Ru-Catalyzed Geminal Hydroboration of Silyl Alkynes via a New gem-Addition Mechanism
Ru-Catalyzed Geminal Hydroboration of Silyl Alkynes via a New gem-Addition Mechanism
复制标题
通过新的宝石加成机制，钌催化硅炔的偕硼氢化反应
DOI：
10.1021/jacs.0c05334
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发表时间：
2020-08-12
影响因子：
15
通讯作者：
Sun, Jianwei
中科院分区：
文献类型：
--
作者：
Feng, Qiang;Wu, Haonan;Sun, Jianwei
虽然1，2-加成代表了最常见的炔硼氢化模式，但本文描述了一种新的1，1-硼氢化模式。这是第一次证明gem-（H，B）加成到炔三键上。在上级[CpRu（MeCN）（3）] PF 6催化剂作用下，HBpin与一系列硅炔反应，在温和条件下，合成了具有完全立体选择性和广泛官能团相容性的硅基乙烯基硼酸酯。锗基炔的延伸和炔基硼酸酯朝向相同类型的产品的硅氢加成也实现了。从机理上讲，该方法的特征在于一种新的途径，其特征在于gem-（H，B）加成以形成关键的α-硼基-α-甲硅烷基Ru-卡宾中间体，然后是甲硅烷基迁移。据信，在硼迁移之前的硼原子和环己烯环丙烯环之间的共面关系中的硼和C-β之间的轨道相互作用是新的反应性的原因。控制实验和DFT（包括分子动力学）计算提供了重要的见解的机制，其中排除了金属亚乙烯基中间体的参与。该研究不仅为炔硼氢化反应的研究，而且为炔的其他偕加成反应的研究提供了新的思路。
While 1,2-addition represents the most common mode of alkyne hydroboration, herein we describe a new 1,1-hydroboration mode. It is the first demonstration of gem-(H,B) addition to an alkyne triple bond. With the superior [CpRu(MeCN)(3)]PF6 catalyst, a range of silyl alkynes reacted efficiently with HBpin under mild conditions to form various synthetically useful silyl vinyl boronates with complete stereoselectivity and broad functional group compatibility. An extension to germanyl alkynes and the hydrosilylation of alkynyl boronates toward the same type of products were also achieved. Mechanistically, this process features a new pathway featuring gem-(H,B) addition to form the key alpha-boryl-alpha-silyl Ru-carbene intermediate followed by silyl migration. It is believed that the orbital interaction between boron and C-beta in the coplanar relationship between the boron atom and the ruthenacyclopropene ring preceding boron migration is responsible for the new reactivity. Control experiments and DFT (including molecular dynamics) calculations provided important insights into the mechanism, which excluded the involvement of a metal vinylidene intermediate. This study represents a new step forward not only for alkyne hydroboration but also for other geminal additions of alkynes.