Coupling Products In High Yields Research Articles

A Convoluted Polyvinylpyridine‐Palladium Catalyst for Suzuki‐Miyaura Coupling and C−H Arylation

AbstractThe development of highly active and reusable supported catalysts for Suzuki‐Miyaura coupling and catalytic C−H arylation is important for fundamental and applied chemistry, with these reactions being used to produce medical compounds and functional materials. Herein, we found that a mesoporous composite made of a linear poly(4‐vinylpyridine) and tetrachloropalladate acted as a dual‐mode catalyst for a variety of cross‐coupling reactions, with both Pd nanoparticles and a Pd complex catalyst being observed under different conditions. The polyvinylpyridine‐palladium composite 1 was readily prepared via the molecular convolution of poly(4‐vinylpyridine) and sodium tetrachloropalladate to provide a hardly soluble polymer‐metal composite. The Suzuki‐Miyaura coupling and the C−H arylation of aryl chlorides and bromides with arylboronic acids, thiophenes, furans, benzene, and anisole proceeded in the presence of 0.004 mol% (40 mol ppm) to 1 mol% Pd of 1 to afford the corresponding coupling products in high yields. Furthermore, the catalyst was reused without an appreciable loss of activity. Pharmaceutical compounds and functional materials were synthesized via the coupling reactions. N2 gas adsorption/desorption analysis indicated that the catalyst had a mesoporous nature, which played a crucial role in the catalysis. In the Suzuki‐Miyaura couplings, in situ generated palladium nanoparticles in the polymer matrix were catalytically active, while a polymeric Pd(II) complex was crucial in the C−H arylations. These catalytic species were investigated via XAFS, XPS, far‐infrared absorption, and Raman spectroscopies, as well as DFT calculations.magnified image

Application of GO/COF as a novel, efficient and recoverable catalyst in the Knoevenagel reaction

AbstractHybrid composite based on graphene oxide (GO) and covalent organic framework (COF) [GO/COF] was developed via a simple solvothermal method, at which GO was applied as a platform to load COF based on melamine and terephthaldehyde. The synthesized hybrid nanocomposite was characterized by FT‐IR, XRD, EDX and SEM techniques. Morphological analyses carried out by SEM confirm the successful growth of COF over GO. Then, the resultant composite was employed as an amazing and cost‐effective catalyst in the condensation of several aldehydes with malononitrile and produced the corresponding coupling products in high yields (up to 84%) at room temperature under solvent‐free conditions with an amount of catalyst, 15 mg in a very short reaction time of 10 min. The catalyst could be reused without a noteworthy drop in catalytic activity at least eight times. The use of GO/COF catalyst outcomes under mild reaction conditions in very short reaction time, exceptional catalytic activity, high recyclability and an easy work‐up process for the Knoevenagel condensation.

Cellulose stabilized Fe3O4and carboxylate‐imidazole and Co‐based MOF growth as an exceptional catalyst for the Knoevenagel reaction

In this study, Fe3O4nanoparticles were functionalized with cellulose, and then hybridized with cobalt (II)‐based metal‐organic framework (Co‐MOF) containing carboxylate and imidazole functionalities. FTIR, XRD, FE‐SEM, TEM, BET, EDX, VSM and STA analyses were used to characterize the synthesized samples. The resultant Fe3O4/cellulose/Co‐MOF nanocomposite was applied efficiently as a powerful and economic heterogeneous catalyst in the condensation of a variety of different aromatic aldehydes with malononitrile under solvent‐free conditions at room temperature for 10 min and offered the corresponding coupling products in high yields. The catalyst could be straightforwardly separated by a magnet from the reaction mixture and reused without a noteworthy drop in catalytic activity at least five times. The use of Fe3O4/cellulose/Co‐MOF catalyst outcomes under mild reaction conditions in very short reaction time, outstanding catalytic activity, high recyclability and an easy work‐up process for Knoevenagel condensation.

Palladium(II) complexes containing sterically bulky O, N donor ligands: Synthesis, characterization and catalytic activity in the Suzuki-Miyaura and Sonogashira coupling reactions

A new class of palladium(II)1-(arylazo)naphtholate complexes of the type [Pd(L1-4)2] containing sterically bulky O, N donor functionalized arylazo ligands has been synthesized. These palladium(II) complexes were characterized by elemental analysis and spectral (FT-IR, UV–Vis, 1H NMR and 13C NMR) studies. The molecular structure of the Palladium(II) complexes [Pd(L1)2] and [Pd(L2)2] were established by X-ray crystallography. These complexes were found to efficiently catalyze the Suzuki-Miyaura coupling of arylboronic acids and aryl halides, and the Sonogashira reaction of aryl halides and phenylacetylene in DMF and i-PrOH media to afford the corresponding C–C coupling products in high yields.

Electrochemically Induced Intermolecular Cross-Dehydrogenative C-O Coupling of β-Diketones and β-Ketoesters with Carboxylic Acids.

The electrochemically induced cross-dehydrogenative C-O coupling of β-diketones and β-ketoesters (C-H reagents) with carboxylic acids (O-H reagents) was developed. An important feature of this reaction lies in the selective formation of intermolecular C-O coupling products in high yields, up to 92%, using DMSO as a solvent with a broad substrate scope in an undivided cell equipped with carbon and platinum electrodes at high current density. Electric current acts as a stoichiometric oxidant.

Nitroxyl-Radical-Catalyzed Oxidative Coupling of Amides with Silylated Nucleophiles through N-Halogenation.

A nitroxyl-radical-catalyzed oxidative coupling reaction between amines with an N-protecting electron-withdrawing group (EWG) and silylated nucleophiles was developed to furnish coupling products in high yields, thus opening up new frontiers in organocatalyzed reactions. This reaction proceeded through the activation of N-halogenated amides by a nitroxyl-radical catalyst, followed by carbon-carbon coupling with silylated nucleophiles. Studies of the reaction mechanism indicated that the nitroxyl radical activates N-halogenated amides, which are generated from N-EWG-protected amides and a halogenation reagent, to give the corresponding imines.

Nitroxyl‐Radical‐Catalyzed Oxidative Coupling of Amides with Silylated Nucleophiles through N‐Halogenation

AbstractA nitroxyl‐radical‐catalyzed oxidative coupling reaction between amines with an N‐protecting electron‐withdrawing group (EWG) and silylated nucleophiles was developed to furnish coupling products in high yields, thus opening up new frontiers in organocatalyzed reactions. This reaction proceeded through the activation of N‐halogenated amides by a nitroxyl‐radical catalyst, followed by carbon–carbon coupling with silylated nucleophiles. Studies of the reaction mechanism indicated that the nitroxyl radical activates N‐halogenated amides, which are generated from N‐EWG‐protected amides and a halogenation reagent, to give the corresponding imines.

Silicon-based Cross-coupling of Aryl Tosylates by Cooperative Palladium/Copper Catalysis

A cross-coupling reaction between air- and moisture-stable aryl- or alkyl(triorgano)silanes and aryl tosylates was developed by cooperative palladium/copper catalysis. In order to obtain the coupling products in high yields, the presence of the P,N-heterobidentate ligand 1-[2-(dicyclohexylphosphanyl)phenyl]-N,N-dimethylmethanamine (L1) is crucial. This protocol tolerates a variety of functional groups such as acetyl, cyano, chloro, formyl, and alkoxycarbonyl moieties.

Palladium-Catalyzed C(sp3)–C(sp2) Cross-Couplings of O-(α-Bromoacyl) Cyanohydrins with Boronic Acids: An Entry to Enantio­enriched N-Acylated β-Amino Alcohols

Suzuki-type cross-coupling of enantiomerically enriched O-(α-bromoacyl) cyanohydrins with aromatic boronic acids substituted with electron-withdrawing or electron-donating groups gave the expected coupling products in high yields without racemization. These substrates exhibit higher reactivities than analogous substrates lacking the nitrile function, probably as a result of π-coordination of the nitrile to palladium. Reduction of the nitrile group of the products, with accompanying intramolecular acyl transfer, provides access to biologically interesting N-acylated β-amino alcohols.

ChemInform Abstract: Photoredox α‐Allylation of α‐Halocarbonyls with Allylboron Compounds Accelerated by Fluoride Salts under Visible Light Irradiation.

Organic dyes are an attractive alternative to the use of transition-metal complexes in photoredox catalysis. Herein, we report an inexpensive organic dye (eosin Y)-catalyzed radical coupling of α-bromocarbonyl compounds with allyltrifluoroborates under visible light irradiation. This reaction was accelerated by either Bu4NF or CsF. Based on mechanistic studies, the cation exchange between potassium allyltrifluoroborate and Bu4NF proceeded to generate KF. The generated KF or CsF acts as a Lewis acid to promote a single electron transfer (SET) from eosin Y to α-halocarbonyls. The protocol was applied to bromoesters, bromoketones, and bromoamides to give the coupling products in high yields.

ChemInform Abstract: Reusable Biomacromolecule‐Pd Complex Catalyzed C—C Cross‐Coupling Reactions via C—S Cleavage of Disulfides.

AbstractNatural wool supported Pd(OAc)2‐complex is found to be an effective catalyst for the C—S bonds cleavage and C—C bonds formation from various disulfides with arylboronic acids or terminal alkynes, giving the desired coupling products in high yields.

Photoredox α‐Allylation of α‐Halocarbonyls with Allylboron Compounds Accelerated by Fluoride Salts under Visible Light Irradiation

AbstractOrganic dyes are an attractive alternative to the use of transition‐metal complexes in photoredox catalysis. Herein, we report an inexpensive organic dye (eosin Y)‐catalyzed radical coupling of α‐bromocarbonyl compounds with allyltrifluoroborates under visible light irradiation. This reaction was accelerated by either Bu4NF or CsF. Based on mechanistic studies, the cation exchange between potassium allyltrifluoroborate and Bu4NF proceeded to generate KF. The generated KF or CsF acts as a Lewis acid to promote a single electron transfer (SET) from eosin Y to α‐halocarbonyls. The protocol was applied to bromoesters, bromoketones, and bromoamides to give the coupling products in high yields.

ChemInform Abstract: Pinacol Couplings of a Series of Aldehydes and Ketones with SmI2/Sm/Me3SiCl in DME.

AbstractFollowing the title reaction, aryl aldehydes and arylmethyl ketones are transformed to the corresponding pinacol coupling products in high yields and as mixtures of dl and meso diastereomers.

ChemInform Abstract: An Efficient Palladium N‐Heterocyclic Carbene Catalyst Allowing the Suzuki—Miyaura Cross‐Coupling of Aryl Chlorides and Arylboronic Acids at Room Temperature in Aqueous Solution.

AbstractThis method gives the coupling products in high yields even at low catalyst loadings.

Palladium Nanoparticles Immobilized on Nano‐Silica Triazine Dendritic Polymer (Pdnp‐nSTDP): An Efficient and Reusable Catalyst for Suzuki–Miyaura Cross‐Coupling and Heck Reactions

AbstractA new catalyst based on palladium nanoparticles immobilized on nano‐silica triazine dendritic polymer (Pdnp‐nSTDP) was synthesized and characterized by FT‐IR spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy, energy dispersive X‐ray, transmission electron microscopy and elemental analysis. The size of the palladium nanoparticles was determined to be 3.1±0.5 nm. This catalytic system showed high activity in the Suzuki–Miyaura cross‐coupling of aryl iodides, bromides and chlorides with arylboronic acids and also in the Heck reaction of these aryl halides with styrenes. These reactions were best performed in a dimethylformamide (DMF)/water mixture (1:3) in the presence of only 0.006 mol% and 0.01 mol% of the catalyst, respectively, under conventional conditions and microwave irradiation to afford the desired coupling products in high yields. The Pdnp‐nSTDP was also used as an efficient catalyst for the preparation of a series of star‐ and banana‐shaped compounds with a benzene, pyridine, pyrimidine or 1,3,5‐triazine unit as the central core. Moreover, the catalyst could be recovered easily and reused several times without any considerable loss of its catalytic activity.

Polystyrene-Immobilised Phenanthroline Palladium(II) Complex: A Highly Efficient and Recyclable Catalyst for Oxidative Heck Reactions

Oxidative Heck coupling reactions of arylboronic acids with olefins were carried out in the presence of the polystyrene-immobilised phenanthroline palladium(II) complex using air as a co-oxidant to afford the Heck coupling products in high yields under base-free conditions. This heterogeneous palladium catalyst can be recovered by simple filtration and used for several times without loss of activity or selectivity.

NHC–Pd(II)–Im (NHC = N-heterocyclic carbene; Im = 1-methylimidazole) complexes as efficient catalysts for Suzuki-Miyaura coupling reactions of aryl chlorides

A new type of well-defined N-heterocyclic carbene (NHC)-palladium chloride-imidazole complexes derived from IPr HCl or IMes HCl, PdCl 2 and 1-methylimidazole exhibits high catalytic activity in the room-temperature Suzuki-Miyaura coupling reactions of aryl or heteroaryl chlorides. Moreover, the large-scale (20.0 mmol) couplings in the presence of 0.01 mol% catalyst loading can also give the corresponding coupling products in high yields.

ChemInform Abstract: Nickel‐Catalyzed Alkenylative Cross‐Coupling Reaction of Alkyl Sulfides.

A novel cross-coupling reaction of alkyl aryl sulfides with aryl Grignard reagents has been achieved to produce the alkenyl-aryl coupling products in high yields by using catalytic Ni(cod)2 and a bulky N-heterocyclic carbene ligand, SIPr.

ChemInform Abstract: pH‐Dependent Conjugate Addition of Arylboronic Acids to α,β‐Unsaturated Enones Catalyzed by a Reusable Palladium(II)/Cationic 2,2′‐Bipyridyl System in Water under Air.

AbstractPalladium‐catalyzed conjugate addition reaction of cyclic and acyclic enones with arylboronic acids in water gives coupling products in high yields when an aqueous solution of HBF4 is used to adjust the pH value to 1.0.

ZnCl2-Enhanced Negishi Coupling of Secondary Benzyl Trifluoroacetates

A ZnCl2-enhanced arylation of ­benzyl trifluoroacetates with arylzinc reagents has been developed. The method could be ­applied to a broad variety of differently substituted benzyl trifluoroacetates tolerating bromo functionalities. Also sterically hindered arylzinc reagents were shown to furnish the desired coupling products in high yields.