Chitosan-immobilized Palladium Complex: a Green and Highly Active Heterogeneous Catalyst for Heck Reaction

A green heterogeneous catalyst for Heck reaction-chitosan-immobilized palladium complex was prepared. The catalyst exhibits high activity and stereoselectivity under the moderate reaction conditions. The catalyst can be separated easily from the reaction mixture and reused after washing. Under the suitable reaction conditions, the cross-coupling of iodobenzene (ArI) with acrylic acid (AA) or acrylate can be achieved 93.3% or 99% yield of trans-cinnamic acid or trans-cinnamic ester.

Macroporous magnetic poly(GMA-EGDMA-DVB) microspheres supported palladium complex as an efficient catalyst for Heck reaction

Macroporous magnetic poly(GMA-EGDMA-DVB) microspheres synthesized by suspension polymerization were used as supports for palladium catalyst.The results showed the novel magnetic catalyst can promote Heck reaction of aryl halides with acrylic acid efficiently without an inert atmosphere.In addition,the novel catalyst can be conveniently recovered by applying an external magnet and reused at least five times without significant loss of its activity.

A ligand-free Heck reaction catalyzed by the in situ-generated palladium nanoparticles in PEG-400

A ligand-free Heck reaction catalyzed by in situ-generated palladium nanoparticles in PEG-400 has been developed.This catalytic system is a simple and active protocol for the Heck reaction of aryl halides under mild conditions.Comparative experiments demonstrated that the Heck reaction catalyzed by the palladium nanoparticles in situ-generated under the Heck reaction conditions was carried out much quicker than that by the in ex situ-generated ones.

Palladium-catalyzed highly regioselective Heck reaction of aryl nonaflates with electron-rich olefins

Highly efficient palladium-catalyzed Heck coupling of aryl nonaflates with electron-rich vinyl ethers, and enamides is described. These reactions afforded exclusively the branched products in good yields. The results indicated that aryl nonaflates are effective alternative to the frequently employed aryl triflates.

SYNTHESIS OF POLYBINAPHTHYLS INCORPORATING CHIRAL(R)-1,1'-BI-2,2'-NAPHTHOL ENTITIES WITH p-DIVINYLBENZENE BY Pd-CATALYZED HECK REACTION

Polymer and polymer were obtained by the polymerization of (R)-6,6'-dibromo-2,2'-binaphtho-20-crown-6 (M-1) and (R)-6,6'-dibromo-2,2'-di(methoxyethoxymethyloxy)-1,1'-binaphthyl (M-2) with p-divinylbenzene under Pd- catalyzed Heck reaction. The UV, fluorescence and CD spectra of polymer are similar due to the same linkers present in their polymer chain. Polymers can emit strong blue fluorescence and are expected to have potential applications in polarized blue-light emitting sensors. The chiral conjugated polymers exhibit a strong Cotton effect in their circular dichroism (CD) spectra, indicating a high rigidity of polymer backbone.

Synthesis of 3-Benzyloxy-6-methyl-7-methoxyphenanthrene-9-carboxaldehyde with Utilize Intramolecular Heck Reaction as the Key Step

The substituted phenanthrene-9-carboxyaldehydes are very important intermediates for the syntheses of phenanthroindolizidine and phenanthroquinolizidine alkaloids. The novel title compound was prepared from the reaction of 5 steps starting from the condensation of 3-methoxyl-4-methyl-phenylacetic acid and 4-（benzyloxy）-2-iodobenzaldehyde, followed by esterification, cyclization, reduction, and oxidation. A new method for the preparation of phenanthrene ring via palladium-catalyzed intramolecular Heck reaction was described. The title compound was characterized by IR, ^1H NMR, ^13C NMR, elemental analysis, and MS.

Heck Reactions with Ultralow Concentration of Transition Metals under Microwave Irradiation

The Heck coupling reactions of aryl halides and olefins were performed under the microwave assistance. Interestingly, the ultralow concentration of transition metals (in ppb) coming from the reactants could catalyze the Heck coupling reactions under microwave irradiation, without addition of any catalysts, ligands and phase-transfer agents. The influences of bases, solvents and temperature were discussed, and the reaction rate was enhanced largely in the mixed solvents of NMP and water due to the solubility of base in water.

Pd基MoO_(x)催化剂中金属与载体的相互作用及其对Heck反应的影响

钯(Pd)催化的Heck反应是合成中构建碳-碳键的有效方法之一。金属-载体相互作用(MSI)对于非均相催化剂在某些工业过程中由于金属活性位点暴露或堵塞而显著提高或降低催化性能具有重要意义。本文合成了Pd基MoO_(x)催化剂,利用XRD、XPS、Raman等表征研究了在不同氧化还原处理条件下,钯纳米粒子与氧化钼层的金属-载体相互作用(MSI)在碘苯和丙烯酸甲酯的Heck反应中的性能影响。研究发现Pd/MoO_(3)在氢气条件下的部分还原导致MoO_(x)物种迁移到Pd-NPs的表面并形成包封结构,涂层可能通过空气煅烧重新暴露,MSI导致Pd/MoO_(3)在Heck反应中的催化性能降低。本研究证明了平衡金属-载体相互作用在实际催化剂设计中的重要性,以实现贵金属催化剂在催化Heck反应中的更高利用率。

不对称Heck反应合成手性哌啶衍生物

手性哌啶骨架广泛存在于药物和活性天然产物分子中。本研究发展了一种新型不对称Heck反应,用于合成手性哌啶衍生物。通过对反应条件进行筛选,得到了最优反应条件:催化剂为[Pd(allyl)Cl]_(2)(5 mol%),配体为L5(10 mol%),NaOMe(3.0 equiv)作碱,在110℃的混合溶剂(PhMe/MeOH=5/1)中回流反应20 h。该不对称Heck反应显示出良好的底物普适性,可用于构建多种含有季碳中心的手性哌啶衍生物。

Recent Advances of Catalytic Enantioselective Heck Reactions and Reductive-Heck Reactions

Heck reaction is one of the most important carbon-carbon bond forming reactions with wide applications in organic synthesis.Considerable advances of enantioselective Heck reaction have been achieved in the past decades.This review focuses on recent development of catalytic asymmetric Heck reaction and reductive Heck reaction,which covers intermolecular and intramolecular versions since 2011.The article is organized in terms of the cat-alysts and olefin substrates.

Nanosized Pd assembled on superparamagnetic core–shell microspheres:Synthesis,characterization and recyclable catalytic properties for the Heck reaction

A series of magnetically recyclable Pd/Fe3O4@γ-Al2O3 catalysts were synthesized using the superparamagnetic Fe3O4@γ-Al2O3 core-shell microspheres as the supporter and nano-Pd particles assembled on γ-Al2O3 shell as the active catalytic component. The structure of the catalysts was characterized by X-ray diffraction （XRD）, transmission electron microscopy iTEM）, N2 adsorptiondesorption and vibrating sample magnetometer （VSM）. The catalytic activity and the recyclability properties of the catalysts for the Heck coupling reaction with aryl bromides and the olefins were investigated. The results show that the microspheres of the magnetic Pd/Fe304@γ-Al2O3 catalysts were about 400 nm and the nano-Pd particles assembled on γ-Al2O3 shell were about 3-4 nm in size. The saturation magnetization （MS） of the magnetic catalysts was sufficiently high to allow magnetic separations. In the Heck coupling reactions, the magnetic Pd/Fe304@γ-Al2O3 catalysts exhibited good catalytic activity and recyclability. With Pd/Fe304@γ-Al2O3 （0.021 mol%） catalyst, the bromobenzene conversion and product yield reached about 96.8% and 91.2%, respectively, at 120℃ and in 14 h. After being recycled for six times, the conversion of bromobenzene and the recovery of the catalyst were about 80% and 90%, respectively. The nano-Pd particles were kept well dispersed in the used Pd/Fe304@γ-Al2O3 catalysts.

Preparation and application of SBA-15-supported palladium catalyst for Heck reaction in supercritical carbon dioxide

A new method for the preparation of SBA-15-supported palladium catalyst for Heck reaction in supercritical carbon dioxide was presented.The newly formed SBA-15-supported palladium catalyst（Ph-SBA-15-PPh_3-Pd） exhibited high catalytic activity for the Heck reaction of 4-nitrobromobenzene with methyl acrylate.The catalyst can be reused several times without a loss of activity.

Synthesis of 4-Trifluoromethylated 1,3-Butadienes via Palladium Catalyzed Heck Reaction

1,3-Butadiene plays a key role in modern synthetic chemistry and biochemistry because it is a key intermediate in the synthesis of many drugs.A new and effective method for the synthesis of 4-trifluoromethylated 1,3-butadiene through the fluorinated Heck reaction catalyzed by Pd(0)is described.Without additives,1-chloro-3,3,3-trifluoropropene(an inexpensive CF3 structural unit that is harmless to ozone)reacts with enamide to synthesize 4-trifluoromethylated 1,3-butadienes with good yield,high regioselectivity and chemical selectivity,and strong tolerance of substrate functional groups such as alkynes,aldehyde,and ester groups.

Aqueous-Phase, Palladium-Catalyzed Heck Reaction： The Significant Role of CN-containing Counter Anion

Water-soluble diol-functionalized imidazolium ionic liquid 1, prepared from 2,2-bis（1-methyl-methyl-imida- zolium）propane-l,3-diol bromide, potassium hydroxide, and malononitrile, was used as an efficient phosphine-free ligand for palladium-catalyzed arylation of aryl halides with acrylates in aqueous phase under mild conditions. It was found that the synergistic coordinating action of diol-functionalized imidazolium cation with CN-containing anion played the key role in improving the activity and stability of the catalyst.

Investigation on the Coordination Mode of IL-Supported Diols Used as Phosphine-Free Ligands for Palladium Catalyzed Heck Reaction

The coordination mode of IL-supported diols used as phosphine-free ligands for palladium catalyzed Heck reaction has been investigated by tuning their compositions. The difference in coordination of these IL-supported diols with metal Pd in Heck reaction was related to the changes of the cation rings, leading to the different activities of Pd catalyst in the reaction. The experimental results indicated that the activities of Pd catalyst were affected mainly by n-electron density of the cation rings. Compared to pyridinium and piperidinium cations, imidazolium cations showed the best coordination to metal Pd. In the meantime, C-2 hydrogen and the length of alkyl side chains had impacts on the coordination as well.

Polystyrene microsphere-immobilized palladium(Ⅱ)porphyrin as mild,reusable,and highly efficient catalyst for Heck reaction

A novel Heck reaction catalyst consisting of a palladium（ll） complex of meso-tetra（p- hydroxyphenyl）porphyrin （MTP） and cross-linked chloromethylated polystyrene microspheres （PMs） was successfully prepared via covalent ether bonds between the chloride groups in the PMs and the hydroxyl groups in MTP. The catalyst was characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, and inductively coupled plasma atomic emission spectroscopy （ICP-AES）. This polystyrene-supported palladium-complex was an efficient heterogeneous catalyst for cross-coupling of aryl iodides with ethyl acrylate. The reaction of iodobenzene and ethyl acrylate under N2 at 100 °C and a catalyst concentration of 0.1% gave a gas chromatography product yield of 99.8%, which is much higher than that achieved using a free palladium（II） complex of MTP as the catalyst （41.3%）. The catalyst was recycled up to six times without significant loss of catalytic activity. These results suggest that the immobilized palladium（II） MTP catalyst has potential applications in synthetic and industrial chemistry.

Synthesis and characterization of silica-supported Pd nanoparticles and its application in the Heck reaction

Well-dispersed palladium nanoparticles immobilized onto modified silica （Si02-pr-NH-cyanuric-SH） have been prepared in some facile steps. The catalyst exhibits high catalytic activity in the Heck reaction, and can be easily recovered and reused without significant loss of its activity in several runs.

Heck Reaction Catalyzed by Palladacycle in Neat Water

Cyclopalladated ferrocenylimine has been found to be a type of excellent phosphine-free catalyst for Heck reactions in neat water with both higher yields and turnover numbers than those reported in the literature up to now. Some commercial emulsifying agents, including the commonly used quaternary ammonium salts, have been proved to be excellent additives in the catalysis of the reactions. Not only aromatic iodide, but also aromatic bromide could be coupled with the olefins. All reactions were able to be conducted in air under refluxing condition.

Monodentate phosphorus-coordinated palladium(Ⅱ)complexes as new catalyst for Mizoroki-Heck reaction of aryl halides with electron-deficient olefins

Four novel palladium（（Ⅱ）） complexes coordinated by phosphorus atoms from both 3,5-disubstituted-1H- 1,2,4-diazaphospholes in monodentate fashion were developed as efficient catalyst for the Mizoroki- Heck reaction of aryl halides with electron-deficient olefins. The coupling reaction of awl halide bearig different functional groups with olefin derivatives took place and the corresponding products were isolated in good to excellent yields under optimal conditions. The procedure exhibits good functional group tolerance and wide substrate scope. This Mizoroki-Heck reaction was further achieved using Pd（OAc）2 and 3,5-di-isopropyl-1H-1,2,4-diazaphospholes as combined catalyst, which provide the convenient and alternative method in organic synthesis