ChemInform Abstract: Handbook of Metathesis

Grubbs, Robert H.; Wenzel, Anna G.; O’Leary, Daniel J.; Khosravi, Ezat

doi:10.1002/chin.201546242

Cited by 82 publications

(106 citation statements)

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“…1 It is widely used in the synthesis of pharmaceuticals as well as in the production of pheromones and musks as replacements for toxic, synthetic polycyclic and nitroarene musks. 2 The stereochemistry of the alkene, E or Z, in these cyclic structures is often crucial to the biological activity of a molecule or its olfactory characteristics, and small amounts of impurity of the other stereoisomer in chemical mixtures can drastically decrease their potency.…”

mentioning

confidence: 99%

A Highly Efficient Synthesis of Z‐Macrocycles Using Stereoretentive, Ruthenium‐Based Metathesis Catalysts

Ahmed

Grubbs

2017

Angewandte Chemie

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A highly efficient, Z‐selective ring‐closing metathesis system for the formation of macrocycles using a stereoretentive, ruthenium‐based catalyst supported by a dithiolate ligand is reported. The catalyst is remarkably active as observed in initiation experiments showing complete catalyst initiation at −20 °C within 10 minutes. Macrocyclization reactions generated Z‐products from easily accessible diene starting materials bearing a Z‐olefin moiety. This approach provides a more efficient and selective route to Z‐macrocycles relative to previously reported systems. Reactions were completed within shorter reaction times, and turnover numbers of up to 100 could be achieved. Macrocyclic lactones ranging in size from twelve‐ to seventeen‐membered rings were synthesized in moderate to high yields (67–79 %) with excellent Z‐selectivity (95–99 %).

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mentioning

confidence: 99%

A Highly Efficient Synthesis of Z‐Macrocycles Using Stereoretentive, Ruthenium‐Based Metathesis Catalysts

Ahmed

Grubbs

2017

Angewandte Chemie

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“…For each material the dynamic moduli from each temperature run were superimposed onto a linear master curve at 130 °C using Williams-Landel-Ferry (WLF) theory. 13 The data was analysed using RepTate software. The complex viscosity ƞ* (Pa.s), was calculated using the equation below where Gʹ is elastic modulus (Pa), Gʹʹ is viscous modulus (Pa) and ω is frequency (s -1 ).…”

Section: Rheological Analysismentioning

confidence: 99%

“…10,11,12 Ring opening metathesis polymerisation (ROMP) initiated by Grubbs well-defined ruthenium initiators has been utilised to synthesise well-defined polymers with controlled architectures, molecular weights, dispersities and terminal functionalities. 13 Thermosetting materials have been prepared from ROMP of mixtures of mono-and di-functional norbornene dicarboximide monomers, both containing acetal ester groups. 14,15 They have been shown to be thermally degradable around 200 °C, which is in the same region as the lead-free solder reflow temperature (217 °C); advantageous in the electronic industry as it would allow easy chip removal and replacement, if these materials are used as adhesives.…”

Section: Introductionmentioning

confidence: 99%

Hydrolytic degradation of ROMP thermosetting materials catalysed by bio-derived acids and enzymes: from networks to linear materials

et al. 2016

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. This paper reports the first example of the degradable ROMP thermosetting materials catalysed by bio-derived acids and cutinase from Thermobifida cellulosilytica (Thc_Cut1). The ROMP thermosetting materials are based on norbornene dicarboximides containing acetal ester groups only in the crosslink moiety. The insoluble cross-linked materials were subjected to acid-catalysed hydrolysis using bio-derived acetic and citric acids as well as enzymatic degradation using Thc_Cut1, resulting in the materials becoming completely soluble in dichloromethane.1 H NMR and rheological analysis performed on materials after acid-catalysed hydrolysis showed characteristics indistinguishable to that of the linear polymer analogues. These analyses confirmed the cleavage of the crosslink moiety upon degradation with the main backbone chains remaining intact. The glass transition temperatures of the polymer materials after acid-catalysed hydrolysis were the same of those observed for the linear polymer analogue. TGA showed that the cross-linked polymers thermally stable to 150 °C, beyond which showed weight losses due to the thermal cleavage of the acetal ester linkages.

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“…15 In these compounds M=CHR and M≡CR bonds are formed through what is essentially deprotonation of an α carbon atom in a neopentyl ligand (to give a neopentylidene ligand) or subsequently deprotonation of a neopentylidene ligand (to give a neopentylidyne ligand), respectively. The "α hydrogen abstraction" method of preparing metal-carbon double and triple bonds led to the syntheses of Mo and W alkylidene complexes that will metathesize olefins 16 and Mo and W alkylidyne complexes that will metathesize acetylenes. 17 Rhenium alkylidene complexes that will metathesize olefins eventually also were prepared through α hydrogen abstraction reactions in high oxidation state Re neopentyl complexes.…”

Section: Discovery Of High Oxidation State Multiple Metal-carbon Bondsmentioning

confidence: 99%

“…Most Mo-based or W-based alkene metathesis 16,21 or alkyne metathesis 16,22 catalysts today are four-coordinate.…”

Section: Discovery Of High Oxidation State Multiple Metal-carbon Bondsmentioning

confidence: 99%

Metathesis by Molybdenum and Tungsten Catalysts

Schrock¹

2015

Chimia

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IntroductionIn the early 1970's organometallic, organic, and polymer chemists were attracted to a new type of catalytic reaction called Olefin Disproportionation by Banks and Bailey, who published results in the open literature in 1964; 1 the reaction also was reported by Natta in 1964 2 and had appeared in patents filed at duPont 3 and Standard Oil 4 several years earlier. The basic process, which was shown to be catalyzed by various molybdenum or tungsten, and later rhenium, compounds of unknown type, resulted in an "exchange" of alkylidene (usually CHR, where R = H or alkyl) units in alkenes with one another, e.g., propylene could be equilibrated with ethylene and cis and trans-2-butenes (equation 1) or norbornene could be polymerized through a "ringopening" of its double bonds (equation 2). Although several mechanisms were proposed, the correct one appeared first in a publication by Hérrison and Chauvin in 1971, 5 namely the reversible reaction between a metal complex that contains a metal-carbon double bond (M=CHR) and a C=C bond to yield an intermediate that contains a metallacyclobutane (MC 3 ) ring. A related reaction that involves alkynes was discovered to be catalyzed by a heterogeneous catalyst in 1968 6 and a homogeneous catalyst in 1972. 7 This "alkyne disproportionation" reaction was proposed to consist of a reversible reaction between a M≡CR bond (R≠H) and a C≡C bond to give all possible alkynes via a metallacyclobutadiene intermediate. 8 Neither process resulted in any positional isomerization of the C=C or C≡C bonds. Although Fischer-type "low oxidation state" carbene 9 complexes were known at the time, and the synthesis of carbyne complexes soon followed, 10 they did not promote what came to be known as alkene metathesis 11 and alkyne metathesis, respectively, in the rapid manner often observed for what are now known as "classical" alkene and alkyne metathesis catalysts. However, experiments first published in 1976 showed that polymerization of cyclic olefins, metathesis of linear olefins, enyne metathesis, and polymerization of acetylenes could be initiated by certain Fischer-type carbene complexes, although new alkylidenes of the same type as the initiator were not observed. 12 Classical metathesis catalysts often are formed from metal oxides on silica or alumina 13 or in solution from a variety of metal complexes. An alkylating agent is often required, but simply exposing the supported metal oxide to alkenes or alkynes at high temperatures will generate the catalyst through some unknown mechanism of mechanisms.

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ChemInform Abstract: Handbook of Metathesis

Cited by 82 publications

References 1 publication

A Highly Efficient Synthesis of Z‐Macrocycles Using Stereoretentive, Ruthenium‐Based Metathesis Catalysts

A Highly Efficient Synthesis of Z‐Macrocycles Using Stereoretentive, Ruthenium‐Based Metathesis Catalysts

Hydrolytic degradation of ROMP thermosetting materials catalysed by bio-derived acids and enzymes: from networks to linear materials

Metathesis by Molybdenum and Tungsten Catalysts

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