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Copper‐Polymer Nanocomposite Catalyst for Synthesis of 1,4‐Diphenylbutadiyne‐1,3
Abstract
A new catalyst for cross-coupling synthesis of 1,4-diphenylbutadiyne-1,3 was prepared by thermolysis of copper(II) poly-5-vinyltetrazolate. It presents heterogeneous catalyst, in which copper nanoparticles are supported on polymeric matrix surface. The catalyst is recovered, recycled, and shows high catalytic activity in cross-coupling synthesis of 1,4-diphenylbutadiyne-1,3. The reaction proceeds in aerobic conditions at room temperature in the presence of pyridine.
... Thus, as reported by Zuraev and coworkers, Cu(0) NPs supported on polymer matrixes exhibit high stability of the particles and protection against oxidation, despite their inherent sensitivity to oxygen and water. 23 In addition, the nitrogenated matrix prepared by thermolysis of a copper(II) poly-5-vinyltetrazolate polymer enhanced mass transfer of the substrate during the reaction, resulting in high catalytic activity. PXRD (Powder X-Ray Diffraction) analysis of the catalytic material revealed only the presence of Cu(0) nanocrystalline phases with 30 nm average diameter size; however, the authors did not report XPS data, which could take into account amorphous copper phases. ...
Copper-based nanocatalysts have seen great interest for use in synthetic applications since the early 20th century, as evidenced by the exponential number of contributions reported (since 2000, more than 48 000 works published out of about 81 300 since 1900; results from SciFinder using "copper nanocatalysts in organic synthesis" as keywords). These huge efforts are mainly based on two key aspects: (i) copper is an Earth-abundant metal with low toxicity, leading to inexpensive and eco-friendly catalytic materials; and (ii) copper can stabilize different oxidation states (0 to +3) for molecular and nanoparticle-based systems, which promotes different types of metal-reagent interactions. This chemical versatility allows different pathways, involving radical or ionic copper-based intermediates. Thus, copper-based nanoparticles have become convenient catalysts, in particular for couplings (both homo- and hetero-couplings), transformations that are involved in a remarkable number of processes affording organic compounds, which find interest in different fields (medicinal chemistry, natural products, drugs, materials, etc.). Clearly, this richness in reactivity makes understanding the mechanisms more complex. The present review focuses on the analysis of reported contributions using monometallic copper-based nanoparticles as catalytic precursors applied in coupling reactions, paying attention to those shedding light on the reaction mechanism.
... The product of thermolysis of palladium(II) poly-5-vinyltetrazolate (hereinafter referred to as Pd-Pol) was used as a catalyst for these reactions. The palladium(II) poly-5-vinyltetrazolate was obtained from poly-5-vinyltetrazole, synthesized by polymer-analogous reaction from polyacrylonitrile [13] and palladium(II) chloride (Scheme 3) by the method described in our previous works [14][15] for the synthesis of copper (II) poly-5-vinyltetrazolate. ...
A new catalyst for green Suzuki–Miyaura cross-coupling and Mott-Schottky nitrobenzene reduction processes was prepared by thermolysis of palladium (II) poly-5-vinyltetrazolate. Heterogeneous catalyst includes Pd-nanoparticles supported on polymeric matrix. It presents recoverable and recyclable catalyst and the catalyzed reactions proceed in aqueous media at room temperature in aerobic conditions.
... Классическим методом синтеза производных 1,2,3-триазола является катализируемая солями меди(I) реакция Хьюзгеновского [3+2]-циклоприсоединения азидов к терминальным алкинам [5]. Недавно нами показано, что эффективным катализатором этой реакции является продукт термического разложения поли-5-винилтетразолата меди, представляющий собой полимерную рентгеноаморфную матрицу с инкорпорированными наночастицами меди [6]. С использованием этого нового катализатора при комнатной температуре в водной среде с высоким выходом получен ряд 1,4-и 1,4,5-заме щенных-1Н-1,2,3-триазолов (рис. 1) [7], исследованию антибактериальной активности которых в отношении патогенного штамма Staphylococcus aureus, выделенного от пациента 1 , посвящена настоящая работа. ...
A number of 1,4- and 1,4,5-triazoles have been synthesized using a modified catalytic system for the Huisgen [3+2] cycloaddition reaction. The bactericidal activity of the synthesized compounds has been studied. The synthesized derivatives of 1H-1,2,3-triazoles have demonstrated higher antibacterial activities in relation to the pathogen Staphylococcus aureus strain which can be comparable with the clinically used antibiotic “Cefotaxime”.
An inexpensive, simple, and greener catalytic system with lower toxicity using CuFe 2 O 4 nanoparticles in the presence of piperidine and dry toluene as a solvent has been reported for the synthesis of 1,4‐diphenylbutadiyne‐1,3, via C−H activated aerobic C sp −C sp homocoupling. This protocol provides 66 % of yield at the gram‐scale level making it appropriate for production at a larger scale. The catalyst shows reusability for up to five cycles without losing any significant catalytic activity.
By the strategy of replacing the H2O ligands in the “paddle wheel” shaped copper dimer Cu2(OAc)4(H2O)2 with polyoxometalate (POM) [H2W12O40]⁶⁻ {W12O40} pro-ligands, a novel nano porous 2D network {[Cu2(OAc)4]2(W12O40)}n was obtained. The POM - copper centered redox reactions and stability of the compound were studied by cyclic voltammetry. Furthermore, the compound was found to be a super-efficient homogeneous catalyst (almost 100% conversion) in homo-coupling of terminal alkynes compared with its components and physical mixture under mild conditions with low amounts. The in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) results clearly show the changes of alkyne substances in the catalytic process and the X-ray photoelectron spectroscopy (XPS) results reveal the electron transfer from {W12O40} to Cu(ii) to promote the C-H activation step during the homo-coupling of terminal alkynes. The synergistic Cu(ii)-POM catalytic mechanism was proposed.
Herein, we report the synthesis of nickel-layered double hydroxide amalgamated to Y-zeolite (NiLDH@YZ) hybrids and evaluation of the synergistic effect of various NiLDH@YZ catalysts and mechanochemical agitation on Glaser homocoupling reactions. Nitrogen adsorption-desorption experiments were carried out to estimate the surface area and porosity of NiLDH@YZ hybrids. The basicity and acidity of these hybrids were determined by CO2-TPD and NH3-TPD experiments respectively and this portrayed good acid-base bifunctional feature of the catalysts. The NiLDH@YZ catalyzed mechanochemical Glaser coupling reaction achieved best yield of 83% for 0.5NiLDH@0.5YZ hybrid after 60 mins of agitation, which revealed the highest acid-base bifunctional feature compared to all the investigated catalysts. The developed catalyst has proven itself as a robust and effective candidate that can be successfully employed up to four catalytic cycles without significant loss in catalytic activity, under optimized reaction conditions. This work demonstrated a new strategy for CC bond formation enabled by the synergy between mechanochemistry and heterogeneous catalysis.
Supported catalysts have attracted extensive attention due to their excellent catalytic performance and reliability in heterogeneous catalysis. In this work, we report a general synthesis strategy that achieves the self‐coupling reaction of acetylene derivatives to 1,3‐diyne efficiently under conditions of copper catalyst impregnated on the precursor formed by acetone and urea. The experiments were performed by screening the base, solvent, temperature, and so forth to determine the optimum reaction conditions and then characterization and analysis of the catalyst. The results demonstrate that the Cu/CuO@CN(8) exhibits extraordinary reactivity to the self‐coupling reaction and achieves a high turnover frequency (TOF = 96.8). Typically, the conversion of phenylacetylene reaches 99.9% under the optimal reaction conditions of NaOH (2 mmol) and tert‐butanol (2 ml) and O2 (1 atm) at 60°C for 1 h. Nevertheless, it is worth noting that Cu/CuO@CN(8) has a large specific surface area (626.07 m² g⁻¹) and low metal loading (3.3%) measured by Brunauer Emmett–Teller (BET) and ICP‐OES, respectively. Simultaneously, kinetics and mechanism are also discussed and analyzed, and the thermodynamic energy value is calculated as 22.74 kJ mol⁻¹. Besides, the optimum catalyst can be reused five times under optimal conditions without a significant decrease in reactivity.
The structure of copper(II) poly-5-vinyltetrazolate and the products of its thermolysis has been studied by means of density functional theory and infrared spectroscopy. Copper(II) poly-5-vinyltetrazolate has been obtained and subsequently subjected to thermolysis. Infrared spectra of copper(II) poly-5-vinyltetrazolate and the products of its thermolysis have been recorded. The possible ways of coordination of copper(II) ions with tetrazole-containing ligands were established by analyzing the calculated molecular electrostatic potential distribution and comparing the calculated IR-spectra of the model structures to the experimental ones. It has been shown that the best agreement between the calculated and experimental data is observed for the model with three-coordinated copper(II) ions, which includes both the tetrazole-containing ligands coordinating two copper(II) ions through N(1)- and N(3)-atoms of the tetrazole ring, and the tetrazolecontaining ligands coordinating one copper(II) ion through either the N(2)- or the N(3)-atom. Recently we have shown that the product of thermolysis of copper(II) poly-5-vinyltetrazolate exhibits high catalytic activity in homocoupling of phenylacetylene and Huisgen [3 + 2]-cycloaddition. To establish the structure of the products of thermolysis of copper(II) poly-5-vinyltetrazolate, seven possible products have been proposed based on the analysis of the structure of copper(II) poly-5-vinyltetrazolate and the experimental IR-spectrum. IR-spectra of all proposed products have been calculated and the results of the calculations have been compared with the experimental IR-spectrum of copper(II) poly-5-vinyltetrazolate thermolysis product. It has been shown that the main product of thermolysis is cis-polycyanoacetylene.
Nature abounds with intricate composite architectures composed of hard and soft materials synergistically intertwined to provide both useful functionality and mechanical integrity. Recent synthetic efforts to mimic such natural designs have focused on nanocomposites, prepared mainly by slow procedures like monomer or polymer infiltration of inorganic nanostructures or sequential deposition. Here we report the self-assembly of conjugated polymer/silica nanocomposite films with hexagonal, cubic or lamellar mesoscopic order using polymerizable amphiphilic diacetylene molecules as both structure-directing agents and monomers. The self-assembly procedure is rapid and incorporates the organic monomers uniformly within a highly ordered, inorganic environment. Polymerization results in polydiacetylene/silica nanocomposites that are optically transparent and mechanically robust. Compared to ordered diacetylene-containing films prepared as Langmuir monolayers or by Langmuir-Blodgett deposition, the nanostructured inorganic host alters the diacetylene polymerization behaviour, and the resulting nanocomposite exhibits unusual chromatic changes in response to thermal, mechanical and chemical stimuli. The inorganic framework serves to protect, stabilize, and orient the polymer, and to mediate its function. The nanocomposite architecture also provides sufficient mechanical integrity to enable integration into devices and microsystems.
Sticklike silicate materials containing aligned nanodomains of conjugated polymers were synthesized by sol-gel-based in situ polymerization of ammonium ion terminated diacetylenic surfactant monomers. Upon photoexcitation at 450 nm, the silicate microsticks emit a yellowish green luminescence centered at 550 nm.
Sub-nanometer (d = 0.8 ± 0.2 nm) gold particles homogeneously dispersed on amino-functionalized silica catalyze Glaser-type alkyne coupling, providing corresponding 1,3-diynes under mild conditions. Readily available λ3-iodane PhI(OAc)2 is used as the oxidant and 1,10-phenanthroline as additive. Ten symmetrical 1,3-diynes and three products of heterocoupling contain- ing various functionalities are isolated in high yields. The catalyst can be recycled at least five times giving consistently high isolat- ed yields and maintaining the size and distribution of gold clusters. This unique combination of stable sub-nanometer gold clusters and hypervalent iodine thus paves a hitherto unexplored avenue in organic synthesis employing heterogeneous gold catalysis.
The formation of oxa-tricyclic core of platensimycin was attempted. A key precursor of radical cyclization, cyclic anhydride, was readily prepared from diethylmalonate in 6 steps in good yields. Obtained precursor, diallylmethylene δ-lactone, underwent radical cascade reaction triggered by thiyl radical, giving bicyclic ether in a stereoselective manner. A radical cascade reaction triggered by thiyl radical; an approach toward synthesis of tricyclic structure of platensimycinAll authorsAkio Kamimuraa* & Yusuke KawakamiaDOI:http://dx.doi.org/10.1080/10426507.2015.1064922Published online:06 October 2015PowerPoint slideOriginal jpg (100.00KB)Display full size
Application of a piperidine-appended dimethyl-imidazolium-NTf2 ionic liquid as dual solvent and base in the Sonogashira cross-coupling reaction of aryl-iodides with terminal acetylenes under mild conditions has been demonstrated. The method employs PdCl2(PPh3)2 without copper and external base. It is applicable to the synthesis of SF5-substituted diaryl- and aryl-alkyl-acetylenes, and can also be utilized for efficient homo-coupling of terminal acetylenes under aerobic conditions. The potential for recycling and reuse of this designer-IL offers an added advantage.
The gold-catalyzed oxidative cross-coupling of alkynes to unsymmetrical diynes has been achieved for the first time. N,N-ligand (1,10-Phen) and PhI(OAc)2 were identified as crucial factors to promote this transformation, giving the desired cross-coupled conjugated diynes in excellent hetereo-selectivity (>10:1), good to excellent yields and large substrate tolerability.
A practical oxidative homo- and heterocoupling of terminal alkynes was achieved in CH2Cl2 at 25 °C by using a 3-(2-aminoethylamino)propyl-functionalized MCM-41-immobilized copper(I) complex (MCM-41–2N-CuI, 1 mol-%) as the catalyst, piperidine (0.1 or 3 equiv.) as the base, and air as the environmentally friendly co-oxidant, yielding a variety of symmetrical and unsymmetrical 1,4-disubstituted 1,3-diynes in good to excellent yields. This heterogeneous copper catalyst showed a higher catalytic activity than CuI and can be recovered and recycled by a simple filtration of the reaction mixture and used for at least 10 consecutive runs without any decrease in activity.
Au(I)/Au(III) catalytic cycles are catalytically competent to perform the oxidative coupling of alkynes in the homogeneous phase at room temperature and without any protecting atmosphere. Selectfluor as oxidant, wet acetonitrile as solvent, and sodium carbonate as base are the reagents of choice. Both aromatic and alkyl alkynes can be coupled, and mechanistic studies reveal that at least two gold species having different oxidation states are implicated in the key step of the coupling.
The supported copper hydroxide catalyst on manganese oxide-based octahedral molecular sieve OMS-2 (Cu(OH)x/OMS-2) was designed on the basis of the concept of coupled electron transfer. OMS-2 could act as not only a support for copper hydroxide species but also an electron-transfer mediator (cocatalyst) to generate a rapid electron-transfer path from an alkyne to dioxygen. As a result, Cu(OH)x/OMS-2 showed high catalytic performance (TOF = 540 h–1, total TON = 666, and selectivity >99%) and long life (13 times reuse) for aerobic oxidative alkyne homocoupling.
The homocoupling reaction of alkynes was carried out in the presence of 10 mol% AuCl3 using I2 as oxidant to generate 1,3-diynes products in high yield. The method is simple, safe and efficient. Both aryl and alkyl substituted alkynyl substrates reacted smoothly.
AuClPPh3 also showed comparable catalytic activity to this transformation under a nitrogen atmosphere.
Cu(II)-catalyzed coupling of polymer-bound ω-haloalkyn-l-ols to terminal alkynes proceeds in moderate yield to give unsymmetrical diynes upon hydrolytic removal from the polymer. Formation of the symmetrical homocoupled byproduct is suppressed relative to conventional Cadiot-Chodkiewicz conditions in homogeneous solution.
Cu–Mg–Al hydroxycarbonate, derived from Cu–Mg–Al hydrotalcite, affords yields of >80% for the heterogeneous coupling of phenylethyne to 1,4-diphenylbuta-1,3-diyne in the presence of sodium hydroxide and oxygen.
Total asymmetric synthesis of two components of Panax ginseng showing antitumor activity, i.e., (3R,9R,10R)- and (3S,9R,10R)-Panaxytriol and of both enantiomers of Falcarinol was accomplished. Due to the fact that the synthetic strategy was based on enantio-convergent biotransformations, the occurrence of any undesired stereoisomer was entirely avoided. The absolute configuration of naturally occurring Panaxytriol was confirmed to be (3R,9R,10R) on the basis of optical rotation values. It was shown that enzyme-triggered cascade reactions represent a valuable tool for the synthesis of natural products.
An inexpensive catalytic system, which used a readily available Fe(acac)3 and trace quantity of Cu(acac)2 as the co-catalyst and air as the oxidant for the homo-coupling of terminal alkynes, has been developed. The catalytic system could also apply to the cross-coupling reaction of two different terminal alkynes.
Thermal decomposition of poly-5-vinyltetrazole has been investigated by the methods of chemical and complex thermal analyses under isothermal and nonisothermal conditions, infrared spectroscopy and gas chromatography. Activation parameters of the decomposition process have been evaluated by various methods. The analysis of the obtained data leads to the conclusion that, depending on the conditions of the experiment, decomposition of polymer tetrazole cycles may proceed in two parallel ways: either destruction of the tetrazole rings with elimination of hydrogen azide, or their tautomeric isomerization into the respective azidoazomethine, from which a nitrogen molecule is then ‘chipped off’.
The first total synthesis of naturally occurring (-)-nitidon and its enantiomer is reported. The best of the routes investigated for preparation of these enantiomerically pure compounds involves a modification of the Cadiot-Chodkiewicz reaction and the Sharpless asymmetric epoxidation of an (E)-2-ene-4,6-diyn-1-ol as key steps and proceeds in five steps and 18% overall yield. Both enantiomers of nitidon and some related 6-(1,3-diyn-1-yl)-2H-pyran-2-ones have been found to exhibit significant cytotoxic activity against human cancer cell lines in vitro. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).
CuI-modified zeolites, especially CuI–USY, proved to be very efficient catalysts for the homocoupling of terminal alkynes. Such heterogeneous catalysts offer a very simple (no added ligand) and convenient synthesis of diynes, including carbohydrate derivatives. A strong influence of the zeolite pore size has been observed, high (quantitative) yields being obtained with zeolites having large internal cages. The role of zeolite acidic sites in the reaction has been pointed out. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Interaction of polyacrylonitrile with sodium azide and ammonium chloride leading to the formation of poly(5-vinyl tetrazole) has been studied in detail. The reaction is found to proceed to high conversion extents (up to 94–94.5%) and allows to obtain polymeric products with a wide range of poly(5-vinyl-tetrazole) content. Comparative studies of the structures and properties of the obtained polymers and 5-vinyl tetrazole homopolymer as well as copolymers of 5-vinyl tetrazole with acrylonitrile have been carried out using IR, 13C NMR and complex thermal analysis data.Die zur Bildung von Poly(5-vinyl tetrazol) führende Umsetzung von Polyacrylnitril mit Natriumazid und Ammoniumchlorid wurde untersucht. Die Reaktion geht bis zu hohen Umstzen (94,0–94,5%), dadurch können polymere Produkte mit Poly(5-vinyl tetrazol)-Gehalten in einem breiten Bereich erhalten werden. Durch IR- und 13C NMR-Spektroskopie und komplexe Thermoanalyse wurden vergleichende Untersuchungen über die Strukturen und Eigenschaften der hergestellten Polymeren und Homopolymeren des 5-Vinyltetrazols sowie Copolymeren des 5-Vinyltetrazols und Acrylnitrils durchgeführt.
A variety of mixed palladium(II) complexes bearing N-heterocyclic carbenes (NHCs) and triaryl- and trialkylphosphines [NHC(R2)]Pd(PR′3)I2 (R=Me, t-Bu, (R)-1-phenylethyl; R′=Ph, o-tolyl, cyclohexyl, t-Bu) have been prepared. Crystal structure details of trans-diiodo(1,3-di-tert-butylimidazolin-2-ylidene)(triphenylphosphino)palladium(II) are presented. The complexes were tested as catalysts in the Mizoroki–Heck, Suzuki–Miyaura and Stille reactions as well as in the dimerization of phenylacetylene. In catalytic studies of the Suzuki–Miyaura cross-coupling reaction, the performance of these novel complexes was compared to the results obtained by the corresponding bis(NHC) and bis(phosphine) complexes.
Reaction of benzene solutions of arylacetylenes with 1 equiv. of chloroacetone and 2 equiv. of Et3N, using a mixture of (PPh3)4 Pd and CuJ as catalyst, affords 1,4-diaryl-butadiynes in very good yields. Under similar reaction conditions aliphatic 1-alkynes yield mixtures of simmetrically disubstituted 1,4-dialkyl-1,3-butadiynes and of 3-alkyl-4-(1-alkynyl)-hexa-1,5-diyn-3-enes.
Terminal alkynes undergo self-coupling reactions in the presence of palladium bis(triphenyl phosphine) dichloride, copper(I) iodide iodine and diisopropyl amine to give the corresponding diynes in good yields.
Cited By (since 1996): 14, Export Date: 8 February 2011, Source: Scopus
For the first time, conditions have been found for the palladium-catalyzed desulfitative carbon-carbon cross-coupling of arenesulfonyl chlorides with aryl- and alkylacetylenes. Pd-2(dba)(3)/P(t-Bu)(3) and CuI provide the best catalyst for reactions in re-fluxing THF and in the presence of K2CO3.
The role of the supported Copper Hydroxide on Titanium Oxide as an efficient heterogeneous catalyst for the oxidative alkyne-alkyne homocoupling was analyzed. The catalytic activities for the homocoupling of ethynylbenzene to 1,4-diphenyl-1,3-butadiyne were compared with various catalysts in toluene under oxygen atmosphere. No homocoupling reaction proceeded with bulk copper oxides and hydroxide. The inductively coupled plasma atomic emission spectroscopy analysis revealed that no copper species was found in the filtrate. Therefore, the role of the copper hydroxide species is probably the abstraction of an alkyne hydrogen to form the alkynyl species. The supported copper hydroxide could act as an efficient heterogenous catalyst for the oxidative alkyne-alkyne homocoupling.
Four linear polyacetylenic compounds were synthesized. Pentadeca-6,8,10-triynoic acid 1 and octadeca-8,10,12-triynoic acid 2 were synthesized by using acetylene coupling reactions. The syntheses of (Z)-hexadec-11-en-7,9-diynoic acid 3 and (Z)-octadec-12-en-7,9-diynoic acid 4 by using vinylic telluride coupling reactions were accomplished.
A novel pathway for the homocoupling reaction has been achieved using a similar protocol as the cross-coupling reaction. Ethyl bromoacetate is chosen to initiate the coupling reaction through oxidative addition to a Pd(0) species, and an PdBr(enolate) intermediate is formed. This intermediate can undergo double transmetalation with an alkynyl copper reagent, and reductive elimination produces a variety of diynes in high yields.
[structure: see text] The tetraacetylenic compound, (S)-minquartynoic acid (1), is synthesized in seven linear steps and 17% overall yield from commercially available azelaic acid monomethyl ester. The key step is a one-pot three-component Cadiot-Chodkiewicz reaction to construct the tetrayne unit without using either a diyne or a triyne intermediate.
Bulky trialkylsilyl-protected alkynes such as triethylsilyl (TES), tert-butyldimethylsilyl (TBS), and triisopropylsilyl (TIPS) acetylenes underwent the Cadiot-Chodkiewicz cross-coupling reaction with different bromoalkynes to form a variety of synthetically useful unsymmetrical diynes in good yields. The diyne alcohol 10 was transformed regio- and stereoselectively into enynes by hydrotelluration, carbometalation, and reduction reactions.
[reaction: see text] There are conflicting reports in the literature concerning the absolute sterochemistry at C-3 of the common plant polyacetylene oxylipin (+)-falcarindiol. We have employed olefin cross-metathesis using Grubbs' second generation catalyst and ethylene gas to degrade falcarindiol to the symmetrical 1,9-decadiene-4,6-diyne-3,8-diol. The reaction is completely selective for net removal of the aliphatic side chain. Degradation of (+)-falcarindiol from Tetraplasandra hawaiiensis yields a meso product as shown by chiral HPLC. Hence, (+)-falcarindiol from this source has a (3R,8S)-configuration.
Conjugated polymer/silica nanocomposites with hexagonal, cubic, or lamellar mesoscopic order were synthesized by self-assembly using polymerizable amphiphilic diacetylene molecules as both structure-directing agents and monomers. The self-assembly procedure is rapid and incorporates the organic monomers uniformly within a highly ordered, inorganic environment. By tailoring the size of the oligo(ethylene glycol) headgroup of the diacetylene-containing surfactant, we varied the resulting self-assembled mesophases of the composite material. The nanostructured inorganic host altered the diacetylene polymerization behavior, and the resulting nanocomposites show unique thermo-, mechano-, and solvatochromic properties. Polymerization of the incorporated surfactants resulted in polydiacetylene (PDA)/silica nanocomposites that were optically transparent and mechanically robust. Molecular modeling and quantum calculations and (13)C spin-lattice relaxation times (T(1)) of the PDA/silica nanocomposites indicated that the surfactant monomers can be uniformly organized into precise spatial arrangements prior to polymerization. Nanoindentation and gas transport experiments showed that these nanocomposite films have increased hardness and reduced permeability as compared to pure PDA. Our work demonstrates polymerizable surfactant/silica self-assembly to be an efficient, general approach to the formation of nanostructured conjugated polymers. The nanostructured inorganic framework serves to protect, stabilize, and orient the polymer, mediate its performance, and provide sufficient mechanical and chemical stability to enable integration of conjugated polymers into devices and microsystems.
An efficient, room temperature procedure for the cross-coupling of a range of terminal alkynes, using standard Sonogashira cross-coupling conditions (Pd/Cu) is presented. At higher reaction temperatures, head-to-tail or head-to-head dimerisation affords 1,3- and 1,4-disubstituted enynes, respectively as minor products.
A total synthesis of (3R,9R,10R)-panaxytriol (1) was accomplished enantioselectively (40% overall yield; 30% for the longest sequence). A key step was a Cadiot-Chodkiewicz cross-coupling reaction on two fragments containing, in the aggregate, three unprotected hydroxyl groups. One fragment was synthesized by a highly enantioselective reduction of an enynone. The other arose from a highly enantioselective dihydroxylation of an allylic alcohol.
The conjugated entriyne natural product, (S)-(E)-15,16-dihydrominquartynoic acid (1), is synthesized in five linear steps and 30% overall yield from the known aldehyde 11. The key step is a one-pot in situ desilylation/Cadiot-Chodkiewicz coupling reaction affording the entriyne unit. The bromoalkyne 6 with an omega-carboxylic acid group was found to undergo a copper-catalyzed cross-coupling reaction producing the desired diyne intermediate 10, while the corresponding omega-ester bromoalkyne 14 failed to couple with triethylsilylacetylene under a variety of conditions.
An efficient method for palladium-catalyzed homocoupling reaction of terminal alkynes in the synthesis of symmetric diynes is presented. The results showed that both Pd(OAc)(2) and CuI played crucial roles in the reaction. In the presence of 2 mol % Pd(OAc)(2), 2 mol % CuI, 3 equiv of Dabco, and air, homocoupling of various terminal alkynes afforded the corresponding symmetrical diynes in moderate to excellent yields, whereas low yields were obtained without either Pd(OAc)(2) or CuI. Moreover, high TONs (turnover numbers; up to 940 000 for the reaction of phenylacetylene) for the homocoupling reaction were observed. Under similar reaction conditions, cross-coupling of 1-iodo-4-nitrobenzene with phenylacetylene was also carried out smoothly in quantitative yield. However, the presence of CuI disfavored the palladium-catalyzed Sonogashira cross-coupling reactions of the less active aryl iodides and bromides. In the presence of 0.01-2 mol % Pd(OAc)(2), a number of aryl iodides and bromides were coupled with terminal alkynes in good to excellent yields. It is noteworthy that this protocol employs mild, efficient, aerobic, copper-free, and ligand-free conditions.
[structures: see text] We have conducted key preliminary studies into the in vitro and in vivo cytotoxicity of panaxytriol. Through total synthesis, we prepared and evaluated several synthetic panaxytriol analogues, each of which exhibited enhanced cytotoxicity relative to the natural product. Consequently, we have begun to chart the first in vitro SAR map for the compound, which suggests that the C3 hydroxyl functionality is not critical for biological activity and that, in fact, engagement of the C9-C10 diol as an acetonide actually leads to notably enhanced cytotoxicity. Furthermore, through in vivo investigations, we demonstrated that panaxytriol and panaxytriol acetonide (12) moderately suppress tumor growth with little or no toxicity. Finally, preliminary in vitro evaluation of panaxytriol indicates that it possesses neurotrophic activity.
Efficient total syntheses of the sponge-derived hydrocarbon polyacetylenes callyberynes A-C have been achieved using metal-catalyzed cross-coupling reactions of highly unsaturated 1,3-diyne fragments as the key steps, namely: Cadiot-Chodkiewicz reaction under Alami's optimized conditions (sp-sp), sequential Sonogashira reaction of a cis,cis-divinyl dihalide (sp2-sp), and Kumada-Corriu reaction of an unactivated alkyl iodide (sp3-sp). This last approach constitutes the first application of a metal-catalyzed sp3-sp Kumada-Corriu cross-coupling reaction to the synthesis of a natural product.
In order to provide an authentic standard and to generate pure material for biological testing, an efficient synthetic route to 1 was developed. This represents the first total synthesis of a major bioactive diynone from E. pallida.
- Siemsen
- Jiang
- Aida
- Campbell
- I. D. Campbell
- G. Eglinton
- G. Eglinton
- A. R. Galbraith