共查询到20条相似文献,搜索用时 15 毫秒
1.
New, sterically demanding 1,3-dialkyl-3,4,5,6-tetrahydropyrimidinium salts (2) as NHC precursors have been synthesized and characterized. These salts, in combination with palladium acetate, provided active catalysts for the cross-coupling of aryl chlorides and bromides under mild conditions. The catalytic system was applied to the Heck, Suzuki and benzaldehyde (Kumada) coupling reactions. Catalyst activity was found to be influenced by the presence of a methoxy group on the ring of the p-position of benzyl substituent of the ligand precursor. 相似文献
2.
Song-Se Yi 《Tetrahedron letters》2007,48(38):6771-6775
A chitosan-supported palladium (Pd) (0) catalyst was prepared by simple adsorption of palladium(II) ion onto chitosan beads and a subsequent reduction process. To maintain mechanical stability, the chitosan-supported palladium(0) catalyst was cross-linked with either glutaraldehyde or diglycidyl ether polyethylene glycol. The catalysts were utilized for the Suzuki cross-coupling reaction in water. The catalyst, in the presence of a tetrabutylammonium bromide (TBAB) additive, showed excellent catalytic activity in microwave-prompted Suzuki cross-coupling reactions using various aryl halides and boronic acids. In addition, the catalyst was successfully reused up to five times without significant loss of catalytic activity. 相似文献
3.
In this study, we report recyclable Pd-complexed graphene oxide (GO) catalysts with a bulky N-heterocyclic carbene (NHC) ligand (GO/NHC-Pd) for various cross-coupling reactions in the aqueous phase. To prepare GO/NHC-Pd, the NHC precursor and a trimethoxy-silane linker were combined on the GO surface via condensation, followed by the Pd chelation over GO/NHC. The GO-based catalysts were applied to three types of CC cross-coupling reactions including Suzuki, Heck and Sonogashira reactions in the aqueous phase, to evaluate their catalytic performance. The reusability of the catalysts was tested by performing five consequent cross-coupling reactions. 相似文献
4.
Eunyoung Sin Song-Se Yi Yoon-Sik Lee 《Journal of molecular catalysis. A, Chemical》2010,315(1):99-104
A chitosan-g-mTEG (methoxy triethylene glycol)- or mPEG (methoxy polyethylene glycol)-supported palladium (0) catalyst was prepared for the Suzuki cross-coupling reaction in water. The catalyst showed excellent catalytic activity in the Suzuki cross-coupling reaction without additional phase transfer reagents due to the enhanced solubility of the organic substrate by PEG grafting. In addition, the catalyst could be reused up to five times with the catalytic activity being recovered easily after simple manipulations. 相似文献
5.
《Comptes Rendus Chimie》2017,20(2):132-139
Supported Pd–S-methylisothiourea on magnetic nanoparticles (Pd–SMU-MNPs) as an efficient and magnetically reusable nanocatalyst was prepared and applied for the Heck and Suzuki cross-coupling reactions. All coupling reactions proceeded in short reaction times with good to excellent yields. After completion of reactions, the catalyst was easily separated from the reaction mixture using an external magnetic field and reused for several consecutive runs without significant loss of its catalytic efficiency and activity. This nanomagnetic catalyst was characterized by FT-IR spectroscopy, XRD, VSM, ICP-OES, TEM and SEM techniques. The leaching of the catalyst has been examined by a hot filtration test and ICP-OES analysis. 相似文献
6.
Copper supported on 2-(1H-benzo[d]imidazol-2-yl)aniline (BIA)-functionalized Fe3O4 nanoparticles (Cu-BIA-Si-Fe3O4) as a novel magnetic catalyst was designed and used for the synthesis of new products via Ullmann and Suzuki cross-coupling reactions. The Ullmann reaction was performed by mixing arylboronic acid with aniline derivatives in dimethylsulfoxide solvent. Also, diaryls were synthesized via Suzuki C–C reactions between aryl halides and phenylboronic acid in the same solvent. The prepared materials and catalyst were characterized with various analytical techniques. The Cu-BIA-Si-Fe3O4 catalyst demonstrated catalytic efficiency with good to excellent yields for both types of reactions in comparison with commercial palladium catalysts. Also, the catalyst could be recovered by a simple filtration and retained its activity even after several cycles. 相似文献
7.
Jung Hyun Park Faizan Raza Su-Ji Jeon Hye-In KimTae Woog Kang DaBin YimJong-Ho Kim 《Tetrahedron letters》2014
Graphene oxide (GO) was functionalized with a N-heterocyclic carbene (NHC) precursor, 3-(3-aminopropyl)-1-methylimidazolium bromide ([APMIm][Br]) for the immobilization of palladium catalyst. The GO-supported NHC precursor (IMGO) formed a stable complex with Pd(OAc)2 (GO–NHC–Pd), which showed excellent catalytic activity and fast reaction kinetics in the aqueous-phase Suzuki reaction of aryl bromides and chlorides at relatively mild conditions (1 h at 50 °C). The GO–NHC–Pd catalyst was reused several times without any loss of its catalytic activity in the Suzuki reaction of aryl bromide. 相似文献
8.
Omid Bagheri Faranak Sadegh Majid Moghadam Shahram Tangestaninejad Valiollah Mirkhani Iraj Mohammadpoor‐Baltork Mahsa Safiri 《应用有机金属化学》2014,28(5):337-346
The tetrakis(4‐N‐methylpyridinium)porphyrinatopalladium(II) iodide, [Pd(TMPyP)]I4, supported on Dowex 50WX8 and Amberlite IR‐120 ion‐exchange resins, was used as heterogeneous, recyclable and active catalyst for the Suzuki–Miyaura and Heck cross‐coupling reactions. These catalysts were applied to coupling of various aryl halides with phenylboronic acid and styrene in Suzuki and Heck reactions, respectively, and the corresponding products were obtained in excellent yields and short reaction times. The catalysts could be recovered easily by simple filtration and reused several times without significant loss of their catalytic activity. The catalysts were characterized by diffuse‐reflectance UV–visible spectroscopy and scanning electron microscopy, and their stability was confirmed by TGA. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
9.
Using polymeric nanocomposites incorporated Pd to promote C-C coupling reactions has been found as one of the most successful strategies. In this paper we apply graphene oxide (GO) as an efficient surface immobilized by water-soluble poly (ethylene glycol)-imidazole followed by introduction of PdCl2 salt to obtain the desired catalyst. Catalytic performance of this composite was investigated in the Suzuki–Miyaura cross-coupling reaction under mild reaction conditions and superior results were obtained. The hydrophilic nature of the catalyst and well distribution of Pd lead to superior catalytic activity in water media. Moreover, the Suzuki–Miyaura reaction proceed successfully with excellent yield and short reaction time without any loss of activity even after seven consecutive reaction cycles. 相似文献
10.
Elizabeth Tyrrell 《Journal of organometallic chemistry》2011,696(22):3465-3472
Silica supported palladium NHC complexes have been prepared by two different routes: one involving the reaction of silica-supported imidazolium salts with palladium acetate and a direct immobilisation of a pre-formed complex by reacting a (trimethoxysilylpropyl)-N-aryl-imidazolylidene palladium complex with surface hydroxyl groups. A small range of catalysts of varying steric bulk were prepared in order to evaluate the effect on catalytic conversion. The activity of the palladium catalysts in Suzuki cross-coupling reactions has been established. The catalysts prepared by immobilising pre-formed palladium complexes gave superior results for the conversion of aryl bromides and aryl chlorides. In addition, use of sterically bulky NHCs (such as the N-2,6-(diisopropyl)phenyl-substituted ligand) resulted in increased catalytic activity, which is analogous to the trends noted in homogeneous catalysis. 相似文献
11.
Catalytic activity of palladium(II) diaminocarbene complexes in the Sonogashira and Suzuki reactions
V. N. Mikhailov E. A. Savicheva V. N. Sorokoumov V. P. Boyarskii 《Russian Journal of Organic Chemistry》2013,49(4):551-554
Palladium(II) complexes with chelating and non-chelating diaminocarbene ligands were assessed as catalysts in the cross-coupling reactions of haloarenes with oct-1-yne (Sonogashira reaction) and phenylboronic acid (Suzuki reaction). Both complexes exhibited a higher catalytic activity than traditional phosphine ligandbased systems in the Sonogashira reaction, and they ensured cross-coupling not only with iodoarenes but also with bromoarenes activated by electron-withdrawing substituents. The catalytic activities of the examined complexes in the Suzuki reaction were appreciably different: the palladium(II) complex with the chelating ligand turned out to be considerably less active than the complex with the non-chelating ligand. 相似文献
12.
Vivek Polshettiwar 《Tetrahedron》2008,64(20):4637-4643
The first Pd-N-heterocyclic carbene (NHC) complex in the form of organic silica was prepared using sol-gel method and its application in Heck and Suzuki reactions was demonstrated. These C-C coupling reactions proceeded efficiently under the influence of microwave irradiation, with excellent yield, without any change in catalytic activity for at least five reaction cycles, with negligible Pd concentration in the end product. 相似文献
13.
Bin Luo JiaQing Wang DanHua Ge XinMing Li XueQin Cao Yue Pan HongWei Gu 《中国科学:化学(英文版)》2014,57(9):1310-1314
A simple and efficient system for Suzuki cross-coupling reactions was developed using a ligandless catalyst of Pd nanoclusters generated in situ from Pd(acac)2. The cross-coupling reactions proceeded under mild reaction conditions with a high reaction rate (5 min) to give various biaryls in high yields. The system also exhibited catalytic potential for Heck reaction between aryl bromides and styrene. 相似文献
14.
Emulsion polymerization was examined as a novel route for the synthesis of core/shell superparamagnetic nanoparticles consisting of a highly crystalline gamma-Fe2O3 core and a very thin polymeric shell wall. These nanoparticles were used as soluble supports for immobilizing Pd catalysts to promote Suzuki cross-coupling reactions. Recovery of catalysts was facilely achieved by applying a permanent magnet externally. Isolated catalysts were reused for new rounds of reactions without significant loss of their catalytic activity. 相似文献
15.
16.
Thomas E. Nielsen 《Tetrahedron letters》2005,46(46):7959-7962
Solid-supported masked peptide aldehydes containing 3- or 4-iodophenylalanine residues were subjected to Pd-catalyzed Suzuki cross-coupling reactions with arylboronic acids. The biarylalanines generated were applied in intramolecular N-acyliminium Pictet-Spengler reactions. In this way, a range of pharmacologically interesting aryl-substituted pyrroloisoquinolines was obtained in excellent purity (>95%). 相似文献
17.
Poly(1-methylimidazoliummethyl styrene)-surface grafted-poly(styrene) resin was prepared for the first time as a polymer-supported N-heterocyclic carbene (NHC) precursor for palladium complex by suspension polymerization. To prepare this polymer-supported NHC precursor, 1-methyl-3-(4-vinylbenzyl)imidazolium hexafluorophosphate, [MVBIM][PF6-], was synthesized as a monomer and copolymerized with styrene and DVB in water. This polymer-supported NHC precursor with imidazolium as a ligand, which exists solely on the surface of the resin, was well characterized by FE-SEM, CLSM, and IR spectroscopy. The precursor containing imidazolium readily formed a stable complex with Pd(OAc)2, and this polymer-supported N-heterocyclic carbene-palladium complex exhibited excellent catalytic activity for Suzuki cross-coupling reaction in an aqueous medium. The catalyst was recovered quantitatively from the reaction mixture by simple filtration and was able to be reused for a number of recycles with consistent activity in all of the coupling reactions. 相似文献
18.
Jang-Woong Byun 《Tetrahedron letters》2004,45(9):1837-1840
A novel polymer-supported N-heterocyclic carbene (NHC) was prepared from chloromethyl polystyrene (CM PS) resin using a simple procedure, and was used as the ligand for palladium (Pd) catalysts. The polymer-supported Pd-NHC complexes efficiently catalyzed the Suzuki cross-coupling of aryl halides and phenylboronic acid in good yields and excellent purities under aqueous conditions. 相似文献
19.
A sulfonate-functionalized N-heterocyclic carbene (NHC) was successfully attached to a hyper-cross-linked polymer via an external cross-linking reaction. The structure of Poly-BBIS was confirmed by FTIR spectroscopy, TEM, FESEM, and BET. The Poly-BBIS show a large surface areas (up to 563 m2 g?1) and hydrophilicity, as well as abundant micro-mesoporous, tunable and versatile active sites. The catalytic activity of the Pd derivative Poly-BBIS-Pd2+ was examined for Suzuki–Miyaura cross-coupling reactions in water, followed by an investigation of the reaction mechanism. The Poly-BBIS-Pd2+ gives a yield of 98% for the reaction between bromobenzene and phenylboronic acid with a loading of 0.057 mmol % Pd in water after approximately 2 h. Also, the catalyst can be reused for 5 times without significant loss of activity. This work highlights a low-cost route to the synthesis of heterogeneous catalysts based on hydrophilic sulfonate-functionalized NHC polymers for the Suzuki–Miyaura cross-coupling reaction in water. 相似文献