Showing papers on "Acyclic diene metathesis published in 2015"
TL;DR: The method uses commercially available catalysts to achieve high-yielding, rapid, room-temperature metathesis of solid or liquid olefins on a multigram scale using either no or only a catalytic amount of a liquid.
Abstract: We describe the development of a mechanochemical approach for Ru-catalyzed olefin metathesis, including cross-metathesis and ring-closing metathesis. The method uses commercially available catalysts to achieve high-yielding, rapid, room-temperature metathesis of solid or liquid olefins on a multigram scale using either no or only a catalytic amount of a liquid.
117 citations
TL;DR: Interestingly, disubstituted cyclopropenes were found to present zero-order kinetics, indicating their rapid single addition and the rate-determining ring opening of the low-strain olefin.
Abstract: By judiciously modulating the ring strain and sterics, we developed a class of disubstituted cyclopropenes that selectively underwent single monomer addition in ring-opening metathesis but readily underwent alternating ring-opening metathesis polymerization with low-strain cyclic olefins in a living fashion. The substituents on cyclopropenes effectively inhibited homoaddition and prevented secondary metathesis on the polymer backbone. The resulting polymers had controllable molecular weights and end groups, very low dispersities, and high regularity in microstructure under optimized conditions. 1H and 13C NMR spectroscopy and MALDI-TOF MS showed a rigorously alternating sequence. Interestingly, disubstituted cyclopropenes were found to present zero-order kinetics, indicating their rapid single addition and the rate-determining ring opening of the low-strain olefin.
78 citations
TL;DR: These first neutral and cationic W-oxo-alkylidene-N-heterocyclic carbene (NHC) catalysts are reported, allowing for turnover numbers up to 10,000 in various olefin metathesis reactions including alkenes bearing nitrile, sec-amine, and thioether groups.
Abstract: The synthesis, structure, and olefin metathesis activity of the first neutral and cationic W-oxo-alkylidene-N-heterocyclic carbene (NHC) catalysts are reported. Neutral W-oxo-alkylidene-NHC catalysts can be prepared in up to 90% isolated yield. Depending on the ligands used, they possess either an octahedral (Oh) or trigonal bipyramidal ligand sphere. They can be activated with excess AlCl3 to form cationic olefin metathesis-active W-complexes; however, these readily convert into neutral chloro-complexes. Well-defined, stable cationic species can be prepared by stoichiometric substitution of one chloro ligand in the parent, neutral W-oxo-alkylidene-NHC complexes with Ag(MeCN)2B(ArF)4 or NaB(ArF)4; B(ArF)4 = B(3,5-(CF3)2-C6H3)4. They are highly active olefin metathesis catalysts, allowing for turnover numbers up to 10,000 in various olefin metathesis reactions including alkenes bearing nitrile, sec-amine, and thioether groups.
75 citations
TL;DR: A concise diastereo- and enantioselective route that furnishes the anti-proliferative natural product neopeltolide is now disclosed and Z-selective cross-metathesis reactions, facilitated by Mo and Ru complexes, have been employed in the stereoselectives synthesis of the acyclic dienyl moiety of the target molecule.
Abstract: Molybdenum-, tungsten-, and ruthenium-based complexes that control the stereochemical outcome of olefin metathesis reactions have been recently introduced. However, the complementary nature of these systems through their combined use in multistep complex molecule synthesis has not been illustrated. A concise diastereo- and enantioselective route that furnishes the anti-proliferative natural product neopeltolide is now disclosed. Catalytic transformations are employed to address every stereochemical issue. Among the featured processes are an enantioselective ring-opening/cross-metathesis promoted by a Mo monoaryloxide pyrrolide (MAP) complex and a macrocyclic ring-closing metathesis that affords a trisubstituted alkene and is catalyzed by a Mo bis(aryloxide) species. Furthermore, Z-selective cross-metathesis reactions, facilitated by Mo and Ru complexes, have been employed in the stereoselective synthesis of the acyclic dienyl moiety of the target molecule.
65 citations
TL;DR: Using the glucose derivatives isosorbide and glucarodilactone along with a castor oil derivative, 10-undecenoyl chloride, two monomers were synthesized as discussed by the authors.
Abstract: Using the glucose derivatives isosorbide and glucarodilactone along with a castor oil derivative, 10-undecenoyl chloride, two monomers were synthesized: glucarodilactone undecenoate (GDLU) and isosorbide undecenoate (IU). These monomers were polymerized via acyclic diene metathesis (ADMET) polymerization to yield two homopolymers, P(GDLU) and P(IU), and two copolymers, P1(GDLU-co-IU) and P2(GDLU-co-IU), of similar number-averaged molecular weight and relative composition (51 and 61 kDa, Đ = 1.8 and 1.4, 46:54 and 52:48 mol percent). Comparison of the physical properties and degradation behavior of these polymers revealed divergent characteristics arising from differences in the nature of the carbohydrate building blocks. P(IU) is more thermally stable and has a lower glass transition temperature (Td = 369 °C, Tg = −10 °C) than P(GDLU) (Td = 206 °C, Tg = 32 °C) and P1,2(GDLU-co-IU) (Td = 210 and 203 °C, Tg = 1 and 7 °C). While all of the polymers were stable in acidic and neutral aqueous conditions, the tw...
60 citations
TL;DR: In this paper, a Grubbs-Hoveyda type catalyst precursor for olefin metathesis containing a maleimide moiety in the backbone of the NHC ligand was covalently incorporated in the cavity of the β-barrel protein nitrobindin.
Abstract: A series of Grubbs–Hoveyda type catalyst precursors for olefin metathesis containing a maleimide moiety in the backbone of the NHC ligand was covalently incorporated in the cavity of the β-barrel protein nitrobindin. By using two protein mutants with different cavity sizes and choosing the suitable spacer length, an artificial metalloenzyme for olefin metathesis reactions in water in the absence of any organic cosolvents was obtained. High efficiencies reaching TON > 9000 in the ROMP of a water-soluble 7-oxanorbornene derivative and TON > 100 in ring-closing metathesis (RCM) of 4,4-bis(hydroxymethyl)-1,6-heptadiene in water under relatively mild conditions (pH 6, T = 25–40 °C) were observed.
60 citations
TL;DR: In this paper, the use of C-H activated ruthenium olefin metathesis catalyst compounds in Z-selective OLEF reactions, enantio-Z-Selective OleF reaction, and enantiotargetive OE reaction was discussed.
Abstract: This invention relates generally to C—H activated ruthenium olefin metathesis catalyst compounds which are stereogenic at the ruthenium center, to their preparation, and the use of such catalysts in the metathesis of olefins and olefin compounds. In particular, the invention relates to the use of C—H activated ruthenium olefin metathesis catalyst compounds in Z-selective olefin metathesis reactions, enantio-selective olefin metathesis reactions, and enantio-Z-selective olefin metathesis reactions. The invention has utility in the fields of catalysis, organic synthesis, polymer chemistry, and industrial and fine chemicals chemistry.
55 citations
TL;DR: T tandem ring-opening/ring-closing metathesis (RO/RCM) polymerization of monomers containing two cyclopentene moieties and postmodification via insertion polymerization and the concept of multiple olefin meetingathesis polymerization in which the dicyclopentenes and diacrylate monomers underwent all three ole FinTech transformations in one shot to produce A,B-alternating copolymer is demonstrated.
Abstract: We demonstrated tandem ring-opening/ring-closing metathesis (RO/RCM) polymerization of monomers containing two cyclopentene moieties and postmodification via insertion polymerization. In this system, well-defined polymers were efficiently formed by tandem cascade RO/RCM reaction pathway. Furthermore, these polymers could be transformed to new A,B-alternating copolymers via a sequential cross metathesis reaction with a diacrylate. Additionally, we demonstrated the concept of multiple olefin metathesis polymerization in which the dicyclopentene and diacrylate monomers underwent all three olefin metathesis transformations (ring-opening, ring-closing, and cross metathesis) in one shot to produce A,B-alternating copolymer.
51 citations
TL;DR: In this paper, the first study of low catalyst loading olefin metathesis reactions in air is reported, where TON values of up to 7000 were obtained using non-degassed solvents with commercially available precatalysts Caz-1, Hov-II, and Ind-II.
Abstract: The first study of low catalyst loading olefin metathesis reactions in air is reported. TON values of up to 7000 were obtained using nondegassed solvents with commercially available precatalysts Caz-1, Hov-II, and Ind-II. The simple experimental conditions allow olefin metathesis reactions to be carried out on the benchtop using technical grade solvents in air.
46 citations
TL;DR: In this article, a homogeneous olefin metathesis in water catalysed by a di-ammonium functionalised Ru-alkylidene complex is described.
35 citations
TL;DR: In this article, the authors summarized possible applications of olefin metathesis in rubber chemistry and technology and summarized three main research directives with valuable contributions to the synthesis, recycling, and characterization of elastomers.
Abstract: This article summarizes possible applications of olefin metathesis in rubber chemistry and technology. There are three main research directives with valuable contributions to the synthesis, recycling, and characterization of elastomers. First, ring opening metathesis polymerization as well as acyclic diene metathesis polycondensation yields polyalkenamers with cross-linkable double bonds, and thus can be used for the synthesis of defined rubbers serving as raw materials in rubber technology. Secondly, by cross metathesis reaction, natural rubber (and synthetic rubber) can be functionalized resulting in telechelic polymers or small molecule specialty chemicals. Thirdly, olefin metathesis offers the possibility of degrading the cross-linked rubber network into smaller soluble pieces, enabling different analytical possibilities such as characterization of cross-linking sites, determination of rubber, rubber additives and carbon black, and exploration of the rubber–metal adhesive interface. Additionally, this route can also be used for recycling of rubber products.
TL;DR: In this article, a novel biobased α,ω-diene bearing a thermally curable benzoxazine group is synthesized and polymerized via acyclic diene metathesis (ADMET) using Hoveyda-Grubbs second generation catalyst.
TL;DR: Iodide-containing nitro-Grela-type catalysts have been synthesized and applied to ring closing metathesis (RCM) and cross metatheses (CM) reactions and have exhibited improved efficiency in the transformation of sterically, non-demanding alkenes.
Abstract: Iodide-containing nitro-Grela-type catalysts have been synthesized and applied to ring closing metathesis (RCM) and cross metathesis (CM) reactions. These new catalysts have exhibited improved efficiency in the transformation of sterically, non-demanding alkenes. Additional steric hindrance in the vicinity of ruthenium related to the presence of iodides ensures enhanced catalyst stability. The benefits are most apparent under challenging conditions, such as very low reaction concentrations, protic solvents or with the occurrence of impurities.
TL;DR: The commercially available metathesis pre-catalyst M23 has been evaluated alongside new complex [RuCl2((3-phenyl)indenylidene)(PPh3)(SIPrOMe)] (1), which bears a para-methoxy-substituted N-heterocyclic carbene ligand as mentioned in this paper.
TL;DR: In this paper, the melting points of polyamides converge toward polyethylene, passing through a distinct melting point minimum observed around 110 °C for polyamide with ca. 35 amide groups per 1000 methylene units.
Abstract: Aliphatic polyamides with so far inaccessibly low amide contents were prepared by acyclic diene metathesis (ADMET) copolymerization of N-(undec-10-en-1-yl)undec-10-enamide (1) and undeca-1,10-diene (2) applying different Grubbs and Hoveyda–Grubbs type olefin metathesis catalyst precursors, followed by exhaustive postpolymerization hydrogenation to yield saturated copolymers. These polyamides, containing between 1.0 and ca. 50.5 amide groups per 1000 methylene units, fill the gap between polyamides from classical polymerization approaches, like polycondensation of diamines with diacids, and linear polyethylene. With reduced amide concentrations the melting points of polyamides converge toward polyethylene, passing through a distinct melting point minimum observed around 110 °C for polyamides with ca. 35 amide groups per 1000 methylene units. The minimum goes in hand with a change in the crystal structure related to the different ratios of intersegment interactions from hydrogen bonding and nonpolar van der...
TL;DR: In this article, a mini-review summarizes the latest accomplishments with group 6 metal alkylidene-N-heterocyclic carbene complexes (metal = Mo, W) for use in olefin metathesis.
Abstract: This mini-review summarizes the latest accomplishments with group 6 metal alkylidene-N-heterocyclic carbene complexes (metal = Mo, W) for use in olefin metathesis. Both the fundamentals and the unique features of this novel class of olefin metathesis catalysts are presented. Also, their use and performance in ring-closing metathesis, cross metathesis, homometathesis, and self-metathesis reactions as well as in ring-opening metathesis polymerization and cyclopolymerization is outlined.
TL;DR: In this article, the position of the thermodynamic cis-trans equilibrium of 85 conventional and X-chelated alkylidene-ruthenium complexes (X=O, S, Se, N, P, Cl, I, Br).
Abstract: This work was conducted to provide an overview on the position of the thermodynamic cis–trans equilibrium of 85 conventional and X-chelated alkylidene-ruthenium complexes (X=O, S, Se, N, P, Cl, I, Br). The reported energies (ΔE) were obtained through single-point calculations with M06 functional and TZVP basis set from BP86/SVP-optimized cis- and trans-dichloro geometries and using the polarizable continuum model to simulate the influence of the solvent. Dichloromethane and toluene were selected as examples for solvents with high and low dielectric constants. The obtained relative stabilities of the cis- and trans-dihalo derivatives of the respective alkylidene complexes will serve for a better explanation of their catalytic activity as has been disclosed herein with selected examples.
TL;DR: A series of polyethylenes containing 21-carbon alkyl branches have been synthesized by acyclic diene metathesis (ADMET) polymerization as mentioned in this paper.
Abstract: A series of polyethylenes containing 21-carbon alkyl branches have been synthesized by acyclic diene metathesis (ADMET) polymerization. These 21-carbon alkyl branches are precisely placed on every 15th, 19th, 21st, 23rd, and 39th carbon along the polymer backbone. Precision of primary structures of all polymers is verified by 1H and 13C NMR spectroscopy. All polymers present well-defined melting profiles, even at a high branch incorporation (13.3% mol). The melting temperature increases as the branch frequency decreases, similar to what we observed for short-chain branched polyethylenes. These observations together with a good linear relationship derived from Flory’s theory suggest the exclusion of 21-carbon side chains from polyethylene crystal units.
TL;DR: A system for transfer hydrogenation of alkenes, composed of a ruthenium metathesis catalyst and HCOOH, is presented and it is shown that these hydrogenation conditions are applicable to a wide range ofAlkenes and offer remarkable selectivity.
Abstract: A system for transfer hydrogenation of alkenes, composed of a ruthenium metathesis catalyst and HCOOH, is presented. This operationally simple system can be formed directly after a metathesis reaction to effect hydrogenation of the metathesis product in a single-pot. These hydrogenation conditions are applicable to a wide range of alkenes and offer remarkable selectivity.
TL;DR: In this article, aryl boronic ester and acid-containing polymers have been synthesized via acyclic diene metathesis, showing a unique crystallization behavior not usually seen in cross-linked polymers.
Abstract: Precise aryl boronic ester- and acid-containing polymers have been synthesized via acyclic diene metathesis. High-molecular weight phenyl boronic acid polymers were synthesized. Cross-linked phenyl boronic acid polymers were also synthesized and demonstrate a unique crystallization behavior not usually seen in cross-linked polymers.
TL;DR: In this paper, a bridge-like polyacetylene (PA) with two terminal alkenyl groups was firstly prepared through the third generation Grubbs' catalyst-mediated chain terminating MCP of bis(1,6-heptadiyne), containing a perylene bisimide (PBI) segment, in the presence of 1,4-bis(10-undecenyloxy)-cis-2-butene.
TL;DR: In this paper, the acyclic diene metathesis (ADMET) was adopted for conjugated polymers, poly(arylene vinylene)s, known as promising molecular electronics.
Abstract: This accounts introduces unique characteristics by adopting the acyclic diene metathesis (ADMET) polymerization for synthesis of conjugated polymers, poly(arylene vinylene)s, known as promising molecular electronics The method is more suitable than the other methods in terms of atom efficiency affording defect-free, stereo-regular (exclusive trans) polymers with well-defined chain ends; the resultant polymers possess better property than those prepared by the conventional methods The chain ends (vinyl group) in the resultant polymer prepared by ruthenium-carbene catalyst(s) can be modified by treating with molybdenum-alkylidene complex (olefin metathesis) followed by addition of various aldehyde (Wittig type cleavage), affording the end-functionalized polymers exclusively An introduction of initiating fragment, the other conjugated segment, and one-pot synthesis of end-functionalized block copolymers, star shape polymers can be achieved by adopting this methodology
TL;DR: Acyclic diene metathesis (ADMET) polymerization is a powerful and versatile technique for creating precision polymers as discussed by the authors, which can be achieved by ADMET polymerization of designed symmetrical monomer structures.
Abstract: Acyclic diene metathesis (ADMET) polymerization is a powerful and versatile technique for creating precision polymers. Specialized and well-defined materials, as well as improved understanding of structure–property relationships, can be achieved by ADMET polymerization of designed symmetrical monomer structures. The introduction of functional groups into ADMET polymers, from polar groups to biodegradable moieties, has resulted in an array of precision functional materials with distinct properties and interesting applications.
TL;DR: In this paper, the synthesis and characterization of poly(3-decylselenylene vinylene) (P3DSV) homopolymers and poly( 3-decylon-selenylene- vinylene)-co-poly(3decylthienylene-vinylene) copolymers through acyclic diene metathesis (ADMET) was reported.
Abstract: We report the synthesis and characterization of poly(3-decylselenylene vinylene) (P3DSV) homopolymers and poly(3-decylselenylene vinylene)-co-poly(3-decylthienylene vinylene) (P3DSV-co-P3DTV) copolymers through acyclic diene metathesis (ADMET) polymerization techniques. The obtained polymers were fully characterized. P3DSV was found to possess reduced crystallinity and a smaller bandgap of about 1.6 eV, compared with those of poly(3-decylthienylene vinylene) (P3DTV) analogs. P3DSV-co-P3DTV shows electronic properties between those of the corresponding homopolymers and distinctly different from those of simple blends of the two homopolymers. Our methodology provides a new way to control the physical and electronic properties of low bandgap poly(arylene vinylene)s (PAVs).
TL;DR: In this paper, a cross metathesis of two olefinic partners containing different types of nitrile functionality with acrylonitrile catalysts was reported, and the expected products were obtained.
Abstract: We report the cross metathesis of two olefinic partners containing different types of nitrile functionality. Thus, cross metathesis of fatty nitriles with acrylonitrile have been achieved with olefin metathesis ruthenium catalysts. 10-Undecenenitrile provides 2-dodecenedinitrile with a high turnover number of 13,280 in the green solvent, diethyl carbonate. Cross metathesis with the internal carbon–carbon double bond of oleonitrile gave the expected products, and the cleavage of the internal double bond proved to be more difficult probably owing to faster catalyst decomposition.
TL;DR: In this article, the first generation of modified non-chelating indenylidene ruthenium catalysts was presented. But the performance of the obtained complexes was evaluated in various metathesis reactions demonstrating that the ring-closing metathetic reactions revealed a similar catalytic activity in comparison with the reference indenYLidene catalyst 3.
Abstract: We report on the synthesis and characterization of the first generation of modified non-chelating indenylidene ruthenium catalysts denoted as RuCl2(4-methyl-3-(o-tolyl)-1-indenylidene)(PCy3)25a, RuCl2(3-(p-fluorophenyl)-1-indenylidene)(PCy3)25b, RuCl2(3-(2,6-xylyl)-1-indenylidene)(PCy3)25c and RuCl2(3-(1-naphthyl)-1-indenylidene)(PCy3)25d. The obtained complexes of 5a–d were characterized by means of NMR spectroscopy and elemental analysis. Moreover the structures of 5a–d were confirmed by single-crystal X-ray diffraction and compared with the standard ruthenium indenylidene complex 3 and the chelating benzylidene complex 2. Additionally, the catalytic performances of the obtained complexes 5a–d were evaluated in various metathesis reactions demonstrating that the ring-closing metathesis (RCM) and ring-opening metathesis polymerization (ROMP) reactions revealed a similar catalytic activity in comparison with the reference indenylidene catalyst 3.
TL;DR: Novel photoresponsive linear, graft, and comb-like copolymers with azobenzene chromophores in the main-chain and/or side-chain are prepared via a sequential ring-opening metathesis polymerization and head-to-tail acyclic diene metatheses (ADMET) polymerization in a one-pot procedure using Grubbs ruthenium-based catalysts.
Abstract: Novel photoresponsive linear, graft, and comb-like copolymers with azobenzene chromophores in the main-chain and/or side-chain are prepared via a sequential ring-opening metathesis polymerization (ROMP) and head-to-tail acyclic diene metathesis (ADMET) polymerization in a one-pot procedure using Grubbs ruthenium-based catalysts. The diluted solutions of these as-prepared copolymers containing azobenzene chromophores exhibit photochemical trans-cis isomerization under the irradiation of UV light, followed by their cis-trans back-isomerization in visible light. The rates of photoisomerization are found to be slower than those of back-isomerization, and the rate for the comb-like copolymer is found to be from 3 to 7 times slower than that obtained for the linear or graft copolymer. This is ascribed to the differences in structure of the copolymers and the specific location of azobenzene chromophores in the copolymer, which favor a side-chain graft structure.
TL;DR: In this paper, it was shown that linear α-olefins and internal olefins occur via very different pathways and that olefin and alkane metathesis processes occur via different pathways.
27 Mar 2015
TL;DR: In this paper, the acyclic diene metathesis (ADMET) polymerization of 6-hydroxy-1-10-undecadiene (M1) and 6-acetoxy-1,10-dehydrogenase (M2) by the action of two different catalysts, i.e., the second-generation Grubbs-Hoveyda system ([RuCl2(IMesH2)(CH-2-(2-PrO-C6H4)]) and the dicationic ruthenium al
Abstract: The acyclic diene metathesis (ADMET) polymerization of 6-hydroxy-1,10-undecadiene (M1) and 6-acetoxy-1,10-undecadiene (M2) by the action of two different catalysts, i.e., the second-generation Grubbs-Hoveyda system ([RuCl2(IMesH2)(CH-2-(2-PrO-C6H4)]) (1) and the dicationic ruthenium alkylidene [Ru(DMF)3(IMesH2)(CH-2-(2-PrO-C6H4)] (2, IMesH2 = 1,3-dimesitylimidazolin-2-ylidene) is reported. Biphasic conditions using 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([BDMIM(+)BF4(-)]) and 1,2,4-trichlorobenzene (TCB) are applied. Under the chosen conditions (T = 75 °C, 20 mbar), the use of catalyst 1 results only in the formation of low-molecular-weight polymers (Mn ≤ 10,000 g mol(-1)), while catalyst 2 allows for the high yield synthesis of high-molecular-weight polymers (Mn ≤ 40,000 g mol(-1), yields ≤ 99%). Irrespective of the catalyst used, all polymers display a high trans-content (>95%). Notably, Ru-contamination of the target polymers without any additional purification is as low as 1.2 ppm with catalyst 2. Together with the high yields and high molecular weights, the low Ru-contaminations clearly illustrate the advantages of the biphasic setup.