Miyaura Cross-coupling Reaction Research Articles

Synthesis of novel benzimidazole salts and microwave-assisted catalytic activity of in situ generated Pd nanoparticles from a catalyst system consisting of benzimidazol salt, Pd(OAc)$_{{2}}$, and base in a Suzuki-Miyaura reaction

Novel benzimidazolium salts having N-benzyl or N-(4-substitutedbenzyl) groups were synthesized and their microwave-promoted catalytic activity for the Suzuki--Miyaura cross-coupling reaction were determined using in situ formed palladium(0) nanoparticles (PdNPs) from a catalytic system consisting of Pd(OAc)2/K2CO3 in DMF/H2O. PdNPs were characterized by X-ray diffraction (XRD) pattern and particle size of in situ generated PdNPs from the Pd(111) plane was determined to be of diameter 19.6 nm by the Debye--Scherrer equation. Moreover, the yield of the Suzuki--Miyaura reactions with aryl iodides and aryl bromides was found to be nearly quantitative. The synthesized benzimidazole salts (1--5) were identified by 1H and 13C NMR and IR spectroscopic methods, and micro analysis. The molecular structure of 5 was also determined by X-ray crystallography.

Synthesis of Unsymmetrical, Monosubstituted Bis-terpyridine Derivatives via Suzuki-Miyaura Cross-Coupling

As building blocks for metallo-supramolecular polymers, novel, unsymmetrical, monosubstituted bis-terpyridine derivatives with one electron-donating (OMe) or electron-withdrawing (CN or COOMe) group have been synthesized via the Suzuki― Miyaura cross-coupling reaction. This method is quick, efficient and suitable for the introduction of various substituents at the periphery of pyridine.

Reinvestigation of Aminomethyltrifluoroborates and Their Application in Suzuki−Miyaura Cross-Coupling Reactions

A reinvestigation into the chemical composition of potassium aminomethyltrifluoroborates is reported. These trifluoroborato salts have been reassigned as zwitterionic ammoniomethyltrifluoroborates. Minor adjustments to the previously disclosed reaction conditions are reported that permit a similar level of activity as nucleophiles in Suzuki-Miyaura cross-coupling reactions.

What Makes for a Bad Catalytic Cycle? A Theoretical Study on the Suzuki−Miyaura Reaction within the Energetic Span Model

The Suzuki−Miyaura cross-coupling reaction using PMe3, PPh3, and PtBu3 as ligands was studied theoretically with accurate density functional theory (DFT) methods and the Energetic Span Model. The energetic span model is a tool to compute catalytic turnover frequencies (TOF) from computationally obtained energy states. In this work the model is expanded to include turnover numbers (TON) and off-cycle intermediates. The results show that although the monophosphine route is the fastest pathway, the diphosphine cis route (accessible for small ligands) may also be reactive. The death sentence of the PMe3 catalyst is the possibility to reach the low energy trans diphosphine species, which substantially reduces the TON. In the PPh3 case, the formation of Pd0L3 was found to be the major drawback for efficient catalysis. The PtBu3 system is the most efficient of the three, as only the monophosphine mechanism is accessible.

Palladium Catalysts with Sulfonate-Functionalized-NHC Ligands for Suzuki−Miyaura Cross-Coupling Reactions in Water

Four new Pd(II) complexes containing sulfonate-functionalized N-heterocyclic carbene ligands have been synthesized. All new complexes are palladium bis-NHCs, in which the ligands adopt a monodentate, bis-chelating, and pincer coordination form, so that a good comparison between their catalytic activities can be performed. The complexes have been used in the Suzuki−Miyaura cross-coupling reaction between aryl halides and phenylboronic acid in water and in iPrOH/water. The bis-NHC-palladium complex 1, in which the two NHC ligands are in a relative cis configuration, affords the best catalytic outcomes, with high TON values of 105 for 4-bromoacetophenone and 3.7 × 104 for 4-chloroacetophenone.

Reactivity of Aryldimesitylboranes under Suzuki−Miyaura Coupling Conditions

Sterically protected triarylboron compounds such as BMes2(Ar) have important applications in organic optoelectronic devices and chemical sensors. Furthermore, the Suzuki−Miyaura cross-coupling reaction is the most commonly used method for building the π skeletons of such conjugated materials. We have found that BMes2(Ar) can also be a highly active and effective coupling partner under typical Suzuki−Miyaura coupling conditions. For BMes2(p-Br-Ph), self-coupling leads to the formation of oligomers Mes2B−(Ph)n−Mes, where the products with n = 1 (1), 2 (2), 3 (3), 4 (4) have been isolated and fully characterized. Examination of cross-coupling reactions of BMes2(Ph) with various aryl bromides has established the generality of BMes2(Ar) as a coupling partner.

Optical Operation by Chromophores Featuring 4,5-Dicyanoimidazole Embedded within Poly(methyl methacrylate) Matrices

We have studied photoinduced absorption, birefringence, and optical second-harmonic generation in poly(methyl methacrylate) (PMMA) films doped by organic chromophores featuring 4,5-dicyanoimidazole in the weight content equal to 5%. The chromophores indicated as IM1-IM6 were synthesized from 2-bromo-1-methylimidazole-4,5-dicarbonitrile by either nucleophilic substitution or Suzuki-Miyaura cross-coupling reaction. The samples were obtained as films of several micrometers thickness by the spin-coating method on a quartz substrate. Measurements of the optically induced birefringence were done by the Senarmont method at wavelength 1150 nm, and photoinduced absorption was studied in the spectral range 250-700 nm under optical treatment by 300 mW cw 532 nm laser. Photoinduced optical effects were studied by bicolor 1064 and 532 nm coherent laser pulses. The maximal changes were observed for the ratio between fundamental and writing beam intensities equal to about 7:1. To interpret the observed experimental measurements, theoretical simulations of photoinduced optical properties were performed by quantum chemical computational methods.

Discovery of a Novel Series of Semisynthetic Vancomycin Derivatives Effective against Vancomycin-Resistant Bacteria

Novel semisynthetic vancomycin derivatives with antibacterial activity against vancomycin-resistant S. aureus (VRSA) were prepared. Replacement of Cl groups of vancomycin by Suzuki-Miyaura cross-coupling reaction, which gave the title compounds, is described for the first time. Introduction of a carbon substituent at the amino acid residue 2 of vancomycin led to an enhancement of antibacterial activity against vancomycin-resistant strains, whereas the additional introduction at the amino acid residue 6 resulted in a reduction in activity even against vancomycin-susceptible strains.

Functionalized Mesostructured Silicas As Supports for Palladium Catalysts: Effect of Pore Structure and Collapse on Catalytic Activity in the Suzuki−Miyaura Reaction

Two different Pd complexes are supported on the mercaptopropyltrimethoxy silyl-functionalized mesoporous material KIT-6 and their activity in the Suzuki−Miyaura cross coupling reaction is examined. Remarkably, these materials show a much greater recyclability than the corresponding SBA-15-based materials, which lose activity quickly in the presence of hot aqueous base. The high recyclability of the KIT-6 materials is proposed to result from a greater redistribution of Pd to the external surface of the material, resulting in Pd nanoparticles that are not constrained by the size of the pores. These Pd nanoparticles are then available for catalysis after the material has collapsed, whereas in the case of SBA-15-based materials, the Pd is captured inside the pores such that catalytic activity ceases when the material collapses. Eventually, Ostwald ripening leads to larger particles and a decrease in catalytic activity.

Application of Tautomerism of Ferrocenyl Secondary Phosphine Oxides in Suzuki−Miyaura Cross Coupling Reactions

Application of Tautomerism of Ferrocenyl Secondary Phosphine Oxides in Suzuki−Miyaura Cross Coupling Reactions

Axial Chirality Control During Suzuki−Miyaura Cross-Coupling Reactions: The tert-Butylsulfinyl Group as an Efficient Chiral Auxiliary

An efficient route to a new family of axially chiral biaryl ligands by a Suzuki-Miyaura cross-coupling reaction between ortho,ortho'-disubstituted aryl iodides bearing in ortho position a tert-butyl or p-tolylsulfinyl group and ortho-substituted phenyl boronic acids or esters is described. The comparison between the t-BuSO and p-TolSO groups as chiral controllers is reported. The modularity of the approach is demonstrated by the preparation of a variety of enantiopure axially chiral mixed S/N and S/P ligands.

Asymmetric Synthesis of the C(7)−C(23) Fragment of Iriomoteolide-1a

An efficient synthesis of the C(7)-C(23) fragment 2 of iriomoteolide-1a (1) has been accomplished via a B-alkyl Suzuki-Miyaura cross-coupling reaction followed by deprotection and cyclization to form the cyclic hemiketal core.

Chemistry of bis(2-ethynyl-3-thienyl)arene and related systems. Part 6: preparation of 1,4-bis(2-ethynyl-3-thienyl)benzene derivatives containing fluorine atoms at the 2,3- or 2,5-positions of the benzene ring

Fluorine-substituted 1,4-bis(2-ethynyl-3-thienyl)benzene derivatives were prepared, utilizing Suzuki–Miyaura and Sonogashira cross coupling reactions. Their UV spectra were compared with some related compounds.

Efficient Solid-Phase Synthesis of a Library of Distamycin Analogs Containing Novel Biaryl Motifs on SynPhase Lanterns

Distamycin is a naturally occurring antibiotic that binds to AT-rich sequences in the minor groove of DNA in a noncovalent manner. It continues to be of interest as a "building block" for more-complex small-molecule ligands capable of targeting specific DNA sequences for gene regulation purposes (i.e., transcription factor inhibitors). We report here a convenient and efficient synthesis of a library of 72 novel analogs (3a-f) of the parent distamycin on SynPhase Lanterns. To investigate structure-activity relationships including DNA-binding affinity and sequence-selectivity, two previously unexplored points of diversification have been introduced into the distamycin structure by replacing one of its pyrrole rings with novel biaryl motifs. The key aspects of the synthetic approach include the development of an efficient protocol for preparation of the heterocyclic polyamide chain, optimization of the Suzuki-Miyaura cross-coupling reaction and application of a split-and-mix technique based on radiofrequency encoding. In addition, a series of biaryl carboxamide derivatives (4a-f) has been synthesized utilizing the title library diversity reagents.

Facile Synthesis of Highly Stable Gold Nanoparticles and Their Unexpected Excellent Catalytic Activity for Suzuki−Miyaura Cross-Coupling Reaction in Water

We have demonstrated that poly(2-aminothiophenol)-stablized gold nanoparticles with proper gold size and polymer thickness are active catalysts for Suzuki-Miyaura cross-coupling reaction of aryl halides with arylboronic acids in water and air for the first time. High yields can be obtained with aryl halides or arylboronic acids bearing a variety of substituents. This new finding will undoubtedly broaden the application of gold nanoparticles in organic catalytic reactions.

Convenient Preparation of Cycloalkenyl Boronic Acid Pinacol Esters

A practical method for the preparation of cycloalkenyl boronic acid pinacol esters is described. These important synthetic intermediates are typically made using more expensive methods like transition metal-catalyzed borylation of alkenyl halides or triflates. In this work, they are obtained from the simple corresponding cycloalkanones, which are subjected to Shapiro reaction conditions followed by trapping with a borate ester. The requisite products are obtained in very good to excellent yields, and the reactions can be scaled up to multigram amounts. By providing a simple alternative to common methods that make use of expensive transition-metal catalysts and formation of sensitive intermediates, this convenient method will be useful for the synthesis of ring-containing partners for Suzuki–Miyaura cross-coupling and other reactions employing boronic esters as substrates.

Continuous Flow Microwave-Assisted Reaction Optimization and Scale-Up Using Fluorous Spacer Technology

Microwave-assisted organic synthesis in a laboratory-scale monomodal microwave reactor is investigated for continuous flow applications using fluorous spacer technology. The benchtop continuous flow microwave described allows sequential processing of multiple plugs using small amounts of reagents for reaction optimization, scale-up and array synthesis. The system features online monitoring of temperature, pressure and microwave power. Several different reactions have been scaled up, including a Suzuki−Miyaura cross-coupling reaction and nucleophilic substitutions. In all cases it was possible to optimize the reaction conditions on a small scale (∼300 μL processing volume), and achieve similar conversions on an intermediate scale (∼30 mL), offering the potential for further scale-up without modifying the optimized conditions (direct scalability) producing similar isolated yields in the C−C bond formation reaction.

Oxidation of Hydroxyl‐Substituted Organotrifluoroborates.

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Toward the Development of New Textile/Plastic Electrochromic Cells Using Triphenylamine-Based Copolymers

We report the preparation and characterization of new electrochromic polymers containing a 4-butyltriphenylamine (BuTPA) unit on the main chain. All polymers were obtained through the Suzuki−Miyaura cross-coupling reaction between 4-butyl-N,N-bis((4,4,5,5-tetramethyl-1,3,2-dioxaborolan-4-phenyl)aniline) and several aryl dibromide molecules to modulate the electronic properties of the resulting copolymers. 2,5-Dibromothiophene, 2,5-dibromo(3,4-ethylenedioxythiophene), 3,6-dibromo-N-octylcarbazole, bis(6-bromo-N-octylcarbazol-3-yl), and 2,7-dibromo-3,6-dimethoxy-9,9-dihexylfluorene were used as comonomers and led to five new copolymers, PT(BuTPA), PE(BuTPA), PC(BuTPA), PCC(BuTPA), and PF(BuTPA). These polymers are readily soluble in many common organic solvents, which make them suitable for spray-coating film deposition. Electrochromic cells with the following configuration were assembled: ITO-coated glass or plastic/electrochromic polymer/gel electrolyte/ITO-coated glass or plastic or conducting textile. ...

Oxidation of Hydroxyl-Substituted Organotrifluoroborates

Potassium- and tetra-n-butylammonium organotrifluoroborates containing hydroxyl groups have been prepared and oxidized using several common oxidants. Aryl-, alkenyl-, and alkyltrifluoroborates containing both primary and secondary hydroxyl groups were oxidized in moderate to excellent yields with complete retention of the trifluoroborate moiety. The utility of these oxidized products was demonstrated in a Suzuki-Miyaura cross-coupling reaction.