Stille Coupling Research Articles

Indacenodithiophene Homopolymers via Direct Arylation: Direct Polycondensation versus Polymer Analogous Reaction Pathways

Indacenodithiophene (IDT) based materials are emerging high performance conjugated polymers for use in efficient organic photovoltaics and transistors. However, their preparation generally suffers from long reaction sequences and is often accomplished using disadvantageous Stille couplings. Herein, we present detailed synthesis pathways to IDT homopolymers using C-H activation for all C-C coupling steps. Polyketones are first prepared by direct arylation polycondensation (DAP) in quantitative yield and further cyclized polymer analogously. This protocol is suitable for obtaining structurally well-defined IDT homopolymers, provided that the conditions for cyclization are chosen appropriately and that side reactions are suppressed. Moreover, this polymer analogous pathway gives rise to asymmetric side chain patterns, which allows to fine tune physical properties. Alternatively, IDT homopolymers can be obtained via oxidative direct arylation polycondensation of IDT monomers (oxDAP), leading to IDT homopolymers with similar properties but at reduced yield. Detailed characterization by NMR, IR, UV-vis and PL spectroscopy, and thermal properties, is used to guide synthesis and to explain varying field-effect transistor hole mobilities in the range of 10-6- 10-3 cm2/Vs.

Stille Coupling Catalyzed by Gold Nanoparticles Formed In Situ on Active Carbon

Key words gold catalysis - nanoparticles - Stille coupling - benzyl halides - allylstannanes - dienes

Oligoselenophenes (n and p Type): Synthesis and Properties

An array of semiconducting oligoselenophenes (n and p types), up to hexamer units, has been synthesized by the double Stille coupling methods using tetrakis(triphenylphosphine)palladium(0) as a catalyst. A series of semiconducting oligomers (n and p types) containing mixed hetero-units (hexamers of thiophene and selenophene) have been also synthesized using the Stille coupling reaction. Their thermal properties are systematically studied and compared with those of π-conjugated thiophene based oligomers using DSC and TGA. The field-effect mobility of synthesized n and p type oligomers is analyzed.

Novel conjugated copolymers with dithienyl and cyclopentadithienyl substituted dicyanoethene acceptor blocks

Novel bifunctional acceptor monomer, 2-[bis(5-bromothiophen-2-yl)methylidene]malononitrile, is obtained in three steps in a total yield of 79%. The Stille cross-coupling between this monomer and 2,6-ditin derivative of 4,4-didecyl-4H-silolo[3,2-b: 4,5-b′]dithiophene afforded donor–acceptor polymer whose properties were compared to the analogue containing a planar cyclopenta[2,1-b: 3,4-b′]dithiophene acceptor block. The copolymers have low narrow optical band gaps and effectively absorb visible light, however the former possesses improved solubility and thermal stability as compared to the latter.

Development of green methodologies for Heck, Chan-Lam, Stille and Suzuki cross-coupling reactions.

Organic reactions under green conditions have become popular day by day because of increased use of harmful chemicals leading to environmental hazards. This review focuses the implementation of green chemistry in Suzuki-Miyaura, Heck, Stille and Chan-Lam cross-coupling reactions incorporating a variety of strategies in which ionic liquids, water and microwave irradiations are extensively used.

Steric Protection of Rhodium‐Nitridyl Radical Species

In an attempt to synthesize a mononuclear rhodium nitridyl complex with a reduced tendency to undergo nitridyl radical N–N coupling, we synthesized a bulky analog of Milstein's bipyridine‐based PNNH ligand, bearing a tert‐butyl group at the 6′ position of the bipyridine moiety. A three‐step synthetic route toward this new bulky tBu3PNNH ligand was developed, involving a selective nucleophilic substitution step, followed by a Stille coupling and a final hydrophosphination step to afford the desired 6‐(tert‐butyl)‐6′‐[(di‐tert‐butylphosphino)methyl]‐2,2′‐bipyridine (tBu3PNNH) ligand. This newly developed tBu3PNNH ligand was incorporated in the synthesis of the sterically protected azide complex [Rh(N3)(tBu3PNNH)]. We explored N2 elimination form this species using photolysis and thermolysis, hoping to synthesize a mononuclear rhodium complex with a terminal nitrido moiety. Characterization of the reaction product(s) using NMR, coldspray HR‐ESI‐MS and EPR spectroscopy shows that the material is paramagnetic, and data obtained by MS spectrometry revealed masses corresponding with both monomeric and dimeric nitrido/nitridyl complexes. NMR only reveals broad uncharacteristic signals and the complex is EPR silent at 8K or above. The combined data point to formation of a paramagnetic [(tBu3PNN)Rh(µ‐N)Rh(tBu3PNN)] species. It thus seems that despite its three tBu groups the new ligand is not bulky enough to prevent formation of Rh–N–Rh bridged species. However, the increased steric environment does prevent further reaction with carbon monoxide, which is unable to coordinate to rhodium.

Bioinspired First Stereoselective Total Synthesis of Spinosulfate B

AbstractAn efficient bioinspired stereoselective first total synthesis of spinosulfate B has been accomplished following Jacobsen's hydrolytic kinetic resolution, Stille coupling, olefin‐cross metathesis (OCM), Horner Wadsworth Emmons olefination, and De Brabander's esterification as key steps.

Spectral response of pyridine-terminated thieno[3,4-c]pyrrole-4,6-dione derivatives to boron-containing Lewis acids

Optical band gap is an important parameter of organic semiconductors, which determines their performance and applications. In this paper, two thieno[3,4-c]pyrrole-4,6-dione (TPD) derivatives TPD-2-Py and TPD-4-Py terminated by 2- and 4-substituted pyridine are designed and synthesized with Stille reactions. The results of nuclear magnetic resonance spectra, absorption spectra and emission spectra confirm that TPD-2-Py and TPD-4-Py cooridinate with a Lewis acid tris(pentafluorophenyl)borane (BCF) through the nitrogen atom on the pyridine ring instead of TPD unit. The absorption spectra show that TPD-2-Py and TPD-4-Py have similar absorption, but their absorption spectra are red-shifted after cooridinating with BCF. Further titration experiments indicate that TPD-4-Py is more easily coordinated with BCF, and the maximum absorption peak of TPD-4-Py and BCF complex is bathochromic shift comparing with that of TPD-2-Py and BCF complex. These results demonstrate that the substituted position of pyridine has an important influence on the coordination ability of BCF, and further regulation of the optical band gap can be achieved by changing the substituted position of pyridine substitutents.

Exploiting Unsaturated Carbon-Iodine Compounds for the Preparation of Carbon-Rich Materials.

Conjugated carbon-rich materials have drawn much academic and industrial attention in recent years, due to their intriguing electronic and optical properties and potential applications including organic photovoltaics, flexible and wearable electronics, and chemical and biological sensors. Unsaturated carbon-iodine compounds, mainly the derivatives of iodoalkenes and iodoalkynes, are a class of molecules in which iodine atoms are directly connected to unsaturated carbons. These compounds provide unique advantages in the pursuit of carbon-rich materials, largely due to the Lewis acidity of iodine atoms and the lability of the carbon-iodine bonds. The Lewis acidity and electrophilicity of iodine in unsaturated carbon-iodine compounds make them excellent donors of halogen bonding, which is an attractive interaction between the electrophilic halogen atoms and Lewis basic species. Halogen bonding has emerged as a reliable building block in crystal engineering and supramolecular architectures. In this Account, we illustrate examples of the controlled assembly of diiodopolyynes within host-guest cocrystals that contain oxalamide or urea hosts with appropriate Lewis basic end groups and diiodobutadiyne or diiodohexatriyne guests. Halogen bonding interactions between the host and guest result in an ordered alignment of the diiodopolyynes that allows for a solid-state topochemical polymerization. We have used this approach to prepare poly(diiododiacetylene), PIDA, and poly(iodoethynyliododiacetylene), PIEDA, two conjugated polymers composed only of carbon and iodine. In addition, the polarity of the carbon-iodine bond gives unsaturated carbon-iodine compounds an electron-rich π-system, permitting electrophilic addition reactions with molecular halogens. The halogenated products of these additions can then serve as precursors to other conjugated carbon-rich systems. The lability of the carbon-iodine bond, together with the polarizability of iodine and the higher electronegativity of sp- and sp2-hybridized carbons, open up further possibilities in pursuing novel carbon nanomaterials from unsaturated carbon-iodine compounds. For example, we have developed an iterative method for the synthesis of longer symmetric polyynes from shorter diiodopolyynes, using Stille coupling to the iodine-capped polyynes. The iodination/coupling cycle symmetrically lengthens the polyyne chain by two carbon-carbon triple bonds. This method is particularly helpful for preparing polyynes with an odd number of carbon-carbon triple bonds. In addition, the lability of the carbon-iodine bonds of PIDA leads to facile carbonization by pyrolysis or laser irradiation. More strikingly, diiodoalkenes undergo quantitative elimination of iodine in the presence of Lewis bases. This reaction can be used to eliminate iodine at room temperature from PIDA, in which the carbon-iodine bonds are much more easily broken than in the diiodopolyynes, resulting in graphitic carbon materials.

Transition-metal Nanoparticles Catalyzed Carbon-Carbon Coupling Reactions in Water

The use of transition-metal nanoparticles in catalysis has attracted much interest, and their use in carbon-carbon coupling reactions such as Suzuki, Heck, Sonogashira, Stille, Hiyama, and Ullmann coupling reactions constitutes one of their most important applications. The transition-metal nanoparticles are considered as one of the green catalysts because they show high catalytic activity for several reactions in water. This review is devoted to the catalytic system developed in the past 10 years in transition-metal nanoparticles-catalyzed carbon-carbon coupling reactions such as Suzuki, Heck, Sonogashira, Stille, Hiyama, and Ullmann coupling reactions in water.

Transition Metal-Catalyzed Reactions of Alkynyl Halides.

Transition metal-catalyzed reactions of alkynyl halides are a versatile means of synthesizing a wide array of products. Their use is of particular interest in cycloaddition reactions and in constructing new carbon-carbon and carbon-heteroatom bonds. Transition metal-catalyzed reactions of alkynyl halides have successfully been used in [4+2], [2+2], [2+2+2] and [3+2] cycloaddition reactions. Many carbon-carbon coupling reactions take advantage of metal-catalyzed reactions of alkynyl halides, including Cadiot-Chodkiewicz, Suzuki-Miyaura, Stille, Kumada-Corriu and Inverse Sonogashira reactions. All the methods of constructing carbon-nitrogen, carbon-oxygen, carbon-phosphorus, carbon-sulfur, carbon-silicon, carbon-selenium and carbon-tellurium bonds employed alkynyl halides. The purpose of this review is to highlight and summarize research conducted in transition metalcatalyzed reactions of alkynyl halides in recent years. The focus will be placed on cycloaddition and coupling reactions, and their scope and applicability to the synthesis of biologically important and industrially relevant compounds will be discussed. It can be seen from the review that the work done on this topic has employed the use of many different transition metal catalysts to perform various cycloadditions, cyclizations, and couplings using alkynyl halides. The reactions involving alkynyl halides were efficient in generating both carbon-carbon and carbonheteroatom bonds. Proposed mechanisms were included to support the understanding of such reactions. Many of these reactions face retention of the halide moiety, allowing additional functionalization of the products, with some new products being inaccessible using their standard alkyne counterparts.

Synthesis and characterization of D-A type conjugated electrochromic polymers with cross-linked structure employing a novel and multi-functionalized molecular as the acceptor unit

In this study, three novel conjugated electrochromic copolymers including PIPE-1, PIPE-2 and PIPE-3 were successfully synthesized via Stille coupling reaction. In the synthetic process, a novel and multifunctionalized electron functional unit 5,8,14,17-tetrabromoquinoxaline [2′,3′:9,10]phenanthrene[4,5-abc]phenazine (M2) was selected as the acceptor unit, 6,8-dibromo-3,3-bis-decyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (M1, brominated ProDOT-decyl2) and bis(trimethylstannane) functionalized indacenodithiophene (M3) as donor units. Cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), spectroelectrochemistry, kinetic switching and thermogravimetry (TG) were performed for the three polymers. The three polymers have band gaps at around 2.0eV, and the absorption peaks and colors of the polymers can be changed to some extent by changing the feed ratios of the monomers. The three polymers exhibited good thermal stability. More importantly, the three polymers exhibited high optical contrast and fast response time both in the visible and near-infrared regions. The optical contrast of PIPE-1, PIPE-2 and PIPE-3 in the near infrared region were 67.26%, 66.43% and 57.67%, respectively, and the response time of PIPE-2 at 1500nm was only 0.35s. PIPE-1 changed from wine red (0V) to brown (0.90V) and finally turned blue gray (1.40V). PIPE-2 changed from rose red color (0V) to light brown color at 0.90V, and to light blue color (1.40V). PIPE-3 changed from magenta (0V) to light red color at 0.89V, and to light gray color at 1.02V, and finally became a blue color (1.40V), which suggested that the polymer has multi-chromic property.

Well‐defined structures and nanoscale morphology for all‐conjugated BCPs

A series of conjugated donor–acceptor (D–A) block copolymers (BCPs) were synthesised using a one-pot Stille coupling polycondensation reaction. This involved reaction between a series of mono-bromo-functionalised Poly3-hexylthiophene (P3HT) polymers (P3HT-Br, Mn: 17, 21 and 43 kg/mol) and [N, N ′-bis (2-decyl-tetradecyl)-1,7-dibromo-3,4,9,10-perylene diimide (PBI) and [2,5-bis(trimethylstannyl)-thiophene] (T) monomers. Purification using preparative gel permeation chromatography (GPC) removed any excess P3HT and resulted in BCPs with low polydispersity index values. The P3HT-b-PBIT BCPs were characterised using 1 H-NMR and Fourier-transform infrared spectroscopy. When compared to a P3HT/PBIT polymer blend, the D–A BCP films exhibited a remarkably fine structure with a nanoscale morphology. These results indicated that these D–A BCPs have the potential for use as nanostructured active layers in polymer solar cells.

Extended 2,2'-Bipyrroles: New Monomers for Conjugated Polymers with Tailored Processability.

The synthesis of 2,2′-bipyrroles substituted at positions 5,5′ with pyrrolyl, N-methyl-pyrrolyl and thienyl groups and their application in the preparation of conducting polymers is reported herein. The preparation of these monomers consisted of two synthetic steps from a functionalized 2,2′-bipyrrole: Bromination of the corresponding 2,2′-bipyrrole followed by Suzuki or Stille couplings. These monomers display low oxidation potential compared to pyrrole because of the extended length of their conjugation pathway. The resulting monomers can be polymerized through oxidative/electropolymerization. Electrical conductivity and electrochromic properties of the electrodeposited polymeric films were evaluated using 4-point probe measurements and cyclic voltammetry to evaluate their applicability in electronics.

Synthesis of Pd immobilized on functionalized hexagonal mesoporous silica (HMS–CPTMS–Cy–Pd) for coupling Suzuki–Miyaura and Stille reactions

In this paper, Pd–cytosine complex immobilized on functionalized hexagonal mesoporous silica (HMS–CPTMS–Cy–Pd) as a novel mesoporous catalyst with high activity for the Stille and Suzuki coupling reactions was successfully fabricated. All products were obtained in good to excellent yields at low time reaction. The prepared catalyst has been characterized using various techniques such as FT-IR, XRD, BET, SEM, EDX-MAP, TGA and ICP. Recovery test confirm that the synthesized catalyst can be able to reuse for several times.

In Situ Generated Gold Nanoparticles on Active Carbon as Reusable Highly Efficient Catalysts for a C -C Stille Coupling.

Gold nanoparticle catalysts are important in many industrial production processes. Nevertheless, for traditional C -C cross-coupling reactions they have been rarely used and Pd catalysts usually give a superior performance. Herein we report that in situ formed gold metal nanoparticles are highly active catalysts for the cross coupling of allylstannanes and activated alkylbromides to form C -C bonds. Turnover numbers up to 29 000 could be achieved in the presence of active carbon as solid support, which allowed for convenient catalyst recovery and reuse. The present study is a rare case where a gold metal catalyst is superior to Pd catalysts in a cross-coupling reaction of an organic halide and an organometallic reagent.

Donor−acceptor conjugated polymers containing isoindigo block for novel multifunctional materials for electrochromic, resistance memory, and detector devices

Four novel materials containing isoindigo derivatives were synthesized via Stille coupling reaction. These polymers not only have excellent electrochromic properties (the highest electrochromic efficiency reaches 195 cm2 C−1), but also have low charge transfer resistance (Rct). The range of switching threshold is from −1.7 V to −4.0 V and the current ratio of the device beyond 10−5 for memory device. Moreover, the polymers can also be used as explosive detector. A sharp drop in the fluorescence intensity of the polymer appeared when trinitrotoluene (TNT) or 2, 4, 6-trinitrophenol (TNP) was added.

Synthesis and electrochromic properties of cross-linked and soluble conjugated polymers based on 5, 8, 14, 17-tetrabromoquinoxaline[2′, 3':9,10]phenanthro[4,5-abc]phenazine as the multifunctionalized acceptor unit

Three novel electrochromic copolymers PTPE-1, PTPE-2, and PTPE-3 were synthesized by changing the ratio of donor to acceptor using the Stille coupling polymerization. 5,8,14,17-tetrabromoquinoxaline[2′,3':9,10]phenanthro[4,5-abc] phenazine (monomer b) was first introduced and employed as multi-functionalized unit with bisquinoxaline structure and high planarity, which was used as the acceptor unit. Two electron-rich monomers ProDOT-decyl2 (monomer a) and thiophene (monomer c) are selected as the co-monomers and donor units. The three polymers were tested by X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), spectro-electrochemistry, kinetics, thermogravimetric analysis (TG), etc. All three polymers have narrow band gaps of lower than 1.85 eV and satisfactory thermal stability. As to electrochromic switching properties, the polymers showed high optical contrast and fast response time both in the visible and near-infrared regions. The optical contrasts are 53.35% at 540 nm and 66.49% at 1325 nm for PTPE-3, and its coloration efficiencies are 163 cm2 C−1 at 540 nm, 205 cm2 C−1 at 1325 nm, with fast switch time of less than 1 s. The color changes of three polymers were diversified and distinct, PTPE-1 changes from chestnut color to blue-gray color, PTPE-2 changes from dull red color to wathet color and PTPE-3 changes from deep red color to light blue-gray color. The excellent properties of the polymers might result from their cross-linked structure and consequent formation of the compatible ion transport channel.

Synthesis and electropolymerization of a donor-acceptor-donor trimeric monomer containing 3,4-Propylenedioxythiophene and dithienosilole units

A new dithienosilole and 3,4-propylenedioxythiophene based monomer, namely 2,6-bis(3,3-didecyl-3,4-dihydro-2H-thieno[3,4–b][1,4]dioxepin-6-yl)-4,4-dioctyl-4H-silolo[3,2-b:4,5-b']dithiophene, was synthesized via palladium catalyzed Stille Coupling Reaction and then polymerized electrochemically in an electrolyte solution of 0.1 M lithium perchlorate dissolved in a mixture of dichloromethane and acetonitrile (1:1, v:v). Due to the presence of long alkyl chains on donor and acceptor units, the corresponding polymer was soluble in common organic solvents like tetrahydrofuran, toluene, hexane and dichloromethane. Polymer has both fluorescent and electrochromic properties. Fluorescent polymer emits a reddish pink at 585 nm when excited at 480 nm and the quantum yield was found as 14%. On the other hand, the electrochromic polymer film changed its color from purple to transmissive cyan with 0.65 s switching time upon moving from neutral state to oxidized state and the film has a coloration efficiency of 501 cm2/C as well as 60% optical contrast. The optical band gap of the polymer was also calculated as 1.83 eV with a maximum wavelength at 577 nm.

Synthesis and Properties of Benzodithiophene-Based Donor-Acceptor Metallo-Supramolecular Polymers

Two new conjugated donor-acceptor (D-A) supramolecular building blocks, which contain benzo[1,2-b:4,5-b′]dithiophene (BDT) electron-donating cores modified with alkoxy (BDT-OR) or thiophene (BDT-Th) groups and electron-accepting 2,2′:6′,2″-terpyridine moieties, were synthesized via Pd-catalyzed Stille coupling. Under the introduction of transition metal ion Ru2+, the novel metallo-supramolecular polymers PBDT-OR and PBDT-Th were obtained by self-assembly polymerization of the monomeric building blocks BDT-OR and BDT-Th, respectively. The resulting polymers exhibitbroad absorption band from 300 to 600 nm. The embedding of the transition metal ions Ru2+ into the backbones of the supramolecular polymers increases the electron-withdrawing capacity of the terpyridine moieties. Consequently, the absorption bands of both PBDT-OR and PBDT-Th exhibit red-shift at the longer wavelength compared with the corresponding monomeric building blocks, 622 nm for PBDT-OR and 625 nm for PBDT-Th, which results from intramolecular charge transfer (ICT). The LUMO energy levels of PBDT-OR and PBDT-Th are similar, −3.44 and −3.43 eV, respectively, while their HOMO energy levels are different, −5.25 and 5.17 eV, respectively, due to distinct electron-donating abilities of the BDT cores modified with alkoxy and thiophene groups. PBDT-OR and PBDT-Th show reduced electrochemical energy gaps, 1.81 and 1.74 eV, respectively. Meanwhile, the resulting polymers PBDT-OR and PBDT-Th are thermally stable under 300 and 389 °C, respectively.