Dimerization Of Alkynes Research Articles

Verkade Base in FLP Chemistry–From Stoichiometric C–H Bond Cleavage to the Catalytic Dimerization of Alkynes

Stoichiometric and catalytic reactions of terminal alkynes with various FLPs and Lewis acid–base adducts have been investigated. Reactions of phenylacetylene with FLPs composed of the Verkade base ...

Bulky Diphosphine Acetate Ruthenium Complexes: Synthesis and Catalytic Activity in Ketone Transfer Hydrogenation and Alkyne Dimerization

Several mononuclear ruthenium complexes containing bulky diphosphines have been easily prepared from acetate ruthenium precursors. The cyclohexyl complex [Ru(η2-OAc)2(DCyPF)] (1-cy; DCyPF = 1,1′-bi...

Rhodium(I)-NHC Complexes Bearing Bidentate Bis-Heteroatomic Acidato Ligands as gem-Selective Catalysts for Alkyne Dimerization.

A series of Rh(κ2 -BHetA)(η2 -coe)(IPr) complexes bearing 1,3-bis-hetereoatomic acidato ligands (BHetA) including carboxylato (O,O), thioacetato (O,S), amidato (O,N), thioamidato (N,S), and amidinato (N,N), have been prepared by reaction of the dinuclear precursor [Rh(μ-Cl)(IPr)(η2 -coe)]2 with the corresponding anionic BHetA species. The RhI -NHC-BHetA compounds catalyze the dimerization of aryl alkynes, showing excellent selectivity for the head-to-tail enynes. Among them, the acetanilidato-based catalyst has shown an outstanding catalytic performance reaching unprecedented TOF levels of 2500 h-1 with complete selectivity for the gem-isomer. Investigation of the reaction mechanism supports a non-oxidative pathway in which the BHetA ligand behaves as proton shuttle through intermediate κ1 -HBHetA species. However, in the presence of pyridine as additive, the identification of the common RhIII H(C≡CPh)2 (IPr)(py)2 intermediate gives support for an alternative oxidative route.

Heterogenized catalyst for acetylene dimerization

Heterogenized catalyst for acetylene dimerization

Dimerization of Aromatic Terminal Alkynes Featuring Hydrophilic Functional Groups under Ruthenium and Acid Promoted Catalysis. Competitive Alkyne Hydration upon Substituent Effect

AbstractThe self‐coupling (hydroalkynylation) process of aromatic terminal alkynes RC6H4C≡CH to give dimeric 1,4‐diaryl‐1‐en‐3‐yne products (trans‐RC6H4C≡CCH=CHC6H4R) is catalyzed by the complex [{RuCl(μ‐Cl)(η6‐p‐cymene)}2] with sodium acetate co‐catalyst dissolved in neat acetic acid, the reaction proceeding with high trans‐stereoselectivity under mild conditions (r.t.) even for substrates with protic or polar substituent groups (e. g. R=3‐OH, 4‐CH2OH, 4‐NHAc, ‐CHO, 4‐tetra‐O‐acetyl‐β‐D‐glucopyranoside). In presence of strongly electron donating arene substituents, NMe2 and NH2, the triple bond is activated toward exclusive triple bond hydration by reaction with acetic acid at room temperature also in absence of the ruthenium catalyst.

Piano-Stool Iron Complexes as Precatalysts for gem-Specific Dimerization of Terminal Alkynes

A series of piano-stool Fe–NHC complexes have been prepared and characterized. The NHC ligands used herein possess a benzyl and a mesityl wingtip groups and have different electronic structures wit...

Catalytic Dimerization of Alkynes via C–H Bond Cleavage by a Platinum–Silylene Complex

The cyclodimerization of diphenylacetylene derivatives catalyzed by a platinum–silylene complex is reported. The reaction proceeds via the cleavage of a carbon–hydrogen bond at the position ortho to an alkynyl group, and no additives are needed. Platinum complexes bearing other common ligands, such as phosphines and NHCs, failed to promote this reaction, highlighting the utility of the silylene ligand in this reaction.

Catalytic Alkyne Dimerization without Noble Metals

1,3-Enynes are core structures of various natural products or pharmaceuticals and are broadly used synthons in organic synthesis. Metal-catalyzed alkyne dimerization is a desirable preparation method, due to its perfect atom economy and the readily available alkyne substrates. Controlling the regio- and stereoselectivity remains a challenge, due to the competing formation of the head-to-tail (gem) and head-to-head (E/Z) isomers. Although catalytic systems based on noble metals have been extensively studied, there has been a growing interest to replace these noble metals with environmentally benign and inexpensive alternatives. In this Perspective, we highlight recent advances in catalytic alkyne dimerization, without the use of noble metals.

Unexpected Reactions of Terminal Alkynes in Targeted "Click Chemistry'' Coppercatalyzed Azide-alkyne Cycloadditions.

High efficiency in terms of reaction yield and purity has led to the extensive utilization of copper-catalyzed azide-alkyne cycloaddition (CuAAC) in various fields of chemistry. Its compatibility with low molecular weight alcohols promotes the application in surfactant synthesis to tackle the miscibility constraints of the reactants. For the tuning of surfactant properties, double click coupling of the antipode precursors was attempted. Failure of the CuAAC to provide the targeted product in combination with unexpected reaction outputs led to an investigation of the side reaction. The CuAAC-based coupling of sugar azide with propargyl building block in the presence of copper- (I) catalyst exclusively led to the mono-coupling product in a respectable yield of almost 80%. Besides the unexpected incomplete conversion, the loss of the remaining propargyl group, as indicated by both NMR and MS. On the other hand, application of substantial amounts of CuSO4 under reducing conditions in refluxing toluene/water furnished the alkyne dimer in a moderate yield of 43%, while no change of azide compound was noticed. The Cu(I)-catalyst applied for azide-alkyne cycloadditions enables the homo-coupling of certain terminal alkynes at a higher temperature. Moreover, aromatic propargyl ethers may be cleaved to furnish the corresponding phenol. The copper-catalyzed coupling appeared highly sensitive towards the alkyne compound. Only selected derivatives of propargyl alcohol were successfully dimerized. The observed failure of the Huisgen reaction for the synthesis of sugar-based surfactants may indicate non-recognized constrains of the reaction, which could affect its wide application in bioconjugation. The temperature requirement for the alternative dimerization of terminal alkynes renders this side reaction nonrelevant for typical click couplings, while narrow substrate diversity and moderate yield limit its synthetic application.

Hydrazinylbenzenesulfonic Acid-Modified Nieuwland Catalyst for Acetylene Dimerization Reaction

A novel Nieuwland catalytic system, containing 5 mol% of 4-hydrazinylbenzenesulfonic acid (S8), was developed and exhibited an excellent catalytic performance and good stability in the acetylene dimerization reaction. The acetylene conversion reached 57.1%, while the selectivity of monovinylacetylene (MVA) was 75.1%. The yield of MVA was maintained at 42.9% under an acetylene gas hourly space velocity (GHSV) of 80 h−1 at 80 °C, which was increased by 18.8% over the control Nieuwland catalytic system. The addition of S8 increased the dissolution of CuCl in water, inhibited the polymer formation, and hindered the Cu+ loss during the reaction process, thus improving the activity and the long-term stability of the modified Nieuwland catalyst.

Concise synthesis of thiophene C-nucleoside analogues bearing sugar residues and aromatic residues through dimerization and sulfur heterocyclization of sugar alkynes and substituted iodoethynylbenzene.

The synthesis of thiophene C-nucleoside analogues bearing sugar residues (mono- and disaccharides) and aromatic residues has been achieved by symmetric dimerization of terminal sugar alkynes or unsymmetric dimerization of terminal sugar alkynes and substituted iodoethynylbenzene followed by sulfur heterocyclization in one pot. Homocoupling of terminal sugar alkynes and subsequent sulfur heterocyclization produce thiophene C-nucleoside analogues bearing disaccharides. Unsymmetric dimerization of terminal sugar alkynes and substituted iodoethynylbenzene followed by sulfur heterocyclization give thiophene C-nucleoside analogues bearing monosaccharide and aromatic residues. This approach is concise, general and mild, and is suitable for structurally diverse pyranosides, furanosides, and acyclic sugars. Thirty-two examples have been given and the corresponding products are obtained in moderate to excellent yields.

Dimerization of terminal alkynes promoted by a heterobimetallic Zr/Co complex

Enynes are important synthetic intermediates that are also found in a variety of natural products and other biologically relevant molecules. The most atom economical synthetic route to enynes is via the direct coupling of readily available terminal alkyne precursors. Towards this goal, we demonstrate the formation of 1,3-enynes from terminal alkynes facilitated by a reduced ZrIV/Co-I heterobimetallic complex. An intermediate is trapped as a tBuNC adduct, revealing that bimetallic activation of the terminal C-H bond of the alkyne is an essential mechanistic step.

A novel risedronic acid-modified Nieuwland catalyst for acetylene dimerization

Nieuwland catalyst (NC) was modified with different phosphonic acids (Px) and evaluated for their acetylene dimerization activity in monovinyl acetylene (MVA) production. Nearly 49.2% of acetylene conversion and 80.3% of MVA selectivity were obtained in 5 mol% risedronic acid (P2)-modified NC under an acetylene-gas space velocity of 105 h−1 at 80 °C, which was 17.8% higher than the yield of the control NC. The characterization results of NC and P2–NC indicated that the addition of P2 effectively enhanced the stability of the Cu ions and inhibited oxidation of the active component Cu+, improving their catalytic activity and long-term stability.

Cu(II)Cu(I)/AC Catalysts for Gas–Solid Acetylene Dimerization

Cu(II)Cu(I)/activated carbon (AC) catalysts with different copper chloride and cuprous chloride impregnation orders were firstly prepared. The effect of the Cu(II) additive on the catalytic performance of Cu(I)/AC catalysts for gas-solid acetylene dimerization was assessed, and the catalysts were characterized using XRD, TEM, TPR, TPD, TGA, BET, XPS and ICP-AES. The optimal catalytic performance is obtained using the Cu(II)0.3Cu(I)1/AC catalyst with an average acetylene conversion of 70.0% (reaction conditions: temperature: 100°C; acetylene gas hourly space velocity: 120 h-1). This value is an increase of 33.0% compared with the average acetylene conversion of 37.0% when the Cu(I)1/AC catalyst is used under the same reaction conditions. The results demonstrated that the addition of Cu(II) promoted the dispersion of the active components, inhibited copper loss on the catalysts, and enhanced the adsorption of reactant acetylene on the catalysts. Consequently, the results indicate that a suitable Cu+/Cu2+ mo...

Quantum Chemical Exploration of Intermolecular Reactions of Acetylene.

Quantum chemical explorations of potential energy surfaces showed that acetylene produces various products starting from molecular arrays in short distances of 1.3-2.5 Å. Arrays of (C2 H2 )2 gave cyclobutadiene, tetrahedrane, and acetylene dimers. Arrays of (C2 H2 )3 gave benzene, prismane, benzvalene, Dewar benzene, and acetylene trimers. Arrays of (C2 H2 )4 gave cubane, cyclooctatetranene, and acetylene tetramers. Different forms of initial arrays yielded different sets of products; a parallel array of two monomers gave cyclobutadiene, whereas a cross array gave tetrahedrane. Initial molecular arrays with unusually close contacts were estimated to require local forces of 1-9 × 10-8 N. © 2019 Wiley Periodicals, Inc.

“Golden Age” of Homogeneous Catalysis Chemistry of Alkynes: Dimerization and Oligomerization of Alkynes

History of the development and use of homogeneous metal complex catalysts in the chemistry of acetylene and its derivatives is considered. Achievements of the catalytic chemistry of alkynes in the creation of affective catalytic systems (based on Groups 3—11 and 13 of the Periodic Table) for alkyne dimerization, capable of producing desired dimeric isomers possessing high chemo-, stereo- and regioselectivity are analyzed. The nature of elementary stages in four mechanisms of dimerization and the relations of the nature of organometallic intermediates to the nature of catalyst (metal and ligand), substrate, and type of mechanism, and, hence, to the selectivity of dimerization process are discussed.

Palladium-Catalyzed Arylthiolation of Alkynes Enabled by Surmounting Competitive Dimerization of Alkynes.

By overcoming the unwanted catalytic dimerization of terminal alkynes, palladium-catalyzed carbothiolation of alkynes with heteroaryl sulfides has been accomplished to provide the corresponding β-heteroaryl alkenyl sulfides with high regio- and stereoselectivity. The key for the preferential arylthiolation is the use of arylsulfanyl segments, instead of alkylsulfanyl, for smooth C(heteroaryl)-SR1 bond cleavage and/or of alkylacetylenes that are reluctant to undergo the dimerization. The reaction proceeds under mild and neutral conditions, with various functionalities being thus tolerated.

Evaluation of the Catalytic Capability of cis‐ and trans‐Diquinoxaline Spanned Cavitands

Three new cis‐diquinoxaline spanned cavitands were successfully synthesized. These cis‐diphosphinated derivatives were applied in homogeneous gold‐catalyzed dimerization and hydration of alkynes as well as rhodium‐catalyzed styrene hydroformylation. The results were ranked with those obtained with their trans‐diphosphinated isomeric analogues. The structure‐activity relationship employing these two cavitands reveals that the cis‐ or trans‐positioning of the catalyst centers directly influences cooperation between the two metallic atoms to control catalytic activity, reaction profile, and product selectivity. This comparative study provides us an intellectual basis for future catalytic cavitand chemistry and homogeneous catalysis.

Regio‐ and Stereoselective Synthesis of Enynyl‐Aryl Ethers Enabled by Copper/Iodide Tandem Catalysis

AbstractAn approach to preparing enynyl‐aryl ethers from phenols and phenylacetylenes is described. This method without extra ligands, overcoming the favored Glaser‐Hay dimerization of alkyne, features a wide substrate scope (38 examples including endofolliculina and indole) and the merits of high atom and step economy, good regio‐ and stereoselectivity (Z‐isomers major) in moderate to good isolated yields. Mechanistic studies show that the reaction is enabled by distinctive copper/iodide tandem catalysis.magnified image

Metal-free gem selective dimerization of terminal alkynes catalyzed by a pyridonate borane complex

The metal-free dimerization of alkynes catalyzed by a pyridonate borane complex via a 1,2-carboration is reported.