Aerobic ligand-free Suzuki coupling catalyzed by in situ-generated palladium nanoparticles in water

A simple and efficient procedure for Suzuki coupling of aryl bromides/iodides with aryl- and alkylboronic acids catalyzed by in situ-generated palladium(0) nanoparticles in water without any ligand in open air to produce a variety of functionalized biaryls and alkyl-aryls has been developed. The boronic acids act here as the reducing agent for the formation of Pd nanoparticles. The reactions are remarkably fast (5 min) and high yielding. The catalyst is recyclable up to three runs without loss of efficiency.     

Nation-Teflon bimembrane-supported palladium catalysts for Suzuki coupling reactions

Nation-Teflon bimembrane was used as an efficient support for the preparation and application of heterogeneous palladium catalysts.The supported palladium catalysts exhibit high activity and stability in the Suzuki cross-coupling of aryl bromides with arylboronic acids to afford the corresponding biaryls in good to excellent yields,and can be readily recovered and reused several times without significant loss of activity.     

纳米钯催化苄基氯代物与烯丙基硼酸频哪醇酯的羧化Suzuki偶联反应

CO2是廉价的C1源,同时具有无毒、储量丰富的优点, 符合绿色化学发展要求. 利用 CO2构筑新的 C–C 键是化学固定CO2的重要方法. Β,γ-不饱和酯类结构单元是许多生物活性分子的重要组成部分, 经由双π-烯丙基钯中间体与 CO2反应, 合成新的β,γ-不饱和酯类化合物, 具有重要意义. CO2与有机硼化合物的羧化反应已有报道, 有机硼化合物具有低毒、对水不敏感等优点. 但是已报道的羧化 Suzuki 偶联反应存在诸多缺点: (1) 需要使用含膦或者氮杂环卡宾配体的催化剂, 而这些催化剂的制备过程使前期实验步骤变得冗长, 同时反应液的酸化后处理过程也会造成环境污染; (2) 有机硼试剂的官能团兼容范围窄, 限制了底物范围的拓展. 本课题组以原位生成的纳米钯粒子为催化剂, 在 CO2存在的温和条件下, 高效实现了苄氯与烯丙基硼酸频哪醇酯的羧化 Suzuki 偶联反应. 反应过程中无其它配体加入, 反应结束后不需要酸化或酯化的后处理过程. 该反应将具有广泛的官能团兼容性.本文以 TBAB 稳定的纳米钯粒子为催化剂, 在温和条件下, 实现了氯甲基芳香化合物、烯丙基硼酸频哪醇酯和 CO2的三组分羧化 Suzuki 偶联反应. 最佳反应条件为: Pd(acac)2(5 mol%)、TBAB (0.7 mmol, 1.4 equiv.)、KF (1 mmol, 2.0 equiv.)、苄基卤代物 (0.5 mmol)、烯丙基硼酸频哪醇酯 (0.6 mmol, 1.2 equiv.)、CO2(2.0 Mpa)、溶剂 THF (5 mL), 50 oC 反应 24 h. 在最佳反应条件下, 苯环、萘环以及杂芳环的氯甲基化合物均可发生该羧化反应. 苯环上取代基的位置对产物的收率有影响. 当使用 1-溴甲基萘作为底物时反应也能够发生, 收率与 1-氯甲基萘作为底物时的收率相当. 与已报道有机硼试剂的羧化反应相比, 该反应体系无需加入配体, 原位生成了纳米钯粒子, 避免了催化剂或者配体的复杂制备过程. 该反应中, 氟离子的存在是必要的, 对烯丙基硼酸频哪醇酯具有活化作用.     

Synthesis of arylated chalcone derivatives via palladium cross-coupling reactions

A useful protocol for arylation of the olefin double bond of chalcones to afford tri- and tetra-substituted chalcone derivatives is reported. The protocol begins with the Heck reaction between chalcones and aryl iodides providing β-arylchalcones. This reaction tolerates various functional groups on both rings, as well as deactivated aryl iodides. The products are obtained in moderate to excellent yields and the (E)-β-arylchalcones (E:Z?>?96:4) can be isolated via precipitation. Competitive Heck reactions pointed to a significant effect of ring one substituents on the reaction rate, while substituents on ring two have a much smaller effect. To access α,β-diarylchalcones, a sequential bromination-Suzuki cross coupling strategy was applied to the β-arylated compounds which afforded double arylated chalcone derivatives in 60–99% yield over two steps.     

Suzuki reactions catalyzed by palladium complexes bearing the bulky (2,6-dimesitylphenyl)dimethylphosphine

A new bulky and stable phosphine (2,6-dimesitylphenyl)dimethylphosphine, and representative palladium complexes have been prepared and structurally characterized; some of these complexes prove efficient for coupling of aryl chlorides with arylboronic acids.     

Facile synthesis of palladium nanoparticles supported on urea-based porous organic polymers and its catalytic properties in Suzuki-Miyaura coupling

By using urea linked porous organic polymers as template, a new nano palladium catalyst with low Pd loading can be easily prepared (1.0 wt% Pd only). Although such less amount of Pd was contained in this new catalyst, it is still an effective catalyst for the Suzuki-Miyaura coupling of aryl iodines and aryl boric acids, affording biphenyl products in excellent yields with outstandingly enhanced turnover numbers (up to 10,536) under green solvent (water).     

Polymethyl methacrylate micro-spheres supported palladium: A new catalyst for Heck and Suzuki reactions

Polymethyl methacrylate (PMMA) micro-spheres, a kind of commercially available polymeric material was treated with PdCl₂ and formaldehyde giving a reagent with a palladium loading of 0.79 (wt.%). The Pd-PMMA catalyzed the highly efficient Heck and Suzuki reactions. The reactions can be performed under ligand-free conditions in an air atmosphere. The palladium catalyst is easily separated and can be reusable with negligible leaching of palladium.     

Synthesis and characterizations of N,N,N′,N′-tetrakis (diphenylphosphino)ethylendiamine derivatives: Use of palladium(II) complex as pre-catalyst in Suzuki coupling and Heck reactions

Oxidation of N,N,N′,N′-tetrakis(diphenylphosphino)ethylendiamine (1) with elemental sulfur and selenium gives the corresponding sulfide and selenide, respectively, [(Ph₂P(E))₂NCH₂CH₂N(P(E)Ph₂)₂] (E: S 1a, Se 1b). Complexes of 1 [(M₂Cl₄){(Ph₂P)₂NCH₂CH₂N(PPh₂)₂}] (M: Ni(II) 1c, Pd(II) 1d, Pt(II) 1e) were prepared by the reaction of 1 with NiCl₂ or [MCl₂(COD)] (M = Pd, Pt). The new compounds were characterized by NMR, IR spectroscopy and elemental analysis. The catalytic activity of Pd(II) complex 1d was tested in the Suzuki coupling reaction and Heck reaction. The palladium complex 1d catalyses the Heck reaction between styrene and aryl bromides as well as Suzuki coupling reaction between phenylboronic acid and arylbromides affording stilbenes and biphenyls in high yield, respectively.     

Shape-dependent catalytic activity of copper oxide-supported Pd(0) nanoparticles for Suzuki and cyanation reactions

Palladium nanoparticles supported on different shapes of nanocrystalline CuO are prepared by the treatment of Cu(NO₃)₂ and Pd(OAc)₂ in polyethylene glycol (PEG-6000). The shapes of the CuO/Pd composite are dependent on the amount of PEG used. Suzuki coupling was catalyzed efficiently by the oval-shaped material, whereas the rod shape facilitates the cyanation reaction. The CuO/Pd catalyst is recovered and reused for subsequent Suzuki reactions; however, cyanation poisons the catalyst for further use. Both these reactions are very clean and high yielding.     

Microwave assisted cross-coupling reactions using palladium nanoparticles in aqueous media

Glucose stabilized palladium nanoparticles (PdNPs) have been prepared and the application of NPs in catalyzing both Suzuki and Heck reactions has been explored in aqueous media under microwave conditions. Both electron-rich and electron-deficient aryl halides can be coupled with a variety of boronic acids and styrene to access a wide variety of biaryl compounds and substituted alkenes in good to excellent yields. The catalyst can be recycled and reused four times with minimally affecting the morphology and efficiency of the nanoparticles. A plausible reaction mechanism has been proposed.     

Suzuki reaction of bromoallenes with arylboronic acids using an air-stable palladium complex Pd(Ph_2PCH_2CO_2)_2 as a precatalyst

<正>Suzuki reaction of bromoallenes with arylboronic acids was successfully performed by using an air-stable hemilabile P-O coordinated cyclopalladated complex Pd(Ph_2PCH_2CO_2)_2 as a precatalyst,and the corresponding coupling products were obtained in satisfactory to excellent yields.All products are unknown compounds which were characterized by ~1H NMR,~(13)C NMR,IR,and HRMS.     

Preparation of a palladium dimer with a cobalt-containing bulky phosphine ligand: Its application in palladium catalyzed Suzuki reactions

A palladium dimer with a cobalt-containing phosphine ligand, {(μ-PPh₂CH₂PPh₂)Co₂(CO)₄(μ,η-(tBu)₂PCCC₆H₄-κC¹)Pd(μ-Cl)}₂ (3), was prepared from the reaction of its monomer precursor, (μ-PPh₂CH₂PPh₂)Co₂(CO)₄(μ,η-(tBu)₂PCCC₆H₄-κC¹)Pd(μ-OAc) (2), with LiCl. The crystal structure of 3, determined by X-ray diffraction methods, revealed a doubly chloride-bridged palladium dimeric conformation. Suzuki coupling reactions of bromobenzene with phenylboronic acid were carried out catalytically using these two novel palladium complexes 2 and 3 as catalyst precursors. Factors such as the molar ratio of substrate/catalyst, reaction temperature, base and solvent that might affect the catalytic efficiencies were investigated. As a general rule, the performance is much better by employing 3 than 2 as the catalyst precursor.     

Carbon nanotubes-supported palladium nanoparticles for the Suzuki reaction in supercritical carbon dioxide: A facile method for the synthesis of tetrasubstituted olefins

A facile and efficient method for the synthesis of tetrasubstituted olefins in supercritical carbon dioxide was developed by using carbon nanotubes-supported palladium nanoparticles (Pd/CNTs) as the catalyst. Compared with common Pd/C, Pd/CNTs could more effectively catalyze the reaction of dibromo-substituted olefins with boronic acids, affording the corresponding tetrasubstituted olefins with moderate to good yields. This environmentally benign route with an easy-to-handle catalyst provides an appealing alternative to the currently available methods.     

Immobilization of palladium nanoparticles on ionic liquid-triethylammonium chloride functionalized magnetic nanoparticles: As a magnetically separable,stable and recyclable catalyst for Suzuki-Miyaura cross-coupling reactions

A facile procedure was applied to successfully synthesize novel Pd nanoparticles immobilized on triethanolamine-functionalized magnetic nanoparticles [Fe₃O₄/IL/Pd]. Diverse characterizations (HR-TEM, XRD, FT-IR, TGA, EDX, FE-SEM, ICP, XPS and VSM) were carried out to identify intrinsic traits of the nanoparticles. At room temperature, Fe₃O₄/IL/Pd demonstrated high catalytic activity toward Suzuki-Miyaura cross-coupling reactions in aqueous solution. Based on the results, Fe₃O₄/IL/Pd acted as zwitterionic IL-type heterogeneous catalyst, which could be separated from the reaction mixture, conveniently. Moreover, it exhibited excellent recyclability for at least eight cycles without considerable loss of its activity.     

Schiff base complex of palladium immobilized on magnetic nanoparticles: an efficient and recyclable nanocatalyst for CC coupling reactions

A Schiff base complex of palladium anchored on Fe₃O₄ magnetic nanoparticles as an efficient and magnetically reusable nanocatalyst is reported for C? C bond formation through Heck and Suzuki reactions. The catalyst was easily recovered and reused several times without significant loss of its catalytic efficiency or palladium leaching. The magnetic nanocatalyst was characterized using Fourier transform infrared and inductively coupled plasma atomic emission spectroscopies, thermogravimetric analysis, vibrating sample magnetometry, and transmission and scanning electron microscopies. Copyright © 2016 John Wiley & Sons, Ltd.     

An electrochemical ascorbic acid sensor based on palladium nanoparticles supported on graphene oxide

In this study, an electrochemical ascorbic acid (AA) sensor was constructed based on a glassy carbon electrode modified with palladium nanoparticles supported on graphene oxide (PdNPs-GO). PdNPs with a mean diameter of 2.6 nm were homogeneously deposited on GO sheets by the redox reaction between PdCl₄²⁻ and GO. Cyclic voltammetry and amperometric methods were used to evaluate the electrocatalytic activity towards the oxidation of AA in neutral media. Compared to a bare GC or a Pd electrode, the anodic peak potential of AA (0.006 V) at PdNPs-GO modified electrode was shifted negatively, and the large anodic peak potential separation (0.172 V) of AA and dopamine (DA), which could contribute to the synergistic effect of GO and PdNPs, was investigated. A further amperometric experiment proved that the proposed sensor was capable of sensitive and selective sensing of AA even in the presence of DA and uric acid. The modified electrode exhibited a rapid response to AA within 5 s and the amperometric signal showed a good linear correlation to AA concentration in a broad range from 20 μM to 2.28 mM with a correlation coefficient of R = 0.9991. Moreover, the proposed sensor was applied to the determination of AA in vitamin C tablet samples. The satisfactory results obtained indicated that the proposed sensor was promising for the development of novel electrochemical sensing for AA determination.     

Facile preparation of highly stable and active hybrid palladium nanoparticles: effectual,reusable and heterogeneous catalyst for coupling reactions

Palladium nanoparticles were supported on a bed of Fe₃O₄@‐NH₂@Murexide using a simple and efficient method, and characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, scanning and transmission electron microscopies and inductively coupled plasma optical emission spectrometry. The catalytic system showed great efficiency in cross‐coupling reaction of aryl iodides and arylboronic acid and in Sonogashira cross‐coupling reaction in the green solvent EtOH–H₂O (1:1). The isolation and recovery of the catalyst were simple and facile and it could be used for several successive Suzuki–Miyaura coupling and Sonogashira cross‐coupling reactions. Copyright © 2016 John Wiley & Sons, Ltd.     

Flow-injection simultaneous determination of iron(III) and copper(II) and of iron(III) and palladium(II) based on photochemical reactions of thiocyanato-complexes

The flow injection analysis systems have been developed for the simultaneous determination of iron(III) and copper(II) and of iron(III) and palladium(II) based on the photochemical reactions of their thiocyanato-complexes. In the first system, a sample solution was injected in to nitric acid solution and mixed with ammonium thiocyanate solution, followed by spectrophotometric monitoring of the thiocyanato-complexes formed. Another aliquot of the same sample solution was injected and the thiocyanato-complexes formed in the same way were irradiated by UV light before spectrophotometric monitoring. In another system, the absorbance of thiocyanato-complexes formed by each sample injection was monitored with two flow cells aligned with the same optical path before and after UV irradiation. The difference in the extent of photochemical decomposition of the thiocyanato-complexes enabled simultaneous determinations of iron(III) and copper(II) and of iron(III) and palladium(II) at levels of several μg ml⁻¹ to some tens μg ml⁻¹ in their admixtures. Sample throughputs are 40 and 20 h⁻¹ by the former and latter systems, respectively.     

Suzuki cross-coupling reaction of fluorobenzene with heterogeneous palladium catalysts

In this work, we accomplished for the first time the Suzuki cross-coupling reaction between fluorobenzene and phenylboronic acid with different heterogeneous catalysts and bases. The conversion values obtained are similar to those provided by homogeneous catalysts and activated aryl fluorides.