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首页> 外文期刊>Chemistry: A European journal >Palladium-Catalyzed Cyclization of Allylsilanes with Nucleophilic Displacement of the Silyl Group
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Palladium-Catalyzed Cyclization of Allylsilanes with Nucleophilic Displacement of the Silyl Group

机译：硅烷基的亲核取代对钯硅烷的烯丙基硅烷的环化反应

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摘要

Allylsilanes containing hydroxy or tosylamide groups undergo palladium(II)-catalyzed cyclization to afford derivatives of tetrahydrofuran, piperidine, and pyrrolidine. This catalytic reaction proceeds through an (#eta#-allyl)palladium intermediate that is generated by allylic displacement of the silyl group of the allylsilane precursors. The internal nucleophilic attack on the (#eta#-allyl)palladium intermediates proceeds with high chemo- and regioselectivity. Benzoquinone and copper(II) chloride can be used for regeneration of the palladium(II) catalyst precursor. Mechanistic studies revealed that the copper(II) chloride reoxidant also activates the (#eta#-allyl)palladium intermediate towards nucleophilic attack. Kinetic studies on the formation of the (#eta#-allyl)palladium intermediates showed that the reaction rate is highly dependent on the concentration of chloride ligand and the solvent. The structure and reactivity of the key intermediates of the palladadesilylation process were studied by density functional theory (DFT) calculations, which showed that coordination of the electrophilic palladium(II) catalyst precursor to allylsilanes leads to a relatively weak #beta#-silicon effect. The DFT studies also indicate that the cleavage of the carbon-silicon bond takes place by coordination of a chloride ion to the silicon atom.
机译：含有羟基或甲苯磺酰胺基的烯丙基硅烷经过钯（II）催化的环化反应，得到四氢呋喃，哌啶和吡咯烷的衍生物。该催化反应通过烯丙基硅烷前体的甲硅烷基的烯丙基置换产生的（η-烯丙基）钯中间体进行。对（＃eta＃-烯丙基）钯中间体的内部亲核攻击具有高的化学和区域选择性。苯醌和氯化铜（II）可用于再生钯（II）催化剂前体。机理研究表明，氯化铜（II）再氧化剂还可以激活（＃eta＃-烯丙基）钯中间体向亲核攻击。对（η-烯丙基）钯中间体形成的动力学研究表明，反应速率高度依赖于氯化物配体和溶剂的浓度。通过密度泛函理论（DFT）计算研究了钯金属甲硅烷基化过程中关键中间体的结构和反应活性，表明亲电钯（II）催化剂前体与烯丙基硅烷的配位作用导致＃beta＃-硅效应相对较弱。 DFT研究还表明，碳-硅键的裂解是通过氯离子与硅原子的配位而发生的。

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