Cross-metathesis Reaction Research Articles

ChemInform Abstract: Molybdenum Imido Alkylidene and Tungsten Oxo Alkylidene N‐Heterocyclic Carbene Complexes for Olefin Metathesis

AbstractReview: 48 refs.

Stereoselective total synthesis of cryptomoscatone E1

The stereoselective total synthesis of cryptomoscatone E1 has been accomplished. The strategy involves Carreira’s asymmetric alkynylation and olefin cross-metathesis reactions as key steps.

Multiple Olefin Metathesis Polymerization That Combines All Three Olefin Metathesis Transformations: Ring-Opening, Ring-Closing, and Cross Metathesis.

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.

Stereoselective Total Synthesis of (+)-Anamarine and 8-epi-(–)-Anamarine from d-Mannitol

Stereoselective total synthesis of (+)-anamarine and the first synthesis of 8-epi-(–)-anamarine, its nonnatural diastereomer, were achieved from readily available d -mannitol. The key reactions involved were asymmetric dihydroxylation, cross-metathesis and ring-closing metathesis reactions. The approach is adoptable advantageously for the diversity-oriented synthesis of several related classes of natural products.

Synthesis of amide-functionalized cellulose esters by olefin cross-metathesis

Cellulose esters with amide functionalities were synthesized by cross-metathesis (CM) reaction of terminally olefinic esters with different acrylamides, catalyzed by Hoveyda–Grubbs 2nd generation catalyst. Chelation by amides of the catalyst ruthenium center caused low conversions using conventional solvents. The effects of both solvent and structure of acrylamide on reaction conversion were investigated. While the inherent tendency of acrylamides to chelate Ru is governed by the acrylamide N-substituents, employing acetic acid as a solvent significantly improved the conversion of certain acrylamides, from 50% to up to 99%. Homogeneous hydrogenation using p-toluenesulfonyl hydrazide successfully eliminated the α,β-unsaturation of the CM products to give stable amide-functionalized cellulose esters. The amide-functionalized product showed higher Tg than its starting terminally olefinic counterpart, which may have resulted from strong hydrogen bonding interactions of the amide functional groups.

Oxygen‐chelated indenylidene ruthenium catalysts for olefin metathesis

Olefin metathesis is a transition metal‐mediated transformation that rearranges the carbon atoms of the carbon–carbon double bond of olefins. This reaction has become one of the most important and powerful reactions. Therefore development of new, well‐defined, highly active and selective catalysts is very desirable and a valuable goal. This mini‐review mainly introduces the development of ruthenium catalysts in olefin metathesis highlighting oxygen‐chelated indenylidene ruthenium catalysts. Applying an alkoxyl group on the indenylidene ligand fragment can generate the RuO chelating bond. Additionally, various modifications of the ligand as well as the catalytic activity for ring‐closing metathesis reaction and selectivity of cross metathesis reaction are overviewed. Finally, the perspectives on the development of new catalysts are summarized. Copyright © 2015 John Wiley & Sons, Ltd.

ChemInform Abstract: Z‐Selective Cross Metathesis with Ruthenium Catalysts: Synthetic Applications and Mechanistic Implications

AbstractReview: [20 refs.

Synthesis of a series of novel heteroglycoclusters and homoglycoclusters and the study of their anti-adhesion activities

A new series of mixed-type heteroglycoclusters containing mannose and lactose were synthesized. In the synthesis of rigid scaffold of heteroglycocluster, we found that trans-isomer could be prepared stereoselectively by means of Grubbs olefin cross-metathesis reactions. Moreover, sequential acylation using cyclic anhydride as scaffold could give cis-isomer. These two methods may provide complementarity of stereochemistry in heteroglycocluster assembling. The anti-adhesion activities of these compounds were assessed by Surface Plasmon Resonance (SPR) and static state cell-based adhesion assay. These results indicated that the rigid scaffold might not affect the anti-adhesion activities.

Olefin metathesis meets rubber chemistry and technology

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.

Molybdenum imido alkylidene and tungsten oxo alkylidene N-heterocyclic carbene complexes for olefin metathesis

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.

A cross-metathesis approach to the synthesis of (+)-phomopsolide B

The synthesis of phomopsolide B has been achieved using an olefin cross-metathesis (CM) reaction as key step. Two metathesis partners, enediol and 5-hydroxy vinyl lactone were prepared from l-ascorbic acid. This is the first report of using 5-hydroxy vinyl lactone in an olefin cross-metathesis reaction.

ChemInform Abstract: Catalyst‐Controlled Stereoselective Olefin Metathesis as a Principal Strategy in Multistep Synthesis Design: A Concise Route to (+)‐Neopeltolide.

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.

A concise stereoselective total synthesis of diplodialide C

An asymmetric total synthesis of diplodialide C has been achieved starting from commercially available homoallylic alcohol. Regioselective opening of the chiral epoxide, cross-metathesis reaction, and Yamaguchi macrolactonization were used as the key steps in this synthesis.

Z-selective cross metathesis with ruthenium catalysts: synthetic applications and mechanistic implications.

Olefin cross metathesis is a particularly powerful transformation that has been exploited extensively for the formation of complex products. Until recently, however, constructing Z-olefins using this methodology was not possible. With the discovery and development of three families of ruthenium-based Z-selective catalysts, the formation of Z-olefins using metathesis is now not only possible but becoming increasingly prevalent in the literature. In particular, ruthenium complexes containing cyclometalated NHC architectures developed in our group have been shown to catalyze various cross metathesis reactions with high activity and, in most cases, near perfect selectivity for the Z-isomer. The types of cross metathesis reactions investigated thus far are presented here and explored in depth.

ChemInform Abstract: Synthesis of the Unusual α‐Amino Acid Component of Some Novel Histone Deacetylase Inhibiting Cyclic Peptides.

Abstract A flexible protocol for the synthesis of three lipophilic α-amino acid components of some novel cyclic peptides having important histone deacetylase inhibiting properties has been developed from a common source, which featured a cross-metathesis reaction between two unhindered terminal olefins as the key step.

The driving force role of ruthenacyclobutanes

DFT calculations have been used to determine the thermodynamic and kinetic preference for ruthenacyclobutanes resulting from the experimentally proposed interconversion pathways (olefin and alkylidene rotations) through the investigation of cross-metathesis reaction mechanism for neutral Grubbs catalyst, RuCl2(=CHEt)NHC (A), with ethylene and 1-butene as the substrates. Our results show that although the proposed interconversions are feasible due to the predicted low energy barriers (2-6 kcal/mol), the formation of ruthenacyclobutane is kinetically favored over the competitive reactions involving alkylidene rotations. In comparison with catalyst A, the reaction energy profile for cationic Piers catalyst [RuCl2(=CHPCy3)NHC+] (B) is more endothermic in nature with both ethylene and 1-butene substrates.

ChemInform Abstract: Access to Harmonine, a Chemical Weapon of Ladybird Beetles.

AbstractTitle compound (IV) is synthesized through three simple and practical routes using Wittig approach, cross metathesis reaction, or conversion of compound (VII) prepared from sophorolipids according to literature.

An enantioselective total synthesis of Sch-725674.

An enantioselective total synthesis of Sch-725674, a unique 14-membered macrolactone, has been accomplished in 13 steps. The step-wise dithiane alkylation served as a strategic step to assemble the upper and lower fragments of the molecule, whereas cross metathesis reaction, Yamaguchi macrolactonization and a substrate controlled stereoselective reduction are used as key steps to complete the total synthesis.

A simple and practical preparation of an efficient water soluble olefin metathesis catalyst

A facile gram-scale preparation of a di-ammonium functionalised Ru-alkylidene complex which efficiently catalyses ring-closing metathesis and cross-metathesis reactions in water.

ChemInform Abstract: A Chiral Pool and Cross Metathesis Based Synthesis of Gingerdiols.

Both (3R,5S)- and (3R,5R)-gingerdiols were synthesized. Their 1,3-diol motifs were derived from enantiopure epoxy chiral building blocks that were readily accessible from D-gluconolactone. The effect of deuterating the OH groups of the natural isomer on its optical rotation was also examined. In the course of the syntheses of the targets, an unexplored cross-metathesis (CM) reaction of unprotected 5-substituted pent-1-ene-3,5-diols was investigated, in which the CM product readily underwent an allylic epimerization and oxidation, as the starting diols rearranged into ketones with unprecedented ease. These problems were eventually resolved by performing the CM reaction in toluene in the presence of phenol. The cause of these unexpected, yet very interesting phenomena, was determined to be the presence of the unprotected OH group at C-5 of the 5-substituted pent-1-ene-3,5-diol. A mechanistic rationale is also presented.