Ene-yne Cross-metathesis Research Articles

Ene-yne Cross-Metathesis for the Preparation of 2,3-Diaryl-1,3-dienes

Ene-yne cross-metathesis from alkynes and ethylene is a useful method to produce substituted conjugated butadiene derivatives. If this method has been used with aliphatic alkynes, it has however never been used starting from diarylacetylenes as internal alkynes. We show that the ene-yne cross-metathesis catalyzed by the second generation Hoveyda ruthenium catalyst provides the 2,3-diarylbuta-1,3-dienes under 3 atm of ethylene at 100 °C. The scope and limitations of the reaction have been evaluated starting from unsymmetrical functionalized diarylacetylene derivatives hence leading to unsymmetrical 2,3-diarylbuta-1,3-dienes in a straightforward and environmentally acceptable manner.

Alkene Metathesis Catalysis: A Key for Transformations of Unsaturated Plant Oils and Renewable Derivatives

This account presents the importance of ruthenium-catalysed alkene cross-metathesis for the catalytic transformations of biomass derivatives into useful intermediates, especially those developed by the authors in the Rennes (France) catalysis team in cooperation with chemical industry. The cross-metathesis of a variety of functional alkenes arising from plant oils, with acrylonitrile and fumaronitrile and followed by catalytic tandem hydrogenation, will be shown to afford linear amino acid derivatives, the precursors of polyamides. The exploration of cross-metathesis of bio-sourced unsaturated nitriles with acrylate with further catalytic hydrogenation has led to offer an excellent route to α,ω-amino acid derivatives. That of fatty aldehydes has led to bifunctional long chain aldehydes and saturated diols. Two ways of access to functional dienes by ruthenium-catalyzed ene-yne cross-metathesis of plant oil alkene derivatives with alkynes and by cross-metathesis of bio-sourced alkenes with allylic chloride followed by catalytic dehydrohalogenation, are reported. Ricinoleate derivatives offer a direct access to chiral dihydropyrans and tetrahydropyrans via ring closing metathesis. Cross-metathesis giving value to terpenes and eugenol for the straightforward synthesis of artificial terpenes and functional eugenol derivatives without C=C bond isomerization are described.

ChemInform Abstract: Toward the Synthesis of Amphidinolide P: Optimization of a Model Ene—Yne Metathesis Fragment Coupling.

Abstract Ene–yne cross metathesis was assessed for use as a key fragment coupling in a planned total synthesis of amphidinolide P. A terminal alkyne containing a β,γ-epoxide was synthesized and employed as the alkyne partner in an intermolecular ene–yne metathesis. In the alkene substrate, optimal functionality and reaction conditions were determined. An unprotected allyl alcohol was found to be critical for both high yield and high E-selectivity. Fewer equivalents of the alkene resulted in incomplete reaction and side reactions consumed the terminal alkyne. The best ruthenium carbene precatalysts were found to be the Hoveyda–Grubbs carbene complexes.

Ring-opening metathesis polymerization of vinylnorbornene and following polymer modifications

Ring-opening metathesis polymerization of vinylnorbornene with molybdenum (VI) complex or with Hoveyda-Grubbs type Ru alkylidene complex provided soluble polymers, poly (VNBE)s of Mn about 10 000, having vinyl pendant groups on cyclopentenylenevinylene main chains. Post-polymerization modification via cross-metathesis of pendant vinyl groups with cis-1,4-diacetoxybut-2-ene, 5-hexenyl acetate, allyl acetoacetate, and allyltrimethylsilane was accomplished. Functionalization of poly (VNBE) was also performed via ene-yne cross-metathesis of vinyl pendants with (4-fluorophenyl) acetylene and (2,4-difluorophenyl) acetylene.

Toward the synthesis of amphidinolide P: optimization of a model ene–yne metathesis fragment coupling

Ene–yne cross metathesis was assessed for use as a key fragment coupling in a planned total synthesis of amphidinolide P. A terminal alkyne containing a β,γ-epoxide was synthesized and employed as the alkyne partner in an intermolecular ene–yne metathesis. In the alkene substrate, optimal functionality and reaction conditions were determined. An unprotected allyl alcohol was found to be critical for both high yield and high E-selectivity. Fewer equivalents of the alkene resulted in incomplete reaction and side reactions consumed the terminal alkyne. The best ruthenium carbene precatalysts were found to be the Hoveyda–Grubbs carbene complexes.

Application of Cross Metathesis in Diene and Polyene Synthesis

Olefin metathesis has become a useful method in organic synthesis, rivaling palladium catalyzed C-C bond forming reactions as well as more traditional olefination processes. Olefin cross metathesis (CM) emerged later than ring closing metathesis and ring opening metathesis polymerization due to poor selectivity control. However, after the discovery of more active second generation catalysts and elaboration by Grubbs of an empirical model to predict the outcome of these reactions, cross metathesis has found wide application in the synthesis of various alkenes including those that are sterically demanding or highly functionalized. In recent years enyne cross metathesis and metathetic coupling between alkene and diene or polyene were widely tested as alternative, convenient methods of diene and polyene preparation. In this review the application of ene-diene CM, ene-polyene CM, diene-polyene CM, ene-yne CM and alkene CM combined with other reactions in the synthesis of conjugated dienes and polyenes is presented. The aim of this article is to demonstrate not only the scope of CM application in the synthesis of conjugated dienes and polyenes but also its limitations associated mainly with problems of regio- and stereoselectivity control and how the encountered difficulties led to a better understanding of these processes and the discovery of more effective reaction conditions.

Application of Cross Metathesis in Diene and Polyene Synthesis

Olefin metathesis has become a useful method in organic synthesis, rivaling palladium catalyzed C-C bond forming reactions as well as more traditional olefination processes. Olefin cross metathesis (CM) emerged later than ring closing metathesis and ring opening metathesis polymerization due to poor selectivity control. However, after the discovery of more active second generation catalysts and elaboration by Grubbs of an empirical model to predict the outcome of these reactions, cross metathesis has found wide application in the synthesis of various alkenes including those that are sterically demanding or highly functionalized. In recent years enyne cross metathesis and metathetic coupling between alkene and diene or polyene were widely tested as alternative, convenient methods of diene and polyene preparation. In this review the application of ene-diene CM, ene-polyene CM, diene-polyene CM, ene-yne CM and alkene CM combined with other reactions in the synthesis of conjugated dienes and polyenes is presented. The aim of this article is to demonstrate not only the scope of CM application in the synthesis of conjugated dienes and polyenes but also its limitations associated mainly with problems of regio- and stereoselectivity control and how the encountered difficulties led to a better understanding of these processes and the discovery of more effective reaction conditions. Keywords: Cross-coupling, cross metathesis, diene, enyne metathesis, olefin metathesis, polyene, synthetic methods, tandem reaction

Alkene Metathesis Approach to β-Unsubstituted Anti-Allylic Alcohols and Their Use in Ene–Yne Metathesis

The synthesis of β-unsubstituted, anti-allylic alcohols using a catalytic Evans aldol reaction conjoined with a relay-type ring-closing alkene metathesis is reported. The metathesis step serves to remove a β-alkenyl group, which facilitated the aldol step. The β-substituted enals serve as acrolein surrogates. The products were employed in ene-yne cross metathesis.

ChemInform Abstract: Ene—Yne Cross‐Metathesis with Ruthenium Carbene Catalysts

AbstractReview: 87 refs.

Ene–yne cross-metathesis with ruthenium carbene catalysts

Conjugated 1,3-dienes are important building blocks in organic and polymer chemistry. Enyne metathesis is a powerful catalytic reaction to access such structural domains. Recent advances and developments in ene–yne cross-metathesis (EYCM) leading to various compounds of interest and their intermediates, that can directly be transformed in tandem procedures, are reviewed in this article. In addition, the use of bio-resourced olefinic substrates is presented.

Improving Sustainability in Ene–Yne Cross‐Metathesis for Transformation of Unsaturated Fatty Esters

Ruthenium-catalyzed ene-yne cross-metathesis is performed with stoichiometric proportions of terminal olefins and alkynes. This is made possible by the continuous addition of the alkyne to the reaction mixture. The protocol allows the ene-yne cross-metathesis reaction to be carried out with long-chain terminal olefins and in a one-pot fashion with internal olefins after shortening by ethenolysis. The efficient conversion of renewable unsaturated fatty esters from bioresources into valuable conjugated 1,3-dienes of interest for further transformations is performed using this technique under mild conditions in dimethyl carbonate; an ecofriendly solvent.

Factors Relevant for the Regioselective Cyclopolymerization of 1,6-Heptadiynes, N,N-Dipropargylamines, N,N-Dipropargylammonium Salts, and Dipropargyl Ethers by RuIV−Alkylidene-Based Metathesis Initiators

The factors relevant for the regioselectivity of insertion of various 1,6-heptadiynes, N,N-dipropargylamines, N,N-dipropargylammonium salts and dipropargyl ethers into different Ru(IV)-alkylidenes, i.e., [Ru(CF(3)COO)(2)(IMesH(2))(CHR), (R = 2,4,5-(MeO)(3)-C(6)H(2) (I1), 2-(2-PrO)-5-NO(2)-C(6)H(3) (I3), 2-(2-PrO)-C(6)H(4) (I4)), [Ru(CF(3)COO)(2)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(CH-2-(2-PrO)-5-NO(2)-C(6)H(3))] (I2), [Ru(CF(3)COO)(2)(3-mesityl-1-((1'R)-1'-phenylethyl)-imidazolin-2-ylidene)(CH-2-(2-PrO)C(6)H(4))] (I5) and [Ru(C(6)F(5)COO)(2)(IMesH(2))(CH-2-(2-PrO)-C(6)H(4))] (I6), (IMesH(2) = 1,3-dimesitylimidazolin-2-ylidene), is described. (13)C NMR experiments revealed that all polymers synthesized by the action of I1-I6 consisted virtually solely (>95%) of five-membered repeat units, i.e., (cyclopent-1-enylene)-1,2-vinylenes, 3,4-(1H-2,5-dihydropyrrylenium)-3,4-vinylenes, and (2-pentyl-2,5-dihydrofurylene)-3,4-vinylenes, respectively. The (13)C NMR-based assignments were supported by the synthesis of model compounds, i.e., (cyclopent-3-ene-1,1-diyldimethylbis(tris(3,5-dimethoxyphenyl)carboxylate) (MC1) and N-propyl-N-ethyl-2,5-dihydropyrrolium tetrafluoroborate (MC2), as well as by ene-yne cross metathesis reactions of 3-(propargyloxy)-1-octyne (M6) with trimethylallylsilane. In the polymerization of N-ethyl-N,N-dipropargylamine (M9), an intermediate was isolated that sheds light onto the role of heteroatoms in the 4-position of 1,6-heptadiynes in cyclopolymerization. In addition, in the cyclopolymerization of M9 by I4 the product resulting from back-biting has been isolated and explains for the low polymerization propensity of Ru-alkylidenes for N-alkyl-N,N-dipropargylamines.