Copper-Catalyzed 1,2-Addition of Nucleophilic Silicon to Aldehydes: Mechanistic Insight and Catalytic Systems
Copper-Catalyzed 1,2-Addition of Nucleophilic Silicon to Aldehydes: Mechanistic Insight and Catalytic Systems
复制标题
DOI：
10.1002/chem.201102367
复制
发表时间：
2011-11-01
影响因子：
4.3
通讯作者：
Oestreich, Martin
中科院分区：
文献类型：
--
作者：
Kleeberg, Christian;Feldmann, Evgenia;Oestreich, Martin
用醇铜 (I) 激活 Si-B 元素间键会产生铜基硅亲核试剂，该亲核试剂很容易与醛反应，在水解后生成 α-甲硅烷基醇（即 α-羟基硅烷）。开发了两种独立的方案，一种采用明确的 NHC-CuOtBu 复合物，另一种采用简单的 CuCNNaOMe 组合，无需添加配体。通过化学计量和催化实验以及核磁共振波谱测量详细研究了醛加成的机理。 Si-B 试剂和醛（α-甲硅烷醇的硼酸酯）加成的主要反应产物以及在竞争性 [1,2]-Brook 重排中形成的死端中间体，均进行了晶体学表征。根据这些数据，提出了合理的催化循环。 NHC-CuOtBu 催化装置在高温下表现良好。 CuCNNaOMe 生成反应性更强的催化系统，在显着较低的温度下表现出快速周转。在这些温和的反应条件下，芳香族和脂肪族醛均以良好至非常好的产率转化为相应的α-甲硅烷基醇。
Activation of the Si-B inter-element bond with copper(I) alkoxides produces copper-based silicon nucleophiles that react readily with aldehydes to yield a-silyl alcohols (that is, a-hydroxysilanes) after hydrolysis. Two independent protocols were developed, one employing a well-defined NHC-CuOtBu complex and one using the simple CuCNNaOMe combination without added ligand. The mechanism of the aldehyde addition was investigated in detail by stoichiometric and catalytic experiments as well as NMR spectroscopic measurements. The primary reaction product of the addition of the Si-B reagent and the aldehyde (a boric acid ester of the a-silyl alcohol) and also the dead-end intermediate, formed in the competing [1,2]-Brook rearrangement, were characterized crystallographically. Based on these data, a reasonable catalytic cycle is proposed. The NHC-CuOtBu catalytic setup performs nicely at elevated temperature. A more reactive catalytic system is generated from CuCNNaOMe, showing fast turnover at a significantly lower temperature. Both aromatic and aliphatic aldehydes are transformed into the corresponding a-silyl alcohols in good to very good yields under these mild reaction conditions.