7642-15-1Relevant academic research and scientific papers
Hydrogen transfer from formic acid to alkynes catalyzed by a diruthenium complex
Gao,Jennings,Puddephatt
, p. 915 - 921 (2001)
The diruthenium(0) complex [Ru2(μ-CO)(CO)4(μ-dppm)2] (1) (dppm = Ph2PCH2PPh2), is a catalyst for the transfer hydrogenation, using formic acid as hydrogen donor, of the alkynes PhC≡CPh, PhC≡CMe, EtC≡CEt, and PrC≡CPr but not of the terminal alkynes HC≡CH, PhC≡CH, BuC≡CH, or the alkynes containing one or two electron-withdrawing substituents PhC≡CCO2Me and MeO2CC≡CCO2Me. In the successful reactions, the formic acid is first decomposed to carbon dioxide and hydrogen, which then hydrogenates the alkynes in a slower reaction. In the unsuccessful reactions, the decomposition of formic acid is strongly retarded by the alkyne. In the case with the alkyne PhC≡CH, it is shown that the alkyne reacts with protonated 1 to give first [Ru2(μ-CPh=CH2)(CO)4(μ-dppm) 2][HCO2], which then isomerizes to give the catalytically inactive, stable complex [Ru2(μ-CH=CHPh)(CO)4(μ-dppm)2][HCO 2]. This complex has been structurally characterized and both of the μ-styrenyl complexes are shown to be fluxional in solution.
5 - Endo ring closures of allylic hydroperoxides: Useful routes to 1,2 - dioxolanes involving strongly stereoselective free radical and polar reactions
Courtneidge, John L.,Bush, Melanie,Loh, Lay See
, p. 3835 - 3856 (1992)
Intramolecular cyclisation of simple allylic hydroperoxides to give substituted 1,2 - dioxolanes using electrophilic reagents has been investigated. Closure using mercury(II) acetate and electrophilic halogen reagents (NBS, Br2 ButOC1) occurs by Markovnikov - directed and conformationally strict stereospecificity. Subsequent free - radical reaction of the mercurated dioxolanes involved specific reaction involving reaction from the sterically unprotected face of the intermediate dioxolanyl radical.
Pd, Cu and Bimetallic PdCu NPs Supported on CNTs and Phosphine-Functionalized Silica: One-Pot Preparation, Characterization and Testing in the Semi-Hydrogenation of Alkynes
Sánchez-Resa, Daniel,Delgado, Jorge A.,Fernández-Martínez, Maria Dolores,Didelot, Chloé,De Mallmann, Aimery,Szeto, Ka? C.,Taoufik, Mostafa,Claver, Carmen,Godard, Cyril
supporting information, p. 4970 - 4978 (2021/11/10)
Triphenylphosphine stabilized Pd, Cu and PdCu nanocatalysts supported on carbon nanotubes (CNTs) or phosphorus functionalised silica (P?SiO2) were prepared via a one-pot methodology. The series of P?SiO2 supported catalysts evidenced metal particle sizes of metallic nanoparticles (M-NPs) between 1 and 2.4 nm, smaller than their equivalents on CNTs (2.4–2.6 nm). Such a difference in particle size as a function of the support and the metallic composition indicated the more pronounced mediation of the CNTs support during the formation of the M-NPs when compared to the P?SiO2 support. The series of supported catalysts were tested in the semi-hydrogenation of alkynes providing differences in reactivity which might be correlated with the size and composition of the M-NPs and the nature of corresponding support. The carbon supported catalysts displayed in general higher activities than those supported on silica and the bimetallic catalyst PdCu/CNTs were the most selective for the case of alkyl substituted alkynes. This catalyst could moreover be recycled several times without loss of activity nor selectivity.
Copper(0) nanoparticle catalyzed Z-Selective Transfer Semihydrogenation of Internal Alkynes
Moran, Maria Jesus,Martina, Katia,Bieliunas, Vidmantas,Baricco, Francesca,Tagliapietra, Silvia,Berlier, Gloria,De Borggraeve, Wim M.,Cravotto, Giancarlo
supporting information, p. 2850 - 2860 (2021/05/06)
The use of copper(0) nanoparticles in the transfer semihydrogenation of alkynes has been investigated as a lead-free alternative to Lindlar catalysts. A stereo-selective methodology for the hydrogenation of internal alkynes to the corresponding (Z)-alkenes in high isolated yields (86% average) has been developed. This green and sustainable transfer hydrogenation protocol relies on non-noble copper nanoparticles for reduction of both electron-rich and electron-deficient, aliphatic-substituted and aromatic- substituted internal alkynes. Polyols, such as ethylene glycol and glycerol, have been proven to act as hydrogen sources, and excellent stereo- and chemoselectivity have been observed. Enabling technologies, such as microwave and ultrasound irradiation are shown to enhance heat and mass transfer, whether used alone or in combination, resulting in a decrease in reaction time from hours to minutes. (Figure presented.).
Catalytic Hydrogenation of Alkenes and Alkynes by a Cobalt Pincer Complex: Evidence of Roles for Both Co(I) and Co(II)
Alawisi, Hussah,Arman, Hadi D.,Tonzetich, Zachary J.
, p. 1062 - 1070 (2021/04/09)
The Co(I) complex, [Co(N2)(CyPNP)] (CyPNP = anion of 2,5-bis-(dicyclohexylphosphinomethyl)pyrrole), is active toward the catalytic hydrogenation of terminal alkenes and the semi-hydrogenation of internal alkynes under 2 bar of H2 (g) at room temperature. The products of alkyne semi-hydrogenation are a mixture of E- and Z-alkenes. By contrast, use of the related cobalt(I) precatalyst, [Co(PMe3)(CyPNP)], results in formation of exclusively Z-alkenes. A semi-stable Co(II) species, [CoH(CyPNP)], can also be generated by treatment of degassed solutions of [Co(N2)(CyPNP)] with H2. The CoII-hydride displays activity toward both alkene hydrogenation and isomerization, but its instability hampers implementation as a catalyst. Several species relevant to potential catalytic intermediates have been isolated and detected in solution. These compounds include alkene and alkyne adducts of Co(I) as well as a Co(III) dihydride species. Catalytic results with the compounds examined are most consistent with a process involving shuttling between Co(I) and Co(III) states. However, generation of small quantities of Co(II) during catalytic turnover appears to be responsible for the isomerization observed for alkyne semi-hydrogenation. The interplay of cobalt oxidation states within the same catalyst system is discussed in the context of mechanistic scenarios for catalytic hydrogenation.
Controlling the performance of a silver co-catalyst by a palladium core in TiO2-photocatalyzed alkyne semihydrogenation and H2 production
Fudo, Eri,Imai, Shota,Kojima, Yasumi,Kominami, Hiroshi,Tanaka, Atsuhiro
, (2021/08/24)
Titanium (IV) oxide (TiO2) having palladium (Pd) core-silver (Ag) shell nanoparticles (Pd@Ag/TiO2) was prepared by using a two-step (Pd first and then Ag) photodeposition method. The core-shell structure of the nanoparticles having various Ag contents (shell thicknesses) and the electron states of Pd and Ag were investigated by transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. The effect of the Pd core and the Ag shell was evaluated by hydrogenation of 4-octyne in alcohol suspensions of a photocatalyst under argon and light irradiation. 4-Octyne was fully hydrogenated to 4-octane over Pd/TiO2, whereas 4-octyne was selectively hydrogenated to cis-4-octene over Pd(0.2)@Ag(0.5)/TiO2. Further increase in the Ag content resulted in a decrease in the conversion of 4-octyne. Pd-free Ag/TiO2 was inactive for hydrogenation of alkyne and induced coupling of active hydrogen species (H2 production). Photocatalytic reactions at various temperatures revealed that the change in selectivity (semihydrogenation or H2 production) can be explained by the difference in values of activation energy of the two reactions. An applicability test showed that the Pd@Ag/TiO2 photocatalyst can be used for hydrogenation of various alkynes to alkenes.
Increasing Olefin Metathesis Activity of Silica-Supported Molybdenum Imido Adamantylidene Complexes through E Ligand σ-Donation
Nater, Darryl F.,Paul, Bhaskar,L?tsch, Lukas,Schrock, Richard R.,Copéret, Christophe
, (2021/09/29)
Molybdenum imido adamantylidene complexes with different substituents on the imido ligand (dipp=2,6-diisopropylphenyl, ArF5=C6F5, and tBu) having distinct electron donating abilities were investigated for the metathesis of internal and terminal olefins, for both molecular and silica-supported species using standardized protocols. Here we show that surface immobilization of these compounds results in dramatically increased activity compared to their molecular counterparts. Additionally, we show that electron withdrawing imido groups increase the activity of the compound towards terminal olefins while they simultaneously decrease the ability to metathesize internal olefins. Furthermore, these systems also show high stability when used as initiators in olefin metathesis, although the species that display higher initial activity deactivate faster than those that show more a more moderate reaction rate at first. Our catalytic studies, augmented by DFT calculations, show that all investigated compounds have a remarkably small energy difference between the trigonal bipyramidal (TBP) and square planar (SP) configurations of the metallacyclobutane intermediates, which has previously been linked to high activity.
SYNTHESIS OF PHEROMONE DERIVATIVES VIA Z-SELECTIVE OLEFIN METATHESIS
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Paragraph 0222; 0231, (2021/12/28)
Disclosed herein are methods for synthesizing fatty olefin metathesis products of high Z-isomeric purity from olefin feedstocks of low Z-isomeric purity. The methods include contacting a contacting an olefin metathesis reaction partner, such as acylated alkenol or an alkenal acetal, with an internal olefin in the presence of a Z-selective metathesis catalyst to form the fatty olefin metathesis product. In various embodiments, the fatty olefin metathesis products are insect pheromones. Pheromone compositions and methods of using them are also described.
Mechanism of Z-Selective Hydroalkylation of Terminal Alkynes
Lalic, Gojko,Lee, Mitchell T.
supporting information, p. 16663 - 16672 (2021/10/21)
This paper describes a detailed mechanistic study of the silver-catalyzed Z-selective hydroalkylation of terminal alkynes. Considering the established mechanistic paradigms for Z-selective hydroalkylation of alkynes, we explored a mechanism based on the radical carbometalation of alkynes. Experimental results have provided strong evidence against the initially proposed radical mechanism and have led us to propose a new mechanism for the Z-selective hydroalkylation of alkynes based on boronate formation and a 1,2-metalate shift. The new mechanism provides a rationale for the excellent Z-selectivity observed in the reaction. A series of stoichiometric experiments has probed the feasibility of the proposed elementary steps and revealed an additional role of the silver catalyst in the protodeboration of an intermediate. Finally, a series of kinetic measurements, KIE experiments, and competition experiments allowed us to identify the turnover limiting step and the resting state of the catalyst. We believe that the results of this study will be useful in the further exploration and development of related transformations of alkynes.
Ni-Catalyzed Isomerization-Hydrocyanation Tandem Reactions: Access to Linear Nitriles from Aliphatic Internal Olefins
Gao, Jihui,Ni, Jie,Yu, Rongrong,Cheng, Gui-Juan,Fang, Xianjie
supporting information, p. 486 - 490 (2021/02/05)
A highly regioselective nickel-based catalyst system for the isomerization/hydrocyanation of aliphatic internal olefins is described. This benign tandem reaction provides facile access to a wide variety of aliphatic nitriles in good yields with excellent regioselectivities. Thanks to Lewis acid-free conditions, the protocol features board functional groups tolerance, including secondary amine and unprotected alcohol groups.
