Application In Heck Reaction Research Articles

In situ preparation of palladium nanoparticles in ionic liquid crystal microemulsion and their application in Heck reaction

A simple and an efficient approach for in situ preparation of palladium nanoparticles (Pd NPs) in ionic liquid crystal (ILC) microemulsion is described. Microemulsion was formed by using a ternary mixture of triton X-100/ILC/water (in the ratio of 1.4:0.1:8.5). Three such microemulsions-1, 2 and 3 were formed by using three different ILCs namely ammonium ILC containing a cholesterol core (ILC-1), imidazolium ILC bearing a cholesterol core (ILC-2) and imidazolium ILC containing a biphenyl core (ILC-3), respectively. The Pd NPs were characterised using UV–vis spectroscopy, transmission electron microscopy and X-ray diffraction studies. Among the three, microemulsion-2 which was prepared using ILC-2 yielded stable NPs with an average particle size of ~20 nm. The NPs prepared in all three emulsions were examined as catalyst for Heck reaction. The catalytic efficiency was analysed for four cross-coupling reactions involving iodobenzene with different substituted alkenes namely methyl acrylate, ethyl acrylate, butyl acrylate and styrene. The coupling reactions were completed in a shorter period with good yields. Further, the recyclability test of Pd NPs revealed that the particles showed good activity until third catalytic cycle. The Pd NPs prepared in microemulsion-2 showed better activity compared to those prepared in microemulsions-1 and -3.

Palladium(II) complexes of aminothiazole‐based phosphines: Synthesis, structural characterization, density functional theory calculations and catalytic application in heck reaction

Three Pd(II) complexes of some hemilabile ligands, aminothiazole‐based phosphines, were synthesized to investigate the catalytic activity of them in Heck cross‐coupling reactions. The crystal structures of complexes PdCl2[(Ph2P)HN(C3H2NS)] (C1) and PdCl2[(Ph2P)HN(C7H4NS)] (C3) were determined using X‐ray crystallography, which reveals that the ligand coordinates in a chelating mode through P and N (endocyclic) atoms in square planar geometry. Experimental and theoretical studies (atoms in molecules and natural bond orbital analyses) show that the Pd(II) interacts more strongly with the P atom than the N atom in the chelated ligand, N^P. This trait can promote catalytic activity of the complexes in comparison with our previous work in which chelated ligands with two phosphorus atoms, P^P, were used. The influence of non‐covalent intermolecular interactions on the assembly of the solid‐state structures is also discussed in terms of geometrical analysis. The prepared complexes turn out to be useful pre‐catalysts in Heck cross‐coupling reactions owing to the coordinative flexibility of the hemilabile ligands. The protocol affords the corresponding products in greater yield than the same reactions with bis(phosphino)amine Pd(II) complexes, as the catalysts in our previous work.

Facile green synthesis of Pd/N-doped carbon nanotubes catalysts and their application in Heck reaction and oxidation of benzyl alcohol

Evenly dispersed Pd nanoparticles are facilely and successfully deposited on N-doped carbon nanotubes (Pd/N-CNTs) by employing sodium dodecyl sulfate (SDS) as a salt and polyvinylpyrrolidone (PVP) as both a surface modifier and a stabilizing agent. The presence of SDS and the amount of PVP have significant influences on the formation of evenly dispersed Pd/N-CNTs catalyst. No additional functionalization steps, reducing agents and stabilizers are required as usual to achieve the uniform deposition of Pd NPs over the N-CNTs surfaces. The as-synthesized Pd/N-CNTs catalyst is proved to be very active in the Heck reaction and can be reused at least for 5 times without significant loss of catalytic activity in the aerobic oxidation of benzyl alcohol.

Palladium Complexes with Tetradentate Schiff Bases or their Corresponding Amines: Synthesis and Application in Heck Reactions

AbstractThis article describes the synthesis of six palladium complexes derived from three bis‐imines or their corresponding amines. These metallic complexes were evaluated as promising catalysts for Heck reaction. The potential of such organometallic catalysts was investigated using the coupling between bromobenzene and styrene as reaction model, involving evaluation of ranging bases, different solvents, reaction times and the quantity of palladium catalyst. Our findings indicate that the complexes obtained from amines are better than those from imines. Dimethyl acetamide (DMA) and sodium carbonate were the best solvents and bases in the Heck coupling reaction, respectively. In summary, these Schiff bases and corresponding amines provide an innovative opportunity to develop new catalytic systems for the Heck reaction.

ChemInform Abstract: Phosphine‐Free Tetradentate Salicylaldimine Ligand Complexed with Palladium: First Application in Heck Reactions.

AbstractAdvantages of the introduced method are mild reaction conditions, short reaction times and low palladium loading.

Palladium Nanoparticles Stabilized by an Ionic Polymer and Its Application in Heck Reaction

Palladium Nanoparticles Stabilized by an Ionic Polymer and Its Application in Heck Reaction

ChemInform Abstract: Novel Isoxazoline Ligand with Ferrocene Backbone: Preparation and Application in Heck Reaction with Water as Solvent.

AbstractThe developed catalytic system is even suitable for 1,2‐disubstituted alkenes [cf.

Phosphine-Free Tetradentate Salicylaldimine Ligand Complexed with Palladium: First Application in Heck Reactions

Heck reactions were carried out using phosphine-free tetradentate salicylaldimine ligand complexed with PdCl2 under mild reaction conditions, short reaction time, and low palladium loading. All aryl iodides underwent coupling reactions with olefins, giving corresponding trans-products, with good to excellent yields, whereas aryl bromides gave very poor yields and aryl chlorides failed to react.

Novel isoxazoline ligand with ferrocene backbone: preparation and application in Heck reaction with water as solvent

Two novel isoxazoline N,N‐bidentate ligands with ferrocene backbone have been synthesized and employed for the palladium‐catalyzed Heck coupling reaction. Among them, 1,3‐bis‐(5‐ferrocenylisoxazoline‐3‐yl)benzene was found to be thermally stable and a highly effective ligand for Heck coupling reaction in neat water without N2 protection, affording the desired coupling products in good to excellent yield with high diastereoselectivity. The developed catalytic system was also well workable for 1,2‐disubstituted alkenes, which were less involved in the Heck reaction for its larger steric hindrance. Copyright © 2014 John Wiley & Sons, Ltd.

ChemInform Abstract: The Application of Heck Reaction in the Synthesis of Guaianolide Sesquiterpene Lactones Derivatives Selectively Inhibiting Resistant Acute Leukemic Cells.

AbstractA variety of the new title compounds, e.g. (IIIa), (IVb), (IVd), (Vd), and (IXa) exhibit high potency against doxorubicin‐resistant cell line HL‐60/A.

The application of Heck reaction in the synthesis of guaianolide sesquiterpene lactones derivatives selectively inhibiting resistant acute leukemic cells

A series of guaianolide-type sesquiterpene lactones derivatives with arylation of α-methylene-γ-lactone moiety was synthesized using Heck reactions, and was evaluated for their activities against acute myelogenous leukemia (AML) cell line HL-60 and doxorubicin-resistant cell line HL-60/A. Although all compounds were significantly less active against HL-60 than the parent molecules, surprisingly, compounds 3a, 4c–4e, 5e, and 8d exhibited high potency against doxorubicin-resistant cell line HL-60/A (IC50=6.2–19μM), and their activities against HL-60/A were comparable to that of their parent molecules. In view of their novel activities against HL-60/A, compound 5e with inhibitory activity against HL-60/A (IC50=6.2±0.5μM) was selected for study its preliminary mechanism. The result reveals that compound 5e can obviously induce apoptosis.

N-Heterocyclic Carbene Adducts of Cyclopalladated Ferrocenylpyridine Complex: Synthesis, Structural Characterization and Application in Heck Reaction

Department of Chemistry, Zhengzhou University, Zhengzhou, Henan 450052, ChinaReceived February 3, 2012, Accepted February 25, 2012Key Words : N-Heterocyclic carbene adduct, Palladacycle, Heck reaction, Crystal structurePalladium-catalyzed Heck reaction has become an ex-tremely powerful method in organic synthesis for the formationof carbon-carbon bond.

Preparation of Cobalt‐Containing Ligands with NHC‐ and/or P‐Coordinating Sites and Their Application in Heck Reactions: The Formation of an Unexpected Cobalt‐Containing Zwitterionic Complex

AbstractAn unexpected cobalt‐containing zwitterionic complex, [{(μ‐PPh2CH2PPh2)Co2(CO)4}{μ,η‐(R1)PC≡CCH2(R2)}] (8; R1 = Ph2Bz; R2 = 3‐CoBr3‐1‐benzimidazole), has been obtained during an attempt to modify the imidazole moiety in the alkyne‐bridging dicobalt complex [{(μ‐PPh2CH2PPh2)Co2(CO)4}{μ,η‐Ph2PC≡CCH2(IM)}] (5; IM = benzimidazole) to a carbene‐type substituent by reaction with benzyl bromide. As revealed in the crystal structure of 8, it is clear that the benzyl bromide was nucleophilically attacked by the phosphane moiety of 5 with the result the addition of the benzyl moiety. This phosphane site in 8 is in a tetrahedral environment and presumably cationic in nature. In addition, an unusual anionic species CoBr3– was found to have attached itself to the free nitrogen site of the imidazole moiety. Thus 8 can be regarded as an unusual metal‐containing zwitterionic complex. When the phosphane site of 5 was replaced by a non‐reactive substituent, for example, [{(μ‐PPh2CH2PPh2)Co2(CO)4}{μ,η‐RC≡CCH2(IM)}] (5′: R = H; 5­­_O: R = Ph2(O)P), nucleophilic attack took place exclusively on the imidazole moiety and led to the formation of [{(μ‐PPh2CH2PPh2)Co2(CO)4}{μ,η‐RC≡CCH2(IM′)}+]Br– [9′: R = H; 9_O: R = Ph2(O)P; IM′ = 3‐benzyl‐1H‐benzimidazole]. Complex 9′ could act as a carbene precursor, which was demonstrated by the formation of the bis‐9′‐coordinated palladium complex [trans‐({(μ‐PPh2CH2PPh2)Co2(CO)4}{μ,η‐HC≡CCH2(IM′)})2PdBr2] (11) on treatment with [Pd(cod)Cl2]. Fair‐to‐good efficiencies were observed in Heck reactions employing either isolated 11 or in situ 9′/PdCl2 (2:1) as the catalytic precursor.

Recent Advances in the Application of the Heck Reaction in the Synthesis of Heterocyclic Compounds

This brief review represents the synthesis of heterocyclic compounds via application of Heck reaction in recent years.

Synthesis of palladium-coated magnetic nanoparticle and its application in Heck reaction

In this paper, we synthesized the new palladium catalyst based on magnetic nanoparticles by the “bottom-up” approach, and then its catalytic behavior in the cross coupling of acrylic acid with iodobenzene was investigated. When compared with the traditional palladium catalysts supported on carbon or the others, such catalyst has a good performance in the first run (i.e. TOF of 3749 h −1 for NaOAc base). However, the activity in re-use is poor and especially influenced by the base in the reaction. The results of palladium leaching analysis and TEM image indicate that one of the causes for the above activity drop is the leaching of Pd nanoparticle (or palladium ion) from the surface of magnetic nanoparticle into the solution. Finally, the reaction of styrene with iodobenzene (or bromobenzene) was also employed to investigate its catalytic behavior.

Synthesis of Pd/Fe3O4 nanoparticle-based catalyst for the cross-coupling of acrylic acid with iodobenzene

In this study, catalyst Pd/Fe3O4 based on magnetic body with the size of 8 nm was prepared and characterized by TEM, HRTEM, XPS and VSM methods. The results show that Pd0 atom produced after the first reduction is bound to APTS-coated Fe3O4 nanoparticles by the coordination of –NH2 ligand with Pd0 and then grows into bigger clusters with the increase in the reduction times. However, when the reduction is performed for more than three times, Pd0 atom produced in subsequent reduction is dispersed in aqueous solution instead of depositing around preexisting Pd0 atom or clusters. In order to further investigate its catalytic behavior, Heck reaction of the cross-coupling of acrylic acid with iodobenzene was employed. The activity measurements show that the product yield decreased greatly from 81% for the first times to 53% for the fifth times and then kept constant in the subsequent re-use. One of the important reasons for this is that the catalyst aggregates into big particle and becomes more difficult to be dispersed with the increase in reaction times. In a word, this preliminary work provides the primary understanding of the catalyst based on Fe3O4 nanoparticles and its application in Heck reaction.