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首页> 外文期刊>Chemistry: A European journal >Palladium-Catalyzed Cyclopropanation of Alkenyl Silanes by Diazoalkanes:Evidence for a Pd0 Mechanism
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Palladium-Catalyzed Cyclopropanation of Alkenyl Silanes by Diazoalkanes:Evidence for a Pd0 Mechanism

机译：重氮烷烷钯催化的烯基硅烷的环丙烷化反应：Pd0机理的证据

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摘要

Alkenyl silanes are efficiently converted to the corresponding silyl cyclopropanes in the presence of a slight excess of diazomethane (2C 4 equiv) and a low loading of PdACHTUNGTRENUNG(OAc)2 (<0.5 mol%). Diazoethane and diazobutanecan also be employed and yield silyl cyclopropanes with diastereoselectivities of up to 10:1 for the trans isomer. When conducted on a 4 g scale,the reaction only required a catalyst loading of 5103 mol%, which corresponds to a turnover frequency of 40 000 h1. Competition experiments revealed that vinyl silanes can be selectively cyclopropanated in the presence of an aliphatic terminal alkene and styrene. The complex [Pd0 2ACHTUNGTRENUNG(DVTMS)3] (38, DVTMS=divinyltetramethyldisil-ACHTUNGTRENUNGoxane) proved to be an exceptionally active catalyst for the cyclopropanation reaction, giving complete conversion at 35 8C in 1 min. Intermolecular and intramolecular competition experiments with DVTMS (36), both with PdACHTUNGTRENUNG(OAc)2 and 38, provided strong evidence for a Pd0(alkenyl silane)3 resting state. Detailed density functional calculations on the reaction pathways for the cyclopropanation of trimethylvinylsilane and DVTMS by diazomethane with Pd0 corroborated the experimental observations.
机译：在稍微过量的重氮甲烷（2C 4当量）和低负载的PdACHTUNGTRENUNG（OAc）2（<0.5 mol％）的存在下，烯基硅烷可有效地转化为相应的甲硅烷基环丙烷。也可以使用重氮乙烷和重氮丁烷，得到反式异构体的非对映选择性高达10：1的甲硅烷基环丙烷。当以4g规模进行时，该反应仅需要5103mol％的催化剂负载，这对应于40000h1的周转频率。竞争实验表明，乙烯基硅烷可以在脂肪族末端烯烃和苯乙烯存在下进行选择性环丙烷化。络合物[PdO 2 ACHTUNGTRENUNG（DVTMS）3]（38，DVTMS =二乙烯基四甲基二甲硅烷基-ACHTUNGTRENUNG恶烷）被证明是环丙烷化反应的极活泼催化剂，在35 8C的条件下在1分钟内完全转化。 DVTMS的分子间和分子内竞争实验（36），以及PdACHTUNGTRENUNG（OAc）2和38，都为Pd0（烯基硅烷）3静止状态提供了有力的证据。重氮与Pd0对三甲基乙烯基硅烷和DVTMS进行环丙烷化反应路径的详细密度函数计算，证实了实验结果。

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