Stille Coupling Research Articles

Alkoxyphenyl or alkylphenyl side-chained Thieno[2,3-f]benzofuran polymer for efficient non-fullerene solar cells

In this work, two novel thieno[2,3-f]benzofuran (TBF) unit, with fluorinated alkoxyphenyl or alkylphenyl side chain, were synthesized and characterized. Based on these TBF donor unit and benzodithiophene-4,8-dione (BDD) acceptor, two novel polymers, PTBFPF-BDD and PTBFP-BDD, were prepared by Stille coupling reaction. The conjugated side chain effects on the thermogravimetric, optical, electrochemical, and photovoltaic properties of these polymers were systematically investigated. Both polymers exhibited desirable power conversion efficiency (PCE) of more than 8% after thermal annealing. PTBFP-BDD:ITIC-based devices achieved higher PCE of 8.50% with an open-circuit voltage (VOC) of 0.88 V, a short-circuit current density (JSC) of 16.01 mA/cm2 and a fill factor (FF) of 59.80%. In addition, the devices based on PTBFPF-BDD:ITIC showed an enhanced VOC of 0.92 V due to down-shifted the highest occupied molecular orbital (HOMO) energy levels. The results indicate that the alkylphenyl/alkoxyphenyl substitution of TBF donor units is promising strategy for improving PCE of PSCs.

Symmetric Mixed Sulfur-Selenium Fused Ring Systems as Potential Materials for Organic Field-Effect Transistors.

A reliable synthetic protocol toward a series of fused chalcogenopheno[1]benzochalcogenophene (CBC) building blocks was developed based on a Fiesselmann reaction. The obtained CBC units were applied in McMurry and Stille coupling reactions toward symmetric regioisomeric ene-linked dimers. These π-conjugated compounds were characterized regarding their photophysical and electrochemical properties and proved to be materials with reduced HOMO-LUMO gaps compared to their sulfur-based analogues. Single-crystal X-ray diffraction experiments revealed strong intermolecular selenium-selenium and selenium-carbon interactions depending on the position and number of incorporated selenium atoms. Good field-effect transistor performance with charge carrier mobilities up to 4×10-3 cm2 V-1 s-1 and high on/off ratios could be observed.

BNPs@Cur-Pd as a versatile and recyclable green nanocatalyst for Suzuki, Heck and Stille coupling reactions

Herein, BNPs@Cur-Pd as a versatile and reusable nanocatalyst was successfully synthesized and used for C–C coupling reactions. The Suzuki, Heck and Stille coupling reactions with good to excellent yields were conducted with Pd. Also, the catalyst could be recycled and reused for several sequential runs without considerable Pd leaching or diminishing of reaction yields. This simple methodology can be based on green chemistry protocols by using the boehmite, Curcumin and PEG as support, ligand, and solvent, respectively.

The impact of thermal treatment on the performance of benzo[1,2-b:4,5-b']difuran-based organic solar cells.

The new low bandgap benzo[1,2-b:4,5-b′]difuran (BDF)-based organic small molecule, namely B1, was synthesized by Stille coupling polymerization reactions. B1 was found to be soluble in common organic solvents such as chloroform, toluene and chlorobenzene with excellent film forming properties. The structure of B1 was verified by 1H NMR, GC-MS and elemental analysis. The B1 films exhibit broad absorption bands from 300 to 750 nm. The hole mobility of B1 : PC61BM (1 : 1, w/w) blend film reached up to 7.7 × 10−2 cm V−1 s−1 after thermal annealing by the space-charge-limited current method. BHJ organic solar cells (OSCs) were fabricated with a device structure of ITO/PEDOT : PSS/B1 : C61BM/LiF/Al. When the active layer was thermally annealed at 120 °C, B1 showed the best photovoltaic performance, with a PCE up to 5.0%. We also studied the connection between the morphologies of the active layers and the photovoltaic performance by AFM, PL, etc. Our observation will guide future design for even better small molecules for highly efficient OSCs.

Visible light-driven Suzuki–Miyaura reaction by self-supported Pd nanocatalysts in the formation of Stille coupling-based photoactive microporous organic polymers

Stille coupling results in deposition of Pd NPs on microporous organic polymers, showing excellent photocatalytic performance.

Experimental study of speciation and mechanistic implications when using chelating ligands in aryl-alkynyl Stille coupling.

Neutral palladium(ii) complexes [Pd(Rf)X(P-L)] (Rf = 3,5-C6Cl2F3, X = Cl, I, OTf) with P-P (dppe and dppf) and P-N (PPh2(bzN)) ligands have chelated structures in the solid-state, except for P-L = dppf and X = Cl, were chelated and dimeric bridged structures are found. The species present in solution in different solvents (CDCl3, THF, NMP and HMPA) have been characterised by 19F and 31P{1H} NMR and conductivity studies. Some [Pd(Rf)X(P-L)] complexes are involved in equilibria with [Pd(Rf)(solv)(P-L)]X, depending on the solvent and X. The ΔH° and ΔS° values of these equilibria explain the variations of ionic vs. neutral complexes in the range 183-293 K. Overall the order of coordination strength of solvents and anionic ligands is: HMPA ≫ NMP > THF and I-, Cl- > TfO-. This coordination preference is determining the complexes participating in the alkynyl transmetalation from PhC[triple bond, length as m-dash]CSnBu3 to [Pd(Rf)X(P-L)] (X = OTf, I) in THF and subsequent coupling. Very different reaction rates and stability of intermediates are observed for similar complexes, revealing neglected complexities that catalytic cycles have to deal with. Rich information on the evolution of these Stille systems after transmetalation has been obtained that leads to proposal of a common behaviour for complexes with dppe and PPh2(bzN), but a different evolution for the complexes with dppf: this difference leads the latter to produce PhC[triple bond, length as m-dash]CRf and black Pd, whereas the two former yield PhC[triple bond, length as m-dash]CRf and [Pd(C[triple bond, length as m-dash]CPh)(SnBu3)(dppe)] or [Pd(C[triple bond, length as m-dash]CPh)(SnBu3){PPh2(bzN)}].

The synthesis of unnatural α-alkyl- and α-aryl-substituted serine derivatives.

The synthesis of α-aryl- and α-alkyl-substituted serine derivatives via [3,3]-sigmatropic rearrangement of allyl carbamates as a key step is reported. Allyl carbamates were obtained from the corresponding allyl alcohols. The former were prepared through three approaches. Aryl-substituted ones were synthesized via the Stille coupling reaction of aryl iodides with enantiomerically enriched vinyl stannanes. Conversely, alkyl-substituted allyl alcohols were prepared by an analogous strategy involving the Negishi coupling reaction of enantiomerically enriched vinyl iodides or by enzymatic kineric resolution of the corresponding racemic alcohols.

A facile synthesis of mesoporous graphitic carbon nitride supported palladium nanoparticles as highly effective and reusable catalysts for Stille coupling reactions under mild conditions

This paper reports a facile one-pot synthesis of mesoporous graphitic carbon nitride (mpg-CN) supported Pd NPs, denoted as mpg-CN/Pd, as highly efficient catalysts for Stille C–C coupling reactions under mild conditions.

Total synthesis of dimeric Securinega alkaloids (-)-flueggenines D and I.

We describe the total synthesis of (−)-flueggenines D and I. This features the first total synthesis of dimeric Securinega alkaloids with a C(α)–C(δ′) connectivity between two monomeric units. The key dimerization was enabled by a sequence that involves Stille reaction and conjugate reduction. The high chemofidelity of the Stille reaction enabled us to assemble two structurally complex fragments that could not be connected by other methods. Stereochemical flexibility and controllability at the δ′-junction of the dimeric intermediate render our synthetic strategy broadly applicable to the synthesis of other high-order Securinega alkaloids.

Shuttling Catalyst: Facilitating C−C Bond Formation via Cross‐Couplings with a Thermoresponsive Polymeric Ligand

AbstractA poly(ethylene glycol) (PEG) linked ortho‐MeO‐phenyldicyclohexylphosphine (MeO‐WePhos) ligand has been synthesized to promote Pd‐catalyzed carbon‐carbon bond formation by cross‐couplings including Sonogashira, Heck, Hiyama and Stille reactions, providing corresponding (hetero)aryl substituted alkynes, alkenes and bi(hetero)aryls in good to excellent isolated yields with low Pd loadings. Facilitated by the lower critical solution temperature behaviour of the polymeric monophosphine ligand, the metal‐complex could rapidly shuttle between organic and water phases as regulated by temperature, enabling highly efficient catalyst recycling via a simple phase separation. The chemical structure of ligand was determined by matrix‐assisted laser desorption/ionization‐time of flight mass spectrometry, nuclear magnetic resonance spectrometry and size‐exclusion chromatography measurements. Notably, as demonstrated by the inductively coupled plasma‐atomic emission spectrometry measurement, 98% Pd was kept in the water phase after 6 cycles of catalyst recycling experiments. Given the profound impact of transition‐metal‐catalyzed covalent bond formation and the increasing demand of sustainable chemistry, this work provides an alternative method to conduct cross‐couplings with a polymeric shuttling catalyst.

Dodecatwistarene Imides with Zigzag-Twisted Conformation for Organic Electronics.

1D nonplanar graphene nanoribbons generally have three possible conformers: helical, zigzag, and mixed conformations. Now, a kind of 1D nonplanar graphene nanoribbon, namely dodecatwistarene imides featuring twelve linearly fused benzene rings, was obtained by bottom-up synthesis of palladium-catalyzed Stille coupling and C-H activation. Single-crystal X-ray diffraction analyses revealed that it displays a zigzag-twisted conformation caused by steric hindrance between imide groups and neighboring annulated benzene rings with the pendulum angle of 53°. This conformation is very stable and could not convert into other conformations even when heated up to 250 °C for 6 h. Despite of the highly twisted topology, organic field-effect transistor based on it exhibits electron mobility up to 1.5 cm2 V-1 s-1 after annealing.

Dodecatwistarene Imides with Zigzag‐Twisted Conformation for Organic Electronics

Abstract1D nonplanar graphene nanoribbons generally have three possible conformers: helical, zigzag, and mixed conformations. Now, a kind of 1D nonplanar graphene nanoribbon, namely dodecatwistarene imides featuring twelve linearly fused benzene rings, was obtained by bottom‐up synthesis of palladium‐catalyzed Stille coupling and C−H activation. Single‐crystal X‐ray diffraction analyses revealed that it displays a zigzag‐twisted conformation caused by steric hindrance between imide groups and neighboring annulated benzene rings with the pendulum angle of 53°. This conformation is very stable and could not convert into other conformations even when heated up to 250 °C for 6 h. Despite of the highly twisted topology, organic field‐effect transistor based on it exhibits electron mobility up to 1.5 cm2 V−1 s−1 after annealing.

Palladium‐Catalyzed Carboperfluoroalkylation of Alkynes with Fluoroalkyl Iodides and Arylstannanes

AbstractA tandem Pd‐catalyzed carboperfluoroalkylation through a sequence of iodoperfluoroalkylation and Stille coupling is presented. This novel three‐component transformation proceeds smoothly with excellent regio‐ and stereoselectivities, giving rise to fluoroalkyl‐substituted tri‐ and tetrasubstituted olefins.magnified image

Recyclable heterogeneous palladium-catalyzed carbon–carbon coupling polycondensations toward highly purified conjugated polymers

Conjugated polymers are usually synthesized by homogeneous palladium complexes-catalyzed Heck, Suzuki, and Stille coupling reactions, which suffer from the non- recyclability of expensive palladium catalysts and palladium contamination of the desired polymer due to palladium leaching. In order to overcome these drawbacks, a bidentate phosphino-modified magnetic nanoparticles-anchored palladium complex (PdCl2-Fe3O4@SiO2-2P) as a clean and efficient heterogeneous catalyst for the carbon–carbon coupling polycondensations was developed in present work. The PdCl2-Fe3O4@SiO2-2P catalyst exhibited an enhanced catalytic activity for Heck, Suzuki, and Stille coupling polymerizations, as compared with the most commonly used homogeneous Pd(PPh3)4. Moreover, this heterogeneous palladium catalyst showed advantage of much less palladium impurity (below 13 ppm) in the isolated polymers. Importantly, PdCl2-Fe3O4@SiO2-2P can facilely be separated from the reaction products and recovered by using an external magnetic field, and recycled at least eight times with almost consistent catalytic activity.

Eucalyptol as bio-based solvent for Migita–Kosugi–Stille coupling reaction on O,S,N-heterocycle

We report herein an investigation on the use of eucalyptol as new solvent for organic transformations applied to the Migita-Kosugi-Stille palladium-catalyzed cross-coupling reaction. Heterocycles containing oxygen, sulfur and nitrogen were chosen as starting materials. Eucalyptol turned out to be a viable sustainable alternative to common solvents for this reaction.

Ligand-free, recyclable palladium-functionalized magnetite nanoparticles as a catalyst in the Suzuki-, Sonogashira, and Stille reaction

A magnetically reusable ligand-free Fe3O4 palladium functionalized catalyst system was successfully prepared without the use of reducing agents, but by making use of the reduction potential of magnetite. The stabilizer was variated depending on the investigated reaction, whereby poly(ethylene glycol) (PEG) stabilized nanoparticles were used for the Suzuki reaction, as it requires protic conditions, while oleic acid stabilized nanoparticles were used for the Sonogashira and Stille reaction. It was found that it was possible to perform the Suzuki reaction and the Sonogashira reaction resulting in good to excellent conversions under air. Despite the good results for the Suzuki and the Sonogashira reaction it was not possible to perform the Stille reaction using this easily synthesized catalyst system due to the poisoning of the reusable catalyst by the tin-compound. Furthermore, the reusable catalyst system was recycled and reused for five times, resulting in a separable, straightforward and less time-consuming catalyst system.

Starphenes and Phenes: Structures and Properties

Acenes have been known for a long time but their larger congeners, starphenes and phenes, have only been recently accessible as processable and characterizable derivatives. In this personalized review, we delineate the synthetic approach developed by our group over the last four years. Nickel-mediated Yamamoto coupling of ortho-dibromoacenes generates cyclotrimers. If performed in a shotgun approach, i.e. with substituted 2,3-dibromotetracene or -pentacene in the presence of ortho-dibromobenzene or ortho-dibromoveratrole, trimeric phenes and tetramers would result. Cyclotrimers formed by a pentacenylene and two phenylenes are formally dibenzo[a,c]hexacenes. A direct way to obtain these species is to employ Stille coupling of a dimethylstannafluorene with 2,3-dibromoacenes. If tetrabromoanthracenes or tetrabromopentacenes are fed into this process, tetrabenzopentacene and tetrabenzoheptacenes are easily accessible. Optical and quantum-chemical characterizations provide insight into the electronic situation and aromaticity of these species.

Synthesis of 4,7-Di(2-thienyl)-2,1,3-benzothiadiazole via Direct Arylation

Owing to its unique electrical and optical properties, 4,7-di(2-thienyl)-2,1,3-benzothiadiazole (DTBT) moiety has became one of the most important building block for the synthesis of high-performance conjugated polymers. DTBT is commonly synthesized by Stille or Suzuki coupling reactions which are costly and time-consuming. In this work, DTBT moiety was prepared via an operationally simple method namely direct arylation. This coupling was performed under mild condition, giving the product in good yield.

Design and Characterization of New D-A Type Electrochromic Conjugated Copolymers Based on Indolo[3,2-b]Carbazole, Isoindigo and Thiophene Units.

Two new donor–acceptor (D–A) type organic conjugated random copolymers were successfully synthesized by three-component Stille coupling polymerization of indolo[3,2-b]carbazole (ICZ), isoindigo (IID) and thiophene units, namely PITID-X (X = 1 and 2), with the controlled monomer feed ratios of 3:1:4 and 1:1:2, respectively. The strategy of incorporating different alkyl-branched donor/acceptor units and raw material feed ratios facilitated the improvement of optical properties, solubility, conjugated structure, and electrochromic performance. Cyclic voltammetry, UV-vis-NIR absorption spectra, kinetic and colorimetric measurements of the spray-coated films were recorded in the fabricated three-electrode cells. The results showed that PITID-2, whose optical/electrical properties were better than that of PITID-1, was the candidate electrochromic material due to low band gap of 1.58 eV accompanying the color changing from cyan (neutral state) to gray (oxidized state). The copolymer also illustrated fast bleaching/coloration response time of 2.04/0.33 and 1.35/1.50 s in a 4 s time interval, high coloration efficiency of 171.52 and 153.08 cm2 C−1 and stable optical contrast of 18% and 58% at the wavelength of 675 and 1600 nm, respectively.

Pd Nanoparticle Fabricated Tetrahydroharman‐3‐carboxylic Acid Analog Immobilized CoFe2O4 Catalyzed Fast and Expedient C–C Cross and C–S Coupling

AbstractA novel Pd nanoparticles anchored tryptophan analog ligand immobilized magnetic CoFe2O4 nanocomposite material has been synthesized by post‐functionalization approach. The material has been thoroughly characterized using several advanced analytical techniques. Thereafter, the catalytic application was carried out in the C−C bond formation reactions via Suzuki and Stille cross coupling. Biphenyl derivatives were prepared in both the reactions with high efficiency and short reaction time. The exploration was further continued in the synthesis of aromatic thioethers by C−S coupling using molecular sulfur and haloarenes. The clean ligand‐free protocol, devoid of hazardous chemicals, excellent yields in short reaction time and the reusability of catalyst for several times are the key factors in the methodology.