Cyclotrimerization Of Alkynes Research Articles

Synthesis of Chiral 3‐Substituted Phthalides via Rhodium(I)‐Catalyzed Crossed Alkyne Cyclotrimerization.

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A Highly Efficient and Flexible Synthesis of Substituted Carbazoles by Rhodium‐Catalyzed Inter‐ and Intramolecular Alkyne Cyclotrimerizations.

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New Advances in Selected Transition Metal-Catalyzed Annulations

This account describes the recent advances on the Pd-catalyzed [4+2]-benzannulation reaction, development of chemo- and regiospecific formal [2+2+2]-cyclotrimerization of alkynes, as well as discovery and evolution of the transition metal-catalyzed cycloisomerization of alkynyl ketones and imines into five-membered heteroaromatics.

First total synthesis of the marine illudalane sesquiterpenoid alcyopterosin E.

The first synthesis of the marine illudalane sesquiterpenoid alcyopterosin E was accomplished through a concise ABC ring-formation strategy using a rhodium(I)-catalysed intramolecular alkyne cyclotrimerisation as key connection.

Metallaborane Reaction Chemistry. nido-Dirhodapentaborane Isomer Structures and Stabilities and Utilization of Dirhodaboranes as Catalysts for Alkyne Cyclotrimerization

The reaction of (Cp*Rh)2B2H6 (1) with BH3THF under mild conditions leads to the intermediate (Cp*Rh)2B3H7, which is shown to exist in the two isomeric forms 1,2-(Cp*Rh)2B3H7 (2a) 1,2-(Cp*Rh)2(μ-H)B3H6 (2b) by a solid-state structure of 2a and low-temperature NMR data of the mixture. 1 slowly decomposes at room temperature to yield a number of products including pileo-(Cp*Rh)3B4H4 (4), which has been characterized by a solid-state structure determination. 2 converts on heating to 2,3-(Cp*Rh)2B3H7 (3), of known structure. 1−3 catalyze the cyclotrimerization of both terminal and internal alkynes with differing activities. The rate of catalysis is inhibited by PPh3 and pyridine and competition experiments show evidence for a multistep mechanism with concentration-dependent selectivity. The pathway proposed suggests the borane fragment acts in an ancillary role by providing a cluster environment for the dimetal fragment. Metal polyhedral edge opening on alkyne (or base) addition is proposed as the novel activa...

A Highly Efficient and Flexible Synthesis of Substituted Carbazoles by Rhodium-Catalyzed Inter- and Intramolecular Alkyne Cyclotrimerizations

Eine A→ABC- (oder A→ABCD-)Ringbildungs-Strategie erweist sich als äußerst effizient für den Aufbau substituierter Carbazole [Gl. (1); Ts=Tosyl]. Diese werden durch inter- und intramolekulare Alkincyclotrimerisierungen, vermittelt durch den Wilkinson-Katalysator, aufgebaut, was diese Reaktion bedeutsam für die Natur- und Wirkstoffsynthese macht. Die hierzu benötigten Diine werden durch Kombinationen von Sonogashira- und N-Ethinylierungsreaktionen in wenigen Stufen erhalten. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2002/z19409_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

A highly efficient and flexible synthesis of substituted carbazoles by rhodium-catalyzed inter- and intramolecular alkyne cyclotrimerizations.

An A→ABC or A→ABCD ring-formation strategy proves extremely efficient for generating substituted carbazoles ([Eq. (1)]; Ts=tosyl). Inter- and intramolecular alkyne cyclotrimerizations mediated by Wilkinson's catalyst provide substituted carbazoles of relevance for natural product and drug-related synthesis. The diynes required for these reactions are obtained in a few steps by a combination of Sonogashira and N-ethynylation reactions.

Polymerization of phenylacetylene catalyzed by organoiridium compounds

The compounds [Ir(cod)X] 2 (cod=1,5-cyclooctadiene; X=Cl, OMe) catalyze the polymerization of phenylacetylene, with negligible formation of oligomeric products. At variance, the monoolefin analogue [Ir(cot) 2Cl] 2 (cot=cyclooctene) only promotes alkyne cyclotrimerization. The polymerization reaction proceeds in various solvents such as tetrahydrofuran (THF), chloroform and benzene, but it is most favored when using NEt 3 as reaction medium. The role of the diene in the catalytic reaction is investigated, also in relation to a deactivation process of the catalyst with time. Spectroscopic studies of the catalytic reaction indicate the formation of monomeric iridium-solvent adducts, which are likely to be the initiators of the polymerization reaction. A possible reaction mechanism is proposed, according to the data reported in the literature and the results of the present investigation.

Amphiphilic Resin-Supported Rhodium-Phosphine Catalysts for C-C Bond Forming Reactions in Water

Amphiphilic resin-supported rhodium-phosphine complexes were prepared on polystyrene-poly(ethylene glycol) graft co-polymer (1% DVB cross-linked) beads. The immobilized rhodium complexes exhibited high catalytic activity in water to promote hydroformylation of 1-alkenes, [2+2+2] cyclotrimerization of internal alkynes forming benzene rings, and 1,4-addition of arylboronic acids.

Catalytic C−C Bond Activation in Biphenylene and Cyclotrimerization of Alkynes: Increased Reactivity of P,N- versus P,P-Substituted Nickel Complexes

Reaction of Ni(COD)2 with the bidentate hybrid ligand (iPr)2CH2CH2NMe2 (PN) and PhC⋮CR (R = Ph, tBu, CF3, C⋮CPh) afforded the donor-stabilized mononuclear Ni(0) complexes (PN)Ni(η2-PhC⋮CR) (R = Ph (1), tBu (4), CF3 (5)) and the dinuclear compound (PN)Ni(η2;η2-PhC⋮C−C⋮CPh)Ni(PN) (3), respectively. In the presence of excess alkyne, compounds 1, 3, and 4 turned out to be active species for the catalytic carbon−carbon bond activation in biphenylene and formation of the corresponding 9,10-disubstituted phenanthrenes. However, cyclotrimerization to benzene derivatives instead of C−C bond cleavage occurred with complex 5 in the presence of excess CF3C⋮CPh and biphenylene. In contrast, the corresponding bis-phosphino-substituted species (dippe)Ni(η2-PhC⋮CR) (R = Ph (2), CF3 (9)) showed substantially reduced catalytic activity toward phenanthrene formation or cyclotrimerization reactions.

Selectivity of Surface Defects for the Activation of Supported Metal Atoms: Acetylene Cyclotrimerization on Pd1/MgO

We report on the results of density functional cluster model calculations on thermodynamical and kinetical aspects of the acetylene cyclotrimerization reaction occurring on single Pd atoms deposited with soft-landing techniques on MgO(100) thin films. The different elementary steps of the reaction as well as the transition states involved have been investigated in detail for Pd atoms adsorbed on different sites of MgO to understand the role of the substrate in this reaction. The analysis of the complete reaction path indicates that only basic defect sites such as neutral and charged oxygen vacancies (F and F+ centers) located at the MgO terraces can activate supported Pd atoms for this process.

Methylidynetricobalt nonacarbonyl catalyzed cyclotrimerization of alkynes.

A cobalt carbonyl cluster, methylidynetricobalt nonacarbonyl, catalyzed inter- and intramolecular cyclotrimerization of alkynes producing substituted benzene derivatives in good to excellent yields.

Reactions of the Triosmium−Antimony Cluster Os3(μ-SbPh2)(μ-H)(μ3,η2-C6H4)(CO)9 with Alkynes: C−C Bond Coupling to a Cluster-Bound Phenylene and Catalytic Alkyne Cyclotrimerization

The reaction of the osmium−antimony cluster Os3(μ-SbPh2)(μ-H)(μ3,η2-C6H4)(CO)9, 1, with the terminal alkynes PhC⋮CH and tBuC⋮CH led to products involving C−C bond coupling with the phenylene ligand on the cluster, viz., Os3(μ-SbPh2)(μ,η2-HCC(H)Ph)(μ-η4-C6H4C(H)CPh)(CO)7, 2, and Os5(μ4-Sb)(μ-SbPh2)(μ-H)(μ3,η3-C6H4)(μ,η2-PhCC(H)But)(CO)14, 4. Cluster 1 was also found to be an effective catalyst for the cyclotrimerization of diphenylacetylene to hexaphenylbenzene.

Synthesis of monodisperse oligo-p-phenylenes via rhodium-catalyzed alkyne cyclotrimerization.

[structure: see text] A novel synthesis of monodisperse oligo-p-phenylenes is described that features alkyne cyclotrimerization of ether-linked p-dialkynylarenes. This route introduces solubilizing dihydrofuran and alcohol functional groups that may improve processing of the corresponding polymeric p-phenylene materials.

Oligomerization of trimethylsilyl acetylene to form large molecules on reduced surfaces of TiO 2(0 0 1)

The catalytic cyclotrimerization of alkynes on reduced TiO 2(0 0 1) surfaces has been explored to probe the active sites for carboncarbon bond formation. The influence of surface–adsorbate interactions on the reaction mechanism was further probed by studies designed to characterize the steric effects of differently functionalized alkynes. The chemistry of trimethylsilyl acetylene on surfaces containing Ti 2+ sites clearly demonstrates that cyclotrimerization of heteroatom-containing alkynes is feasible. Trimethylsilyl acetylene can be cyclized to form tris-(trimethylsilyl)-benzene on the reduced titania surface. However, the principal product on both reduced and stoichiometric surfaces of TiO 2(0 0 1) is the hydrogenation product, trimethylvinylsilane (TMVS). The low yield of oligomeric products is attributed to the steric effect of the bulky trimethylsilyl group.

Alkyne oligomerization catalyzed by molybdenum(0) complexes

Three new molybdenum(0) complexes, [Mo(CO) 3(Hpz) 3] ( 1), [Mo(CO) 2(Hpz) 2(DMAD) 2] ( 2), (DMAD=dimethyl acetylenedicarboxylate) and [Mo(CO) 3(1-Me-imidazole) 3] ( 3) were synthesized and characterized. Their activity and selectivity in alkyne cyclotrimerization and co-trimerization reactions was investigated. The molecular structures of 1 and 2 have been determined by unconventional powder and standard single-crystal diffraction methods, respectively. 1 consists of a pseudo-octahedral complex of C 3 symmetry, with the ligands in fac disposition; complex 2, of idealized C 2 symmetry, is obtained by substitution of one CO and one pyrazole in 1 by two DMAD ligands, and shows the rare trans configuration of π-bound acetylenic moieties.

Photosubstitution of (Fulvalene)tetracarbonyldiruthenium by Alkenes and Alkynes: First Observation of Alkyne Coupling on Fulvalene Dimetals and Synthesis of a (Fulvalene)dimetallacyclopentadiene(alkene) Complex

Irradiation (λmax = 300−375 nm) of FvRu2(CO)4 (1, Fv = η5:η5-bicyclopentadienyl) or (μ2-η1:η5-cyclopentadienyl)2Ru2(CO)4 (2) with dimethyl cis- or trans-butenedioate resulted in FvRu2(η2-trans-CHRCHR)(CO)3 (3, R = CO2CH3). Prolonged irradiation of 1−3 provided FvRu2(η2-trans-CHRCHR)2(CO)2 (4a, R = CO2CH3) and FvRu2(η2-cis-CHRCHR)(η2-trans-CHRCHR)(CO)2 (4b, R = CO2CH3). Photocatalytic isomerization of cis to trans alkene occurred in the presence of 1−4. Irradiation of 1−3 with dimethyl butynedioate produced FvRu2(μ2-η2-dimethyl butynedioate)(CO)3 (5). Prolonged irradiation of 1−5 with the alkyne afforded FvRu2(μ2-η2:η4-CRCRCRCR)2(CO) (6, R = CO2CH3). Irradiation of a THF solution of 6 generated FvRu2(μ2-η2:η4-CRCRCRCR)2(THF) (7, R = CO2CH3). Photochemical alkyne cyclotrimerization was observed in the presence of 1−7. In the presence of CO, 7 reverted to 6 thermally. Heating 7 in the presence of dimethyl cis-butenedioate, thiophene, PPh3, or dimethyl sulfoxide (DMSO) afforded FvRu2(μ2-η2:η4-CRCRCRCR)2(L) (8, R = CO2CH3, L = cis-CHRCHR; 9, L = thiophene; 10, L = PPh3; 11, L = DMSO). Irradiation (300 nm) of a THF solution of 8, 9, or 11 provided 7, while 10 was inert. Thermal conversion of 8 to 10 or 11 was effected only at relatively high temperatures. Treatment of 9 with dimethyl cis-butenedioate, PPh3, or DMSO yielded 8, 10, and 11, respectively. Heating 11 at 210 °C in molten PPh3 afforded slowly 10. Kinetic experiments on the conversion of 9 to 10 point to dissociative substitution, Ea = 30.5 kcal mol-1. Complexes 3−8 have been characterized by X-ray crystal analyses.

Synthesis of bent [4]phenylene (cyclobuta[1,2-a:3,4-b']bisbiphenylene) and structure of a bis(trimethylsilyl) derivative: the last [4]phenylene isomer.

The syntheses of the title compounds were accomplished by cobalt-catalyzed alkyne cyclotrimerizations using two strategies; the properties of the bent phenylene frame reflect the combined effects of benzocyclobutadienofusion of the component [3]phenylene substructures.

The first cobalt catalyzed [2 + 2 + 2] alkyne cyclotrimerization in aqueous medium at room temperature.

Chelate complex 1 (5 mol%) was found to catalyze the [2 + 2 + 2] cyclization of terminal alkynes in good yields in a 80/20 mixture of water and ethanol at room temperature without further activation.

ChemInform Abstract: Metalative Reppe Reaction. Organized Assembly of Acetylene Molecules on Titanium Template Leading to a New Style of Acetylene Cyclotrimerization.

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