Ruthenium-catalyzed Cross-metathesis Research Articles

Synthesis of New Dehydrodieugenol Derivatives via Olefin Cross Metathesis and In Vitro Evaluation of Their Trypanocidal Activity

Ruthenium-catalyzed cross metathesis using biseugenol (1) with electron-deficient olefins methyl (2a) and ethyl (2b) acrylates, acrylic acid (2c), acrylonitrile (2d), and methyl methacrylate (2e) derivatives have been conducted to afford respective derivatives 3a–3e with good yields and excellent conversion rates. Activity of prepared compounds against trypomastigote and amastigote forms of Trypanosoma cruzi and mammalian cytotoxicity have been evaluated. The results obtained indicate that the IC50 values for amastigotes of compounds 3b and 3d are quite similar to those of biseugenol (1), but unlike this compound, they show reduced toxicities with SI values similar to those of the standard drug benznidazol.

Hybrid Inorganic-Organic Cross-Metathesis between Diborenes and Acetylene.

The ruthenium-catalyzed cross-metathesis of alkenes and alkynes, which splits the alkene C═C double bond and couples one-half to each carbon of the alkyne C≡C triple bond, is one of the most efficient tools for the synthesis of 1,3-dienes, with wide-ranging applications, including pharmaceutical and polymer chemistry. In contrast, inorganic main-group metathesis reactions are restricted to a handful of examples of heavier p-block multiple bonds (P═P, Ge═Ge, and E≡E, E = Ge, Sn, Pb). We now report the first examples of thermally induced, transition-metal-free cross-metathesis between an organic alkyne and inorganic cyclic alkyl(amino)carbene (CAAC)-stabilized B═B double bonds, which yield fully planar, π-delocalized 1,8-diaza-3,6-diboraoctatetraenes. Density functional theory studies show that these compounds have an open-shell singlet biradical ground state with a thermally accessible closed-shell state. In-depth computational mechanistic analyses show that they are formed via a biradical cycloaddition-cycloreversion mechanism. Finally, unlike their organic counterparts, these B,N-analogues of octatetraene can undergo two-electron chemical reduction to form diamagnetic dianions.

A Cross-Metathesis/Aza-Michael Reaction Strategy for the Synthesis of Cyclic and Bicyclic Ureas

The synthesis of cyclic and bicyclic ureas via a ruthenium-catalyzed cross-metathesis / aza-Michael reaction strategy between protected alkenyl ureas and Michael acceptors is described. The substrates for these reactions are generated in 1-3 steps from commercially available materials, and products are formed in moderate yield with up to >20:1 diastereoselectivity.

Modification of Polyhedral Oligomeric Silsesquioxanes (POSS) Molecules by Ruthenium Catalyzed Cross Metathesis.

The scope of ruthenium (Ru)-catalyzed cross metathesis (CM) of allyl-decorated polyhedral oligomeric silsesquioxanes (POSS) was explored. A variety of different commercial and non-commercial ruthenium complexes were tested to determine that the nitro-activated Ru catalyst is optimal for this transformation. The reported transformation was used to prepare selected hybrid steroid-POSS compounds.

Simple access to alkoxysilyl telechelic polyolefins from ruthenium-catalyzed cross-metathesis depolymerization of polydienes

The first functional cross-metathesis (CM) depolymerization of commercial (co)polydienes using a ruthenium catalyst and an acyclic bis(trialkoxysilyl) difunctionalized chain-transfer agent (CTA), [(EtO)3Si(CH2)3NHC(O)OCH2CH]2 (1), towards the synthesis of low viscosity liquid α,ω-bis(trialkoxysilyl) telechelic (co)polydienes is reported. The reactivity of three commercial grades of liquid (co)polydienes (P1–P3, polybutadienes (PBDs) or poly(butadiene-co-isoprene) (P(BD-co-IP))) differing in their end-functionalization, in the amount of 1,2-vinyl and in their dispersity, was explored. Operating conditions for effective production of α,ω-bis(trialkoxysilyl) telechelic PBDs or P(BD-co-IP)s with high chemoselectivity (80–90wt%) and catalytic productivity (non-optimized TON up to 24000) were established. The chemoselectivity of this tandem metathesis reaction was assessed in particular through detailed 2D NMR analyses. An original approach combining the CM depolymerization of PBD with the ring-opening functional metathesis polymerization (ROMP) of a cycloolefin in the presence of CTA 1has also been next implemented affording low viscosity liquid α,ω-bis(trialkoxysilyl) telechelic copolydienes. The viscosity of the (co)polyolefins was investigated by rheological analyses.

Synthesis of Bioactives Coumarin Derivatives, Phthalocyanines and Terminal Conjugated Dienes via a Ruthenium Catalyzed Cross-Metathesis: Application to Renewable Resources

This study aimed for the synthesis of 4-Aryl-2-amino-6-(4-hydroxy coumarin-3-yl) pyridine-3-carbonitriles derivatives 4, suitable for use as antibacterial, anti-oxidant and anti-inflammatory activities via a versatile, readily accessible 3-((2E)-3(aryl)prop-2-enoyl)-2H-chromen-2-one, 3, which was prepared by refluxing 3-acetyl-4-hydroxycoumarin with aromatic aldehydes in chloroform in the presence of a catalytic amount of piperidine. Then the direct reaction of the obtained chalcones 3 with malonitrile in the presence of ammonium acetate in one step gave products 4. Most of the new compound 4 exhibit moderate antibacterial activity against Gram Negative bacterial strains (E. coli, K. pneumonia, S. typhi and S. flexneri). In addition, the compounds 4 were investigated for anti-oxidant activities by super oxide radical, DPPH (2,2-Diphenyl-1-picrylhydrazyl), and hydroxyl radical scavenging assays, where most of the compounds displayed significant antioxidant activities. Furthermore, these 4-Aryl-2-amino-6-(4-hydroxy coumarin-3-yl) pyridine-3-carbonitriles 4 were evaluated for anti-inflammatory activity by indirect haemolytic and lipoxygenase inhibition assays where compounds revealed good activity. The preparation of novel metal-free phthalocyanines and metallophthalocyanine complexes 11 and 12 (MPcs, M = Co, Zn, Cu and Mn), with four peripheral 6-hydroxy-4-methylcoumarin and 6-hydroxycoumarin substituents, were also prepared by cyclotetramerization of compounds 7 and 10 with the corresponding metal salts (Zn(OAc)2.2H2O, Co(OAc)2.4H2O, CuCl, Mn(OAc)2.4H2O) as a template for macrocycle formation in 2-(N,N-dimethylamino)ethanol.The electronic spectra of these compounds exhibit a band of coumarin identity together with characteristic bands of the phthalocyanine core. The new compounds were screened for antibacterial activity. Most of them are active against E. coli and S. aureus. In addition, some novel 3-acetylcoumarin derivatives 17 were prepared in good yields. Their invitro antioxidant activities were assayed by the quantitative 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity method. In this way, novel coumarin phtalonitriles derivatives 42-44 were synthesized.The synthesis of these coumarin phtalonitriles was resulting from a nucleophilic aromatic substitution reaction between 4-nitrophtalonitrile and coumarins derivatives. The complexing properties of the coumarin derivatives toward alkali metal, alkaline earth metal, some transition metals and some heavy metal cations have been investigated in acetonitrile by means of UV spectrophotometry absorption and conductivity methods. Thus, the stoichiometry of the complexes formed and their stability constants were determined. We report also in this book chapter a sequence of two ruthenium-catalyzed transformations, namely olefin cross metathesis with allylic chloride followed by elimination, which gives a straightforward access to terminal 1,3-dienes from natural products. The structures of all the new obtained compounds were confirmed by elemental analysis, IR, and multinuclear/multidimensional NMR spectroscopy (1H, 13C-NMR, NOESY, HMBC) which allowed assignment of the complete network of proton and carbon atoms).

Iterative catalyst controlled diastereodivergent synthesis of polypropionates

Polypropionates are synthesized using a combination of a copper-catalyzed asymmetric allylic alkylation, ruthenium-catalyzed cross-metathesis and iridium-catalyzed asymmetric allylic etherification.

Sequential Deconjugative Electrophilic Fluorination/Cross-Metathesis: Toward the Synthesis of Fluoro Analogues of Biologically Active Compounds

For the first time, a deconjugative electrophilic fluorodesilylation reaction was accomplished. γ-Silyl butenamides were treated with Selectfluor to provide α-fluoro-β,γ-unsaturated amides. Other sources of electrophilic fluorine were not efficient or gave protodesilylated side products. The electrophilic fluorodesilylation reaction was followed by a ruthenium-catalyzed cross-metathesis of the resulting functionalized allylic fluoride. The fluorodesilylation/cross-metathesis sequence is ideal for the synthesis of fluoro analogues of symbior­amide.

Solid-supported cross-metathesis and a formal alkane metathesis for the generation of biologically relevant molecules.

Solid-phase synthetic strategies toward the generation of libraries of biologically relevant molecules were developed using olefin cross-metathesis as a key step. It is remarkably the formal alkane metathesis based on a one-pot, microwave-assisted, ruthenium-catalyzed cross-metathesis and reduction to obtain Csp3-Csp3 linkages.

Cross-metathesis of biosourced fatty acid derivatives: a step further toward improved reactivity.

The improved catalytic conversion of bioresources, namely unsaturated fatty acid derivatives, is presented. The targeted reaction is ruthenium-catalyzed cross-metathesis with functionalized olefins (α,β-unsaturated esters), that affords shorter diesters. These can be used as biosourced (pre)monomers for the production of polyesters. It is demonstrated that switch from terminal to internal cross-metathesis partners (that is, from methyl acrylate to methyl crotonate) allows use of ppm-level catalyst loadings, while retaining high productivity and selectivity. This was exemplified on a commercial biosourced fatty acid methyl esters mixture, using minimal purification of the substrate, on a 50 g scale. We propose that this improved catalytic behavior is due to the sole presence of more stable alkylidene intermediates, as the notoriously unstable ruthenium methylidene species are not formed using an internal functionalized olefin.

Ruthenium-catalyzed cross-metathesis with electron-rich phenyl vinyl sulfide enables access to 2,3-dideoxy-d-ribopyranose ring system donors

Microwave irradiation effectively accelerates the cross-metathesis reaction of 2-deoxy-d-ribose hydroxyalkene and derivatives with electron-rich phenyl vinyl sulfide using commercially available ruthenium-based catalysts, thus providing a flexible metal-mediated route to 2,3-dideoxy-d-ribopyranose ring system donors.

Sequential Ag-catalyzed carboxylative coupling/Ru-catalyzed cross-metathesis reactions for the synthesis of functionalized 2-alkynoates

Sequential reactions can provide efficient access to a variety of important organic compounds that would be otherwise difficult to obtain using conventional methods and readily available starting materials. Based on the importance of 2-alkynoates in organic synthesis, the current research aimed to develop a method for the convenient synthesis of functionalized 2-alkynoates from terminal alkynes, CO 2 , terminal alkene-derived bromides, and methyl acrylate using a combination of the carboxylative coupling and cross-metathesis reactions. The initial ligand-free silver-catalyzed carboxylative coupling reactions of a variety of different aryl-substituted terminal alkynes and CO 2 with 5-bromopentene and 6-bromohexene provided a series of 4-pentenyl 2-alkynoates and 5-hexenyl 2-alkynoates, respectively, in good yield. These resulting 2-alkynoates were further transformed into methyl ( E )-6-acetylenecarboxy-2-hexenoates and ( E )-7-acetylenecarboxy-2-heptenoates in moderate to good yields by their cross-metathesis reactions with methyl acrylate in the presence of the Grubbs-Hoveyda catalyst. All of the new products characterized spectroscopically. 通过将Ag催化的羧化偶联反应与Ru催化的交叉复分解反应串联, 用端炔/二氧化碳/端烯基取代的溴代物和甲基丙烯酸甲酯高效高产率地合成了一系列官能团化的炔酸酯. An efficient and convenient method has been developed for the synthesis of functionalized 2-alkynoates in good yield from terminal alkynes, CO 2 , terminal alkene-derived bromides, and methyl acrylate via the combination of silver-catalyzed carboxylative coupling and ruthenium-catalyzed cross-metathesis reactions.

Preparation of a Nylon-11 Precursor from Renewable Canola Oil

We report a multi-catalytic sequence to a valuable nylon-11 precursor, methyl 11-aminoundecanoate, which is prepared by a ruthenium-catalysed cross-metathesis and a highly regioselective palladium-catalysed amination–hydrogenation reaction, from canola oil, a renewable, natural vegetable oil feedstock.

Reactivity of terminal phenylpentenes in a ruthenium-catalyzed cross-metathesis reaction: construction of linear bifunctional C-8 alkenes

In the present study the behavior of 1-functionalized 2-phenylpent-4-enes in the presence of ruthenium-based metathesis catalysts was investigated. The experimental observations revealed that the outcome of the reaction depends very much on the combination of olefinic partners used in the reaction; only certain combinations delivered satisfactory amounts of unsymmetrical cross-metathesis products, i.e., bifunctional C-8 alkenes.

Grafting onto a renewable unsaturated polyester via thiol–ene chemistry and cross-metathesis

Methyl 10-undecenoate was modified to its corresponding malonate derivative by the reaction with sodium hydride in dimethyl carbonate. This malonate was then polymerized with 1,6-hexanediol, catalyzed by 1.0mol% titanium (IV) isopropoxide, to a poly(malonate) bearing C9 aliphatic side-chains with terminal double bonds. The double bonds of this poly(malonate) were used for grafting onto reactions by either ruthenium-catalyzed cross-metathesis reactions with acrylates or thiol–ene addition reactions. Several examples are shown for both methods. For the cross-metathesis reactions, 1.0mol% Hoveyda–Grubbs 2nd generation (HG II) catalyst was used with 10.0 equivalents of the respective acrylate under bulk conditions at 40°C. The thiol–ene additions were carried out with 1.0equivalents of the respective thiol in THF with 5.0mol% 2,2-Dimethoxy-2-phenylacetophenone (DMPA) under UV (365nm) irradiation. Moreover, we have shown that a carboxylic acid group can be easily installed via thiol–ene addition and that the resulting polymer can be further modified by the Passerini three-component reaction with quantitative conversion.

Polyamide precursors from renewable 10-undecenenitrile and methyl acrylate via olefin cross-metathesis

The ruthenium-catalyzed cross-metathesis of the unsaturated fatty acid derivative 10-undecenenitrile 1 arising from castor oil with methyl acrylate produces a C12 nitrile ester with high turnover number. This product has potential as a new bio-sourced intermediate for the production of polyamides. This route competes favourably with the reverse cross-metathesis of methyl 10-undecenoate with acrylonitrile leading to the same C12 α,ω-amino ester 7 after hydrogenation of the carbon–carbon double bond and the nitrile functionality.

Eugenol as a renewable feedstock for the production of polyfunctional alkenes via olefin cross-metathesis

The ruthenium-catalyzed cross-metathesis of eugenol derivatives with electron deficient olefins is reported. It is shown that in the presence of ruthenium catalysts, eugenol and its O-protected derivatives have a high tendency to undergo carbon–carbon double bond migration before and after metathesis leading to the formation of conjugated styrene derivatives. The addition of 1,4-benzoquinone suppresses these isomerization reactions and provides an efficient access to new polyfunctional phenol derivatives upon cross-metathesis of the biosourced eugenol with acrylates, acrylonitrile and acrylamides.

Synthesis of galactofuranose-based acceptor substrates for the study of the carbohydrate polymerase GlfT2

Despite the prevalence and importance of carbohydrate polymers, the molecular details of their biosynthesis remain elusive. Many enzymes responsible for the synthesis of carbohydrate polymers require a ‘primer’ or ‘initiator’ carbohydrate sequence. One example of such an enzyme is the mycobacterial galactofuranosyltransferase GlfT2 (Rv3808c), which generates an essential cell wall building block. We recently demonstrated that recombinant GlfT2 is capable of producing a polymer composed of alternating β-(1,5) and β-(1,6)-linked galactofuranose (Gal f) residues. Intriguingly, the length of the polymers produced from a synthetic glycosyl acceptor is consistent with those found in the cell wall. To probe the mechanism by which polymer length is controlled, a collection of initiator substrates has been assembled. The central feature of the synthetic route is a ruthenium-catalyzed cross-metathesis as the penultimate transformation. Access to synthetic substrates has led us to postulate a new mechanism for length control in this template-independent polymerization. Moreover, our investigations indicate that lipids possessing but a single galactofuranose residue can act as substrates for GlfT2.

Ruthenium-Catalyzed Cross-Metathesis between Diallylsilanes and Electron-Deficient Olefins

Diallysilanes can be selectively coupled with electron-deficient olefins under cross-metathesis (CM) conditions using the Hoveyda-Grubbs catalyst to produce mono- and/or bis-CM compounds in good yield. The formation of the mono- and the bis-CM compounds depends on the nature of the electron-deficient olefin.

Controlled Synthesis of (S,S)-2,7-Diaminosuberic Acid: A Method for Regioselective Construction of Dicarba Analogues of Multicystine-Containing Peptides

A method to facilitate regioselective formation of multiple dicarba isosteres of cystine is described. A sequence of ruthenium-catalyzed cross metathesis and rhodium-catalyzed hydrogenation of nonproteinaceous allylglycine derivatives has been developed to achieve high-yielding and unambiguous formation of diaminosuberic acid derivatives. Allylglycine derivatives readily undergo ruthenium-catalyzed metathesis and hydrogenation to yield diaminosuberic acid derivatives in near quantitative yield. Under the same experimental conditions, prenylglycine was found to be inert to both Grubbs' and Wilkinson's catalyzed metathesis and hydrogenation, respectively, but was readily activated for metathesis via cross metathesis with Z-butene. Subsequent cross metathesis of the metathesis-formed crotylglycine derivative, followed by hydrogenation, yielded the second diaminosuberic acid derivative in excellent yield.