Reaction Of Terminal Alkynes Research Articles

Carbon-nitrogen bond formation via the reaction of terminal alkynes with a dinuclear side-on dinitrogen complex.

The dinuclear dinitrogen complex ([P2N2]Zr)2(mu-eta2:eta2-N2) reacts with terminal aryl alkynes to generate a new species in which the dinitrogen unit has been functionalized. The products formed have the general formula ([P2N2]Zr)2(mu-eta2:eta2-N2CCAr)(mu-CCAr) and display a styryl-hydrazido unit bridging the two Zr centers along with a bridging arylalkynide. The crystal structures of three of these products are reported. A mechanism is proposed for this process that involves cycloaddition of the alkyne to the side-on dinitrogen unit followed by protonation of the Zr-C bond by a second equivalent of terminal alkyne. A fluxional process is operative in solution that equilibrates the phosphorus nuclei at high temperature; in the slow exchange limit, the two [P2N2]Zr ends of complex are inequivalent as evidenced by four resonances in the 31P NMR spectrum for the inequivalent phosphorus donors. This C-N bond-forming reaction is unique in that an activated dinitrogen fragment undergoes a reaction with an alkyne.

Highly Regioselective Palladium/Copper‐Catalyzed Cross‐Coupling Reactions of Terminal Alkynes and Allenes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Substituent Effects in Discotic Liquid Crystals

A series of novel mesogens have been prepared by a five-fold Sonogashira reaction of terminal acetylenes with a functionalized pentabromophenol. The corresponding side chain polymers were prepared by a polymer analogous substitution reaction. The mesogens differ in the nature of the substituents, linking five hexyl tails to the aromatic core, i.e. CH2, O, S, SO2 and CONH groups. A wide range of mesophases and corresponding transition temperatures has been detected, ranging from low melting nematic phases to highly stable columnar phases. The widely variable phase behavior is described in terms of specific intermolecular interactions.

Highly Regiocontrolled Pd‐Catalyzed Cross‐Coupling Reaction of Terminal Alkynes and Allenylphosphine Oxides.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Formation of a cyclobutylidene ring: intramolecular [2 + 2] cycloaddition of allyl and vinylidene C=C bonds under mild conditions.

Intramolecular [2 + 2] cycloaddition of two C=C bonds in vinylidene complexes [Ru(eta5-C9H7){=C=C(R)H}(PPh3){kappa1-(P)-PPh2(C3H5)][BF4] affords cyclobutylidene complexes [Ru(eta5-C9H7){kappa2-(P,C)-(=CC(R)HCH2CHCH2PPh2)}(PPh3)][BF4], which can be also obtained by reaction of terminal alkynes with [Ru(eta5-C9H7)(PPh3){kappa3-(P,C,C)-PPh2(C3H5)}][PF6]. The reaction proceeds under mild conditions via vinylidene complexes, and the activation parameters were determined by kinetic studies.

Reaction of Terminal Alkynes with Hydrazines to Give Nitriles, Catalyzed by TpRuCl(PPh3)2: Novel Catalytic Transformation Involving a Vinylidene Ruthenium Intermediate.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Reaction of Terminal Alkynes with Hydrazines To Give Nitriles, Catalyzed by TpRuCl(PPh3)2: Novel Catalytic Transformation Involving a Vinylidene Ruthenium Intermediate

The reaction of terminal alkynes with hydrazines in the presence of TpRuCl(PPh3)2 (Tp = tris(pyrazolyl)borate) as a catalyst gave nitriles. This reaction involves the intermolecular attack of nitrogen nucleophiles at the α-carbon atom of (vinylidene)metal intermediates which are generated from terminal alkynes.

Mechanistic Studies of the Hydrogenation of Alkynes with Os3(CO)10(μ-H)2 Using para-Hydrogen as a Probe

The reactions of 1-pentyne and acetylene with Os3(CO)10(μ-H)2 in the presence of para-H2 at 3−4 atm and 50−60 °C have been studied. An attempt is made to understand the nature of the intermediates in the catalytic hydrogenation process and the mechanistic relationship of the various organometallic clusters formed to each other and to the overall hydrogenation process. It was found that of the four products usually formed by the reaction of terminal alkynes with Os3(CO)10(μ-H)2, only the σ-π-vinyl complex Os3(CO)10(μ-η2-CHCHR)(μ-H) (A R = H or n-Pr) goes on to yield alkene and the starting Os3(CO)10(μ-H)2. The μ-η2-acetylido complex Os3(CO)10(μ-η2-CCR)(μ-H) (B), a product that results from the loss of hydrogen, is not formed under these conditions, as might be expected, in the presence of excess H2. The μ3-η2-alkyne complex Os3(CO)9(m-CO)(μ3-η2-HCCR) (C) is formed when Os3(CO)10(CH3CN)2 reacts with the subject alkynes in the presence of para-H2, but does not react with para-hydrogen. An unstable α-β-unsatu...

Microwave assisted Mannich reaction of terminal alkynes on alumina

Terminal alkynes, secondary amines, and formaldehyde undergo a Mannich reaction at room temperature in the presence of CuCl on Al2O3 without any organic solvent as reaction medium. The reaction can be promoted by microwave irradiation and is complete within one minute.

FREE RADICAL REACTION OF SODIUM ARENESULFINATES WITH ACETYLENES: NEW REGIO- AND STEREOSELECTIVE PREPARATION OF (E)-β-(PHENYLSELENO)VINYL SULFONES

ABSTRACT 1Free radical reaction of terminal acetylenes with sodium arenesulfinates and diphenyl diselenide in aqueous acetic acid afforded high yields of the regio- and stereoselective (E)-β-(phenylseleno)vinyl sulfones.

Synthesis and Properties of Coil-Shaped 2,3-Thienylene-Ethynylene Oligomers

A series of 2,3-thienylene-ethynylene oligomers have been synthesized by repeated application of the Pd-catalyzed coupling reaction of terminal alkynes and thienyl iodides as the key building steps. The analytical GPC molecular weights, much deflated relative to the actual molecular weights, strongly suggest a coil shape for the conformation of the oligomers in solution. Their electronic absorption and emission spectral features are discussed.

New Reaction of Terminal Acetylenes with Nitrates in the Presence of Sulfur Trioxide: Heterocyclization into 3-Acyl-5-Aryl(Alkyl)Isoxazoles

New Reaction of Terminal Acetylenes with Nitrates in the Presence of Sulfur Trioxide: Heterocyclization into 3-Acyl-5-Aryl(Alkyl)Isoxazoles

A New and Improved Synthesis of trans-1,2-Diiodoalkenes and Their Stereospecific and Highly Regioselective Trifluoromethylation

Reaction of terminal alkynes with iodine in the presence of CuI (5%) in acetonitrile under reflux for several hours gave the trans-1,2-diiodoalkenes in high yields. The trifluoromethylation of thes...

Some acetylene and hydride chemistry of group 8 metal complexes with cyclopentadienyls and their analogous ligands

The reactivities of several ruthenium complexes with closely related ligands Cp, Cp*, PCP (2,6-(PPh 2CH 2) 2C 6H 3) and Tp (hydrotris(pyrazolyl)borate) towards terminal acetylenes are compared. While reactions of terminal acetylenes with ruthenium complexes such as CpRuCl(PR 3) 2, Cp*RuCl(PR 3) 2 and TpRuCl(PR 3) 2 usually give vinylidene, allenylidene, hydroxyvinylidene or vinylvinylidene complexes, unusual coupling products are produced in the reactions of terminal acetylenes with analogous Ru(PCP) complexes. The structures of group 8 metal hydride complexes of the formula LRuH 3(L′) (L=Cp, Cp*, Tp; L′=PPh 3) and [LMH 2(L′) 2] + (L=Cp, Cp*, Tp; L′=tertiary phosphine) have also been compared in terms of the relative stability of dihydrogen vs. dihydride forms and cis vs. trans-dihydride isomers. Although both Cp and Tp are isoelectronic and both facially coordinate to metal centers, they have different abilities to stabilize the dihydrogen ligand. The difference is reflected in the fact that CpRuH 3(PPh 3) and [CpRuH 2(PPh 3) 2] + are classic metal hydride complexes but TpRuH(H 2)(PPh 3) and [TpRu(H 2)(PPh 3) 2] + are dihydrogen complexes. Complexes of the formula [C 5R 5)MH 2(PP)] + (M=Fe, Ru, Os; PP=chelating diphosphine) can adopt either the pure dihydrogen form, or a mixture of dihydrogen and trans-dihydride forms, or pure trans-dihydride form, or a mixture of cis- and trans-dihydride forms, depending on metals, C 5R 5 and the chelating ring sizes of diphosphines.

Ruthenium Catalyzed Homocoupling of Terminal Alkynes

Several complexes of the type RuTp(L)(L′)Cl (L, L′=P, N, O donors) were tested with respect to their ability of promoting catalytic C–C-coupling reactions of terminal acetylenes. When L=tertiary phosphine, predominantly dimerization occurs, RuTp(PPh3)2H being the most efficient pre-catalyst. In the absence of a phosphine ligand, polymerization takes place with RuTp(COD)Cl as the most effective pre-catalyst. Both product distribution and conversion depend strongly on the substituent of the alkyne and to a lesser extent on the co-ligands of the ruthenium complex. The catalytically active species is the 16e− alkynyl complex RuTp(L)(–C*C–R) which in case of L=PCy 3 and R=Bu n could be trapped as RuTp(PCy3)(–C*CBu n )(CO).

Selenothioic AcidS-Esters: Synthesis, Characterization, and Trend for Stability

Selenothioic acid S-alkyl esters were synthesized from the reaction of terminal acetylenes with n-butyllithium, selenium, and alkanethiols in moderate to high yields. The use of substituted benzenethiols or (triphenylsilyl)acetylene allowed for the isolation of S-aryl esters. The synthesis of α-aryl selenothioic acid S-alkyl esters was attained by the acid-catalyzed reaction of selenoacetic acid Se-alkynyl esters with thiols in good yields. 77Se NMR studies showed that the chemical shifts in a series of the esters were downfield of that in selenoester by about 500 ppm and were upfield of that in selenoketone by about 600 ppm. In the visible spectra the absorptions of the esters were observed at about 340 and 568 nm. X-ray molecular structure analyses of α-silyl esters showed that the bond distances in the selenocarbonyl group were 1.792 and 1.785 Å, respectively. The formation of 1,3-diselenetane was confirmed from the decomposed products of S-phenyl ester. The trend for the stability of selenothioic acid S-esters is discussed on the basis of these synthetic results.

セレノチオ酸Ｓ‐エステル，ジセレノ酸エステル：合成，安定性，反応性

A series of selenothioic acid S-esters and diselenoic acid esters have been synthesized by the following three types of methods : (1) reactions of terminal acetylenes with n-butyllithium, selenium and thiols; (2) reactions of selenoic acid O-methyl esters with aluminum chalcogenolates; (3) reactions of selenothioacetic acid S-esters with aldehydes and/or allylic bromides in the presence of a base. On the basis of synthetic results, the general trends for the relative stability of the esters have been proposed. Among several types of esters, one of the most simple esters, i.e., selenium and sulfur counterparts of acetic acid esters are the most stable. The introduction of aromatic substituents does not necessarily enhance the stability of the esters. Reactions of the esters toward heavy metal salts, such as nickel chloride, zinc iodide, and cadmium acetate, electron deficient alkynes, and reducing agents provided new synthetic methods of a variety of organoselenium compounds.

Reactions of Terminal Alkynes with Group 6−Group 10 Heterobimetallics

Reactions of Terminal Alkynes with Group 6−Group 10 Heterobimetallics

Palladium‐Catalyzed Reactions of Propargylic Compounds in Organic Synthesis

AbstractPalladium was used in organic synthesis for long time only as a heterogeneous catalyst for hydrogenating unsaturated compounds. But in recent years palladium compounds have found broad application as homogeneous catalysts. In the last decade, homogeneous catalysis relying on transition metal complexes has led to innovations in organic synthesis. Complexes of various transition metals are now used for organic synthesis, and each metal has its own characteristic features. Palladium complexes are the most versatile and used extensively in organic synthesis, particularly for carbon–carbon bond formation. Palladium‐catalyzed reactions can be classified into several groups based on their substrates: organic halides, allylic compounds, conjugated dienes, alkenes, and alkynes. Propargylic compounds undergo a variety of palladium‐catalyzed transformations and make up one important class of these reactions. It is well known that copper and silver salts promote or catalyze several reactions of propargylic compounds. However, palladium compounds, particularly Pd0 complexes, show catalytic activities entirely different from those of silver and copper salts. Advances in the research on the palladium‐catalyzed reactions of propargylic compounds in the last decade have made the scope of the reactions clear. The ready availability of numerous propargylic alcohols and their esters by the reaction of terminal alkynes with carbonyl compounds clearly enhances the synthetic utility of their reactions. Palladium complexes, in particular palladium phosphane complexes, are soluble in organic solvents and behave as active catalysts under homogeneous conditions.

ChemInform Abstract: Copper‐Catalyzed Reaction of Terminal Alkynes with Nitrones. Selective Synthesis of 1‐Aza‐1‐buten‐3‐yne and 2‐Azetidinone Derivatives.

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