Carbon-carbon Coupling Reactions Research Articles

Spatially Controlled Suzuki and Heck Catalytic Molecular Coupling

The initiation and control of chemical coupling has the potential to offer much within the context of "bottom up" nanofabrication. We report herein the use of a palladium-modified, catalytically active, AFM probe to initiate and spatially control surface-confined Suzuki and Heck carbon-carbon coupling reactions. These "chemically written reactions", detectable by lateral force and chemically specific optical and topographic labeling, were patterned with line widths down to 15 nm or approximately 20 molecules. Catalyzed organometallic coupling was, in this way, carried out at subzeptomolar levels. By varying the catalyst-substrate interaction times, turnover numbers of (0.6-1.2) x 10(4) and (3.0-5.0) x 10(4) molecules s(-1) were resolved for Suzuki and Heck reactions, respectively.

The reaction of porphyrins with α,β-acetylenic ketone/ester (Morita-Baylis-Hillman) promoted by MgI2 and subsequent Sonogashira coupling reactions

The stereoselective synthesis of (Z)-β-iodovinyl ketones/esters of Morita-Baylis-Hillman (MBH) porphyrin adducts has been achieved with a tandem formation of C - C and C - I bonds in a three-component reaction. The reaction is promoted by MgI 2 as a Lewis acid, as well as an iodine source for a Michael-type addition. The MBH adducts are efficiently oxidized to the corresponding ketones with Dess-Martin periodinane (DMP). These scaffolds are further used in a palladium-catalyzed Sonogashira carbon-carbon coupling reaction to obtain highly extended porphyrin systems.

Functionalized Ionic Liquids as New Supports for Peptide Coupling and Traceless Catalyzed Carbon-Carbon Coupling Reactions

A new strategy to obtain pure ionic liquid support with a high loading (3 mmol/g) of primary amino groups is reported. The compatibility of the imidazolium unit was demonstrated with DIC or DCC coupling reactions of protected amino acids and with classical cleavage of BOC or Fmoc protecting groups. In addition, this is the first report of a traceless ionic liquid support based on a silicon linker with a high loading (3 mmol/g) of aryl bromide reactive groups used in a palladium-catalyzed carbon-carbon coupling reaction.

N‐Boc‐L‐Valine‐Connected Amidomonophosphane Rhodium(I) Catalyst for Asymmetric Arylation of N‐Tosylarylimines with Arylboroxines.

A catalytic asymmetric arylation of sterically tuned imines with arylboroxines was developed by using N-Boc-l-valine-connected amidomonophosphane rhodium(I) catalyst in n-PrOH. The TMS group used for the steric tuning of imines is convertible to other functionalities that are applicable as a key foothold for the carbon-carbon bond-forming coupling reactions.

Copper-free monomeric and dendritic palladium catalysts for the Sonogashira reaction: substituent effects, synthetic applications, and the recovery and re-use of the catalysts.

A series of bis(tert-butylphosphine)- and bis(cyclohexylphosphine)-functionalized Pd(II) monomers and polyamino (DAB) dendritic catalysts were synthesized and investigated for Sonogashira carbon-carbon coupling reactions in a copper-free procedure. The influence of phosphine substituents (tBu versus Cy) on the reaction kinetics was investigated by a GPC technique to monitor the reactions. The dendritic catalysts containing the cyclohexylphosphine ligands could be recovered and reused without loss of efficiency until the fifth cycle. The dendritic Pd(II) catalysts show a negative dendritic effect, that is, the catalyst efficiency decreases as the dendrimer generation increases.

Water-in-CO2Emulsions: Reaction Vessels for the Production of Tetra-Ethyl Pyrone

Water-in-CO2 (W/C) emulsions formed using a nickel Triton X-100 surfactant complex (Ni-surfactant) were used as microreactors for the carbon-carbon coupling reaction between hex-3-yne and CO2 to produce tetra-ethyl pyrone (TEP). The structure of the product, which was isolated in the CO2 phase, was determined using gas chromatography mass spectrometry (GC-MS) and infrared spectroscopy. The Ni-surfactant acted as both an emulsion forming agent and a water soluble catalyst for this carbon-carbon coupling reaction. The optimum yield of TEP was determined to be 69% after 72 h, at a temperature of 70 degrees C and a pressure of 206 bar. The ease with which the emulsion could be collapsed allowed the facile separation of products from the catalyst and any unreacted starting material. Product selectivity in the W/C emulsions was found to be greater than that obtained using conventional organic methodologies.

Novel crosslinkable polymers containing nonlinear optical chromophores

Novel crosslinkable polymers for second-order nonlinear optics (NLO) were synthesized using palladium catalyzed carbon-carbon coupling reaction. Nonconjugated α,ω-diyne derivatives (DANS-6, MONS-6) containing a choromophores were used as a crosslinkable moiety in polymer backbone. In order to improve the molecular weight and electro-optical properties of NLO active polymers, copolyme s were synthesized with diiodobenzene (DIB) and DANS-6 or MONS-6 with various feed ratio of diethyldipropargylmalonate (DEDPM). Polymerization yield was quantitative and the resulting polymers were completely soluble in organic solvents and easily spin cast onto the ITO substrate. During the present polymers were annealed at 160°C for 1 hr, the absorption intensity was drastically decreased which was due to the thermal crosslinking of the acetylenic unit in the polymer backbone.

Carbon-carbon and carbon-nitrogen coupling reactions catalyzed by palladium nanoparticles derived from a palladium substituted Keggin-type polyoxometalate.

Palladium 15-20 nm particles stabilized by a Keggin-type polyoxometalate were prepared by reduction of K(5)PPdW(11)O(39) with H(2). The nanoparticles were shown to be effective catalysts for Suzuki-, Heck-, and Stille-type carbon-carbon coupling and carbon-nitrogen coupling reactions of bromoarenes in aqueous media. Chloroarenes were also reactive in reaction media without solvent. [reaction: see text]

Effect of chemical composition on the neutral reaction products produced during electron beam irradiation of carbon tetrachloride/water (ice) films

The neutral reaction products formed during electron beam irradiation of carbon tetrachloride/water (ice) films have been studied as a function of the film's initial CCl4 ∶ H2O ratio using a combination of reflection absorption infrared spectroscopy, mass spectrometry and X-ray photoelectron spectroscopy. When the initial CCl4 ∶ H2O ratio was high, the dominant reaction products in the film were C2Cl4 and a partially chlorinated carbonaceous film (CClx) formed as the result of carbon–carbon coupling reactions in the film. In these CCl4 rich films, chlorine is partitioned mainly into the gas phase while CO is the dominant carbon-containing gas phase species. As the CCl4 ∶ H2O ratio decreases, CO2 becomes an increasingly important reaction product at the expense of species generated from carbon–carbon coupling reactions, while chlorine is increasingly partitioned as HCl in the film, producing H3O+ and Cl−. The production of both H2 and O2 from electron stimulated reactions associated with H2O are suppressed in CCl4/H2O films, although oxygen is more efficiently quenched in the presence of CCl4.

Discovery of new fluorescent materials from fast synthesis and screening of conjugated polymers.

A combinatorial approach was developed for the synthesis and the screening of a large variety of conjugated polymers. The parallel synthesis of 96 polyaryleneethynylene derivatives was performed on a 12 x 8 format from diethynyl and dibromoaryl building blocks, via a palladium-catalyzed carbon-carbon coupling reaction. The qualitative distinction between fluorescent and nonfluorescent polymers as well as between the different emission colors were obtained from a simple visual test or via a 96-well plate reader spectrofluorimeter. New solid-state blue-emitting polymers were detected.

Synthesis of Liquid-Crystalline, Highly Luminescent π-Conjugated 1,3,5-Triazine Derivatives by Palladium-Catalyzed Cross-Coupling Reaction

A new class of 2,4,6-triphenyl-1,3,5-triazine derivatives having long alkoxyl side chains have been synthesized by a Pd(0)/Cu(I)-catalyzed carbon-carbon coupling reaction. These compounds behave as liquid-crystalline materials and show quantum yields higher than 70% in photoluminescence.

Heck reaction catalyzed by PD-modified zeolites.

[Pd]-exchanged NaY zeolites have been prepared, characterized, and applied for the first time for catalytic carbon-carbon coupling reactions. The catalysts exhibit a high activity and selectivity toward the Heck reaction of aryl bromides with olefins for small palladium concentrations (< or =0.1 mol % of Pd). The catalysts can easily be separated from the reaction mixture and reused after washing without loss in activity. No limitation to the diffusion of adducts in the zeolite cages was observed (for linear alkenes). The electronic nature of the aryl bromides and the olefins has a dominating effect on the reaction yield and selectivity. The heterogeneous catalysts quantitatively convert all types of all aryl bromide (complete conversion of bromobenzene within 30 min) and activated aryl chlorides under standard reaction conditions. Product form selectivity is observed in the Heck reaction with cyclic olefins.

Synthesis of Oligopyridines and Their Metal Complexes as Precursors to Topological Stereoisomers

[structure: see text]. Palladium-based carbon-carbon coupling reactions in sequence with halogen-exchange chemistry on a series of heterocycles lead to an efficient synthetic strategy for oligopyridines that bind metal ions such as ruthenium to form coordination racks. The particular structures are designed to form terpyridine subunits for octahedral binding. Reaction of 4,6-diiodopyrimidine produces a "double-bay" terpyridine from which binuclear coordination complexes have been formed.

Effect of ligands on the divalent palladium- catalyzed carbon-carbon coupling reactions. Highly enantioselective synthesis of optically active g-butyrolactones

Abstract In the palladium (II) -catalyzed enyne coupling reactions, the nitrogen-containing ligand plays the same role as the halide ion to inhibit the β-hydride elimination. Employing the pymox or bisoxazoline as ligands, the catalytic asymmetric cyclization of (Z) -4'-acetoxy-2'-butenyl 2-alkynoates initiated by acetoxypalladation was established with high efficiency (up to 92% ee) to afford the optically active γ-butyrolactones.

Dendrimer-encapsulated metal nanoparticles: synthesis, characterization, and applications to catalysis.

This Account reports the synthesis and characterization of dendrimer-encapsulated metal nanoparticles and their applications to catalysis. These materials are prepared by sequestering metal ions within dendrimers followed by chemical reduction to yield the corresponding zerovalent metal nanoparticle. The size of such particles depends on the number of metal ions initially loaded into the dendrimer. Intradendrimer hydrogenation and carbon-carbon coupling reactions in water, organic solvents, biphasic fluorous/organic solvents, and supercritical CO2 are also described.

Influence of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers on stereoselective catalysis in water

The first application of (EO)n-(PO)m-(EO)n triblock copolymers as surfactants in asymmetric hydrogenation is described. We observed a dependence of the activity and enantioselectivity on the asymmetric hydrogenation of methyl (Z)-α-acetamidocinnamate on the length of the (PO)m domain of the copolymer. The activity and enantioselectivity were observed to be independent of the hydrophilic-lipophilic-balance (HLB) or the critical micelle concentration (cmc) of the copolymer. The size of the (EO)n unit does not play an important role, however the addition of a small amount of SDS enhances the enantioselectivities significantly. The triblock copolymers were also successfully used as phase transfer reagent in two-phase Suzuki carbon-carbon coupling reactions. The use of polymeric reagents in micellar and phase-transfer systems has the advantage that these reagents can be easily separated from the reaction mixture by means of a membrane.

Formation of η3-Allyl and Its Cryogenic Coupling Reaction with Allyl Bromide on Cu(100)

Over the past three decades, a variety of transition metal-catalyzed coupling reactions between organometallic nucleophiles and organic halide electrophiles have become important processes for the formation of carbon-carbon bond in both heterogeneous catalysis and organometallic chemistry. The authors report for the first time the facile formation of 1,5-hexadiene at cryogenic temperatures (110 K) while dosing allyl bromide on Cu(100) covered with {eta}{sup 3}-allyl and bromide atoms. This cryogenic coupling reaction in ultrahigh vacuum (UHV) conditions is akin to metal-catalyzed coupling reactions in solutions and on heterogeneous catalysts. Furthermore, it contrasts with typical carbon-carbon coupling reactions of adsorbed alkyl and vinyl groups on Cu and other transition metals under ultrahigh vacuum (UHV) conditions. These workers also report the first high-resolution reflection absorption infrared spectrum (RAIRS) of the chemisorbed {eta}{sup 3}-allyl group. Such spectra have the potential to address ambiguities in the mechanistic interpretations of the formation of C{sub 3} species, for example, propylene.

Carbon-carbon coupling reaction between a Fischer-type metalaalkylidyne and a cyclopallaclated benzyldiphenylphosphine complex

The carbyne carbon atom of the metalaalkylidyne compound (η 5 -C 5 H 5 )(CO) 2 Mo≡C- p T ol is readily coupled with the palladated carbon atom of the compound obtained via the ortho -palladation of the benzyl group of the benzyldiphenylphosphine ligand, [2-(C 6 H 4 )CH 2 P(C 6 H 5 ) 2 PdI] 2 , whose Pd-C bond was known to be inert towards insertion reaction of internal alkynes under similar conditions. The resulting heterodimetallic compound has been characterised by a crystal structure analysis. L'atome de carbone carbynique du composé molybdaalkylidyne (η 5 -C 5 H 5 )(CO) 2 Mo≡C- p Tol est rapidement couplé avec le carbone σ lié au palladium du complexe cyclopalladé [2-(C 6 H 4 )CH 2 P(C 6 H 5 ) 2 PdI] 2 , obtenu par la métallation directe du groupe benzyle de la benzyldiphénylphosphine par le palladium(II), alors que ce dernier composé ne conduit pas avec les alcynes internes à une réaction de couplage analogue. La structure du composé hétérobimétallique a été déterminée par une étude de diffraction des rayons X.

Model catalyst builds five-carbon chains

Although the ability to convert coal into liquid fuels and chemicals could reduce a country's dependence on imported oil, the low price of crude oil in world markets makes petroleum-based processes more attractive economically and, hence, much more widely used. But that situation could change if the complicated chemistry that drives coal-to-fuels processes—like Fischer-Tropsch synthesis—were understood in more detail. Researchers at Northwestern University, Evanston, 111., have just taken a step in that direction by demonstrating that a certain model molybdenum catalyst can form 1-alkenes (up to 1-pentene) by stringing together small carbon species on its surface under highly controllable conditions [ J. Amer. Chem. Soc. , published Aug. 6 ASAP, http://pubs.acs.org/journals/jacsat]. Because of the tiny numbers of molecules present in ultrahigh-vacuum experiments, bimolecular surface reactions occur infrequently, explains Northwestern chemistry professor Peter C. Stair. And carbon-carbon coupling reactions...

Aromatic aldehydes from benzylbromides via Cobalt(I) mediated benzyl radicals in the presence of aerial oxygen: a mild oxidation reaction in neutral condition

Abstract Co(PPh 3 ) 3 Cl has been shown to be a novel mediator for the conversion of benzylic bromides to aromatic aldehydes under mild conditions in the presence of aerial oxygen probably via benzylic radicals. In the absence of oxygen, the carbon-carbon coupling reactions have been utilised to afford a series of functionalised benzylic dimers.