Yan Zhi-Bo, Peng Meng, Chen Qi-Long, Lu Ka, Tu Yong-Qiang, Dai Kun-Long, Zhang Fu-Min, Zhang Xiao-Ming
State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University Lanzhou 730000 P. R. China
School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs, Shanghai Jiao Tong University Shanghai 200240 P. R. China.
Chem Sci. 2021 Jun 8;12(28):9748-9753. doi: 10.1039/d1sc02344f. eCollection 2021 Jul 21.
A versatile silylation of heteroaryl C-H bonds is accomplished under the catalysis of a well-defined spirocyclic NHC Ir(iii) complex (SNIr), generating a variety of heteroarylsilanes. A significant advantage of this catalytic system is that multiple types of intermolecular C-H silylation can be achieved using one catalytic system at α, β, γ, or δ positions of heteroatoms with excellent regioselectivities. Mechanistic experiments and DFT calculations indicate that the polycyclic ligand of SNIr can form an isolable cyclometalated intermediate, which leaves a phenyl dentate free and provides a hemi-open space for activating substrates. In general, favorable silylations occur at γ or δ positions of chelating heteroatoms, forming 5- or 6-membered C-Ir-N cyclic intermediates. If such an activation mode is prohibited sterically, silylations would take place at the α or β positions. The mechanistic studies would be helpful for further explaining the reactivity of the SNIr system.
在一种结构明确的螺环NHC Ir(III)配合物（SNIr）催化下，实现了杂芳基C-H键的通用硅基化反应，生成了多种杂芳基硅烷。该催化体系的一个显著优点是，使用一种催化体系可以在杂原子的α、β、γ或δ位实现多种类型的分子间C-H硅基化反应，且区域选择性优异。机理实验和密度泛函理论计算表明，SNIr的多环配体可以形成一种可分离的环金属化中间体，该中间体留下一个游离的苯基齿，并为活化底物提供一个半开放空间。一般来说，有利的硅基化反应发生在螯合杂原子的γ或δ位，形成5元或6元C-Ir-N环状中间体。如果这种活化模式在空间上受到阻碍，硅基化反应将发生在α或β位。这些机理研究将有助于进一步解释SNIr体系的反应活性。
