Pd-catalyzed Suzuki Cross-coupling Reaction Research Articles

(Mechano)synthesis of azomethine- and terpyridine-linked diketopyrrolopyrrole-based polymers

Three efficient synthetic approaches towards new azomethine- and terpyridine-containing 2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (diketopyrrolopyrrole, DPP) based polymers, such as P1 and P2, are reported. The first approach involves the Pd-catalyzed synthesis via two- or three-component Suzuki or Stille cross-coupling reaction in solution. The second approach involves Pd-catalyzed Suzuki cross-coupling reaction under ball-milling conditions. And, finally, the third approach involves Pd-free condensation reaction under ball-milling conditions. The newly obtained polymers exhibited absorbance around 700 nm and emission around 900 nm, and, thus, these polymers are considered to be NIR-fluorophores.

Leveraging Metal and Ligand Reactive Sites for One Pot Reactions: Ligand-Centered Borenium Ions for Tandem Catalysis with Palladium.

Tandem catalysts that perform two different organic transformations in a single pot are highly desirable because they enable rapid and efficient assembly of simple organic building blocks into more complex molecules. Many examples of tandem catalysis rely on metal-catalyzed reactions involving one or more metal complexes. Remarkably, despite surging interest in the development of chemically reactive (i. e., non-innocent) ligands, there are few examples of metal complexes that leverage ligand-centered reactivity to perform catalytic reactions in tandem with separate catalytic reactions at the metal. Here we report how multifunctional Pd complexes with triaminoborane-derived diphosphorus ligands, called TBDPhos, appear to facilitate borenium-catalyzed cycloaddition reactions at the ligand, and Pd-catalyzed Stille and Suzuki cross-coupling reactions at the metal. Both transformations can be accessed in one pot to afford rare examples of tandem catalysis using separate metal and ligand catalysis sites in a single complex.

Enhanced support effects in single-atom copper-incorporated carbon nitride for photocatalytic suzuki cross-coupling reactions

Conditioning the nature of metal active sites for better performance by well designing and constructing the support material is always appealing in heterogeneous catalysis. Herein, Cu species was introduced into the bulk phase of carbon nitride to strengthen the interlayer connection and optimize the electronic structure. The resulting material (CN-Cu) demonstrated an enhanced support effect for Pd catalyzed Suzuki cross-coupling reactions under light illumination. Detailed characterizations showed that Cu species were atomically incorporated in intra/interlayer of CN framework through coordinating with pyridinic nitrogen, leading to improved light absorption and more efficient charge carrier transfer. More importantly, the electronic effect of CN-Cu to the surface Pd was enhanced by the electron drift from Cu to N, thereby rendered an electron-rich Pd surface. Such Pd surfaces allowed faster electron injection from Pd(0) to the LUMO of aryl halides and therefore accelerate the rate-determining step of the coupling reaction.

Synthesis and Photophysical Properties of Fluorescent 6-Aryl-D-π-A Coumarin Derivatives.

A series of 6-aryl coumarin dyes were synthesized in satisfactory yields by Pd-catalyzed Suzuki cross-coupling reactions with a panel of boronic acids and coumarin bromides. Photophysical studies highlighted a large Stoke shift and interesting fluorescence quantum yield for these compounds. Optical properties were also investigated with the aid of quantum chemical calculations. The treatment of selected coumarin dyes with increasing amounts of trifluoroacetic acid showed that their fluorescence can be strongly influenced by pH (fluorescence quenching at high acid concentrations), while the addition of Fe3+ and Al3+ metal ions allowed to highlight dichotomous behavior with the corresponding reduction in fluorescence with the increase of [Fe3+] or [Al3+]. Finally, biological assays and fluorescence microscopy imaging investigations indicated that these compounds can be used as potential biomarkers in living and fixed cells.

Introduction of a Recyclable Basic Ionic Solvent with Bis-(NHC) Ligand Property and The Possibility of Immobilization on Magnetite for Ligand- and Base-Free Pd-Catalyzed Heck, Suzuki and Sonogashira Cross-Coupling Reactions in Water

A new versatile and recyclable NHC ligand precursor has been developed with ligand, base, and solvent functionalities for the efficient Pd-catalyzed Heck, Suzuki and Sonogashira cross-coupling reactions under mild conditions. Furthermore, NHC ligand precursor was immobilized on magnetite and its catalytic activity was also evaluated towards the coupling reactions as a heterogeneous catalyst. The NHC ligand precursor was prepared with imidazolium functionalization of TCT followed by a simple ion exchange by hydroxide ions. However, the results revealed an excellent catalytic activity for the both homogeneous and heterogeneous catalytic systems. 1.52 g.cm−3 and 1194 cP was obtained for the density and viscosity of the NHC ligand precursor respectively. On the other hand, the heterogeneous type could be readily recovered from the reaction mixture and reused for several times while preserving its properties. Heterogeneous nature of the magnetic catalyst was studied by hot filtration, mercury poisoning, and three-phase tests. High to excellent yields were obtained for all entries for the both homogeneous and heterogeneous catalysts, which reflects the high consistency of the catalyst.

Synthesis, characterization, photophysical properties, and computational studies onN-hexylphenothiazine/cyanopyridine based π-conjugated copolymers

In this paper, π-conjugated copolymers, namely N-hexylphenothiazine/cyanopyridine/phenyl/benzothiadiazole, N-hexylphenothiazine/cyanopyridine/phenyl/9,9-dihexylfluorene, and N-hexylphenothiazine/cyanopyridine/phenyl/9,9-diethylhexylfluorene were readily synthesized via Pd-catalyzed Suzuki cross-coupling reaction. The polymer structures and their photophysical properties were characterized by elemental analysis,1H NMR, GPC, TGA, XRD, UV-vis absorption and PL spectroscopy measurements. The coupling agent effect on photophysical properties of copolymers was investigated to rationally design polymers with particular physical properties to be employed in optoelectronic devices. The UV-vis absorption spectroscopy of copolymers showed λmaxat a range of ∼334–474 nm and red-shifted in their films to a range of ∼342–381 nm. These copolymers displayed highly intense fluorescence in their solutions and films. The PL spectra of copolymers indicated red and near-infrared light, rendering them a prospect for being red and near-infrared light-emitting materials for PLEDs. XRD analysis demonstrated a d-spacing range of ∼3.79–4.32 Å, reflecting π-π stacking and some degree of crystallinity in some polymers, and only P1 and P2 showed peaks in the small-angle region, indicating lamellar structures. To understand the relationship between molecular structures of target materials and their photophysical and photovoltaic properties, density functional theory (DFT) and its time-dependent form (TD-DFT) were employed.

Selective Arylation of 2-Bromo-4-chlorophenyl-2-bromobutanoate via a Pd-Catalyzed Suzuki Cross-Coupling Reaction and Its Electronic and Non-Linear Optical (NLO) Properties via DFT Studies.

In the present study, 2-bromo-4-chlorophenyl-2-bromobutanoate (3) was synthesized via the reaction of 2-bromo-4-chlorophenol with 2-bromobutanoyl bromide in the presence of pyridine. A variety of 2-bromo-4-chlorophenyl-2-bromobutanoate derivatives (5a–f) were synthesized with moderate to good yields via a Pd-catalyzed Suzuki cross-coupling reaction. To find out the reactivity and electronic properties of the compounds, Frontier molecular orbital analysis, non-linear optical properties, and molecular electrostatic potential studies were performed.

Density functional theory-supported studies of structural and electronicproperties of substituted-phenol derivatives synthesized by efficient O- orC-arylation via Chan–Lam or Suzuki cross-coupling reactions

The present study reports the efficient synthesis and computational studies of the structural and electronic properties of some interesting substituted phenol derivatives. Efficient and versatile procedures to synthesize a series of diaryl ether derivatives (2a-2c, 4a-4h) and bis-arylated products (5a-5c) are described. In this manuscript, using the commercially available starting material 1 and 3, a 1-step approach was developed by means of Cu(II)-mediated Chan-Lam and Pd-catalyzed Suzuki cross-coupling reactions to synthesize diaryl ether and bis-arylated products with moderate to good yields. The starting substrates, 2-bromo-4-methylphenol 1 or 2,4-dibromophenol 3, were both treated with several arylboronic acids, which led to the development of new carbon-oxygen bonds through Chan--Lam reactions. In addition, the hydroxyl group of 2,4-dibromophenol 3 was protected with isopropyl bromide to produce 4, which was then treated with arylboronic acids to synthesize the corresponding bis-arylated products through Suzuki cross-coupling reactions. Density functional theory calculations provided insight into the structural and electronic properties of the synthesized compounds. An analysis of the frontier orbitals and other reactivity descriptors, including the ionization potential, electron affinity, chemical hardness, electronic chemical potential, and electrophilicity index, is presented, which shows that compound 4c was the most reactive, while 4f and h were the most stable.

Photoactive Boron-Nitrogen-Carbon Hybrids: From Azo-borazines to Polymeric Materials.

In this paper, we describe synthetic routes for preparing a novel switchable BNC-based chromophore, composed of a borazine core peripherally functionalized with azobenzene moieties. Capitalizing on the Pd-catalyzed Suzuki cross-coupling reaction between a tris-triflate borazine and an organoboron azobenzene derivative, a photoswtichable azo-borazine derivative was successfully prepared. The molecule showed reversible E/Z photoisomerization upon irradiation at the maximum of the intense π-π* absorption feature (360 nm). X-ray crystallographic investigations revealed a nonplanar orientation of the three azobenzene moieties and the trans configuration of the -N═N- bonds. Building on the synthetic versatility of the borazine-azobenzene derivative, we used this photoactive scaffold to engineer soluble BN-doped polythiophene polymers. Photophysical characterization performed in solvents of different polarity suggested that the polymer undergoes intramolecular charge transfer (ICT).

Enantiodivergent Pd-catalyzed C-C bond formation enabled through ligand parameterization.

Despite the enormous potential for the use of stereospecific cross-coupling reactions to rationally manipulate the three-dimensional structure of organic molecules, the factors that control the transfer of stereochemistry in these reactions remain poorly understood. Here we report a mechanistic and synthetic investigation into the use of enantioenriched alkylboron nucleophiles in stereospecific Pd-catalyzed Suzuki cross-coupling reactions. By developing a suite of molecular descriptors of phosphine ligands, we could apply predictive statistical models to select or design distinct ligands that respectively promoted stereoinvertive and stereoretentive cross-coupling reactions. Stereodefined branched structures were thereby accessed through the predictable manipulation of absolute stereochemistry, and a general model for the mechanism of alkylboron transmetallation was proposed.

Modification of oligodeoxynucleotides by on-column Suzuki cross-coupling reactions.

The on-column functionalization of oligodeoxynucleotides via base-free Suzuki cross-coupling reactions is reported herein. These cross-coupling reactions were carried out with various boronic acids and either full-length modified oligonucleotides containing one or more 2'-deoxy-5-iodouridine (5IdU) monomer(s) or on oligonucleotide fragments immediately after incorporation of 5IdU. Five different functionalities were coupled to oligonucleotides containing one or three attachment points.

Synthesis of 2,3-Disubstituted 1,4-Naphthoquinones via Metal-Free C(sp2)-H Functionalization Followed by Suzuki Cross-Coupling Reactions

A synthetic strategy has been developed for the synthesis of 2,3-disubstituted-1,4-naphthoquinones. This synthetic protocol consists of metal-free tert-Butyl hydroperoxide (TBHP)-mediated oxidative benzoylation followed by Pd-catalyzed Suzuki-cross coupling reactions. Benzaldehyde, benzylalcohol and toluene were efficiently used as benzoyl radical source for the benzoylation of 1,4-naphthoquinones. By this protocol, a wide range of 1,4-naphthoquinones with different substitution patterns were efficiently prepared in a sequential way with good to excellent yields.

Donor-Acceptor Triphenylvinyl and Tetraphenyl Conjugates: Synthesis, Aggregation and Computational Studies

Triphenylvinyl (TPV) substituted bisthiazole 4 and tetraphenylethylene (TPE) substituted triphenylamine functionalized oxazole 5 were designed and synthesized by the Pd-catalyzed Suzuki cross-coupling reaction. The TPV 4 shows Aggregation-induced emission (AIE) behavior and TPE 5 shows aggregation-caused quenching (ACQ) in THF/water mixture due to π-π stacking. The TGA analysis reveals that the TPE 5 show better thermal stability as compared to TPV 4.

Cs -Symmetric Triphenylamine-Linked Bisthiazole-Based Metal-Free Donor-Acceptor Organic Dye for Efficient ZnO Nanoparticles-Based Dye-Sensitized Solar Cells: Synthesis, Theoretical Studies, and Photovoltaic Properties.

Herein, we have designed a metal-free donor–acceptor dye by incorporating an electron deficient bisthiazole moiety as a linker in between the electron donor triphenylamine and cyanoacetic acid acceptor. The bisthiazole-based organic dye D1 was synthesized using the Pd-catalyzed Suzuki cross-coupling and Knoevenagel condensation reactions. On the basis of the optical, electrochemical, and computational studies, dye D1 showed a better electronic interaction between the donor and acceptor moieties. As-synthesized C2 symmetric triphenylamine-linked bisthiazole-based organic dye D1 has four anchoring groups, which play a significant role for better adsorption on the ZnO surface along with the enhanced kinetics of photoexcited electron injection. Consequently, photovoltaic properties of the organic dye D1 has been carried out by fabricating the ZnO nanoparticles (ZnO NPs)-based solar device. We obtained the maximum incident photon-to-current conversion efficiency of about 56.20%, with a short-circuit photocurrent density (Jsc) of 13.60 mA cm–2, which results in a power conversion efficiency (PCE) of 4.94% under AM 1.5 irradiation (100 mW cm–2). The high PCE value is the result of proficient electron injection from ELUMO of dye D1 to the conduction band of ZnO NPs, as suggested by the computational calculations. Electrochemical impedance spectroscopy measurement is carried out to calculate the electron lifetime and also reveals the insight to the reduced charge recombinations at the various active interfaces of the photovoltaic device.

Carbazolyl-substituted quinazolinones as high-triplet-energy materials for phosphorescent organic light emitting diodes

A series of carbazolyl-substituted quinazolinones were designed and synthesized by the Pd-catalyzed Buchwald-Hartwig, Suzuki and Heck cross-coupling reactions. Their optical, photophysical, thermal, electrochemical, and electroluminescent properties were investigated. The characterization of the synthesized compounds was carried out using experimental and theoretical methods. The determined geometries of the compounds lead to the HOMO distribution on the quinazolinone moiety and the different donor substituents. The synthesized compounds form glasses with the glass transition temperatures ranging from 97 to 159 °C. Their solutions in tetrahydrofuran absorb electromagnetic radiation in the range of 210–420 nm and emit in the range of 350–600 nm. The Stokes shifts recorded for the dilute solutions of compounds ranged from 48 to 134 nm, while those observed for the solid films were similarly in the range of 46–113 nm. The highest fluorescence quantum yield of 44.3% was recorded for the solution of 3-(9-ethyl-9H-carbazol-3-yl)-5-((E)-2-(9-ethyl-9H-carbazol-3-yl)ethenyl)-2-methylquinazolin-4(3H)-one. The triplet energy levels established for the dilute solutions of the compounds from their phosphorescence spectra at 77 K were found to be in the range of 2.55–2.99 eV. The ionization potentials of the synthesized compounds established by photoelectron emission technique in air ranged from 5.35 to 5.66 eV. The electrochemical properties of the derivatives were studied by cyclic voltammetry. All the studied compounds showed irreversible oxidation and no reduction waves. Their repeated cyclic voltammetry scans displayed increasing changes in the cyclic voltammetry traces, proving that a series of electro-polymerization reactions of the radical cations occurred. Time-of-flight hole drift mobility of the solid layer of 5-(bis(4-tert-butyldiphenyl)amino)-3-(9-ethyl-9H-carbazol-3-yl)-2-methylquinazolin-4(3H)-one reached 1.1 × 10−3 cm2/Vs at an electric field of 8.1 × 105 V/cm. This compound was tested as a host in the green and blue phosphorescent organic light emitting diodes achieving maximum external quantum efficiencies of ca. 7.1 and 6.9%, respectively.

C2-Symmetric ferrocenyl bisthiazoles: synthesis, photophysical, electrochemical and DFT studies.

A series of donor-acceptor ferrocenyl substituted bisthiazoles 3-8 were designed and synthesized by the Pd-catalyzed Suzuki, Heck, and Sonogashira cross-coupling reactions. Their photophysical, electrochemical and computational studies reveal strong donor-acceptor interactions. The photonic and electrochemical studies show that the ferrocenyl bisthiazoles with vinyl linkage ferrocenyl-bisthiazole 4, show better electronic communication compared to rest of the ferrocenyl bisthiazoles. The time dependent density functional theory (TD-DFT) calculation at B3LYP on the ferrocenyl substituted bisthiazoles 3-5 was performed, in which the ferrocenyl-bisthiazole 4 shows strong donor-acceptor interactions compared to the Fc-bisthiazoles 3 and 5. The thermal stability of the ferrocenyl substituted bisthiazoles 3-8 is reported, in which Fc-bisthiazole 8 shows high thermal stability. The single crystal structures of ferrocenyl-bisthiazoles 3 and 5 are reported.

ChemInform Abstract: An Efficient Synthesis of 4‐Substituted Coumarin Derivatives via a Palladium‐Catalyzed Suzuki Cross‐Coupling Reaction.

An efficient Pd-catalyzed Suzuki cross-coupling reaction of sterically crowded 4-chlorocoumarin derivatives with air- and moisture-stable potassium organotrifluoroborates is developed. This methodology has been used to generate a series of novel alkyl, aryl, and vinyl substituted coumarin derivatives in good to excellent yields. The twisted conformation of the vinyl groups in the X-ray crystal structures of (2-oxo-4-vinyl-2H-chromen-3-yl)methyl acetate (2) and (2-oxo-4-vinyl-2H-chromen-3-yl)methyl 2,2,2-trichloroacetimidate (3), along with the atropisomerism of 3-(hydroxymethyl)-4-(2-methoxyphenyl)-2H-chromen-2-one (1d), are evidence of the steric crowding in these adducts.

Aggregation induced emission and mechanochromism in pyrenoimidazoles

Pyrene-based solid state emitters 3a and 3b were designed and synthesized by the Pd-catalyzed Suzuki cross-coupling reaction. Pyrenoimidazoles 3a and 3b exhibit strong AIE and reversible mechanochromic behavior with color contrast between blue and green.

An efficient synthesis of 4-substituted coumarin derivatives via a palladium-catalyzed Suzuki cross-coupling reaction

An efficient Pd-catalyzed Suzuki cross-coupling reaction of sterically crowded 4-chlorocoumarin derivatives with air- and moisture-stable potassium organotrifluoroborates is developed. This methodology has been used to generate a series of novel alkyl, aryl, and vinyl substituted coumarin derivatives in good to excellent yields. The twisted conformation of the vinyl groups in the X-ray crystal structures of (2-oxo-4-vinyl-2H-chromen-3-yl)methyl acetate (2) and (2-oxo-4-vinyl-2H-chromen-3-yl)methyl 2,2,2-trichloroacetimidate (3), along with the atropisomerism of 3-(hydroxymethyl)-4-(2-methoxyphenyl)-2H-chromen-2-one (1d), are evidence of the steric crowding in these adducts.

Synthesis and antituberculosis activity of novel 5-styryl-4-(hetero)aryl-pyrimidines via combination of the Pd-catalyzed Suzuki cross-coupling and SNH reactions

Combination of the Suzuki cross-coupling and nucleophilic aromatic substitution of hydrogen (SNH) reactions proved to be a convenient method for the synthesis of 5-styryl-4-(hetero)aryl substituted pyrimidines from commercially available 5-bromopyrimidine. All intermediate 5-bromo-4-(hetero)aryl substituted pyrimidines and also the targeted 5-styryl-4-(hetero)arylpyrimidines were found to be active in micromolar concentrations in vitro against Mycobacterium tuberculosis H37Rv, avium, terrae, and multi-drug-resistant strain isolated from tuberculosis patients in Ural region (Russia). It has been found that some of these compounds possess a low toxicity and have a bacteriostatic effect, comparable and even higher with that of first-line antituberculosis drugs.