Stille Cross-coupling Reaction Research Articles

A remarkable regiocontrol in the palladium-catalyzed silylstannylation of fluoroalkylated alkynes – highly regio- and stereoselective synthesis of multi-substituted fluorine-containing alkenes

On treating fluorine-containing internal alkynes with 1.2 equiv. of (trimethylsilyl)tributyltin in the presence of 2.5 mol% of Pd(PPh3)2Cl2 in THF at the reflux temperature for 6 h, the silylstannylation reaction proceeded smoothly to afford the corresponding silylstannylated adducts in high yields in a highly regio- and cis-selective manner. Switching the palladium catalyst from Pd(PPh3)2Cl2 to Pd(t-BuNC)2Cl2 promoted the formation of silylstannylated adducts with opposite regioselectivity. The thus obtained silylstannylated adducts were subjected to Stille cross-coupling reactions to furnish the corresponding fluoroalkylated vinylsilanes whose C-Si bond was converted to a C-C bond by treating with aldehyde in the presence of TBAF and Zn(OTf)2, the corresponding fluoroalkylated tetra-substituted alkenes being afforded in moderate to good yields with a defined stereochemistry.

A new polymer from fluorinated benzothiadiazole and alkoxylphenyl substituted benzo[1,2-b:4,5-b′]dithiophene: Synthesis and photovoltaic applications

A new donor–acceptor conjugated polymer (PBDTPO-FBT), which consists of a fluorinated benzothiadiazole (FBT) electron-acceptor unit and an electron-donor segment of alkoxylphenyl substituted benzo[1,2-b:4,5-b′]dithiophene (BDTPO), was synthesized according to the Stille cross-coupling reaction. The resulting copolymer was characterized by TGA, GPC, UV–vis absorption spectroscopy and cyclic voltammetry measurements. PBDTPO-FBT possesses good thermal stability with 5% weight loss temperature of 410°C and shows broad absorption at 300–800nm with an optical bandgap of 1.53eV. Cyclic voltammetry measurement exhibits HOMO and LUMO energy levels of −5.43eV and −3.72eV, respectively. The hole mobility of PBDTPO-FBT:PC71BM (1:1, w/w) reaches up to 3.8×10−3cm2/V/s by the space-charge-limited current (SCLC) method. By using 3% 1,8-diiodooctane (DIO) as the solvent additive, the polymer solar cell with the configuration of ITO/PEDOT:PSS/PBDTPO-FBT:PC71BM (1:1, w/w)/Ca/Al demonstrates a power conversion efficiency of 2.70% with Voc=0.70V, Jsc=7.23mA/cm2 and FF=47.08%, under the illumination of AM 1.5G, 100mW/cm2.

Synthesis of Thiophene 1,1-Dioxides and Tuning Their Optoelectronic Properties

A 2,5-bis(tributylstannyl)thiophene 1,1-dioxide was prepared from 2,5-bis(trimethylsilyl)thiophene 1,1-dioxide, bis(tributyltin) oxide, and tetrabutylammonium fluoride (TBAF). The 2,5-bis(tributylstannyl)thiophene 1,1-dioxide and a 2,5-diiodothiophene 1,1-dioxide were utilized in a series of Stille cross-coupling reactions to afford thiophene 1,1-dioxides with either electron-donating or electron-withdrawing substituents. Electron-withdrawing groups greatly facilitate the reduction of these sulfone heterocycles, and -C6H4-p-NO2 substituents produce a 510 mV shift as compared to a thiophene 1,1-dioxide with two phenyl groups.

Effect of spacer insertion in a commonly used dithienosilole/benzothiadiazole-based low band gap copolymer for polymer solar cells

Dithienosilole-benzothiadiazole based low bandgap copolymers remain promising material for organic photovoltaics. A new copolymer, poly[(4,4′-dioctyldithieno[3,2-b:2′,3′-d]silole-2,6-diyl)-alt-{4,7-bis[2-(3-hexyl)thienyl]-2,1,3-benzothiadiazole-5,5′-diyl}] (PDTSDTBT) was designed by introducing a thiophene spacer bearing a hexyl chain at β-position in the main backbone and compared to its analog poly[(4,4′-dioctyldithieno[3,2-b:2′,3′-d]silole-2,6-diyl)-alt-(2,1,3-benzothiadiazole-4,7-diyl)] (PDTSBT). In PDTSDTBT, linear alkyl chains on silicon were chosen due to facile and cheap access and the inserted 3-hexylthiophene units were chosen to increase solubility and molar mass, a weak point with PDTSBT. The two parameters are important to optimize photovoltaic performances. To compare characteristics, PDTSDTBT of molar masses greater than, and equal to a sample of PDTSBT, were prepared. Pd-catalyzed Stille cross-coupling reactions in a micro-wave reactor to promote an efficient copolymerisations. A strong absorption ranging from 370nm to 800nm and a good thermal stability were observed. PDTSDTBT showed better solubility and higher degree of crystallinity. Facile synthesis of high molar masses meant that higher efficiencies, around 40% greater, could be obtained with PDTSDTBT. The polymer was demonstrated to be susceptible to improvement through the use of device-additives. For example, under initial optimisations using PDTSDTBT:PC60BM blend at a ratio of 1:1 delivered a power conversion efficiency of 2.13% with JSC=7.73 (mA/cm2), under AM 1.5 (100mW/cm2) illumination.

Novel multicolored electrochromic polymers containing phenanthrene-9,10-quinone and thiophene derivatives moieties

Two novel monomers 2,7-bis(3-ethylthiophen-2-yl)-9,10-phenanthrenequinone (ETPQ) and 2,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9,10-phenanthrenequinone (DDPQ) were successfully synthesized via Stille cross coupling reaction. Meanwhile, the corresponding polymers PETPQ and PDDPQ were synthesized electrochemically and characterized carefully. Both polymer films displayed multi-colored electrochromism. The PETPQ film showed a yellow color at neutral state, and with the increase of the applied potential, its color switched from yellowish green to green, and then light blue, finally a blue color in the oxidized state was observed. The color of the PDDPQ film was red in its neutral state, and turned to blue in the oxidized state, in intermediate states, violet red and purple colors were observed. Moreover, the parameters (coloration efficiency, optical contrast and response time) of the two interesting polymers were all reasonable and satisfactory. The dual-type electrochromic device based on PETPQ film (or PDDPQ film) and PEDOT film was constructed and characterized as well. Both of them revealed excellent properties.

N,N-Dimethylformamide-stabilized palladium nanoclusters as catalyst for Migita–Kosugi–Stille cross-coupling reactions

N,N-Dimethylformamide-stabilized palladium nanoclusters showed high catalytic activity for Migita–Kosugi–Stille cross-coupling reactions. The present cross-coupling reaction proceeded efficiently using very small Pd catalyst loadings under ligandless, and even an open air, conditions. The reactions proceeded smoothly in good yields and with high turnover numbers of up to 3.5 × 104.

Synthesis, size-dependent optoelectronic and charge transport properties of thieno(bis)imide end-substituted molecular semiconductors

The synthesis of two new thieno(bis)imide (TBI, N) end functionalized oligothiophene semiconductors is reported. In particular, trimer (NT3N) and pentamer (NT5N) have been synthesized and characterized. Two different synthetic approaches for their preparation were tested and compared namely conventional Stille cross coupling and direct arylation reaction via C–H activation. Theoretical calculations, optical and electrochemical characterization allowed us to assess the role of the π-conjugation extent, i.e., of the oligomer size on the optoelectronic properties of these materials. In both TBI ended compounds, due to the strong localization of the LUMO orbital on the TBI unit, the LUMO energy is almost insensitive to the oligomer size, this being crucial for the fine-tailoring of the energy and the distribution of the frontier orbitals. Surprisingly, despite its short size and contrarily to comparable TBI-free analogues, NT3N shows electron charge transport with mobility up to μN=10−4cm2V−1s−1, while increasing the oligomer size to NT5N promotes ambipolar behavior and electroluminescence properties with mobility up to μN=0.14cm2V−1s−1 and to μP=10−5cm2V−1s−1.

On the Configurational Stability of Chiral Heteroatom-Substituted [D1]Methylpalladium Complexes as Intermediates of Stille and Suzuki-Miyaura Cross-Coupling Reactions.

Enantiomerically pure (S)-tributylstannyl[D1]methanol and (R)- and (S)-tributylstannyl[D1]methyl benzoates were Stille-coupled with bromobenzene and benzoyl chloride in 1,4-dioxane and toluene using [(Ph3P)4Pd] or [(Ph3P)2PdCl2] either alone or in combination with CuCN as cocatalyst at temperatures up to 80 °C. The products were found to be enantiomerically pure. (R)- and (S)-N-(tributylstannyl[D1]methyl)phthalimides gave enantiomerically pure products with benzoyl chloride, but with bromobenzene protected phenyl[D1]methylamines gave products of only 52–69 % ee depending on the solvent used. Tributyl(thio[D1]methyl)stannanes could not be Stille-coupled with benzoyl chloride or with bromobenzene. Similarly, dimethyl phenyl[D1]methylboronate underwent a Suzuki–Miyaura coupling with bromobenzene to give phenyl[D1]methylsilane with 99 % ee. All couplings followed a retentive course and, except in one case, the intermediate [XCHDPdLn] complexes were found to be microscopically configurationally stable.

Synthesis and photovolatic properties of new poly(quarterselenophene) and poly(quarterselenophene-alt-quarterthiophene)s

Poly [3,3‴-didodecylquaterselenophene] (PQS) and poly[3,3‴-didodecylquaterselenophene-alt-didodecylquaterthiophene] (PQSQT), have been synthesized by using a Stille cross-coupling reaction. The weight-averaged molecular weights (Mw) of PQS and PQSQT were found to be 18,900Da and 22,300Da with polydispersity indices of 1.71 and 1.99, respectively. Photophysical measurements found the low bandgaps of 1.73eV for PQS and 1.86eV for PQSQT. The field-effect mobilities of PQS and PQSQT were determined to be 6.0×10−3 and 0.05cm2/Vs, respectively. The influence of the selenium and sulfur atoms in the polymer backbones were investigated with regard to device performances. The polymers were combined with the PC71BM ([6,6]-phenyl C71-butyric acid methyl ester) acceptor to fabricate bulk heterojunction solar cells with power conversion efficiencies of 0.73–2.37% under AM 1.5G (100mW/cm2) conditions.

Synthesis and biological activity of benzo-fused 7-deazaadenosine analogues. 5- and 6-substituted 4-amino- or 4-alkylpyrimido[4,5-b]indole ribonucleosides

Two series of new 4-aminopyrimido[4,5-b]indole ribonucleosides bearing phenyl or hetaryl group at position 5 or 6 have been prepared by Suzuki or Stille cross-coupling reactions employing X-Phos ligand with (het)arylboronic acids or stannanes. A series of 4-substituted nucleosides has been also prepared by Pd-catalyzed cross-couplings or nucleophilic substitution. Some of these compounds displayed moderate antiviral activities against HCV and dengue viruses.

Synthesis of donor–acceptor type new organosilicon polymers and their applications to dye-sensitized solar cells

Donor–acceptor type new organosilicon polymers that consisted of bithiophene unit as the donor and benzochalcogenadiazole or pyridine as the acceptor were synthesized by the Stille cross coupling reactions of bis(iodothienyl)benzochalcogenadiazoles or bis(bromothienyl)pyridine with 1,2-bis(trimethylstannylthienyl)disilane. The photoreactions of these polymers with TiO2 electrodes led to the polymer-modified electrodes by the formation of Si–O–Ti linkages. The pyridine-containing polymer pT4Py could be attached to the TiO2 surface also under the dark conditions by N–Ti coordination. The polymer-modified TiO2 were applied to dye sensitized solar cells and the highest power conversion efficiency of 0.40% was obtained with the TiO2 electrode photochemically-modified by pT4Py.

ChemInform Abstract: Halogenated Quinolines as Substrates for the Palladium‐Catalyzed Cross‐Coupling Reactions to Afford Substituted Quinolines.

AbstractReview: 85 refs.

Stereoretentive Pd-catalysed Stille cross-coupling reactions of secondary alkyl azastannatranes and aryl halides

The development of transition metal-catalysed cross-coupling reactions has greatly influenced the manner in which the synthesis of complex organic molecules is approached. A wide variety of methods are now available for the formation of C(sp(2))-C(sp(2)) bonds, and more recent work has focused on the use of C(sp(3)) electrophiles and nucleophiles. The use of secondary and tertiary alkyl nucleophiles in cross-coupling reactions remains a challenge because of the propensity of these alkyl groups to isomerize under the reaction conditions. Here, we report the development of a general Pd-catalysed process for the stereoretentive cross-coupling of secondary alkyl azastannatrane nucleophiles with aryl chlorides, bromides, iodides and triflates. Coupling partners with a wide range of electronic characteristics are well tolerated. The reaction occurs with minimal isomerization of the secondary alkyltin nucleophile, and with retention of absolute configuration. This process constitutes the first general method to use secondary alkyltin reagents in cross-coupling reactions.

Solvent free hydrostannation and Stille reactions using ionic liquid supported organotin reagents

Hydrostannation reactions were performed cleanly using ionic liquid supported organotin reagents. These green reducing agents were used both under free radical and palladium-catalyzed conditions. One of the new ionic liquid supported organotin reagents so obtained was evaluated successfully in Stille cross-coupling reactions to give aryl-substituted allylic alcohols in solvent free conditions.

Modulation of electronic properties of π-conjugated copolymers derived from naphtho[1,2-b:5,6-b′]dithiophene donor unit: A structure-property relationship study

A set of three donor-acceptor conjugated (D-A) copolymers were designed and synthesized via Stille cross-coupling reactions with the aim of modulating the optical and electronic properties of a newly emerged naphtho[1,2-b:5,6-b′]dithiophene donor unit for polymer solar cell (PSCs) applications. The PTNDTT-BT, PTNDTT-BTz, and PTNDTT-DPP polymers incorporated naphtho[1,2-b:5,6-b′]dithiophene (NDT) as the donor and 2,2′-bithiazole (BTz), benzo[1,2,5]thiadiazole (BT), and pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP), as the acceptor units. A number of experimental techniques such as differential scanning calorimetry, thermogravimetry, UV–vis absorption spectroscopy, cyclic voltammetry, X-ray diffraction, and atomic force microscopy were used to determine the thermal, optical, electrochemical, and morphological properties of the copolymers. By introducing acceptors of varying electron withdrawing strengths, the optical band gaps of these copolymers were effectively tuned between 1.58 and 1.9 eV and their HOMO and LUMO energy levels were varied between −5.14 to −5.26 eV and −3.13 to −3.5 eV, respectively. The spin-coated polymer thin film exhibited p-channel field-effect transistor properties with hole mobilities of 2.73 × 10−3 to 7.9 × 10−5 cm2 V−1 s−1. Initial bulk-heterojunction PSCs fabricated using the copolymers as electron donor materials and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) as the acceptor resulted in power conversion efficiencies in the range of 0.67–1.67%. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2948–2958

Efficient Stille Cross-coupling Reaction Catalysed by the Pd(OAc)2/orotic Acid Catalytic System

An efficient Pd(OAc)2/orotic acid catalytic system has been developed for the Stille cross-coupling reaction. In the presence of Pd(OAc)2 and orotic acid, various halides including aryl iodides, aryl bromides, vinyl bromides, and aryl chlorides were coupled efficiently with aryl- and vinyltin compounds to afford the corresponding biaryls and stilbenes. The high catalytic efficacy of Pd(OAc)2/orotic acid has also been demonstrated.

Synthetic Aspects and Electro-Optical Properties of Fluorinated Arylenevinylenes for Luminescence and Photovoltaics

In this review, the main synthetic aspects and properties of fluorinated arylenevinylene compounds, both oligomers and polymers, are summarized and analyzed. Starting from vinyl organotin derivatives and aryl halides, the Stille cross-coupling reaction has been successfully applied as a versatile synthetic protocol to prepare a wide series of π-conjugated compounds, selectively fluorinated on the aromatic and/or vinylene units. The impact of fluoro-functionalization on properties, the solid state organization and intermolecular interactions of the synthesized compounds are discussed, also in comparison with the non-fluorinated counterparts. Luminescent and photovoltaic applications are also discussed, highlighting the role of fluorine on the performance of devices.

Synthesis and Photovoltaic Performance of Pyrazinoquinoxaline Containing Conjugated Thiophene-Based Dendrimers and Polymers

Pyrazinoquinoxaline-based building blocks were incorporated into both π-conjugated dendrimers and polymers. The dendrimers were synthesized using a convergent/divergent approach whereas the donor/acceptor copolymers were synthesized via Stille cross-coupling reactions. The structurally defined dendrimers and the π-conjugated polymers were investigated with respect to their optical and electronic properties as well as their performance in photovoltaic devices. Because of the presence of the electron-deficient pyrazinoquinoxaline moiety, the absorption spectra of the materials under investigation were red-shifted with respect to the all thiophene-containing materials. Power conversion efficiencies up to 1.7 and 0.8% were obtained from blends of second-generation dendrimers and polymers with PC71BM, respectively.

Synthesis of indolo[3,2-b]carbazole-based random copolymers for polymer solar cell applications

In addition to preparing two indolocarbazole-based random copolymers (named as r-PICTBT1 and r-PICTBT2), this work investigated their feasibility for bulk heterojunction polymer solar cells (PSCs). These copolymers consisted of commercially available 3,9-dibromo-5,11-dioctyl-5,11-dihydroindole[3,2-b]carbazole, 2,5-bis(trimethylstannyl) thiophene and dibromobenzo[c][1,2,5]thiadiazole by varying the feed in ratios via Stille cross-coupling reactions. The photophysical and electrochemical properties of the resulting copolymers could be fine-modulated easily by adjusting the feed ratios of monomers. Both copolymers in the thin film state exhibited two obvious peaks and a vibronic shoulder in the absorption spectra. Electrochemical experiments indicated that the highest occupied molecular orbital energy levels were −4.95, −5.00eV; meanwhile, the lowest unoccupied molecular orbital energy levels were −3.38, −3.54eV for r-PICTBT1 and r-PICTBT2, respectively. Bulk heterojunction PSCs composed of an electron-donor copolymer blended with an electron acceptor [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) or [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) at a weight ratio of 1:1 or 1:3 were investigated. Moreover, the r-PICTBT2/PC71BM-based (w/w=1:1) PSC performed the best with an open-circuit voltage of 0.54V, short-circuit current of 6.83mA/cm2, fill factor of 0.44, and power conversion efficiency of 1.63%.

Anchoring of Palladium onto Surface of Porous Metal–Organic Framework through Post-Synthesis Modification and Studies on Suzuki and Stille Coupling Reactions under Heterogeneous Condition

An ecofriendly solid catalyst has been synthesized by anchoring palladium(II) into post synthetically modified metal organic framework IRMOF-3. The pore of IRMOF-3 was first modified with pyridine-2-aldehyde. The amine group of IRMOF-3 upon condensation with pyridine-2-aldehyde afforded a bidentate Schiff base moiety in the porous matrix. The Schiff base moieties were used to anchor palladium(II) ions. The prepared catalyst has been characterized by UV-vis, IR spectroscopy, X-ray powder diffraction, and nitrogen sorption measurements. Framework structure of the catalyst is not being destroyed in the multistep synthesis procedure as evidenced in X-ray powder diffraction studies. The catalyst has shown high activity toward the Suzuki and Stille cross-coupling reaction in 20% H2O/EtOH and EtOH medium, respectively, at 80 °C. The immobilized complex did not leach or decompose during the catalytic reactions, showing practical advantages over the homogeneous catalysis.