Sequential Protocol for C(sp3)–H Carboxylation with CO2: Transition-Metal-Catalyzed Benzylic C–H Silylation and Fluoride-Mediated Carboxylation
摘要:
One of the most challenging transformations in current organic chemistry is the catalytic carboxylation of a C(sp(3))-H bond using CO2 gas, an inexpensive and ubiquitous Cl source. A sequential protocol for C(sp(3))-H carboxylation by employing a nitrogen-directed, metal-assisted, C-H activation/catalytic silylation reaction in conjunction with fluoride-mediated carboxylation with CO2 was established. The carboxylation proceeded only at the benzylic C(sp(3))-Si bond, not at the aromatic C(sp(2))-Si, which is advantageous for further manipulations of the products.
Ruthenium-catalyzed silylation of sp3 C-H bonds at a benzylic position with hydrosilanes gave benzylsilanes. For this silylation reaction, Ru3(CO)12 complex showed high catalytic activity. This silylation proceeded at the methyl C-H bond selectively. For this silylation reaction, pyridyl and pyrazolyl groups, and the imino group in hydrazones, can function as a directing group. Several hydrosilanes
作者:Shun Liu、Qiao Lin、Chunshu Liao、Jing Chen、Kun Zhang、Qiang Liu、Bin Li
DOI:10.1039/c9ob00609e
日期:——
The first application of a RuHCl(CO)(PPh3)3–OAc catalytic system on the selective intermolecular mono C–H silylation of 2-aryl N-heterocycles using HSiEt3 as the silylating reagent has been described. This protocol features good functional group tolerance and high regioselectivity, and has potential for gram scale-up, which provides a convenient and practical pathway for the synthesis of versatile
已经描述了RuHCl(CO)(PPh 3)3 -OAc催化体系在使用HSiEt 3作为甲硅烷基化试剂的2-芳基N-杂环的选择性分子间单C H H甲硅烷基化中的首次应用。该方案具有良好的官能团耐受性和较高的区域选择性,并且具有克级放大的潜力,这为多功能有机硅烷化合物的合成提供了方便实用的途径。该催化体系也可用于具有挑战性的sp 3 C–H键的甲硅烷基化。
Sequential Protocol for C(sp<sup>3</sup>)–H Carboxylation with CO<sub>2</sub>: Transition-Metal-Catalyzed Benzylic C–H Silylation and Fluoride-Mediated Carboxylation
作者:Tsuyoshi Mita、Kenichi Michigami、Yoshihiro Sato
DOI:10.1021/ol301431d
日期:2012.7.6
One of the most challenging transformations in current organic chemistry is the catalytic carboxylation of a C(sp(3))-H bond using CO2 gas, an inexpensive and ubiquitous Cl source. A sequential protocol for C(sp(3))-H carboxylation by employing a nitrogen-directed, metal-assisted, C-H activation/catalytic silylation reaction in conjunction with fluoride-mediated carboxylation with CO2 was established. The carboxylation proceeded only at the benzylic C(sp(3))-Si bond, not at the aromatic C(sp(2))-Si, which is advantageous for further manipulations of the products.
An effective and versatile strategy for the synthesis of structurally diverse heteroarylsilanes <i>via</i> Ir(<scp>iii</scp>)-catalyzed C–H silylation
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