E-Z isomerization in Suzuki cross-couplings of haloenones: ligand effects and evidence for a separate catalytic cycle
E-Z isomerization in Suzuki cross-couplings of haloenones: ligand effects and evidence for a separate catalytic cycle
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DOI：
10.1039/c7ob02925j
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发表时间：
2018-02-21
影响因子：
3.2
通讯作者：
Hultin, Philip G.
中科院分区：
文献类型：
--
作者：
Chehal, Navneet K.;Budzelaar, Peter H. M.;Hultin, Philip G.
通常认为卤代烯烃的铃木交叉偶联是在保留烯烃立体化学的情况下发生的。在研究 E-1,2-二氯乙烯基苯基酮上的铃木交叉偶联时，我们惊讶地观察到广泛的异构化。更令人惊讶的是，所使用的配体强烈影响异构化程度：DPEphos和Xantphos产生96%异构化交叉偶联产物，而在不存在膦配体的情况下的反应或使用t-BuXantphos的反应产生94%的立体化学保留。虽然 Pd 催化乙烯基偶联中的 E-Z 异构化先前被归因于交叉偶联催化循环内的事件，但我们为这些反应中单独的 Pd 催化异构化过程提供了实验和计算证据。
Suzuki cross-coupling of haloalkenes is generally assumed to occur with retention of the alkene stereochemistry. While studying Suzuki cross-couplings on E-1,2-dichlorovinyl phenyl ketone, we were surprised to observe extensive isomerization. More surprisingly, the ligand employed strongly influenced the degree of isomerization: DPEphos and Xantphos led to 96% isomerized cross-coupled product whereas reactions in the absence of a phosphine ligand, or reactions employing t-BuXantphos, gave 94% retention of stereochemistry. While E-Z isomerization in Pd-catalyzed vinylic couplings has previously been attributed to events within the cross-coupling catalytic cycle, we present experimental and computational evidence for a separate Pd-catalyzed isomerization process in these reactions.