Palladium-Catalyzed Negishi Cross-Coupling Reaction of Aryl Halides with (Difluoromethyl)zinc Reagent.

Cross-coupling reactions of aryl halides catalyzed by transition metals such as Pd, Ni, Cu etc have shown to be effective tools for the generation of carbon–carbon and carbon–heteroatom bonds. However, because of the difficulties associated with the oxidative addition of organohalides or pseudohalides on gold complexes, such cross- coupling reactions are non-trivial in gold catalysis. Recent research revealed that gold- catalyzed cross-coupling reactions of aryl iodides are possible and the current article shall briefly discuss the state-of-the-art in the field.

The palladium-catalyzed cross-coupling reaction of aryl iodides with 3,3,3-triethoxy-1-propyne gave 1-aryl-3,3,3-triethoxy-1-propynes which were converted to the corresponding ethyl arylpropiolates. The arylpropiolates were also synthesized from the cross-coupling reactions of aryl iodides with 2-ethoxycarbonyl-1-ethynylzinc chloride or ethyl (tributylstannyl)propiolate, but the reactions were not generally applicable

We have developed a C-O cross-coupling reaction of (hetero)aryl iodides with silver carboxylates via a AuI/AuIII catalytic cycle. The transformation featured exclusive chemoselectivity and moisture/air insensitivity. Aromatic and aliphatic (including primary, secondary, and tertiary) silver carboxylates are all suitable substrates. Moreover, this protocol worked well intermolecularly and intramolecularly. Most importantly, good yields were obtained regardless of the substrates' electronic effect and steric hindrance.

By encaging the PdCl2(py)2 complex (py = pyridine) in the interior space of silicalite-1 hollow spheres (SHS), a novel solid palladium catalyst, PdCl2(py)2@SHS, was successfully prepared. The structure and composition of the solid catalyst was characterized by SEM, TEM, XRD, N2 sorption, FT-IR and XPS. This catalyst afforded fast conversions for the Suzuki–Miyaura cross-coupling reactions of various aryl halides and arylboronic acids even at Pd loadings of 0.0188 mol% in aqueous media. The turnover frequency (TOF) could be up to 63 210 h−1 under mild conditions in air. In particular, because of the antileaching effect of the surrounding zeolitic shell toward the entrapped Pd species, PdCl2(py)2@SHS showed outstanding stability and reusability, which could be reused at least 10 times without appreciable loss of its activity. The developed solid catalyst combined with the mild conditions represented one of the most efficient heterogeneous systems for the Suzuki–Miyaura cross-coupling reactions of aryl halides.

By encaging the PdCl2(py)2 complex (py = pyridine) in the interior space of silicalite-1 hollow spheres (SHS), a novel solid palladium catalyst, PdCl2(py)2@SHS, was successfully prepared. The structure and composition of the solid catalyst was characterized by SEM, TEM, XRD, N2 sorption, FT-IR and XPS. This catalyst afforded fast conversions for the Suzuki–Miyaura cross-coupling reactions of various aryl halides and arylboronic acids even at Pd loadings of 0.0188 mol% in aqueous media. The turnover frequency (TOF) could be up to 63 210 h−1 under mild conditions in air. In particular, because of the antileaching effect of the surrounding zeolitic shell toward the entrapped Pd species, PdCl2(py)2@SHS showed outstanding stability and reusability, which could be reused at least 10 times without appreciable loss of its activity. The developed solid catalyst combined with the mild conditions represented one of the most efficient heterogeneous systems for the Suzuki–Miyaura cross-coupling reactions of aryl halides.

Synthesis and characterization of palladium nanoparticles immobilized on graphene oxide functionalized with triethylenetetramine or 2,6-diaminopyridine and application for the Suzuki cross-coupling reaction

The palladium-catalyzed cross-coupling reaction of aryl iodides with 3,3,3-triethoxy-1-propyne gave 1-aryl-3,3,3-triethoxy-1-propynes which were converted to the corresponding ethyl arylpropiolates. The arylpropiolates were also synthesized from the cross-coupling reactions of aryl iodides with 2-ethoxycarbonyl-1-ethynylzinc chloride or ethyl (tributylstannyl)propiolate, but the reactions were not generally applicable

An improved palladium-catalyzed Hiyama cross-coupling reaction is reported. In the presence of PdCl 2 (MeCN) 2 , P(o-tol) 3 and TBAF, a number of ArX (X = I, Br, Cl) were coupled with ArSi(OMe) 3 efficiently to afford the desired cross-coupled products in moderate to excellent yields. It is noteworthy that this protocol is conducted under relatively low Pd loadings and solvent-free conditions.

CuO/AB was found to be a simple and efficient catalyst for the N-arylation of a variety of nitrogen-containing heterocycles, giving the products in excellent yields.

The palladium-catalyzed cross-coupling reaction of aryl halides with isoquinoline-1,3(2 H,4 H)-diones for the synthesis of 4-aryl isoquinoline-1,3(2 H,4 H)-diones was developed. The reaction conditions exhibit remarkable compatibility with various aryl halides and isoquinoline-1,3(2 H,4 H)-diones, and the product could be conveniently transformed to 4-aryl tetrahydroisoquinolines. (±) Dichlorofensine was synthesized using this protocol in two steps with an overall yield of 71%.

The carbonylative cross-coupling of potassium vinyl trifluoroborate or 2,4,6-trivinyltricycloboroxane with aryl iodides under mild conditions affords aryl vinyl ketones. The optimisation of the reaction conditions leads to the targeted enones in good yields in the case of the aryl substrates bearing donor substituents in meta or para position. Much more moderate yields were observed with aryl substrates bearing withdrawing substituents.

Palladium-catalyzed cross-coupling reaction between aryl halides and terminal acetylenes (commonly referred to as the Mizoroki-Heck reaction) is a highly versatile, powerful and popular tool for the synthesis of variously substituted olefins, dienes and precursors to conjugated polymers. This reaction has also been utilized for the preparation of natural products,and pharmaceuticals. The traditional Mizoroki-Heck reaction is typically performed with 1-5 mol% of a palladium catalyst along with a phosphine or phosphorusligands in the presence of a suitable base. However, phosphine ligands are toxic, expensive, unrecoverable, and unstable at high temperatures; thus the development of a phosphine-free palladium catalyst is a topic of enormous interest. Moreover, the Mizoroki-Heck reaction still show some limitations, especially in relation to the use of certain reagents. In particular, a major restriction of palladium-catalyzed coupling processes has been the poor reactivity of cheaper and readily available aryl chlorides and aryl bromides in comparison with more active aryl iodides. Therefore, the search for efficient catalysts for the cross-coupling of olefins with deactivated aryl bromide and towards activated aryl chloride is under progress. Herein, we present a Pd(II) catalyst system based on a commercially available diazacrown ether or cryptand-22, PdCl2-C22, that is very active homogeneous catalyst under aerobic conditions. This catalytic system is efficiently used for the Mizoroki-Heck cross-coupling reactions of aryl iodides, bromides as well as chlorides with various olefins. The remarkable chelating effect of this N- and O-containing ligand and its flexibility assists in stabilizing the reactive palladium intermediates, and suppresses the Pd black formation even at high temperature under air.

An investigation into Pd-catalyzed C-N cross-coupling reactions of aryl iodides is described. NaI is shown to have a significant inhibitory effect on these processes. By switching to a solvent system in which the iodide byproduct was insoluble, reactions of aryl iodides were accomplished with the same efficiencies as aryl chlorides and bromides. Using catalyst systems based on certain biarylphosphine ligands, aryl iodides were successfully reacted with an array of primary and secondary amines in high yields. Lastly, reactions of heteroarylamines and heteroaryliodides were also conducted in high yields.

A number of benzimidazole derivatives (1-8) were synthesized and the catalytic activity of these compounds in a catalytic system including Pd(OAc)_2 and K_2CO_3 in DMF-H_2O was evaluated in Heck-Mizoroki and Suzuki-Miyaura cross-coupling reactions of aryl iodides, bromides, and chlorides with styrene and arylboronic acids under microwave irradiation and aerobic conditions. The yields of both the Heck-Mizoroki and the Suzuki-Miyaura cross coupling reactions with aryl iodides and aryl bromides were nearly quantitative. The synthesized 1-substituted benzimidazole (1) and benzimidazole salts (2-8) were identified by ^1H- and ^{13}C-NMR and IR spectroscopic methods, and micro analysis. The molecular structure of 7 was also determined by X-ray crystallography.

Nickel-catalyzed C–P cross-coupling reactions of aryl iodides with H-phosphinates