Palladium-catalyzed Suzuki Cross-coupling Research Articles

Synthesis of Fused-Ring Derivatives Containing Bifluorenylidene Units via Pd-Catalyzed Tandem Multistep Suzuki Coupling/Heck Cyclization Reaction.

A series of bifluorenylidene derivatives has been facilely synthesized via a palladium-catalyzed tandem multistep Suzuki cross-coupling and Heck cyclization in one pot. The tandem reaction involves two sequential Suzuki couplings and a subsequent Heck cyclization. The target products are obtained in good yields up to 94%. Even in an extended conjugated substrate, the anticipated products can be prepared.

β-Pyrrole functionalized push-pull BODIPYs: Synthesis, photophysical, electrochemical, thermal and computational studies

A series of [Formula: see text]-pyrrole functionalized push-pull BODIPYs BDP 1-06 were designed and synthesized via Palladium-catalyzed Suzuki cross-coupling reaction and by increasing the oxidation state of the sulfur atom in the thiazine ring. The effect of various donor entities on the photophysical, electrochemical, thermal, and computational studies of the BODIPY was investigated. The absorption spectra of the push-pull BODIPY BDP 2 show a red shift compared to the rest of the BDPs, due to strong donor-acceptor interaction. The phenothiazine-5,5-dioxide functionalized BODIPY BDP 6 exhibit a blue shift in the UV-vis region compared to the phenothiazine substituted BODIPY BDP 5 due to the weak donor ability of the phenothiazine-5,5-dioxide unit. The electrochemical studies were performed for the push-pull BODIPYs BDP 1–6 to analyze the effect of different donor groups on the redox properties of the BODIPY. The thermogravimetric analysis of the BODIPYs BDP 1–6 shows that BDP 2 exhibits excellent thermal stability compared to BDP 1, 3, 4, 5, and 6. The theoretical studies reveal that the phenothiazine-5,5-dioxide substituted BODIPY BDP 6 exhibits a large HOMO–LUMO gap compared to phenothiazine functionalized BODIPY BDP 5 due to the low donor ability of the phenothiazine-5,5-dioxide unit. The theoretical calculations were consistent with the experimental observations.

Integrating a Luminescent Porous Aromatic Framework into Indicator Papers for Facile, Rapid, and Selective Detection of Nitro Compounds.

Porous aromatic framework materials with high stability, sensitivity, and selectivity have great potential to provide new sensors for optoelectronic/fluorescent probe devices. In this work, a luminescent porous aromatic framework material (LNU-23) was synthesized via the palladium-catalyzed Suzuki cross-coupling reaction of tetrabromopyrene and 1,2-bisphenyldiborate pinacol ester. The resulting PAF solid exhibited strong fluorescence emission with a quantum yield of 18.31%, showing excellent light and heat stability. Because the lowest unoccupied molecular orbital (LUMO) of LNU-23 was higher than that of the nitro compounds, there was an energy transfer from the excited LNU-23 to the analyte, leading to the selective fluorescence quenching with a limit of detection (LOD) ≈ 1.47 × 10−5 M. After integrating the luminescent PAF powder on the paper by a simple dipping method, the indicator papers revealed a fast fluorescence response to gaseous nitrobenzene within 10 s, which shows great potential in outdoor fluorescence detection of nitro compounds.

Palladium and Nickel Catalyzed Suzuki Cross-Coupling with Alkyl Fluorides.

Suzuki cross-coupling of benzylic and unactivated aliphatic fluorides with aryl- and alkenylboronic acids has been achieved via mechanistically distinct Pd and Ni catalyzed pathways that outperform competing protodeboronation, β-hydride elimination, and homocoupling processes. The utility is demonstrated with more than 20 examples including heterocyclic structures, 1,1-disubstituted and trans-1,2-disubstituted alkenes, and by the incorporation of acetonitrile into functionalized (hetero)arenes.

Facile synthesis of 4-aryl-N-(5-methyl-1H-pyrazol-3-yl)benzamides via Suzuki Miyaura reaction: Antibacterial activity against clinically isolated NDM-1-positive bacteria and their Docking Studies

The production of new pyrazole amide derivatives ( 6a-h) and their potential against New Delhi metallo-β-lactamase-1 (NDM-1) producing bacteria was described in the present manuscript. The 4-bromo- N -(5-methyl-1 H -pyrazol-3-yl)benzamide (5 ) was synthesized via direct amidation of protected 5-methyl-1 H -pyrazol-3-amine (3) . The target pyrazole amide derivatives (6a-h) were synthesized in moderate to excellent yield via Palladium catalyzed Suzuki cross-coupling of intermediate molecule (5) with different aryl and heteroaryl boronic acids. NMR and Mass Spectrometry were used to characterize the derivatives. The in vitro antibacterial effect against NDM-1-positive Acinetobacter baumannii and Klebsiella pneumoniae of newly synthesized analogues (6a-h) were determined by Agar well diffusion method. Moreover, MIC and MBC values were also evaluated against the tested bacteria. In addition, the Molecular Docking study of pyrazole amide derivatives (6a-h) against the NDM producing A. baumannii was performed to investigate the intermolecular interaction. The binding affinity and their values were compared with L-captopril. The 6b had greatest potential value and was appeared as a promising antibacterial agent.

Design, synthesis and characterization of π-conjugated 2,5-diphenylsubstituted-1,3,4-oxadiazole-based D-π-A-π’-D′ form of efficient deep blue functional materials: Photophysical properties and fluorescence “Turn-off” chemsensors approach

This paper primarily deals with the design and synthesis of three novel conjugated organic molecules containing 1,3,4-oxadiazole unit (abbreviated as CHEM-6(a-c)) with Donor-π-Acceptor-π’-Donor’ structures by utilizing palladium catalyzed Suzuki cross coupling reaction. Molecular structures of these compounds were characterized by using various spectroscopic and analytical techniques namely 1H NMR, 13C NMR, FT-IR, GC–MS and elemental analysis. Optical properties of these compounds have been investigated by using UV–visible absorption and fluorescence spectroscopy. Also, the PL investigations on solid state samples (as thin films) were carried out. Furthermore, solvatochromism and Density Functional Theory (DFT) computations are studied in detail. The experimentally measured optical band gap (Egopt) values of compounds CHEM-6a, CHEM-6b and CHEM-6c were determined to be 3.11, 3.03 and 2.70 eV, respectively. The DSC and TGA results revealed that the compounds exhibit good thermal stabilities. Current results indicate that the compounds CHEM-6(a-c) are promising candidates and could play an important role in the field of optoelectronic devices and possibly find potential applications in development of OLEDs. In addition, the compounds CHEM-6(a-c) showed an interesting property of chemical sensing for Hg(II) ion which can be clearly observed by naked eyes from the changes in solution color and fluorescence (under UV excitation).

Efficient Synthesis of Novel 1,3,4-Oxadiazoles Bearing a 4-N,N-Dimethylaminoquinazoline Scaffold via Palladium-Catalyzed Suzuki Cross-Coupling Reactions.

Two series of novel (symmetrical and unsymmetrical) quinazolinylphenyl-1,3,4-oxadiazole derivatives were synthesized using palladium-catalyzed Suzuki cross-coupling reactions. The presented synthetic methodology is based on the use of bromine-substituted 2-phenyl-4-N,N-dimethylaminoquinazolines and either a boronic acid pinacol ester or a diboronic acid bis(pinacol) ester of 2,5-diphenyl-1,3,4-oxadiazole. The reactions are conducted in a two-phase solvent system in the presence of catalytic amounts of [1,1′-bis(diphenylphosphino)ferrocene]-dichloropalladium(II), sodium carbonate, and tetrabutylammonium bromide, which plays the role of a phase-transfer catalyst. The luminescence properties of the obtained compounds are discussed in the context of applying these compounds in optoelectronics. Specifically, two highly-conjugated final products: N,N-dimethyl-2-phenyl-6-(4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl)quinazolin-4-amine (8f) and 6,6′-(4,4′-(1,3,4-oxadiazole-2,5-diyl)bis(4,1-phenylene))bis(N,N-dimethylquinazolin-4-amine (9f), which contain a 1,3,4-oxadiazole moiety connected to a quinazoline ring by a 1,4-phenylene linker at the 6 position, exhibit strong fluorescence emission and high quantum yields.

A three-step sequence strategy for facile construction of donor–acceptor type molecules: triphenylamine-substituted acenes

A new synthetic strategy was successfully developed for highly efficient construction of triphenylamine-substituted polycyclic aromatic hydrocarbons (PAHs), including anthracenes, tetraphenes, pentaphenes, and trinaphthylene. These molecules exhibited special structural characteristics, including donor–acceptor–donor (D–A–D) and donor–acceptor (D–A). Diverse aryl iodides coupled well with chlorinated 2-methyl benzaldehydes via a transient ligand-directed C–H bond arylation strategy to furnish various PAH precursors. The subsequent palladium-catalyzed Suzuki cross-couplings with 4-(diphenylamino)phenylboronic acid produced corresponding triphenylamine derivatives. Further, Brønsted acid promoted cycloaromatization generated the triphenylamine-substituted PAHs readily. The photophysical properties was investigated by UV–vis absorption and fluorescence emission spectroscope together with density functional theory (DFT) calculations.

Photophysical, thermal properties, solvatochromism and DFT/TDDFT studies on novel conjugated D-A-π-A-D form of small molecules comprising thiophene substituted 1,3,4-oxadiazole

In this paper, we report the design and synthesis of a series of novel conjugated thiophene substituted 1,3,4-oxadiazole derivatives BSTO-4(a-f) of Donor-Acceptor-π-Acceptor-Donor form by utilizing palladium catalyzed Suzuki cross coupling reaction. Structures were characterized by using spectroscopic techniques namely FT-IR, 1H NMR, 13C NMR and Mass spectra. Their thermal, photophysical and solvatochromic properties were studied in detail. Also, the PL investigations in the solid state were carried out. Furthermore, theoretical calculations such as density functional theory (DFT) were performed to get a better understanding of the intramolecular charge transfer property and electronic structures of the compounds. Experimentally measured optical bandgap values are in the range 3.02 to 3.54 eV. All compounds exhibit Stokes shifts in the range of 2776–3964 cm−1 and fluorescence quantum yields (Φf) in the range of 0.06–0.70 in chloroform. These derivatives exhibit high thermal stability that is the 5% weight loss temperature of derivatives are in the range 178–356 °C and the compounds BSTO-4(b, e and f) had the glass transition temperatures (Tg) at 107 °C, 147 °C and 68 °C, respectively. These results demonstrate that the novel thiophene substituted 1,3,4-oxadiazole compounds are promising candidates for potential applications in development of OLEDs, organic electronic devices/optoelectronic devices.

Synthesis and Reactivities of Triphenyl Acetamide Analogs for Potential Nonlinear Optical Material Uses

We have synthesized aniline based amides (3a–h) via palladium catalyzed Suzuki cross coupling of N-(2,5-dibromophenyl) acetamide with different arylboronic acids in moderate to good yields. A variety of functional groups were well tolerated in reaction conditions. For exploring the possible applications as optoelectronic devices, the nonlinear optical (NLO) properties of all synthesized derivatives (3a–h) were investigated with the help of density functional theory (DFT) methods. The frontier molecular orbitals analysis and reactivity descriptors were investigated for exploring the reactivities.

Solvent-free Suzuki and Stille cross-coupling reactions of 4- and 5-halo-1,2,3-triazoles

An environmentally friendly and efficient synthesis of fully substituted 1,2,3-triazoles comprises solvent-free palladium-catalyzed Suzuki cross-coupling of halo-1,2,3-triazoles with pinacol arylboronates. The efficiencies of Stille and Suzuki reactions with halotriazoles under solvent-free conditions were compared.

Synthesis of 3,4-Biaryl-2,5-Dichlorothiophene through Suzuki Cross-Coupling and Theoretical Exploration of Their Potential Applications as Nonlinear Optical Materials

We report herein the efficient one-pot synthesis of 3,4-biaryl-2,5-dichlorothiophene derivatives (2a–2i) via a palladium-catalyzed Suzuki cross-coupling reaction. A series of thiophene derivatives were synthesized, starting from 3,4-dibromo-2,5-dichlorothiophene (1) and various arylboronic acids using Pd(PPh3)4 and K3PO4 with moderate to good yields. For further insights about the structure and property relationship, density functional theory (DFT) calculations were performed. A relaxed potential energy surface (PES) scan was performed to locate the minimum energy structure. A frontier molecular orbitals analysis was performed to explain the reactivity of all synthesized derivatives. As the synthesized derivatives had extended conjugations, therefore the first hyperpolarizability (βo) was calculated to investigate their potential as non-linear optical (NLO) materials and significant βo values were found for the 2b and 2g derivatives.

Synthesis of New 2-Arylbenzo[b]furan Derivatives via Palladium-Catalyzed Suzuki Cross-Coupling Reactions in Aqueous Media

A series of novel benzofuran derivatives containing biaryl moiety were designed and synthesized by the Suzuki cross-coupling reactions. The reactions, performed in the presence of K2CO3, EtOH/H2O and Pd(II) complex as catalyst, gave the corresponding products in good to excellent yields. The methodology allows the facile production of heterobiaryl compounds, a unique architectural motif that is ubiquitous in medicinal chemistry.

Highly conjugated D-π-A-π-D form of novel benzo[b]thiophene substituted 1,3,4‑oxadiazole derivatives; Thermal, optical properties, solvatochromism and DFT studies

We have designed and synthesized a series of novel highly conjugated Donor-π-Acceptor-π-Donor form of unsymmetrical benzo[b]thiophene substituted 1,3,4‑oxadiazole derivatives UBTO-3(a–e) by utilizing Wittig Reaction followed by palladium catalyzed Suzuki cross coupling reaction and characterized by using standard spectroscopic techniques viz., 1H, and 13C NMR, FT-IR and GC–MS. To improve the intramolecular charge transfer property and to explore the optical properties of target compounds, Donor-Acceptor-Donor groups are linked via extending π conjugation through a phenyl spacer with para linkages. Optical/solvatochromic properties are studied in detail by UV–Vis absorption and fluorescence spectroscopy. Optical bandgap values were ranging from 2.266 to 2.704 eV. The derivatives exhibit high thermal stability that is the 5% weight loss temperature of derivatives are in the range 204–367 °C and the glass transition temperatures of the compounds UBTO-3(c, d and e) are at 146 °C, 140 °C and 133 °C respectively. Synthesized derivatives have better solubility in common organic solvents. Experimentally measured quantum yields (Φ) are in the range of 0.09 to 0.39 in toluene solvent and the molecules exhibit Stokes shifts in the range of 45–100 nm. Density functional theory computations have been performed to explore intramolecular charge transfer property and structure-property relationship of the probes. The novel unsymmetrical benzo[b]thiophene substituted 1,3,4‑oxadiazole derivatives are potential candidates and could play a significant role in organic light-emitting devices (OLED)/optoelectronic applications.

Total Synthesis of (±)-Exotine B.

The heterodimeric indole/coumarin natural product exotine B was synthesized for the first time. The carbon skeleton of the natural product was formed rapidly by a palladium-catalyzed Suzuki cross-coupling reaction and a gallium-catalyzed three-component [4 + 3] cycloaddition reaction. An alternative biosynthesis of exotine B is proposed based on the total synthesis. Improved syntheses of coumarin natural products gleinadiene and coumurrayin are also reported.

Organic phototransistors with bulk heterojunction sensing-channel layers containing soluble difluorinated diketopyrrolopyrrole acceptor

Here we report synthesis of a difluorinated diketopyrrolopyrrole (DPP) derivative, 3,6-bis(5-((E)-3,5-difluorostyryl)thiophen-2-yl)-2,5-bis(2-ethylhexyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (EHD3FV), and its application as a photosensing electron acceptor in the bulk heterojunction (BHJ)-type organic phototransistors (OPTRs). EHD3FV was synthesized via the palladium-catalyzed Suzuki cross-coupling reaction between 3,6-bis(5-bromothiophen-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione and trans-2(3,5-difluorophenyl) vinyl boronic acid pinacol ester. The pristine EHD3FV film showed optical absorption up to >850 nm, while its highest occupied molecular orbital (HOMO) energy reached −5.87 eV. The EHD3FV molecules were mixed with poly(3-hexylthiophene) (P3HT) leading the BHJ (P3HT:EHD3FV) sensing-channel layers for OPTRs. The OPTRs fabricated exhibited noticeable photoresponses upon illumination with different wavelengths of visible light (550 nm and 700 nm). The best responsivity (photoresponse) was achieved at the 8:2 (P3HT:EHD3FV) composition, even though the transistor performances in the dark became lower as the EHD3FV content increased. The present result supports the capability of EHD3FV as a photosensing electron acceptor in the BHJ-type OPTRs.

A Decatwistacene with an Overall 170° Torsion.

Two different lengths of twistacenes, namely hexatwistacene and decatwistacene, induced by steric hindrance between imide groups and neighboring annulated benzene rings, were synthesized by bottom-up synthesis of palladium-catalyzed Suzuki cross-coupling and C-H activation. Single-crystal X-ray analyses revealed that decatwistacene, which is the longest twistacene reported, exhibits an astonishing overall end-to-end torsion angle of about 170°, the largest torsion angle reported. Both twistacenes have an enhanced solubility and stability with respect to light and oxygen owing to their large twisting deformations together with much lower LUMO levels caused by the introduction of imide groups, opening a window to the narrowest chiral graphene nanoribbons with good stability and processability.

Conjugated Polyelectrolyte Based Sensitive Detection and Removal of Antibiotics Tetracycline from Water.

A new conjugated polyelectrolyte poly[5,5'-(((2-phenyl-9H-fluorene-9,9-diyl)bis(hexane-6,1-diyl))bis(oxy))diisophthalate] sodium (PFPT) was synthesized via the palladium-catalyzed Suzuki cross-coupling polymerization method and successfully applied for the rapid, real time, and highly sensitive detection of antibiotics tetracycline (Tc) in 100% aqueous media via photoinduced electron transfer with detection limit in the ppb level. Remarkably, PFPT could also be applied for the trace analysis of Tc in serum samples having recoveries well in the range 92-97% with relative standard deviations (RSD) of 1.01-1.14%, confirming reliability of the present method for the analysis of Tc. Additionally, PFPT was blended with the abundant natural polysaccharide chitosan to form CS-PFPT composite films and developed as a biopolymer based membrane for the removal of Tc from water samples with a good adsorption capacity of 3.12 mg g-1, thus finding vital application in the treatment of antibiotic infested wastewater.

Simultaneous exploration of TBAF·3H 2 O as a base as well as a solvating agent for the palladium catalyzed Suzuki cross-coupling of 4-methyl-7-nonafluorobutylsulfonyloxy coumarins under microwave irradiation

A concise, efficient and facile protocol for the synthesis of a variety of 4-methyl-7-aryl/heteroaryl coumarins has been developed by utilizing the palladium catalyzed Suzuki cross-coupling reaction of 4-methyl-7-nonafluorobutylsulfonyloxy coumarin with a wide range of electronically diverse boronic acids under microwave irradiation. In the presence of a suitable catalyst, ligand and base, the coupling reaction proceeded smoothly to give the biaryls in satisfactory to exceptional yields. The dual role of TBAF·3H2O as a base as well as a solvating agent and the utilization of dppp as a ligand with moderate bite angle (91°) were found to be instrumental for the success of the reaction. Prominent features of this optimization conditions include: shorter reaction times, good to excellent yield and exceptional tolerance to a wide variety of functional groups.

Synthesis, characterization and biological activities of 3-aryl-1,4-naphthoquinones – green palladium-catalysed Suzuki cross coupling

Antifungal and trypanocidal aryl-1,4-naphthoquinones were prepared through an aqueous Suzuki protocol with reflux or microwave irradiation.