- A highly active, heterogeneous catalyst for alkyne metathesis
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(Chemical Equation Presented) An alkylidyne molybdenum amide complex is attached to nontoxic, amorphous silica to form a highly active, recyclable heterogeneous catalyst for alkyne metathesis. The catalyst does not undergo alkyne polymerization, can be utilized at a loading of 1 mol% at room temperature, and has shown unprecedented metathesis activity for the homodimerization of 2-propynylthiophene, a substrate that was previously problematic for alkyne metathesis.
- Weissman, Haim,Plunkett, Kyle N.,Moore, Jeffrey S.
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- In situ Mo(CO)?-based catalysts for alkyne metathesis: Silanols vs phenols as co-catalysts under thermal and photochemical activation
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A systematic study on the use of silanols and phenols as effective activators in Mo(CO)? – based catalytic systems for metathesis of 4-decyne and 1-phenyl-1-propyne is reported. In comparison with traditionally used phenols, aryl-substituted silanols exhibit high activating potential of molybdenum species even at lower concentrations (2 mol% of Mo(CO)? and 4–20 mol% of silanol depending on the alkyne) at toluene reflux. Silylated phenols and silanols are also suitable as co-catalysts. Additionally, Mo(CO)?/silanol catalytic system is shown to be efficiently activated by UV-irradiation at room temperature, whereas it is less effective for metathesis reactions performed in the presence of phenols.
- Zaranek, Maciej,Robaszkiewicz, Jakub,Janica, Iwona,Gauvin, Regis M.,Pawlu?, Piotr,Mortreux, André
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- Selective terminal alkyne metathesis: Synthesis and use of a unique triple bonded dinuclear tungsten alkoxy complex containing a hemilabile ligand
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The in situ synthesis of new alkyne metathesis catalysts is described, with particular emphasis on the search for tris-alkoxytungsten-based terminal alkyne metathesis. In that context, hemilabile, ether-containing alkoxy ligands have proved to be suitable and have led to the design and use of a sterically hindered hemilable ligand for the synthesis of a well-defined binuclear, triple-bonded W ≡ W complex. This complex is shown to be a highly active and selective catalyst precursor for terminal alkyne metathesis, and allows the unprecedented metathesis of phenylacetylene.
- Coutelier, Olivier,Nowogrocki, Guy,Paul, Jean-Francois,Mortreux, Andre
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- Rh(III)-Catalyzed [5 + 2] Oxidative Annulation of Cyclic Arylguanidines and Alkynes to 1,3-Benzodiazepines. A Striking Mechanistic Proposal from DFT
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A novel and mild Rh(III)-catalyzed [5 + 2] oxidative annulation between cyclic arylguanidines and alkynes efficiently affords 1,3-benzodiazepines (pentacyclic guanidines). The use of O2 as the sole oxidant in place of commonly used metal oxidants such as AgOAc clearly improves the efficiency of the oxidative annulation process. The mechanism of the cycloaddition most likely involves the formation of an eight-membered rhodacycle. DFT calculations support a striking mechanistic proposal for the [5 + 2] oxidative annulation.
- Martínez-Yá?ez, Nuria,Suárez, Jaime,Cajaraville, Ana,Varela, Jesús A.,Saá, Carlos
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supporting information
p. 1779 - 1783
(2019/03/29)
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- The Direct Conversion of α-Hydroxyketones to Alkynes
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Alkynes are highly important functional groups in organic chemistry, both as part of target structures and as versatile synthetic intermediates. In this study, a protocol for the direct conversion of α-hydroxyketones to alkynes is reported. In combination with the variety of synthetic methods that generate the required starting materials by forming the central C-C bond, it enables a highly versatile fragment coupling approach toward alkynes. A broad scope for this novel transformation is shown alongside mechanistic insights. Furthermore, the utility of our protocol is demonstrated through its application in concert with varied α-hydroxyketone syntheses, giving access to a broad spectrum of alkynes.
- Ghiringhelli, Francesca,Nattmann, Lukas,Bognar, Sabine,Van Gemmeren, Manuel
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p. 983 - 993
(2019/01/24)
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- Rhodium(iii)-catalyzed unreactive C(sp3)-H alkenylation of N-alkyl-1H-pyrazoles with alkynes
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The first example of pyrazole-directed rhodium(iii)-catalyzed unreactive C(sp3)-H alkenylation with alkynes has been described, which showed a relatively broad substrate scope with good functional group compatibility. Moreover, we demonstrated that the transitive coordinating center pyrazole could be easily removed under mild conditions.
- Li, Tongyu,Liu, Chang,Wu, Shaonan,Chen, Chen C.,Zhu, Bolin
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supporting information
p. 7679 - 7683
(2019/08/30)
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- Asymmetric Covalent Triazine Framework for Enhanced Visible-Light Photoredox Catalysis via Energy Transfer Cascade
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Complex multiple-component semiconductor photocatalysts can be constructed that display enhanced catalytic efficiency via multiple charge and energy transfer, mimicking photosystems in nature. In contrast, the efficiency of single-component semiconductor photocatalysts is usually limited due to the fast recombination of the photogenerated excitons. Here, we report the design of an asymmetric covalent triazine framework as an efficient organic single-component semiconductor photocatalyst. Four different molecular donor–acceptor domains are obtained within the network, leading to enhanced photogenerated charge separation via an intramolecular energy transfer cascade. The photocatalytic efficiency of the asymmetric covalent triazine framework is superior to that of its symmetric counterparts; this was demonstrated by the visible-light-driven formation of benzophosphole oxides from diphenylphosphine oxide and diphenylacetylene.
- Huang, Wei,Byun, Jeehye,R?rich, Irina,Ramanan, Charusheela,Blom, Paul W. M.,Lu, Hao,Wang, Di,Caire da Silva, Lucas,Li, Run,Wang, Lei,Landfester, Katharina,Zhang, Kai A. I.
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supporting information
p. 8316 - 8320
(2018/06/29)
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- A Mild Rhodium Catalyzed Direct Synthesis of Quinolones from Pyridones: Application in the Detection of Nitroaromatics
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A rhodium catalyzed direct regioselective oxidative annulation by double C-H activation is described to synthesize highly substituted quinolones from pyridones. The reaction proceeds at mild conditions with broad scope and wide functional group tolerance. These novel quinolones were explored to recognize nitroaromatic compounds.
- Biswas, Aniruddha,Giri, Dipanjan,Das, Debapratim,De, Anurima,Patra, Sanjib K.,Samanta, Rajarshi
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p. 10989 - 10996
(2017/10/27)
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- Rhodium-Catalyzed C-H Annulation of Nitrones with Alkynes: A Regiospecific Route to Unsymmetrical 2,3-Diaryl-Substituted Indoles
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The direct C-H annulation of anilines or related compounds with internal alkynes provides straightforward access to 2,3-disubstituted indole products. However, this transformation proceeds with poor regioselectivity in the synthesis of unsymmetrically 2,3-diaryl substituted indoles. Herein, we report the rhodium(III)-catalyzed C-H annulation of nitrones with symmetrical diaryl alkynes as an alternative method to prepare 2,3-diaryl-substituted N-unprotected indoles with two different aryl groups. One of the aryl substituents is derived from N?C-aryl ring of the nitrone and the other from the alkyne substrate, thus providing the indole products with exclusive regioselectivity.
- Yan, Hao,Wang, Haolong,Li, Xincheng,Xin, Xiaoyi,Wang, Chunxiang,Wan, Boshun
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supporting information
p. 10613 - 10617
(2015/09/02)
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- Mechanism and scope of the base-induced dehalogenation of (E)-diiodoalkenes
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A wide range of nucleophiles have induced the elimination of iodine from (E)-diiodoalkenes to form alkynes under surprisingly mild conditions. The iodide anion is particularly efficient, and can drive the reaction to completion in less than 1 hour at room temperature in a polar aprotic solvent. Detailed investigations have suggested the reaction has a bimolecular polar mechanism. The deiodination reaction can be driven to completion with 1 equiv. of nucleophile and is partially catalytic with substoichiometric amounts of deiodinating reagent. Kinetic analysis of the stoichiometric iodide-induced reaction indicated an overall pseudo-first-order behavior. The reaction exhibited strong solvent effects, with much slower reactions observed in protic solvents than in polar aprotic solvents. The substrate dimethyl (2E)-2,3-diiodo-butene-2-dioate demonstrated orthogonal reactivity for either elimination or hydrolysis, depending on the solvent and nucleophile used. This reaction is a major pathway for all the diiodoalkenes examined, and represents a challenge and an opportunity for using these substrates in organic synthesis.
- Resch, Daniel,Lee, Chang Heon,Tan, Siew Yoong,Luo, Liang,Goroff, Nancy S.
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supporting information
p. 730 - 737
(2015/01/30)
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- Room-temperature carbonization of poly(diiododiacetylene) by reaction with Lewis bases
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Poly(diiododiacetylene) (PIDA) is a conjugated polymer containing an all-carbon backbone and only iodine atom substituents. Adding a Lewis base to the blue PIDA suspension at room temperature leads first to rapid disappearance of the absorption peaks attributed to PIDA, followed more slowly by release of free iodine. The resulting solid material gives a Raman scattering spectrum consistent with graphitic carbon, and it has a much higher conductivity than PIDA itself. Further investigation has led to the discovery of a previously unreported transformation, the reaction of a Lewis base such as pyrrolidine with a trans-diiodoalkene to form the corresponding alkyne. The generality of this iodine elimination further suggests that reaction of PIDA with Lewis bases dehalogenates the polymer, presenting a new method to prepare carbon nanomaterials at room temperature under very mild conditions.
- Luo, Liang,Resch, Daniel,Wilhelm, Christopher,Young, Christopher N.,Halada, Gary P.,Gambino, Richard J.,Grey, Clare P.,Goroff, Nancy S.
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supporting information; experimental part
p. 19274 - 19277
(2012/01/06)
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- HETEROGENEOUS ALKYNE METATHESIS
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The present invention provides heterogeneous organometallic catalysts for alkyne metathesis, including the metathesis of internal alkynes. Organometallic precursors are covalently bonded to the oxygen atoms of metal oxide supports to form catalysts having carbyne functionality. The heterogeneous catalysts provide improved turn-over frequencies at lower reaction temperatures than conventional catalysts.
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Page/Page column 7
(2008/06/13)
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- Adducts of thianthrene- and phenoxathiin cation radical salts with symmetrical alkynes. Structure and formation of cumulenes on alumina leading to α-diketones, α-hydroxyalkynes, and α-acetamidoalkynes
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Thianthrene cation radical tetrafluoroborate (Th.+BF 4-) added to 2-butyne, 3-hexyne, 4-octyne, and 5-decyne in MeCN to form trans bisadducts E(Th+)C=C(Th+)R, where E = Me, Et, Pr, Bu (7a-d). Phenoxathiin cation radical tetrafluoroborate (PO .+BF4-) added similarly to the last three alkynes to form adducts E(PO+)C=C(PO+)E, 8b-d. Cyclic monoadducts were not found. The trans structures of 7 and 8 were deduced with X-ray crystallography (7c) and NME spectroscopy. When solutions of adducts in CHCl3 and MeCN were deposited on activated alumina, elimination of thianthrene (Th) and phenoxathiin (PO) occurred almost quantitatively. Detailed studies with (7b-d) indicated that a cumulene (15) was formed by the elimination of Th and that 15 was subsequently converted into small amounts of other products. In CHCl3, these products were the respective alkyne, thianthrene 5-oxide, an α-diketone (11), an α-hydroxyalkyne (12), and hydrogen. The same products were formed in MeCN along with an α-acetamidoalkyne (13). The formation of 15 and products derived from it is explained and was confirmed by preparation and reactions of 2,3,4-hexatriene.
- Shine, Henry J.,Rangappa, Paramashivappa,Marx, John N.,Shelly, Dennis C.,Ould-Ely, Teyeb,Whitmire, Kenton H.
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p. 3877 - 3883
(2007/10/03)
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- The effect of vicinyl olefinic halogens on cross-coupling reactions using Pd(0) catalysis
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(trans) 1-Chloro-2-iodoethylene (3), (trans) 1-bromo-2-iodoethylene (4), (trans) 1,2-diiodoethylene (5) and (cis and trans) 1,2-dibromoethylene (11) were reacted under Suzuki, Sonogashira and Negishi cross-coupling conditions using Pd catalysis to obtain mono coupled products. Only olefin template 3 provided the desired coupling products reliably under all reaction conditions. Compound 5 did not provide cross coupled products under any of the reaction conditions used. The Negishi reaction was the only one that worked for templates 4 and 11. Studies indicate that oxidative addition of the most reactive carbon-halogen bond to Pd(0) is followed by elimination of the second halide, when the second halide is a bromide or an iodide. This happens to a much lesser degree when the second halogen is a chloride. Graphical Abstract.
- Organ, Michael G.,Ghasemi, Haleh,Valente, Cory
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p. 9453 - 9461
(2007/10/03)
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- A spontaneous fragmentation: From the Criegee zwitterion to coarctate Mobius aromaticity
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The extremely fast fragmentation of the spiroozonides prepared from formaldehyde O-oxide and three-membered ring ketones proceeds via the coarctate transition state 1. The ozonides decompose at temperatures as low as -90°C to form carbon dioxide, alkene/alkyne, and formaldehyde (the topology of the structure of 1 is depicted on the right). The mechanism is in accordance with the rules for the stereochemical course of coarctate reactions.
- Berger, Christian,Bresler, Christian,Dilger, Ulrich,Geuenich, Daniel,Herges, Rainer,Roettele, Herbert,Schroeder, Gerhard
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p. 1850 - 1853
(2007/10/03)
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- XVII. Spaltung von 1,1'-Bicyclopropyliden (butterfly olefin) mit Lithiumpulver zu 1,6-Dilithio-3-hexin ueber (1,3-Dilithiopropyliden)cyclopropan als isolierbare Zwischenstufe
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While for the reductive cleavage of a cyclopropane ?-bond usually two lithium atoms are necessary, with the same amount of lithium two ?-bonds of the "butterfly olefin" 4 are cleaved.On the way to 1,6-dilithio-3-hexyne (7) (1,3-dilithiopropylidene)cyclopropane (8) can be isolated provided that diethyl ether is used as the solvent.
- Maercker, Adalbert,Klein, Klaus-Dieter
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p. C35 - C38
(2007/10/02)
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- Mn(I)-Induced 1,6-Demethanation across the CC Triple Bond of Linear Alkynes in the Gas Phase. A Case for the Generation of Manganese Cycloalkynes?
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Complexes of Mn(alkynes)+ were generated in the gas phase and found to exhibit a reactivity which is even richer than that of the analogous Fe(alkyne)+ species.Among the many unimolecular dissociations, the Mn+-induced demethanation of 4-octyne is of particular interest.The study of isotopomers and the effects of alkyl chain lengths reveals the operation of an unprecedented 1,6-elimination mode across the CC triple bond, and the experimental results may be explained by invoking the intermediate generation of the as yet unknown metallacycloalkynes.The implications of the unexpected, rich gas-phase ion chemistry of Mn+ with regard to theoretical models are discussed.
- Schulze, Christian,Schwarz, Helmut
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- Selective Synthesis of Alkynes by Catalytic Dehydrogenation of Alkenes over Polymer-supported Palladium Acetate in the Liquid Phase
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A heterogenized palladium acetate catalyst, in the presence of oxygen and perchloric acid in ethanol-water caused the direct conversion of terminal and internal monoalkenes into the corresponding alkynes, under mild conditions and in high yields; Wacker-type ketonization occurs with the same reagents in dioxane-water.
- Cum, Giampietro,Gallo, Raffaele,Ipsale, Salvatore,Spadaro, Agatino
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p. 1571 - 1573
(2007/10/02)
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- Homogeneous Metathesis of Functionalized Alkynes
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Various functionalized disubstituted acetylenes, including esters, are prepared metathetically with high selectivity on molybdenum based homogeneous catalytic systems; this procedure is a useful tool for the synthesis of acetylenes, which can provide cis- or trans-olefins by further selective hydrogenation.
- Petit, Michele,Mortreux, Andre,Petit, Francis
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p. 1385 - 1386
(2007/10/02)
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