- The site-selectivity and mechanism of Pd-catalyzed C(sp2)-H arylation of simple arenes
-
Control over site-selectivity is a critical challenge for practical application of catalytic C-H functionalization reactions in organic synthesis. Despite the seminal breakthrough of the Pd-catalyzed C(sp2)-H arylation of simple arenes via a concerted metalation-deprotonation (CMD) pathway in 2006, understanding the site-selectivity of the reaction still remains elusive. Here, we have comprehensively investigated the scope, site-selectivity, and mechanism of the Pd-catalyzed direct C-H arylation reaction of simple arenes. Counterintuitively, electron-rich arenes preferably undergo meta-arylation without the need for a specifically designed directing group, whereas electron-deficient arenes bearing fluoro or cyano groups exhibit high ortho-selectivity and electron-deficient arenes bearing bulky electron-withdrawing groups favor the meta-product. Comprehensive mechanistic investigations through a combination of kinetic measurements and stoichiometric experiments using arylpalladium complexes have revealed that the Pd-based catalytic system works via a cooperative bimetallic mechanism, not the originally proposed monometallic CMD mechanism, regardless of the presence of a strongly coordinating L-type ligand. Notably, the transmetalation step, which is influenced by a potassium cation, is suggested as the selectivity-determining step.
- Kim, Daeun,Choi, Geunho,Kim, Weonjeong,Kim, Dongwook,Kang, Youn K.,Hong, Soon Hyeok
-
p. 363 - 373
(2021/01/14)
-
- Pillar[5]arene-based N-heterocyclic carbene ligand for Pd-catalysed Suzuki reaction
-
A pillar[5]arene-based N-heterocyclic carbene ligand was prepared by reaction of bromoethoxy pillar[5]arene with excess 1-methylimidazole at 130?°C in the absence of solvent and used as a catalyst for the Suzuki coupling reaction. Excellent yields were obtained when the Suzuki reactions were carried out under ambient atmosphere in ethanol, employing 0.2?mol% ligand, 1?mol% PdCl2(CH3CN)2 and 1.5?mmol of K2CO3. The novel pillar[5]arene-based imidazolium salt is a promising material for the construction of highly active supramolecular catalytic systems.
- Xiao, Xue-Dong,Liu, Jia-Qi,Bai, Ya-Li,Wang, Rui-Hua,Wang, Jun-Wen
-
-
- Sulfadiazine iron palladium nano-composite particle and preparation method thereof
-
The invention discloses a sulfadiazine iron palladium nano composite particle and a preparation method thereof. According to the invention, two metal salt solutions, at a certain ratio, are added in a sulfadiazine-containing organic ligand. The obtained product is subjected to hydrothermal reaction at a certain temperature. After the reaction is over, the obtained product is cooled to the room temperature, filtered and dried to obtain a corresponding metal-ligand nano composite particle. The method is simple in preparation process, low in cost and suitable for mass production. Through controlling the amounts of reactants, the reaction time and the reaction temperature, the particle size of the sulfadiazine iron palladium nano composite particle and the dispersibility thereof are effectively controlled. The prepared sulfadiazine iron palladium nano composite particle is a functionalized nano particle containing iron and palladium, and is stable in performance. The particle can be used for catalyzing the C-C bond coupling reaction, and is high in catalytic efficiency. The yield can be up to over 95% by adopting the particle. Therefore, the sulfadiazine iron palladium nano composite particle has a wide application prospect in the catalysis field.
- -
-
Paragraph 0030; 0031
(2018/02/04)
-
- Fluorenone nickel pyridine nano-cluster and method for preparing same
-
The invention discloses a fluorenone nickel pyridine nano-cluster and a method for preparing the same. The fluorenone nickel pyridine nano-cluster and the method have the advantages that fluorenone pyridine organic ligand solution is added into metal salt solution drop by drop, reaction products are ultrasonically dispersed after reaction is completely carried out, are centrifugally separated from one another, are washed and are dried under vacuum conditions to obtain the ligand-metal nano-cluster, procedures for preparing the fluorenone nickel pyridine nano-cluster are simple, and the fluorenone nickel pyridine nano-cluster is low in cost; solvents, the concentration of reactants, the reaction time and the temperatures can be changed, and accordingly the morphology of the fluorenone nickel pyridine nano-cluster can be effectively regulated and controlled; C-C cross coupling reaction can be efficiently catalyzed by the fluorenone nickel pyridine nano-cluster prepared by the aid of the method, the yield can reach 70% at least, and accordingly the fluorenone nickel pyridine nano-cluster can be widely applied to the field of catalysis.
- -
-
Paragraph 0033; 0034
(2016/12/26)
-
- Trace amount CuII (ppm) and mixture design of CuII/PdII catalyzed Suzuki cross-coupling reactions based on the cooperative interaction of metal with a conjugated pyridylspirobifluorene
-
Self-assembly of Cu/psf sheets and layer-by-layer (LbL) growth of PEI-(Cu/psf)n films were carried out and characterized (psf = 2,2′,7,7′-tetra(4-pyridyl)-9,9′-spirobifluorene). A mixture design was performed to evaluate the singular and combined catalytic effects of Cu(ii), Pd(ii) and psf ligands in the Suzuki cross-coupling reactions. The results showed that copper exhibited high catalytic activities in the presence of psf ligands. The (CuII/psf)n films were used as the reservoirs of catalysts capable of gradually discharging highly active catalytic moieties to promote the coupling reactions with ultra low Cu-loadings (as low as 1.4 × 10-5 mol%). This journal is
- Li, Xing,Zhang, Jie,Zhao, Yayun,Zhao, Xiuhua,Li, Feng,Li, Taohai,Li,Chen, Liang
-
supporting information
p. 6265 - 6270
(2015/03/18)
-
- A highly active multi-usable palladium pyridylfluorene film-based catalyst for C-C cross-coupling reactions
-
The two terminal pyridyl nitrogen atoms of 2,7-bis(4-pyridyl)fluorene (1) were coordinated to Pd(II) ions to give self-assembled, multilayer films using the layer-by-layer (LbL) method. The films were prepared by alternately dipping the substrate, pre-coated with a polyethyleneimine layer, in aqueous solutions of PdCl2 and ethanol solutions of 1. The resulting films were characterized using UV-visible absorption spectroscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy, scanning electron microscopy (SEM) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). UV-visible spectra and SEM images show almost uniform growth of the film in a near ideal LbL manner. AFM images show that nanostructured aggregates of Pd(II) complexes form on the surface. With an increase in the number of Pd(II)/1 bilayers, more particulate aggregates are distributed on the surface. When released from the substrate, the Pd(II) complex nanostructure shows high catalytic activity for Suzuki-Miyaura and Mizoroki-Heck cross-coupling reactions. The catalyst loading is as low as 9.1 × 10-3 mol% Pd, as measured using ICP-AES, and high turnover numbers of up to 1.08 × 104 are obtained.
- Zhao, Xiuhua,Zhao, Yayun,Zhang, Jie,Li, Xing
-
p. 840 - 845
(2016/01/25)
-
- Pd- and Ni-Pyridyl Complexes Deposited as Films for Suzuki-Miyaura and Mizoroki-Heck Cross Coupling Reactions
-
A pyridyl fluorene ligand, 2,7-bis(4-pyridyl)-9,9-diethylfluorene (1), has been synthesized by a simple route. The ability of the two linearly terminal pyridyl nitrogen atoms of 1 to coordinate with the Pd(II) or Ni(II) ions has enabled the use of 1 as a linking ligand in the preparation of (PdCl2/1) n, (Ni(NO3)2/1) n films, PdCl2/1 and Ni(NO3)2/1 complex. The resulting films and complexes were characterized by UV-vis spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectrometer. The application of films and complexes as catalysts for Suzuki-Miyaura and Mizoroki-Heck reactions was carried out. (PdCl2/1) n films show high catalytic activity in the reactions with the Pd loading of ppm. (Ni(NO3)2/1) n multilayers as the active catalytic moieties for these reactions were investigated with very low Ni(II)-loading. Graphical Abstract: The (Pd or Ni/1) n multilayer films were used as high active catalysts for the C-C formation with extremely low M(II)-loading in ppm level.[Figure not available: see fulltext.]
- Zhao, Xiuhua,Zhang, Jie,Zhao, Yayun,Li, Xing
-
p. 2010 - 2019
(2015/12/26)
-