已成为许多研究的重点。最近，人们认识到过渡金属和光氧化还原催化的合并是设计具有挑战性的Csp3-Csp2键形成交叉偶联反应的有力策略。但是，这些反应需要金属（例如Ni）来激活Csp2-卤素键。在当前的研究中，我们开发了一种新的基于光催化的，无金属的方法，以实现在衍生自羧酸的烷基片段与a，β-芳基取代的乙烯基卤化物的乙烯基部分之间形成Csp3-Csp2键。通过使用简单的有机染料4CzIPN（作为单电子转移型光催化剂）和可见光激活的交叉偶联过程具有化学选择性，电子立体选择性和高效。而且，在长时间照射反应混合物时，用作能量转移光催化剂的4CzIPN促进最初形成的烯烃的异构化为富含Z-异构体的混合物。