温控聚乙二醇两相体系中纳米钯催化肉桂醛选择性加氢反应

将具有“高温混溶、室温分相”功能的聚乙二醇4000(PEG₄₀₀₀)与甲苯-正庚烷组成的两相体系用于纳米钯催化的肉桂醛选择性加氢反应中.在优化的反应条件下,肉桂醛转化率和氢化肉桂醛选择性分别为99%和98%.钯纳米催化剂经简单分相即可与产物分离,且循环使用8次,其活性和选择性基本保持不变.     

钯基氧还原和乙醇氧化反应电催化剂:关于结构和机理研究的一些近期见解

质子交换膜燃料电池和直接乙醇燃料电池已成为可持续性清洁能源研究的一个聚焦点.在燃料电池中,氧还原反应和乙醇氧化反应是两个重要的反应,其相关高活性、高稳定性并且廉价的催化剂的研发仍然存在很多问题,极大地制约了燃料电池的大规模商业化应用.其中的挑战主要来自于对纳米催化剂结构和反应机理的有限认识.由于实验表征理论计算的结合,...     

Fe3O4 – Glutathione stabilized Ag nanoparticles: A new magnetically separable robust and facile catalyst for aqueous phase reduction of nitroarenes

The heterostructured Ag nanoparticles decorated Fe₃O₄ Glutathione (Fe₃O₄‐Glu‐Ag) nanoparticles (NPs) were synthesized by sonicating glutathione (Glu) with magnetite and further surface immobilization of silver NPs on it. The ensuing magnetic nano catalyst is well characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), powder X‐ray diffraction (PXRD), thermogravimetric analysis (TGA). The prepared Fe₃O₄‐Glu‐Ag nanoparticles have proved to be an efficient and recyclable nanocatalyst with low catalyst loading for the reduction of nitroarenes and heteronitroarenes to respective amines in the presence of NaBH₄ using water as a green solvent which could be easily separated at the end of a reaction using an external magnet and can be recycled up to 5 runs without any significant loss in catalytic activity. Gram scale study for the reduction of 4‐NP has also being carried out successfully and it has been observed that this method can serve as an efficient protocol for reduction of nitroarenes on industrial level.     

Nanosilica‐anchored Pd(II)‐Schiff base complex as efficient heterogeneous catalyst for activation of aryl halides in Suzuki–Miyaura cross‐coupling reaction in water

A nanosilica (derived from rice husk)‐anchored Pd(II)–Schiff base complex has been synthesized and characterized. This immobilized complex has been found to be a very effective and recyclable heterogeneous catalyst for the Suzuki–Miyaura cross‐coupling reaction of various aryl halides with arylboronic acid in aqueous medium under mild conditions. The products were identified using ¹H NMR and mass spectral studies. This complex can be easily filtered out from the reaction medium and reused up to six times without significant loss of catalytic activity. Since the reaction proceeds under mild conditions in aqueous medium as well as the catalyst being recyclable, it provides an environmentally benign alternative route to the existing protocols for the Suzuki–Miyaura reaction.     

A highly efficient procedure for the synthesis of quinoxaline derivatives using polyvinylpolypyrrolidone supported triflic acid catalyst （PVPP.OTf）

A polyvinylpolypyrrolidone supported triflic acid was shown to be useful as a recyclable heterogeneous catalyst for the rapid and efficient synthesis of quinoxaline derivatives in good-to-excellent yields. The catalyst is easily prepared, air-stable, reusable, and easily removed from the reaction mixtures.     

Silver nanoparticles immobilized onto poly(4‐vinylpyridine)‐functionalized magnetic nanoparticles: A robust magnetically recyclable catalyst for oxidant‐free alcohol dehydrogenation

A heterogeneous and recyclable catalyst with a high loading of silver nanoparticles was synthesized via the silver nanoparticles being supported onto the surface of magnetic nanoparticles coated with poly(4‐vinylpyridine). The synthesized catalyst was used in the dehydrogenation of alcohols to corresponding carbonyl compounds. A broad diversity of alcohols was converted into their corresponding carbonyl compounds in excellent yields. The catalyst was easily recovered by applying an external magnetic field and reused for seven reaction cycles without considerable loss of activity. The catalyst was fully characterized using various techniques.     

One‐step synthesis of Pt@three‐dimensional graphene composite hydrogel: an efficient recyclable catalyst for reduction of 4‐nitrophenol

A Pt@three‐dimensional graphene (Pt@3DG) composite hydrogel with a unique porous nanostructure was prepared and used as an efficient, recyclable and robust catalyst for the reduction of 4‐nitrophenol to 4‐aminophenol under mild conditions. The influence of graphene architecture on catalytic activities was comparatively investigated by loading the same amount of Pt on reduced graphene oxide. Pt@3DG exhibits a very high catalytic activity owing to the three‐dimensional macroporous framework with high specific surface area, numerous activation sites and efficient transport pathways. Moreover, catalyst separation can be easily achieved by simple filtration, and the catalyst can be reused for at least five runs, maintaining its high catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Imidazolium-modified poly(l-leucine) catalyst: an efficient and recoverable catalyst for Juliá-Colonna reactions

A novel, easily recyclable imidazolium-modified poly(amino acid) catalyst was prepared. This catalyst exhibits high activity for the asymmetric epoxidation of α,β-unsaturated ketones without any pre-activation. The enantioselectivity was up to 99% ee for epoxidation of p-methoxychalcone. Compared to classical Juliá-Colonna catalysts, this insoluble, powdery catalyst can dramatically reduce the reaction time and can be easily recycled by a simple filtration after the reaction. More importantly, the recycled catalyst has been successfully reused for seven cycles without deterioration in catalytic efficiency.     

Environmentally Friendly Preparation of 3,4-Dihydropyrimidin-2(1H)-thiones Catalyzed by Al(H2PO4)3

An efficient, facile, simple, and green synthetic protocol for the Biginelli reaction has been developed for the preparation of 3,4-dihydropyrimidin-2(1H)-thione derivatives under thermal and microwave irradiation, solvent-free conditions, in the presence of aluminum hydrogen phosphate, Al(H₂PO₄)₃, as an environmentally friendly heterogeneous recyclable catalyst, in high to excellent yields and short reaction time. In addition, the catalyst could be easily recovered from the reaction mixture by simple filtration and reused several times without any loss of activity.     

聚乙二醇-水介质中水溶性膦稳定的钌催化芳香酮的不对称加氢反应

在聚乙二醇-400-水介质中,以(1S,2S)-1,2-二苯基乙二胺的磺酸钠盐为手性修饰剂,考察了水溶性三(间-磺酸钠苯基)膦稳定的Ru催化苯乙酮及其衍生物的不对称加氢反应.结果表明,该催化剂体系具有良好的催化活性和对映选择性.在优化反应条件下,苯乙酮转化率和对映选择性分别为100％和84.9％.经正己烷萃取后,催化剂...     

Magnetically recyclable copper modified GO/Fe3O4 catalyst for efficient synthesis of quinazolinones

A series of bioactive quinazolinones were effectively synthesized by the condensation of halide benzamide with amino acid using magnetically recyclable GO/Fe_3O_4–CuI as catalyst. Magnetic GO/Fe_3O_4–CuI was prepared via a simple chemical method and characterized by FTIR, powder XRD, and SEM.This heterogeneous copper catalyst can be easily separated from reaction mixtures by an external permanent magnet and reused without any obvious loss in activity which shows its applicability as a reusable and promising catalyst for quinazolinones synthesis.     

A recyclable and highly effective sulfated TiO2-P25 for the synthesis of quinoxaline and dipyridophenazine derivatives at room temperature

Sulfated TiO₂-P25 has been prepared using H₂SO₄ and used for the synthesis of quinoxaline and dipyridophenazine derivatives. Sulfate loading by H₂SO₄ increases the Lewis acidity of TiO₂-P25. This catalyst gives excellent yield with less reaction time and it is an inexpensive, easily recyclable catalyst for this reaction.     

Poly(4-vinylpyridine)：As a green, efficient and commercial available basic catalyst for the synthesis of chromene derivatives

Poly(4-vinylpyridine) is reported as a green,commercial available and efficient basic recyclable catalyst for the synthesis of chromene derivatives.This catalyst can be easily recovered by simple filtration and recycled up to 5 consecutive runs without any loss of its efficiency.     

Effective one-pot synthesis of tetrahydrobenzo[b]pyran derivatives using nickel Schiff-base complex immobilized on iron oxide nanoparticles

Nickel Schiff-base complex immobilized on silica-coated Fe₃O₄ as a heterogeneous catalyst was designed and characterized by different techniques, such as Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), inductively coupled plasma (ICP) and vibrating sample magnetometry (VSM) thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET). The synthesized nanocatalyst has been explored as a new and efficient recyclable heterogeneous catalyst for the one-pot three-component synthesis of tetrahydrobenzo[b]pyran derivatives. The reaction proceeds smoothly to supply the respective products in excellent yields and low reaction times. The catalyst can be easily recovered by a magnetic field and reused for eight consecutive reaction cycles without significant loss of activity.     

可重复使用的新型催化剂的合成、表征及在绿色条件下催化Suzuki和Heck反应:锚合在磁性纳米多孔的MCM-41上Pd(0)希夫碱络合物

将Pd希夫碱络合物固定在磁性的MCM-41表面上,做为环境友好且可循环使用的新型多相纳米催化剂,并采用红外光谱、振动探针式磁强计、能量散射谱、透射电镜、扫描电镜、热重、电感耦合等离子体发射光谱和X-射线衍射等对其进行了全面的表征.然后将该催化剂用于以PEG为绿色溶剂的一步法Suzuki和Heck合成反应中,均以较高收率得到目标产物.该法主要优点为反应时间短、反应条件绿色友好、操作简便、无需使用有毒的有机溶剂、催化剂使用量低,且底物适用性广.更为重要的是,通过外部磁场即可方便地将催化剂从反应混合物中分离出来,可重复使用数次而活性和稳定性未见明显下降.     

Sulfonated palladium(II) N‐heterocyclic carbene complex immobilized on nano–micro size poly(4‐vinylpyridinium chloride) for Suzuki‐Miyaura cross‐coupling reaction

The sulfonated palladium(II) N‐heterocyclic carbene complex Pd^II(NHC)SO₃^?, supported on poly(4‐vinylpyridinium chloride), was used as a heterogeneous, recyclable and active catalyst for the Suzuki–Miyaura reaction. This catalyst was applied for coupling of various aryl halides with phenylboronic acid and the corresponding products were obtained in excellent yields and short reaction times. The catalyst was characterized using Fourier transform infrared and diffuse reflectance UV–visible spectroscopies, scanning electron microscopy and elemental analysis. After each reaction, the catalyst was recovered easily by simple filtration and reused several times without significant loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

One-pot,solvent-free and efficient synthesis of 2,4,6-triarylpyridines catalyzed by nano-titania-supported sulfonic acid as a novel heterogeneous nanocatalyst

Nano titania-supported sulfonic acid (n-TSA) has found to be a highly efficient, eco-friendly and recyclable heterogeneous nanocatalyst for the solvent-free synthesis of 2, 4, 6-triarylpyridines through one-pot three-component reaction of acetophenones, aryl aldehydes and ammonium acetate. This reported method illustrates several advantages such as environmental friendliness reaction conditions, simplicity, short reaction time, easy work up, reusability of catalyst and high yields of the products. One new compound is reported too. Furthermore, the catalyst could be recycled after a simple work-up, and reused at least six times without substantial reduction in its catalytic activity.     

Self-assembled complexes of non-cross-linked amphiphilic polymeric ligands with inorganic species: highly active and reusable solid-phase polymeric catalysts

I present herein the development of highly active and reusable polymeric catalysts produced by self-assembly process of non-cross-linked amphiphilic polymeric ligands with inorganic species. Thus, PWAA 1 prepared from H3PW12O40 and poly[(N-isopropylacrylamide)-co-(acrylamide with ammonium salt)] is suitable for oxidation of alcohols, amines, and sulfides in aqueous hydrogen peroxide. PdAS 2 produced by self-organization of (NH4)2PdCl4 and poly[(N-isopropylacrylamide)10-co-diphenylphosphinostyrene] is an excellent recyclable catalyst for Suzuki-Miyaura reaction in water, water-organic solvent, and organic solvent. It is commercially available from Tokyo Kasei Kogyo (TCI). PdAS-V 3 assembled from (NH4)2PdCl4 and poly[(N-isopropylacrylamide)5-co-diphenylphosphinostyrene] provides recycling system of itself for Mizorogi-Heck reaction. TiSS 4 made from Ti(O-i-Pr)4 and poly(styryl-linked binaphtholate-co-styrene) promotes an enantioselective carbonyl-ene reaction as a recyclable catalyst.     

Pd(0) complex of fuberidazole modified magnetic nanoparticles: A novel magnetically retrievable high-performance catalyst for Suzuki and Stille C-C coupling reactions

Fuberidazole has been successfully immobilized onto nano-Fe₃O₄ supported (3-chloropropyl)trimethoxysilane (3-CPTS) leading to a novel functionalized magnetic nanoparticle (FB/MNP). The Pd(0) complex, Pd-FB/MNP, was prepared by grafting Pd (OAc)₂ on FB/MNP and subsequent reduction of a synthesized Pd (II) complex using NaBH₄. Pd-FB/MNP has been characterized by FT-IR, SEM, TGA, XRD, ICP, EDS, BET and VSM. The Pd(0) complex proved to be an efficient phosphine- and halide-free recyclable heterogeneous catalyst for Suzuki as well as for Stille C-C coupling reactions showing high catalytic activity (up to 98%). Its catalytic activity in both reactions has been studied in PEG-400 as a green solvent. Besides, the selectivity of aryl iodide and aryl bromide over aryl chloride is observed during the C-C coupling reaction. The catalyst could be recovered easily from the reaction mixture using an external magnet device and recycled several times without considerable loss in activity. Additionally, the results of a palladium leaching test of the nano-catalyst demonstrate that no leaching of Pd took place during the C-C coupling process making the procedure environmentally friendly.     

Chemoselective Hydrazine‐mediated Transfer Hydrogenation of Nitroarenes by Co3O4 Nanoparticles Immobilized on an Al/Si‐mixed Oxide Support

Cobalt oxide nanoparticles (size 2 to 3.5 nm) were successfully impregnated on an alumina–silica (mixed oxide) support through an experimentally viable and easily reproducible protocol. The prepared material was well characterized by XRD, HR‐TEM, BET surface area, EDX and XPS analyses. Porous alumina–silica having a high surface area served as a protective heterogeneous support on which the well‐dispersed Co₃O₄ nanoparticles served as an active catalytic species for the hydrazine‐mediated transfer hydrogenation of nitroarenes. About 2 mol % of the active catalyst in ethanol at 60 °C was adequate for a successful conversion. Moreover, transfer hydrogenation of nitroarenes by the catalyst was found to take place chemoselectively in the presence of other labile functional groups such as halide, alkene, nitrile, carbonyl, and ester. This inexpensive catalyst was also able to catalyze the reaction on a gram scale reaction and found to be robust and recyclable up to eight runs.