Palladium-catalyzed Suzuki Coupling Research Articles

Well-Balanced Ambipolar Charge Transport of Diketopyrrolepyrrole-Based Copolymers: Organic Field-Effect Transistors and High-Voltage Logic Applications.

A poly (3,6-bis(thiophen-2-yl)-2,5-bis(2-decyltetradecyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione-co-(2,3-bis(phenyl)acrylonitrile)) (PDPADPP) copolymer, composed of diketopyrrolopyrrole (DPP) and a cyano (nitrile) group with a vinylene spacer linking two benzene rings, is synthesized via a palladium-catalyzed Suzuki coupling reaction. The electrical performance of PDPADPP in organic field-effect transistors (OFETs) and circuits is investigated. The OFETs based on PDPADPP exhibit typical ambipolar transport characteristics, with the as-cast OFETs demonstrating low field-effect hole and electron mobility values of 0.016 and 0.004cm2 V-1 s-1 , respectively. However, after thermal annealing at 240°C, the OFETs exhibit improved transport characteristics with highly balanced ambipolar transport, showing average hole and electron mobility values of 0.065 and 0.116cm2 V-1 s-1 , respectively. To verify the application of the PDPADPP OFETs in high-voltage logic circuits, compact modeling using the industry-standard small-signal Berkeley short-channel IGFET model (BSIM) is performed, and the logic application characteristics are evaluated. The circuit simulation results demonstrate excellent logic application performance of the PDPADPP-based ambipolar transistor and illustrate that the device annealed at 240°C exhibits ideal circuit characteristics.

A practical total synthesis of wedelolactone

Wedelolactone, a benzofuran based natural product that can be isolated from Eclipta prostrata, exhibits a variety of biological activities. It is inefficient to obtain wedelolactone from natural sources, so it is of great significance to perform total synthesis study on this important compound. In the current study, a novel total synthesis of wedelolactone featuring palladium-catalyzed Suzuki coupling and acid-promoted intramolecular transesterification was discovered. In comparison with those reported total synthesis routes, the current strategy is more convenient and efficient, and can be used as a potential route for large scale production.

Linker Engineering of 2D Imine Covalent Organic Frameworks for the Heterogeneous Palladium-Catalyzed Suzuki Coupling Reaction.

Covalent organic frameworks (COFs) are an emerging class of porous organic polymers that have been utilized as scaffolds for anchoring metal active species to act as heterogeneous catalysts. Though several examples of such COFs exist, a thorough experimental and computational analysis on such catalysts is limited. In this work, a series of two-dimensional (2D) imine COFs (TTA-DFB COF (N), TTA-TBD COF (N∧O), and TTA-DFP COF(N∧N)) were synthesized by using suitable building units to obtain three different coordination sites (N, N∧O, and N∧N). These were post-modified with Pd(II) to catalyze the Suzuki-Miyaura coupling reaction. Pd@TTA-DFB COF, where Pd(II) was coordinated to N sites, showed the fastest reactivity and lower stability. Pd@TTA-DFP COF showed highest stability but slowest reactivity. Pd@TTA-TBD COF was the best among the three with both high stability and fast reactivity. By combining both experimental and computational results, we conclude that the Pd(II) to Pd(0) reduction is a key step in the difference between the catalytic reactivities of the three COFs. This study demonstrates the importance of the building block approach to design COFs for efficient heterogeneous catalysis and to understand the fate of the reaction profile.

Recyclable palladium-catalyzed Suzuki coupling of aromatic triazine esters: A practical one-pot synthesis of aryl ketones from aromatic acids

An efficient heterogeneous palladium-catalyzed Suzuki coupling of aromatic triazine esters with arylboronic acids has been developed. The reaction proceeds smoothly in toluene at 110 °C using 2 mol% of MCM-41-bound bidentate phosphine palladium complex [MCM-41-2P-Pd(OAc)2] as catalyst and provides a novel and practical method for the synthesis of aryl ketones starting from readily available aromatic acids in a one-pot procedure with moderate to excellent yields. The MCM-41-2P-Pd(OAc)2 catalyst can be reused at least seven times without any apparent decrease in its catalytic activity.

Total synthesis of decarboxyaltenusin.

The total synthesis of decarboxyaltenusin (5’-methoxy-6-methyl-[1,1’-biphenyl]-3,3’,4-triol), a toxin produced by various mold fungi, has been achieved in seven steps in a yield of 31% starting from 4-methylcatechol and 1-bromo-3,5-dimethoxybenzene, where the longest linear sequence consists of five steps. The key reaction was a palladium-catalyzed Suzuki coupling of an aromatic boronate with a brominated resorcin derivative.

Palladium-catalyzed synthesis of pyrimidine substituted diaryl ethers through Suzuki Miyaura coupling reactions: Experimental and DFT studies

Aryl and hetero-aryl substituted pyrimidine derivatives demonstrate widespread applications in nonlinear optics (NLO), agrochemical and therapeutic drugs. Therefore, 2-(4-phenoxyphenyl)pyrimidine (2-PPP) and 5-(4-phenoxyphenyl) pyrimidine (5-PPP) were synthesized by palladium-catalyzed Suzuki coupling approach. The structure elucidation of synthesized products was done by 1H-NMR, 13C-NMR, and UV–vis spectroscopic analyses. The natural bond orbital (NBO) analysis was performed using density functional theory (DFT) assisted M06/6-311G** functional, which confirmed the existence of delocalization process and the hyper-conjugative interaction with representative transitions as π(C10-N16)→π*(C14-N17) and π(C26-N30)→π*(C9-N31) having stabilization energies of 36.30 and 36.55 kcal/mol for 2-PPP and 5-PPP, respectively. The small energy ΔE LUMO HOMO gap as 5.330 eV in 2-PPP and 4.975 eV in 5-PPP was evident from the frontier molecular orbital (FMO) analysis, computed at TD-DFT/M06/6-311G** level, Both the NBO and the FMO analysis predicted promising NLO molecular response. Furthermore, HF, LC-BLYP, CAM-B3LYP, M06-2X, and M06 methods, along with the 6-311G** basis set, were utilized to acquire the NLO findings of 2-PPP and 5-PPP. M06 and HF methods indicated the largest and lowest values of average polarizability ⟨α⟩ and first hyperpolarizability (βtot), respectively for both the compounds 2-PPP and 5-PPP. The ⟨α⟩ and βtot values of 2-PPP and 5-PPP were observed as 7.0 and 7.3 times and 15 and 36 times higher than the urea molecule, respectively. Both compounds hold fine NLO characteristics, thus recommended for future NLO applications.

Polydibenzothiophene: Effect of molecular weight on photoelectric performance

Polydibenzothiophene (PDBT) was synthesized via palladium-catalyzed Suzuki coupling reaction from 2,8-dibromodibenzothiophene and 2,8-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-dibenzothiophene. Since molecular weight is an important factor determining the organic photoelectric performance, PDBT was prepared with molecular weight (Mn) varying from 6 kDa (extracted by dichloromethane, PDBT-D) to 12 kDa (extracted by chloroform, PDBT-C). Amorphous PDBT-D and PDBT-C both emitted blue photoluminescence with close PLQYs of 3.6 and 2.8 % in CHCl3, showed similar electrochemical band gap of 2.26 and 2.18 eV, presented no significant thermal transitions, and exhibited uniform homogeneous morphology. The photoelectric performance exhibited the obvious different compared with monomer DBT, observing obvious Tm and Tc as well as compact coralline surface morphology. To better understand the influence of Mn for the above organic photoelectric performance, DFT calculations were performed. We have calculated different repetitive unit of DBT, signed as (DBT)n, n means the number of repetitive unit. In this theoretical calculation, when the repetitive unit of DBT increase to 9 and 12, namely (DBT)9 and (DBT)12, the LUMO/HOMO levels and even dipole moment were not changed. Videlicet, in our model system, Mn of PDBT surpass about 1.6 kDa, its organic photoelectric properties would perform no significant change. The study provide guidance for effect research of molecular weight on photoelectric performance.

A Two-Dimensional Coordination Polymer Formed from Cobalt(II) and an Extended Dipyridyl Ligand

The synthesis of the extended dipyridyl ligand 4,4′-(2,5-dimethyl-1,4-phenylene)dipyridine (L) in an improved yield via the palladium catalysed Suzuki coupling of 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (1) and 1,4-dibromo-2,5-dimethylbenzene (2) is reported along with its use to form a two-dimensional coordination polymer [Co2L2(OAc)4(H2O)2]n. The coordination polymer consists of one-dimensional chains of octahedral cobalt ions bridged by acetate ligands which are connected to form two dimensional sheets with square lattice (sql) topology via the dipyridyl ligands (L). The structure contains small voids totalling ~6.6% of the unit cell volume. The crystal structures 1, L, L·2H2O, and L·2HNO3 are also reported.

Antioxidant Properties of Synthesis Nanometallic Pd-Ni@2- Mercaptoethanol as Effective Catalyst for Suzuki-Miyaura Reactions

The palladium-catalyzed Suzuki coupling reaction is one of the most effcient strategies for constructing a carbon-carbon bond. In recent years, bimetallic catalysts have become candidates for the Suzuki coupling reaction. In this work, Pd-Ni@2-Mercaptoethanol nanoparticles were synthesized for the Suzuki-Miyaura cross-coupling of arylboronic acids with aryl bromides, in the N,Ndimethylformamide/ water mixture catalyzed by Pd-Ni: A simple and efficient reaction performed in a solvent, without a ligand, and in open air. We found that the Suzuki-Miyaura reactions are remarkably fast (5 min), with high yields and the products are highly pure. The Pd-Ni@2-Mercaptoetanol nanoparticles have a narrow size distribution with a mean crystallite size of 10 nm. Radical scavenging activities of the complexes have been evaluated by using DPPH, DMPD+ and ABTS+ assays. IC50 values (µg/ml) of the complexes and standards on DPPH, DMPD+ and ABTS+ respectively following the sequences.

Hydrophilic Pd/MgO Nanosystem for the Highly Efficient Aqueous-Phase Catalysis of Suzuki–Miyaura Reactions

Palladium-catalyzed Suzuki coupling reactions are regarded as one of the most effective methods for making C–C bonds; however, a green synthesis to substitute the use of abundant organic solvents h...

Bay-Substituted Thiaza[5]helicenes: Synthesis and Implications on Structural and Spectroscopic Properties.

A series of bay-substituted thiaza[5]helicenes was synthesized to investigate the effect of different substituents on the properties of these helicenes. These thiaza[5]helicenes with different substituents were prepared in a straightforward manner through indole- and benzo[b]thiophene synthesis, palladium-catalyzed Suzuki coupling, oxidative cyclization, and functional group interconversion reactions. We investigated the impact of these different bay area substituents compared to the unsubstituted thiaza[5]helicene on the structural parameters and studied the steady-state electronic spectroscopy of these thiaza[5]helicenes in toluene and acetonitrile. We found that different functional groups influence the solid state structure and spectroscopic properties, but a single substituent in the bay area of a thiaza[5]helicene was not enough to prevent enantiomerization at room temperature.

The dibenzothiophene-S,S-dioxide and spirobifluorene based small molecules promote Low roll-off and Blue organic light-emitting diodes

Blue organic light-emitting diodes (OLEDs) are of great significance in the fields of flat-panel display and solid-state lighting sources. Herein, two blue small molecules, consisting of spirobifluorene and dibenzothiophene-S,S-dioxide units (FSO-37SF and FSO-28SF) were successfully synthesized by the simple palladium-catalyzed Suzuki coupling reaction. The resulting molecules exhibited excellent thermal stability with thermal decomposition temperatures over 480 °C and high photoluminescence quantum efficiency up to 95.4% in solution. Ascribing to the introduction of unique spirobifuorene in dibenzothiophene-S,S-dioxide backbone, both of FSO-37SF and FSO-28SF showed the weak intermolecular interaction. Through the electroluminescent characterization, the donor-acceptor (D-A) typed FSO-37SF in the neat device exhibited a low roll-off and stable blue emission with Commission International de L’Eclairge (CIE) coordinates of (0.19, 0.14). Besides, the FSO-28SF in the neat device obtained a low turn-on voltage of 3.0 V in spite of broad emission. However, in the doping device with mCP as host, the FSO-28SF displayed higher luminance efficiency with CIE coordinates of (0.16, 0.06) and a narrow full-width at half maximum (FWHM) of 60 nm, which was very close to the CIE of the high-definition television (HDTV) standard blue.

A series of novel BODIPY-fluorene copolymers: Synthesis, characterization, optical-electronic and nonlinear optical properties.

A series of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) with different connection sites and conjugation length and fluorene alternating conjugated polymers have been synthesized via palladium-catalyzed Suzuki coupling reaction. The polymers were fully characterized by 1H NMR spectroscopy and gel permeation chromatography (GPC), and their properties were measured by thermogravimetric analysis (TGA), UV-vis absorption spectroscopy, cyclic voltammetry (CV), photoluminescence (PL) spectroscopy, the Z-scan technique, and theoretical calculation using density-functional theory (DFT) method. The results indicate that the connection sites and conjugation length of BODIPY have great effect on the optical-electronic and nonlinear optical properties of the conjugated BODIPY- fluorene copolymers although they don't affect the polymerization process. The absorption and emission peaks of P1 exhibit red shifts compared to those of P2 and P3. The polymers show good nonlinear optical properties that are closely related to the connection sites of the BODIPY pendants. P1 exhibits relatively richer nonlinear optical (NLO) properties than P2 and P3. The third order nonlinear optical coefficient (χ(3)) of P1 is 3.57 × 10-11 esu, which is ~4 times larger than those of P2 and P3.

Sterically hindered N-heterocyclic carbene/palladium(ii) catalyzed Suzuki-Miyaura coupling of nitrobenzenes.

Palladium-catalyzed denitrative Suzuki coupling of nitroarenes using 2-aryl-5-(2,4,6-triisopropylphenyl)-2,3-imidazolylidene[1,5-a]pyridines as the ligands is described. The key to success is the use of the NHC ligands which show strong donating ability and suitable steric hindrance allowing the successful oxidative addition of Ar-NO2 bonds. Both aromatic and aliphatic boronic acids are tolerated, and a variety of biphenyls and alkylarenes were obtained in good to excellent yields.

Synthesis of Triarylmethanes via Palladium-Catalyzed Suzuki Coupling of Trimethylammonium Salts and Arylboronic Acids.

An efficient palladium-catalyzed Suzuki coupling of 1,1-diarylmethyl-trimethylammonium triflates with arylboronic acids is reported. This reaction offers a novel approach to triarylmethane derivatives in good to excellent yields with the palladium-catalyzed C-N bond cleavage as the key feature. Broad substrate scope regarding both reaction partners are observed. Moreover, reactive functional groups such as vinyl and formyl groups are conserved in this transformation.

Palladium-catalyzed stereoselective intramolecular cyclization and Suzuki coupling of N-arylsulfonyl-α-chloroenamides promoted by a γ-hydroxy group

The Suzuki reaction of both (E)- and (Z)-α-chloro-γ-hydroxyenamides with benzeneboronic acid by using Pd2(dba)3, tBu3P, and Cs2CO3 proceeded stereoselectively to afford only (E)-trisubstituted enamides. Also, palladium-catalyzed intramolecular cyclization of (E)- and (Z)-α-chloro-γ-hydroxyenamides bearing an N-arylsulfonyl group took place stereoselectively to give the corresponding (E)-2,3-dihydrobenzoisothiazole 1,1-dioxides. The γ-hyroxy group in α-chloroenamides was found to accelerate the present palladium-catalyzed carbon-carbon bond forming reactions.

Enhancement of thermal stability and photoluminescent performance of blue light emitting material by incorporating adamantane moieties into carbazole system

ABSTRACTA facile route to improve photoluminescent performance and service lifetime of a promising blue light emitting material is reported and demonstrated here using a copolymer system of N-(2-ethylhexyl)-2,7-carbazole (Cz) and 1,3,5,7-tetrakis- (4-bromophenyl) adamantane (TBA). The copolymers were successfully synthesized by palladium-catalyzed Suzuki coupling reactions. Structure and molecular weight of the materials were characterized by FT-IR and 1H-NMR spectroscopies, elemental analysis and gel permeation chromatography. The influence of adamantane content on the thermal stability and photoluminescent performance of the synthesized copolymers was investigated in detail. DSC results showed that glass transition temperature increased dramatically, from 68°C for neat carbazole, to 88°C, 120°C and 152°C, after the addition of 10%, 20%, and 30% TBA, respectively. The same trend was found when thermal decomposition temperature at 5% weight loss was evaluated from TGA data. Importantly, this increased stability can be extended to thermo-optical performance, with the Cz-TBA system showing higher color purity and stronger emission intensity within blue light wavelength than carbazole alone. Nevertheless, measurements of emitting spectral stability at a broader temperature range (100–200°C) and photoluminescence quantum yield suggested that there is a delicate trade-off between the performance and adamantane content.

Alcohol-soluble conjugated poly(fluorene-co-thiophene) as an electron-transport material for polymer light-emitting diodes

ABSTRACTA series of alternating polyfluorene copolymers containing fluorene (P1-OF), bithiophene (P2-BT), and thiophene (P3-TH) moieties have been synthesized via a palladium-catalyzed Suzuki coupling reaction. Among them, the P3-TH polymer highly contains hydroxyl groups which provides enough solubility in polar solvents such as alcohols and dimethylformamide. Multilayer polymer light-emitting diodes have been fabricated using a semiconducting polymer, F8BT, as an emissive layer and the methanol-soluble P3-TH as an electron-transport layer. By the device configuration of ITO/PEDOT/TFB/F8BT/P3-TH/LiF/Al, it shows a luminescence efficiency of 1.48 cd/A and a turn-on voltage of 4.6 V. The emission with maxima at 448 nm and 495 nm which fell in the blue region with the CIE coordinates (x = 0.18, y = 0.24).

Facile benzofuran synthesis: Palladium-catalyzed carbonylative Suzuki coupling of methyl 2-(2-iodophenoxy)acetates under CO gas-free conditions

A palladium-catalyzed carbonylative Suzuki coupling of methyl 2-(2-iodophenoxy)acetates with arylboronic acids has been developed. The reactions were performed under CO gas-free conditions and the obtained products act as a direct precursor for the synthesis of highly functionalized benzofuran derivatives.

Computational Studies of Versatile Heterogeneous Palladium-Catalyzed Suzuki, Heck, and Sonogashira Coupling Reactions

This perspective focuses on the mechanistic insights and complexity, which are difficult to acquire from pure experimental techniques, of the computational studies of Pd-catalyzed Suzuki, Heck, and Sonogashira carbon–carbon bond-forming reactions. These reactions consist of three fundamental steps including oxidative addition (OA), transmetalation (TM), and reductive elimination (RE) for the generation of carbon–carbon bonds from the bond-forming reactions of aryl halides (R1X) and organometallic species (R2M). Computational studies of these coupling reactions allow us to understand specific reaction pathways in the analysis of OA (resolving the linkage between coordination number and selectivity in Suzuki reaction), TM (the function of the base in the Suzuki reaction and various mechanistic options in the Sonogashira reaction), and RE (way of efficient β-hydride elimination in the Heck reaction). In addition, the reaction pathways and complexities in the full catalytic cycle of each reaction along with t...