On the role of PIII ligands in the conjugate addition of diorganozinc derivatives to enones.
On the role of PIII ligands in the conjugate addition of diorganozinc derivatives to enones.
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关于 PIII 配体在二有机锌衍生物与烯酮的共轭加成中的作用。
DOI：
10.1002/chem.200400316
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
T. Schrader
中科院分区：
文献类型：
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作者：
Tatjana Pfretzschner;Lutz Kleemann;Birgit Janza;K. Harms;T. Schrader
对不同手性PIII配体催化二乙基锌与环己酮的共轭加成反应的机理研究，提供了对其反应机理的新见解。EPR光谱表明，过量的ZnEt2可将催化量的铜(OTf)2原位转化为CuI物种。实验证据支持烯酮、Et2Zn和催化剂之间存在1：1：1的临界三元络合物，支持从带有一或两个配体分子的预先形成的混合铜/锌簇合物中进行限速还原消除或碳铜化。得到了CuIL2络合物的晶体结构，该晶体结构显示了催化剂在试剂和底物的加入下的转化率。核磁共振光谱分析和VT实验表明，空间位阻可能阻止第二配体分子在CuI阳离子上络合，导致基于CuX.L物种的预催化剂速度极快。
A mechanistic study on the conjugate addition of diethylzinc to cyclohexenone catalyzed by various chiral PIII ligands, provides new insights into its mechanism. Complete in situ conversion of the catalytic amount of Cu(OTf)2 into CuI species by excess ZnEt2 is demonstrated by EPR spectroscopy. Experimental evidence is presented in favor of a critical ternary 1:1:1 complex between enone, Et2Zn and catalyst, supporting a rate-limiting reductive elimination or carbocupration from a preformed mixed Cu/Zn cluster carrying one- or two-ligand molecules. A crystal structure has been obtained for a CuIL2 complex, which shows catalytic turnover on addition of reagent and substrate. NMR spectroscopic analyses and VT experiments reveal that steric hindrance may prevent complexation of a second ligand molecule on the CuI cation, leading to extremely fast precatalysts based on CuX.L species.