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.     

Synthesis of biphenyl anilines using iodo phenylformamides via a one-pot Suzuki coupling reaction

We have developed a novel and economical synthesis of biphenyl anilines via a one-pot Suzuki coupling reaction with iodo phenylformamides. This literature is an unprecedented approach to biphenyl anilines replacing costly aminophenylboronic acids with economical iodo anilines for the preparation of biphenyl anilines. It also provides a viable synthesis toward substituted biphenyl anilines where the required aminophenylboronic acids are not readily available.     

Nickel-promoted ligand-free palladium-catalyzed Suzuki coupling reaction

Summary A Ni-promoted ligand free palladium catalyst system for Suzuki coupling of aryl bromides has been developed in high efficiency under mild reaction conditions. It was obtained in situ by introducing NiCl₂ to PdCl₂/PVP using a parallel high-throughput screening technique. A wide range of aryl bromides bearing a variety of functional groups was evaluated.     

Arylation of halogenated pyrimidines via a Suzuki coupling reaction

The Suzuki coupling reaction has been used extensively for the synthesis of a wide variety of unsymmetrical biaryl compounds. We have extended this reaction to demonstrate the utility of preparing monophenyl-, diphenyl-, or triphenylpyrimidine depending on the reaction conditions. Further, it has been shown that chloropyrimidine substrates are preferable over iodo-, bromo-, or fluoropyrimidines.     

A modular approach to catalytic synthesis using a dual-functional linker for Click and Suzuki coupling reactions

The stable benzylazido-boronate ester 1 is presented as an example of a dual-functional linker that allows the synthetically valuable boronate motif to be clicked onto other molecules under mild conditions. The utility of the azido-boronate motif as a modular building block is demonstrated in the rapid synthesis of drug-like structures employing sequential catalytic azide-alkyne cycloaddition and Suzuki coupling reactions.     

Spatially resolved NMR thermometry of an operating fixed-bed catalytic reactor

An MRI-based approach for the thermometry of an operating packed-bed catalytic reactor was implemented. It was employed for the spatially resolved NMR thermometry of the bed of Pd/gamma-Al2O3 catalyst beads in the course of propylene hydrogenation reaction. This was achieved by detecting the spatially resolved axial 1D profiles of the 27Al NMR signal intensity of Al2O3 in the course of the reaction. The experimental results demonstrate a clear correlation between the 27Al NMR signal intensity and the catalyst temperature measured with a thermocouple (25-250 degrees C), and reveal the existence of pronounced temperature gradients along the catalyst bed.     

Suzuki coupling reaction of 1,6,7,12-tetrabromoperylene bisimide

[STRUCTURE: SEE TEXT] 1,6,7,12-Tetrabromoperylene-3,4,9,10-tetracarboxylic acid bisanhydride and the corresponding tetrabrominated perylene bisimide were first synthesized with high yields. The Suzuki coupling reaction of novel tetrabromoperylene bisimide with phenylbonoric acid was studied. The four bromines in the bay position of the perylene core were substituted successfully to yield 1,6,7,12-teraphenylperylene bisimide. The photochemical properties of the novel perylene bisimides were studied and presented.     

Efficient synthesis of isoflavone analogues via a Suzuki coupling reaction

Analogues of 3-aryl-8-isobutyl-5,6,7-trihydroxy-2-methyl-4H-chromen-4-one were synthesized with high yields via the Suzuki coupling reaction of 3-iodo-8-isobutyl-5,6,7-trimethoxy-2-methyl-4H-chromen-4-one with different aryl boronic acids.     

Iminophosphine palladium catalysts for Suzuki carbonylative coupling reaction

Three iminophosphine ligands having soft phosphorus and hard nitrogen atoms and their Pd(II) complexes were synthesized and characterized using ¹H NMR, ¹³C NMR, ³¹P NMR and Fourier transform infrared spectroscopic techniques. Also, electrochemical properties of the iminophosphines and their Pd(II) complexes were investigated in acetonitrile–tetrabutylammonium perchlorate solution with cyclic and square wave voltammetry techniques. All Pd(II) complexes were evaluated as catalysts for carbonylative cross‐coupling reactions of aryl iodides with phenylboronic acid. The Suzuki carbonylation of aryl iodides at 80 °C under balloon pressure of carbon monoxide in the presence of K₂CO₃ as a base was examined, and good to high conversions and excellent selectivities were obtained.     

In-situ synthesis of a palladium-polyaniline hybrid catalyst for a Suzuki coupling reaction

Palladium-catalyzed cross-coupling reactions are one of the most frequently used synthetic tools for the construction of new carbon-carbon bonds in organic synthesis. The present study describes the use of palladium-polyaniline composite material as a catalyst for the Suzuki coupling of aryl halides. Palladium-polyaniline nanocomposite material was synthesized using an in-situ technique in which palladium acetate and aniline hydrochloride were used as the precursors of the composite. Electron microscopy imaging showed that the palladium particles were well-dispersed within the polymer matrix and were typically 3-5 nm in diameter. The metal-polymer composite material was used as a catalyst for the coupling of phenylboronic acid with aryl halides in the presence of an inorganic base and showed excellent yield with high TOF values.     

Spatially resolved characterization of PEFCs using simultaneously neutron radiography and locally resolved impedance spectroscopy

A method for performing neutron radiography and locally resolved impedance spectroscopy simultaneously in situ in an operating polymer electrolyte fuel cell (PEFC) is presented. The new method provides concurrently spatially resolved information about the local cell performance, the locally limiting processes, and the liquid water distribution. Information about the impact of water on cell performance and limiting processes can be gained in situ on a local scale in an operating PEFC. The method was applied to a PEFC operated on pure H₂/O₂ in co-flow mode under low humidity operating conditions. The results show that in co-flow mode strong flooding and severe drying can occur at the very same time in different sections of a PEFC.     

Synthesis and catalytic activity of a poly(N,N-dialkylcarbodiimide)/palladium nanoparticle composite: a case in the Suzuki coupling reaction using microwave and conventional heating

Poly(N,N-dialkylcarbodiimide) was found to be an effective polymeric ligand system for preparing and stabilizing palladium nanoparticles (1-5 nm). The composite material prepared in situ was found to be a robust catalyst for the Suzuki coupling reaction under microwave or regular heating.     

Room-temperature oxidative Suzuki coupling reaction of 1,2,3-triazole N-oxides

This study develops a new efficient pathway for synthesis of 2,4-disubstituted 1,2,3-triazoles through regioselective direct arylation between 2-aryl-1,2,3-triazole N-oxides and Ar-B(OH)₂. The reaction proceeds smoothly at room temperature and exhibits good yield and high C5 position selectivity. The possible pathway of oxidative Suzuki coupling is also discussed. This simple methodology can be used to construct 2,4-disubstituted 1,2,3-triazole moiety.     

The catalytic activity of a novel recyclable alkoxypalladium complex in Suzuki reaction

A novel palladium complex based on N,O-ligand was synthesized, which shows a high catalytic activity in the Suzuki cross-coupling reaction without using any phosphine ligand. More importantly, no significant loss of the catalytic activity was observed after six recycles. We suggest that this catalyst has commercial and industrial potential in the future.     

Spatially resolved electrochemiluminescence through a chemical lens

Electrochemiluminescence (ECL) microscopy is an emerging technique with a wide range of imaging applications and unique properties in terms of high spatial resolution, surface confinement and favourable signal-to-noise ratio. Despite its successful analytical applications, tuning the depth of field (i.e., thickness of the ECL-emitting layer) is a crucial issue. Indeed, the control of the thickness of this ECL region, which can be considered as an “evanescent” reaction layer, limits the development of cell microscopy as well as bioassays. Here we report an original strategy based on chemical lens effects to tune the ECL-emitting layer in the model [Ru(bpy)₃]²⁺/tri-n-propylamine (TPrA) system. It consists of microbeads decorated with [Ru(bpy)₃]²⁺ labels, classically used in bioassays, and TPrA as the sacrificial coreactant. In particular we exploit the buffer capacity of the solution to modify the rate of the reactions involved in the ECL generation. For the first time, a precise control of the ECL light distribution is demonstrated by mapping the luminescence reactivity at the level of single micrometric bead. The resulting ECL image is the luminescent signature of the concentration profiles of diffusing TPrA radicals, which define the ECL layer. Therefore, our findings provide insights into the ECL mechanism and open new avenues for ECL microscopy and bioassays. Indeed, the reported approach based on a chemical lens controls the spatial extension of the “evanescent” ECL-emitting layer and is conceptually similar to evanescent wave microscopy. Thus, it should allow the exploration and imaging of different heights in substrates or in cells.

A versatile mechanism based on a chemical lens to control the electrochemiluminescence (ECL) spatial distribution is presented. Changing the buffer capacity modifies the rate of ECL reactions, and therefore the thickness of the ECL-active layer.     

Spatially resolved force spectroscopy of bacterial surfaces using force-volume imaging

Force spectroscopy using the atomic force microscope (AFM) is a powerful technique for measuring physical properties and interaction forces at microbial cell surfaces. Typically for such a study, the point at which a force measurement will be made is located by first imaging the cell using AFM in contact mode. In this study, we image the bacterial cell Shewanella putrefaciens for subsequent force measurements using AFM in force-volume mode and compare this to contact-mode images. It is known that contact-mode imaging does not accurately locate the apical surface and periphery of the cell since, in contact mode, a component of the applied load laterally deforms the cell during the raster scan. Here, we illustrate that contact-mode imaging does not accurately locate the apical surface and periphery of the cell since, in contact mode, a component of the applied load laterally deforms the cell during the raster scan. This is an artifact due to the deformability and high degree of curvature of bacterial cells. We further show that force-volume mode imaging avoids the artifacts associated with contact-mode imaging due to surface deformation since it involves the measurement of a grid of individual force profiles. The topographic image is subsequently reconstructed from the zero-force height (the contact distance between the AFM tip and the surface) at each point on the cell surface. We also show how force-volume measurements yield applied load versus indentation data from which mechanical properties of the cell such as Young's modulus, cell turgor pressure and elastic and plastic energies can be extracted.     

CuI-catalyzed Suzuki coupling reaction of organoboronic acids with alkynyl bromides

A CuI-catalyzed Suzuki cross-coupling reaction of organoboron derivatives with alkynyl bromides has been developed. In the presence of CuI (10 mol %) and 8-hydroxyquinoline (20 mol %), organoboron derivatives including aromatic and alkenyl boronic acids, potassium aryltrifluoroborates, and sodium tetraphenylborate reacted smoothly with 1-bromo-2-substituted acetylene to generate the corresponding cross-coupling products in good to excellent yields in C₂H₅OH. It is important to note that aromatic N,O-ligand 8-hydroxyquinoline is the most effective ligand for the reaction.     

Green synthesis of novel chalcone and coumarin derivatives via Suzuki coupling reaction

Chalcones and coumarins are important naturally occurring plant constituents and display a wide range of pharmacological and biological activities. In an environmentally benign approach, synthesis of biphenyl chalcone and coumarin derivatives was successfully accomplished via Suzuki coupling by using PEG-400 as a solvent under microwave irradiation. Salient feature of this methodology includes: short reaction time, good to excellent yields, and prominent tolerance of different functional groups.     

Design and synthesis of potential β-sheet nucleators via Suzuki coupling reaction

Three series of compounds characterized by biphenylic structure were synthesized in order to develop new scaffolds able to induce β-sheet folding in the peptides. Microwave flash heating was used in order to shorten reaction times and to enhance the obtained yields. Simulated annealing molecular dynamics simulations demonstrated that some of the compounds were capable of adopting a 15-membered intramolecularly hydrogen-bonded conformation, which supports an antiparallel β-sheet structure.     

Palladium incorporated on carbonaceous catalyst for Suzuki coupling reaction in water

A new palladium incorporated carbonaceous catalyst Pd@CCSO₃HNH₂ was synthesized by introducing palladium on glucose derived carbocatalyst. The catalyst was well characterized and was used for the Suzuki coupling of phenyl boronic acid with different aryl halides under aqueous conditions. This green methodology represents a ligand free, cost-effective and operationally convenient method for the synthesis of a variety of biaryl’s under the conditions that are tolerant for a broad range of functional groups with good to excellent yields. Moreover, the catalyst could be easily recycled and reused at least five times without any significant loss of its catalytic activity.