- Chemo- and regioselective dimerization of terminal alkynes promoted by methylaluminoxane
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(figure presented) Methylalumoxane (MAO) was found to be an active catalytic precursor for the chemo- and regioselective dimerization of a wide range of aryl-and alkyl-substituted terminal alkynes yielding the corresponding geminal dimers A. For an olefin
- Dash, Aswini K.,Eisen, Moris S.
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- Rhodium(I)-N-heterocyclic carbene catalyst for selective coupling of N-vinylpyrazoles with alkynes via C-H activation
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The complex [Rh(μ-Cl)(IPr)(η2-coe)]2 {IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-carbene, coe = cis-cyclooctene} efficiently catalyzes the coupling of alkynes and N-vinylpyrazole via C-H activation, leading to Markovnikov-selecti
- Azproz, Ramn,Rubio-Prez, Laura,Di Giuseppe, Andrea,Passarelli, Vincenzo,Lahoz, Fernando J.,Castarlenas, Ricardo,Prez-Torrente, Jess J.,Oro, Luis A.
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- Alkynyldichlorogalliums are Unstable in Hydrocarbon Solvents Dimerization of Alkynyldichlorogalliums via Carbogallation
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Alkynyldichlorogalliums dimerize in hydrocarbon solvents via carbogallation giving 1,1-dimetallo-1-buten-3-yne derivatives.
- Yamaguchi, Masahiko,Hayashi, Akio,Hirama, Masahiro
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- Variation on the π-Acceptor Ligand within a RhI?N-Heterocyclic Carbene Framework: Divergent Catalytic Outcomes for Phenylacetylene-Methanol Transformations
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A series of neutral and cationic rhodium complexes bearing IPr {IPr=1,3-bis-(2,6-diisopropylphenyl)imidazolin-2-carbene} and π-acceptor ligands are reported. Cationic species [Rh(η4-cod)(IPr)(NCCH3)]+ and [Rh(CO)(IPr)(L)2]+ (L=pyridine, CH3CN) were obtained by chlorido abstraction in suitable complexes, whereas the cod-CO derivative [Rh(η4-cod)(IPr)(CO)]+ was formed by the carbonylation of [Rh(η4-cod)(IPr)(NCCH3)]+. Alternatively, neutral derivatives of type RhCl(IPr)(L)2 {L=tBuNC or P(OMe)3} can be accessed from [Rh(μ-Cl)(η2-coe)(IPr)]2. In addition, the mononuclear species Rh(CN)(η4-cod)(IPr) was prepared by cyanide-chlorido anion exchange, which after carbonylation afforded the unusual trinuclear compound [Rh{1κC,2κN-(CN)}(CO)(IPr)]3. Divergent catalytic outcomes in the phenylacetylene-methanol transformations have been observed. Thus, enol ethers, arisen from hydroalkoxylation of the alkyne, were obtained with neutral Rh?CO catalyst precursors whereas dienol ethers were formed with cationic catalysts. Variable amounts of alkyne dimerization, cyclotrimerization or polymerization products were obtained in the absence of a strong π-acceptor ligand on the catalyst.
- Galiana-Cameo, María,Passarelli, Vincenzo,Pérez-Torrente, Jesús J.,Di Giuseppe, Andrea,Castarlenas, Ricardo
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p. 2947 - 2957
(2021/07/16)
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- Ru-catalyzed (E)-specific ortho-C-H alkenylation of arenecarboxylic acids by coupling with alkenyl bromides
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In the presence of [p-cymene)RuCl2]2, (E)-configured alkenyl bromides couple with aromatic carboxylates to form ortho-vinylbenzoic acids. This C-H vinylation proceeds in high yields without any activating phosphine ligands and has an excellent functional group tolerance. Starting from commonly available (E/Z)-mixtures of alkenyl bromides, (E)-configured vinyl arenes or dienes are formed exclusively. Mechanistic studies show that this selectivity is achieved because the (E)-configured alkenyl bromides undergo a smooth coupling, whereas the (Z)-isomers are rapidly eliminated with the formation of alkynes.
- Belitz, Florian,Goo?en, Lukas J.,Hu, Zhiyong,Papp, Florian,Zhang, Guodong
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supporting information
p. 3541 - 3545
(2021/05/31)
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- N-Heterocyclic Carbene-Catalyzed 1,4-Alkylacylation of 1,3-Enynes
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The radical relay coupling reaction recently emerged as a powerful synthetic strategy for producing tetrasubstituted allenes. However, bond-forming processes involving the allenyl radical intermediate are mostly limited to those promoted by transition metals. In this report, we describe that a ketyl radical generated from single-electron oxidation of the Breslow intermediate is an excellent coupling partner of allenyl radicals. An organocatalytic 1,4-alkylacylation of 1,3-enynes occurred smoothly in the presence of an aldehyde, a radical precursor, and an N-heterocyclic carbene catalyst. This transformation showed remarkable tolerance to both aromatic and aliphatic aldehydes, enyne substitution, and diversified radical precursors.
- Cai, Yuxing,Chen, Jiean,Huang, Yong
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supporting information
p. 9251 - 9255
(2021/11/30)
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- Stereo- A nd regioselective dimerization of alkynes to enynes by bimetallic syn-carbopalladation
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Enynes are important motifs in bioactive compounds. They can be synthesized by alkynea'alkyne couplings for which a number of mechanisms have been suggested depending on catalyst type and dominant product isomers. Regarding bimetallic pathways, hydrometalations and anti-carbopalladations have been discussed to account for the formation of geminally substituted and (Z)-configured enynes, respectively. Here we report a bimetallic alkynea'alkyne coupling that yields (E)-configured enynes. An unusual type of acetylide Pd bridging was found in putative catalytic intermediates which is arguably responsible for the regio- A nd stereochemical reaction outcome. Mechanistic studies suggest that a double μa'κ:η2 acetylide bridging enables a bimetallic syn-carbometalation. Interestingly, depending on the reaction conditions, it is also possible to form the geminal regioisomer as major product with the same catalyst. This regiodivergent outcome is explained by bi-versus monometallic reaction pathways.
- Pfeffer, Camilla,Wannenmacher, Nick,Frey, Wolfgang,Peters, René
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p. 5496 - 5505
(2021/05/31)
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- Construction of modular Pd/Cu multimetallic chainsvialigand- And anion-controlled metal-metal interactions
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The presence of Pd?Cu and Pd?Pd interactions as well as the order of metal atoms in a chain held by a modular polynucleating ligand is controlled by the coordinating ability of the anions, leading to selective formation of bi- and tetranuclear Pd/Cu and P
- Deolka, Shubham,Fayzullin, Robert R.,Govindarajan, Ramadoss,Khaskin, Eugene,Khusnutdinova, Julia R.,Pal, Shrinwantu,Rivada-Wheelaghan, Orestes
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supporting information
p. 10206 - 10209
(2021/10/14)
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- Synthesis of 6-Adamantyl-2-pyridone and Reversible Hydrogen Activation by the Corresponding Bis(perfluorophenyl)borane Complex
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We herein describe the two-step synthesis of 6-Adamantyl-2-pyridone from 1-Acetyladamantane. The borane complex derived from 6-Adamantyl-2-pyridone and the Piers borane liberates dihydrogen at 60 °C. The reverse reaction, hydrogen activation by the formed pyridonate borane is accomplished under mild conditions. The mechanism of the hydrogen activation is studied by DFT computations.
- Wech, Felix,Müller, Tizian,Becker, Jonathan,Gellrich, Urs
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p. 666 - 672
(2020/11/19)
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- Metal-Ligand Cooperative Proton Transfer as an Efficient Trigger for Rhodium-NHC-Pyridonato Catalyzed gem-Specific Alkyne Dimerization
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The mononuclear square-planar Rh{κ2-X,N-(Xpy)}(η2-coe)(IPr) (X = O, NH, NMe, S) complexes have been synthesized from the dinuclear precursor [Rh(μ-Cl)(IPr)( η2-coe)]2 and the corresponding 2-heteroatom-pyridinate salts. The Rh-NHC-pyridinato derivatives a
- Galiana-Cameo, María,Urriolabeitia, Asier,Barrenas, Eduardo,Passarelli, Vincenzo,Pérez-Torrente, Jesús J.,Di Giuseppe, Andrea,Polo, Víctor,Castarlenas, Ricardo
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p. 7553 - 7567
(2021/06/30)
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- Verkade Base in FLP Chemistry-From Stoichiometric C-H Bond Cleavage to the Catalytic Dimerization of Alkynes
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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 N[CH2CH2NPri]3
- Brar, Amandeep,Mummadi, Suresh,Unruh, Daniel K.,Krempner, Clemens
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supporting information
p. 4307 - 4311
(2020/10/02)
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- Rhodium(I)-NHC Complexes Bearing Bidentate Bis-Heteroatomic Acidato Ligands as gem-Selective Catalysts for Alkyne Dimerization
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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 reacti
- Galiana-Cameo, María,Borraz, Marina,Zelenkova, Yaroslava,Passarelli, Vincenzo,Lahoz, Fernando J.,Pérez-Torrente, Jesús J.,Oro, Luis A.,Di Giuseppe, Andrea,Castarlenas, Ricardo
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supporting information
p. 9598 - 9608
(2020/07/13)
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- Highly Regio- and Stereoselective Ni-Catalyzed Hydrocyanation of 1,3-Enynes
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A highly regio- and stereoselective hydrocyanation of 1,3-enynes was implemented by nickel/diphosphine catalysts. A wide range of highly regio- and stereoselective alkenyl nitriles were efficiently prepared. In this transformation, both the tethered alken
- Sun, Feilong,Ni, Jie,Cheng, Gui-Juan,Fang, Xianjie
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supporting information
p. 5956 - 5960
(2020/05/08)
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- Piano-Stool Iron Complexes as Precatalysts for gem-Specific Dimerization of Terminal Alkynes
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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 within the NHC rings. The catalytic activities of these Fe co
- Liang, Qiuming,Hayashi, Kasumi,Rabeda, Karolina,Jimenez-Santiago, Jose L.,Song, Datong
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p. 2320 - 2326
(2020/07/06)
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- Regio- and Stereoselective Synthesis of 2-Hydroxymethyl-1,3-enynes by Rhodium-Catalyzed Decarboxylative C?C Coupling
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A regio- and stereoselective protocol for rhodium(I)-catalyzed decarboxylative C?C coupling between propiolic acids and propargyl alcohols has been achieved. This efficient catalytic approach could facilitate the preparation of a diversity of synthetically valuable 2-hydroxymethyl-1,3-enynes with high Z-stereoselectivity. Notably, non-terminal alkynes were smoothly transformed into the target products that show intriguing synthetic utility. (Figure presented.).
- Lu, Shi-Chao,Chang, Zhi-Xin,Xiao, Yu-Liang,Li, Hong-Shuang
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supporting information
p. 4831 - 4836
(2019/10/28)
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- Active Iron(II) Catalysts toward gem-Specific Dimerization of Terminal Alkynes
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We report the syntheses and catalytic activity of a series of piano-stool iron complexes with the general formula [FeClCp (NHC)] (where NHC = N-heterocyclic carbene) toward the gem-specific dimerization of terminal alkynes. In comparison to our first-gene
- Liang, Qiuming,Sheng, Kai,Salmon, Andrew,Zhou, Vivian Yue,Song, Datong
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p. 810 - 818
(2019/01/14)
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- Copper-Catalyzed Radical 1,4-Difunctionalization of 1,3-Enynes with Alkyl Diacyl Peroxides and N-Fluorobenzenesulfonimide
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Many reactions involving allenyl ion species have been studied, but reactions involving allenyl radicals are less well understood, perhaps because of the inconvenience associated with the generation of short-lived allenyl radicals. We describe here a versatile method for the generation of allenyl radicals and their previously unreported applications in the intermolecular 1,4-carbocyanation and 1,4-sulfimidocyanation of 1,3-enynes. With the assistance of the trifunctional reagents, alkyl diacyl peroxides or N-fluorobenzenesulfonimide, a range of synthetically challenging multisubstituted allenes can be prepared with high regioselectivity. These multisubstituted allenes can be easily transformed into synthetically useful structures such as fluorinated vinyl cyanides, lactones, functionalized allenyl amides, 1-aminonaphthalenes, and pyridin-2(1H)-ones, and several novel transformations are reported. The results of radical scavenger and radical clock experiments are consistent with the proposed allenyl radical pathway. Density functional theory (DFT) and IR spectroscopy studies suggest the formation of an isocyanocopper(II) species in the ligand exchange step. On the basis of the results of IR, DFT, and diastereoselectivity studies, an isocyanocopper(II)/copper(I) catalytic cycle is proposed, which differs from the previously considered Cu(III) mechanism in cyanation reactions.
- Zhu, Xiaotao,Deng, Weili,Chiou, Mong-Feng,Ye, Changqing,Jian, Wujun,Zeng, Yuehua,Jiao, Yihang,Ge, Liang,Li, Yajun,Zhang, Xinhao,Bao, Hongli
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p. 548 - 559
(2019/01/04)
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- Rhodium- N-Heterocyclic Carbene Catalyzed Hydroalkenylation Reactions with 2-Vinylpyridine and 2-Vinylpyrazine: Preparation of Nitrogen-Bridgehead Heterocycles
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Dinuclear rhodium-NHC complexes of formula [Rh(μ-Cl)(NHC)(η2-coe)]2 react with 2-vinylpyridine to yield the chelate compounds RhCl(NHC)(κ-N,η2-CH2=CHC5H4N) {NHC = IPr, 1,3-bis(2,6-diisoprop
- Azpíroz, Ramón,Di Giuseppe, Andrea,Passarelli, Vincenzo,Pérez-Torrente, Jesús J.,Oro, Luis A.,Castarlenas, Ricardo
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p. 1695 - 1707
(2018/06/18)
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- Enol Ester Synthesis via Cobalt-Catalyzed Regio- and Stereoselective Addition of Carboxylic Acids to Alkynes
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A cobalt-catalyzed highly regio- and stereoselective hydro-oxycarbonylation of alkynes is reported. Both terminal and internal alkynes can react with carboxylic acids to afford enol esters in high yields. The catalyst generated from Co(BF4)2, tridentate phosphine ligand L5, and zinc in situ exhibits much higher reactivity than the corresponding cobalt/diphosphine complex.
- Chen, Jia-Feng,Li, Changkun
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supporting information
p. 6719 - 6724
(2018/11/21)
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- Terminal Alkyne Coupling Reactions through a Ring: Mechanistic Insights and Regiochemical Switching
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The mechanism and selectivity of terminal alkyne coupling reactions promoted by rhodium(I) complexes of NHC-based CNC pincer ligands have been investigated. Synthetic and kinetic experiments support E- and gem-enyne formation through a common reaction seq
- Storey, Caroline M.,Gyton, Matthew R.,Andrew, Rhiann E.,Chaplin, Adrian B.
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supporting information
p. 12003 - 12006
(2018/09/11)
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- Pseudo-tetrahedral Rhodium and Iridium Complexes: Catalytic Synthesis of E-Enynes
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The reactions of the rhodium(I) and iridium(I) complexes [M(PhBP3)(C2H4)(NCMe)] (PhBP3=PhB(CH2PPh2)3?) with alkynes have resulted in the synthesis of a new family of p
- Geer, Ana M.,Julián, Alejandro,López, José A.,Ciriano, Miguel A.,Tejel, Cristina
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p. 17545 - 17556
(2018/11/23)
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- Synthesis of α-pyrones by catalytic oxidative coupling of terminal alkynes and carbon dioxide
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The use of the complex [(dippe)Ni(μ-H)]2(1) as a catalyst precursor (10?mol%) in the presence of a variety of terminal alkynes and CO2allowed the production of substituted α–pyrones. This reaction occurs using relatively mild conditions (50?°C, 150 psi of CO2) with good to modest yields, depending on the nature of the substituents in the corresponding alkyne. The produced α–pyrones were characterized by different analytical methods and spectroscopic techniques.
- Oliveros-Cruz, Saray,Arévalo, Alma,García, Juventino J.
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- Phosphinito palladium(ii) complexes as catalysts for the synthesis of 1,3-enynes, aromatic alkynes and ynones
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An air-stable phosphinito palladium(ii) complex (Ph1-Phoxide) has been found to be an efficient catalyst in the formation of C-C bonds. The coupling of terminal alkynes formed gem-1,3-enynes as the only reaction products. Aromatic alkynes can be synthesized from the coupling of terminal alkynes and haloaromatic compounds (Sonogashira coupling). The phosphinito palladium(ii) complex also catalyses the coupling between acyl chlorides and terminal alkynes (Sonogashira coupling), furnishing ynones in excellent yields.
- Islas,Cárdenas,Gavi?o,García-Ríos,Lomas-Romero,Morales-Serna
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p. 9780 - 9789
(2017/02/15)
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- Iron-Catalyzed gem-Specific Dimerization of Terminal Alkynes
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We report a gem-specific homo- and cross-dimerization of terminal alkynes catalyzed by a well-defined iron(II) complex containing Cp* and picolyl N-heterocyclic carbene (NHC) ligands, and featuring a piano-stool structure. This catalytic system requires n
- Liang, Qiuming,Osten, Kimberly M.,Song, Datong
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supporting information
p. 6317 - 6320
(2017/05/22)
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- Lanthanide-Catalyzed Reversible Alkynyl Exchange by Carbon–Carbon Single-Bond Cleavage Assisted by a Secondary Amino Group
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Lanthanide-catalyzed alkynyl exchange through C?C single-bond cleavage assisted by a secondary amino group is reported. A lanthanide amido complex is proposed as a key intermediate, which undergoes unprecedented reversible β-alkynyl elimination followed by alkynyl exchange and imine reinsertion. The in situ homo- and cross-dimerization of the liberated alkyne can serve as an additional driving force to shift the metathesis equilibrium to completion. This reaction is formally complementary to conventional alkyne metathesis and allows the selective transformation of internal propargylamines into those bearing different substituents on the alkyne terminus in moderate to excellent yields under operationally simple reaction conditions.
- Shao, Yinlin,Zhang, Fangjun,Zhang, Jie,Zhou, Xigeng
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supporting information
p. 11485 - 11489
(2016/10/24)
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- A rhodium(i)-oxygen adduct as a selective catalyst for one-pot sequential alkyne dimerization-hydrothiolation tandem reactions
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An air-stable rhodium(i)-oxygen adduct featuring a CNC-pincer ligand, based on 1,2,3-triazol-5-ylidenes, catalyzes the homo-dimerization and hydrothiolation of alkynes, affording the gem-enyne and α-vinyl sulfide isomers, respectively, with excellent selectivity. A one-pot stepwise strategy allows the selective catalytic preparation of non-symmetric bis-vinyl sulfides, as well as the alkyne dimerization-hydrothiolation tandem reactions.
- Kleinhans, George,Guisado-Barrios, Gregorio,Liles, David C.,Bertrand, Guy,Bezuidenhout, Daniela I.
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supporting information
p. 3504 - 3507
(2016/03/04)
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- Selective Oligomerization and [2 + 2 + 2] Cycloaddition of Terminal Alkynes from Simple Actinide Precatalysts
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A catalyzed conversion of terminal alkynes into dimers, trimers, and trisubstituted benzenes has been developed using the actinide amides U[N(SiMe3)2]3 (1) and [(Me3Si)2N]2An[κ2-(N,C)-CH2Si(CH3)N(SiMe3)] (An = U (2), Th (3)) as precatalysts. These complexes allow for preferential product formation according to the identity of the metal and the catalyst loading. While these complexes are known as valuable precursors for the preparation of various actinide complexes, this is the first demonstration of their use as catalysts for C-C bond forming reactions. At high uranium catalyst loading, the cycloaddition of the terminal alkyne is generally preferred, whereas at low loadings, linear oligomerization to form enynes is favored. The thorium metallacycle produces only organic enynes, suggesting the importance of the ability of uranium to form stabilizing interactions with arenes and related π-electron-containing intermediates. Kinetic, spectroscopic, and mechanistic data that inform the nature of the activation and catalytic cycle of these reactions are presented. (Chemical Equation Presented).
- Batrice, Rami J.,McKinven, Jamie,Arnold, Polly L.,Eisen, Moris S.
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p. 4039 - 4050
(2015/09/01)
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- Gold-Catalyzed Rearrangement of Alkynyl Donor-Acceptor Cyclopropanes to Construct Highly Functionalized Alkylidenecyclopentenes
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A gold-catalyzed 1,7-addition-cyclization-elimination cascade sequence performed on a range of alkynyl-substituted donor-acceptor-type cyclopropanes provides facile entry to highly functionalized exo-alkylidenecyclopentenes under very mild conditions. Iso
- Chen, Huiyu,Zhang, Jing,Wang, David Zhigang
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p. 2098 - 2101
(2015/05/13)
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- Gem-selective cross-dimerization and cross-trimerization of alkynes with silylacetylenes promoted by a rhodium-pyridine-n-heterocyclic carbene catalyst
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The gem-selective cross-dimerization and -trimerization of silylacetylenes with alkynes through C-H activation using a rhodium(I)-pyridine-N-heterocyclic carbene catalyst have been developed. This reaction is applied to various aliphatic or aromatic termi
- Azpíroz, Ram?n,Rubio-Pérez, Laura,Castarlenas, Ricardo,Pérez-Torrente, Jesús J.,Oro, Luis A.
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p. 2587 - 2592
(2015/04/14)
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- Easily available nickel complexes as catalysts for the intermolecular hydroamination of alkenes and alkynes
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A series of nickel complexes of the type [(P-P)NiX2] ((P-P) = bisphospines or bisphosphites, X = chloride, triflate) were used as catalysts for the hydroamination of both activated and unactivated alkenes and alkynes with pyrrolidine. In general, the use of activated unsaturations, such as acrylonitrile, required mild reaction conditions (e.g. 100 °C and 4 h) in comparison with other non-activated alkenes. Particularly with a series of alkynes, the use of nickel(ii) centers diminished or even inhibited the formation of otherwise undesired homocoupling and/or transfer hydrogenation by-products, such as the ones obtained in the presence of zerovalent nickel. When using less activated substrates, better selectivity was obtained, although harsher reaction conditions were needed. From a general perspective, the results of this report strongly support the potential use of nickel as a good candidate for further application in the hydroamination of organic unsaturations by means of screening of several π acceptor ligands. The Royal Society of Chemistry.
- Reyes-Sanchez, Adan,Garcia-Ventura, Ilnett,Garcia, Juventino J.
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p. 1762 - 1768
(2014/01/06)
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- Reactivity switch enabled by counterion: Highly chemoselective dimerization and hydration of terminal alkynes
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A counterion-controlled reactivity tuning in Pd-catalyzed highly chemoselective and regioselective dimerization and hydration of terminal alkynes is reported. The use of acetate as counterion favors the formation of an alkenyl alkynyl palladium intermediate which forms hitherto less reported 1,3-diaryl-substituted conjugated enynes after reductive elimination. Using chloride, which is a better leaving group, leads to anion exchange on the alkenylpalladium intermediate with hydroxide which after reductive elimination and tautomerization delivered the hydration products.
- Xu, Caixia,Du, Weiyuan,Zeng, Yi,Dai, Bin,Guo, Hao
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supporting information
p. 948 - 951
(2014/03/21)
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- Carboxylate switch between hydro- and carbopalladation pathways in regiodivergent dimerization of alkynes
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Experimental and theoretical investigation of the regiodivergent palladium-catalyzed dimerization of terminal alkynes is presented. Employment of N-heterocyclic carbene-based palladium catalyst in the presence of phosphine ligand allows for highly regio- and stereoselective head-to-head dimerization reaction. Alternatively, addition of carboxylate anion to the reaction mixture triggers selective head-to-tail coupling. Computational studies suggest that reaction proceeds via the hydropalladation pathway favoring head-to-head dimerization under neutral reaction conditions. The origin of the regioselectivity switch can be explained by the dual role of carboxylate anion. Thus, the removal of hydrogen atom by the carboxylate directs reaction from the hydropalladation to the carbopalladation pathway. Additionally, in the presence of the carboxylate anion intermediate, palladium complexes involved in the head-to-tail dimerization display higher stability compared to their analogues for the head-to-head reaction. Track changer: The regiodivergent palladium-catalyzed dimerization of terminal alkynes was studied. High regio- and stereoselectivity was achieved for both head-to-head and head-to-tail dimerization reactions. Computational studies suggest hydropalladation to favor head-to-head dimerization under neutral conditions. Addition of carboxylate anions switches the reaction from hydropalladation to carbopalladation pathway securing head-to-tail coupling (see scheme).
- Zatolochnaya, Olga V.,Gordeev, Evgeniy G.,Jahier, Claire,Ananikov, Valentine P.,Gevorgyan, Vladimir
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supporting information
p. 9578 - 9588
(2014/08/18)
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- Formation of unsaturated vicinal Zr+/P frustrated lewis pairs by the unique 1,1-carbozirconation reactions
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Treatment of the metallocene cation complexes [Cp2MCH 3]+[B(C6F5)4] - (M = Zr or Hf) with trimethylsilyl(diarylphosphino)acetylenes Ar2P-C≡C-SiMe3 (Ar = Ph
- Xu, Xin,Kehr, Gerald,Daniliuc, Constantin G.,Erker, Gerhard
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supporting information
p. 12431 - 12443
(2014/11/08)
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- Pseudotetrahedral rhodium(I) complexes
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A combination of four-electron donors, such as alkynes, with strongly donating and strong-field scorpionate ligands is appropriate to create pseudotetrahedral rhodium(I) environments, as found in [Rh(PhBP 3)(HCi£CPh)], which promotes Hi-C bond
- Geer, Ana M.,Julian, Alejandro,Lopez, Jose A.,Ciriano, Miguel A.,Tejel, Cristina
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supporting information
p. 2732 - 2736
(2014/03/21)
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- Pyridine-enhanced head-to-tail dimerization of terminal alkynes by a rhodium-N-heterocyclic-carbene catalyst
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A general regioselective rhodium-catalyzed head-to-tail dimerization of terminal alkynes is presented. The presence of a pyridine ligand (py) in a Rh-N-heterocyclic-carbene (NHC) catalytic system not only dramatically switches the chemoselectivity from alkyne cyclotrimerization to dimerization but also enhances the catalytic activity. Several intermediates have been detected in the catalytic process, including the π-alkyne-coordinated RhI species [RhCl(NHC)(η2-HC ≡CCH2Ph)(py)] (3) and [RhCl(NHC){η2-C(tBu) ≡C(E)CH=CHtBu}(py)] (4) and the RhIII-hydride-alkynyl species [RhClH{-C ≡CSi(Me) 3}(IPr)(py)2] (5). Computational DFT studies reveal an operational mechanism consisting of sequential alkyne Ci£ H oxidative addition, alkyne insertion, and reductive elimination. A 2,1-hydrometalation of the alkyne is the more favorable pathway in accordance with a head-to-tail selectivity. Control plan: Addition of pyridine to rhodium-N-heterocyclic- carbene catalysts not only switches the chemoselectivity from alkyne cyclotrimerization to dimerization, but also enhances the catalytic activity for the formation of 1,3-enynes (see figure). A 2,1-hydrometalation of the alkyne is the more favorable pathway calculated by DFT.
- Rubio-Perez, Laura,Azpiroz, Ramon,Di Giuseppe, Andrea,Polo, Victor,Castarlenas, Ricardo,Perez-Torrente, Jesus J.,Oro, Luis A.
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p. 15304 - 15314
(2013/11/06)
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- A ruthenium-based catalytic system with switchable selectivity between cyclotrimerization and enyne metathesis/Diels-Alder reactions of terminal alkynes
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In this study, we report a practical catalytic system, [RuCl 2(p-cymene)]2/IPr (IPr: 1,3-bis(2,6 diisopropylphenyl) imidazol-2-ylidene), that can switch between cyclotrimerization and cross enyne metathesis. The cyclotrimerization reaction of phenylacetylene catalyzed by [RuCl2(p-cymene)]2 can be switched to enyne metathesis by the introduction of a sterically hindered N-heterocyclic carbene. The 1,3-diene formed during this reaction reacts with dienophiles to form the Diels-Alder adduct. A practical one-pot synthesis method, utilizing enyne metathesis/Diels-Alder reactions, was used to construct cyclic compounds in an efficient manner.
- Karabulut, Solmaz,Sariaslan, Begüm,?ztürk, Bengi ?zgün
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- The alkynyl moiety as a donor for donor-acceptor cyclopropanes
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The first trans-selective [3 + 2]-cycloaddition of a new type of donor-acceptor cyclopropane with aldehydes is presented. 2,2-Disubstituted cyclopropanes, bearing an alkyne moiety as the sole donor entity, were transformed to highly substituted tetrahydro
- Haubenreisser, Stefan,Hensenne, Peter,Schroeder, Sebastian,Niggemann, Meike
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p. 2262 - 2265
(2013/06/27)
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- Iron-catalyzed direct synthesis of densely Substituted benzofurans and naphthopyrans from phenolic compounds and propargylic alcohols
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A one-pot cascade reaction for the synthesis of polysubstituted benzofurans and naphthopyrans from simple phenols and propargylic alcohols catalyzed by iron(III) is presented. The results demonstrate that the structural specificity for the formation of fu
- Yuan, Feng-Quan,Han, Fu-She
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p. 537 - 547
(2013/05/08)
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- A Bronsted acid-catalyzed generation of palladium complexes: Efficient head-to-tail dimerization of alkynes
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A Bronsted acid Ph2P(O)OH can efficiently catalyze the reaction of a Pd(0) complex with an alkyne to produce a novel alkenyl(alkynyl)palladium complex via selective hydropalladation and ligand exchange processes. On the basis of this finding, a
- Chen, Tieqiao,Guo, Cancheng,Goto, Midori,Han, Li-Biao
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supporting information
p. 7498 - 7500
(2013/08/23)
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- Dual gold catalysis: σ,π-propyne acetylide and hydroxyl-bridged digold complexes as easy-to-prepare and easy-to-handle precatalysts
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A series of dinuclear gold σ,π-propyne acetylide complexes were prepared and tested for their catalytic ability in dual gold catalysis that was based on the reaction of an electrophilic π-complex of gold with a gold acetylide. The air-stable and storable catalysts can be isolated as silver-free catalysts in their activated form. These dual catalysts allow a fast initiation phase for the dual catalytic cycles without the need for additional additives for acetylide formation. Because propyne serves as a throw-away ligand, no traces of the precatalyst are generated. Based on the fast initiation process, side products are minimized and reaction rates are higher for these catalysts. A series of test reactions were used to demonstrate the general applicability of these catalysts. Lower catalyst loadings, faster reaction rates, and better selectivity, combined with the practicability of these catalysts, make them ideal catalysts for dual gold catalysis. Traceless dual-activation catalysts: Air-stable π-coordinated propyne acetylide gold complexes proved to be powerful precatalysts for dual gold catalysis (see scheme). A fast catalyst transfer to the starting substrates initiates the catalytic cycle. Reaction yields and selectivity were improved without the need for basic additives or activation by silver salts. Copyright
- Hashmi, A. Stephen K.,Lauterbach, Tobias,N?sel, Pascal,Vilhelmsen, Mie H?jer,Rudolph, Matthias,Rominger, Frank
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p. 1058 - 1065
(2013/02/23)
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- Hydrido-cobalt catalyst as a selective tool for the dimerisation of arylacetylenes: Scope and theoretical studies
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A simple hydrido-cobalt complex efficiently catalyses the highly regio- and stereoselective dimerisation of various terminal arylacetylenes under mild conditions. The corresponding (E)-1,4-enynes are obtained as sole isomers with good to excellent yields. DFT calculations revealed that the reaction proceeds via a C-H activation/hydrocobaltation pathway. Copyright
- Ventre, Sandrine,Derat, Etienne,Amatore, Muriel,Aubert, Corinne,Petit, Marc
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supporting information
p. 2584 - 2590
(2013/10/21)
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- Rhodium-catalyzed dimerization of arylacetylenes and addition of malonates to 1,3-enynes
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An 8-quinolinolato rhodium catalyst was found to be effective for head-to-tail selective dimerization of arylacetylenes. Formation of substituted cyclopentene and allene derivatives via alkyne dimerization and subsequent addition of malonates was also cat
- Mochizuki, Katsufumi,Sakai, Kazunori,Kochi, Takuya,Kakiuchi, Fumitoshi
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p. 2088 - 2092
(2013/08/23)
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- 1,2,3-Triazole: Unique ligand in promoting iron-catalyzed propargyl alcohol dehydration
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A 1,2,3-traizole-promoted iron(III)-catalyzed propargyl alcohol dehydration was developed for the synthesis of conjugated enynes. The desired conjugated enynes were prepared in good to excellent yields (up to 95%) with a large substrate scope and excellen
- Yan, Wuming,Ye, Xiaohan,Akhmedov, Novruz G.,Petersen, Jeffrey L.,Shi, Xiaodong
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supporting information; experimental part
p. 2358 - 2361
(2012/06/18)
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- Palladium-catalyzed conjugate addition of terminal alkynes to enones
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A practical protocol for the hydroalkynylation of enones using Pd catalysis is reported. The reaction proceeds efficiently with a variety of alkynes as well as with several cyclic and acyclic enones, providing synthetically relevant β-alkynyl ketones in good to excellent yields.
- Villarino, Lara,Garcia-Fandino, Rebeca,Lopez, Fernando,Mascarenas, Jose L.
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experimental part
p. 2996 - 2999
(2012/08/28)
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- Gold-catalyzed regioselective dimerization of aliphatic terminal alkynes
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A gold-catalyzed regioselective homodimerization of -aliphatic terminal alkynes is described. Bulky and less Lewis acidic t-BuXPhosAuNTf2 is the preferred catalyst, and the additive, anhydrous NaOAc, substantially facilitates the reaction. Geor
- Sun, Sheng,Kroll, Julien,Luo, Yingdong,Zhang, Liming
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scheme or table
p. 54 - 56
(2012/02/04)
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- Dimerization of terminal arylalkynes in aqueous medium by ruthenium and acid promoted (RAP) catalysis: Acetate-assisted (sp)C-(sp2)C bond formation
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The hexamethylbenzene ruthenium(II) dimer [{RuCl(m-Cl)(h6-C 6Me6)}]2 (5 mol%), tested among a series of ruthenium(II) and ruthenium(IV) complexes, represents an efficient precatalyst source for the dimerization of terminal arylalkynes ArCΞ CH [Ar=C 6H5, 3,4,5-(OMe)3C6H2, 4-MeOC 6H6, 2-MeOC6H6, 4-MeC 6H6, 2,4,5-Me3C6H2, 4-BrC 6H6, 4-ClC6H6, 4-FC 6H6, 4-HC(=O)C6H6, 4-CH 2=CHC6H6, 3-NCC6H6, 4-O2NC6H6, 4-EtO2C-(CH2)3OC6H 6, 4-HO(CH2CH2O)3C6H 6, 3-HO(CH2CH2O)3-C 6H6] in acetic acid/water mixture (1:1, v/v). The reactions proceed for 24 h at room temperature under heterogeneous conditions and afford the dimeric enyne derivatives (E)-Ar-CH=CH-C-C-Ar in high yields and stereoselectivity. The preformed acetato complex [RuCl(h6-C 6Me6)(k2-OAc)] catalyzes the dimerization of phenylacetylene under analogous conditions, with rapid substrate conversion. The presence of cosolvents of acetic acid different from water reduces dramatically the efficiency and selectivity of the reaction. The aqueous medium facilitates the activation stage of the precatalyst by assisting the splitting of the ruthenium dimer. The addition or generation in situ of acetate salts results in shorter reactions times (0.5-3 h) and excellent yields, due to the rapid formation of active acetato complexes. Circumstantial evidence indicates that the p-bound alkyne molecule is activated by intramolecular proton abstraction. This is currently the most efficient, E-selective and wide-scope catalytic system for the alkyne dimerization reaction in protic aqueous media.
- Coniglio, Alessandra,Bassetti, Mauro,Garcia-Garrido, Sergio E.,Gimeno, Jose
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experimental part
p. 148 - 158
(2012/03/27)
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- Palladium-catalyzed acylation and/or homo-coupling of aryl- and alkyl-acetylenes
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Allyl or benzyl halides, through a Pd(0)-catalyzed reaction and under CO pressure, generate acyl-palladium/halides that, in the presence of a base and an aryl- and alkyl-acetylene, undergo nucleophilic acyl substitution giving conjugated acetylenic ketones. Diynes, resulting from alkyne/alkyne homo-coupling, were instead the main products in reactions performed without allyl or benzyl halides. Moreover, dimerization, trimerization, and cyclotrimerization reactions of acetylenes were observed in reaction carried out even without base.
- Perrone, Serena,Bona, Fabio,Troisi, Luigino
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experimental part
p. 7386 - 7391
(2011/10/09)
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- Probing the steric limits of rhodium catalyzed hydrophosphinylation. P-H addition vs. dimerization/oligomerization/polymerization
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The reactivity of secondary phosphine oxides containing bulky organic fragments in hydrophosphinylation reactions has been investigated using several rhodium based catalysts. Upon heating in a focused microwave reactor, HP(O)(2-C6H4M
- Richard, Marcia E.,Reese, Kyle P.,Stone, Joshua J.,Pickett, Phillip D.,Tillman, Eric S.,Stockland Jr., Robert A.
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experimental part
p. 123 - 129
(2011/02/17)
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- A novel and efficient method for the olefination of carbonyl compounds with Grignard reagents in the presence of diethyl phosphite
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The widely available carbonyl compounds react with Grignard reagents in the presence of diethyl phosphite to give the corresponding olefins in good to excellent yields: A range of conjugated dienes, terminal olefins, multisubstituted-alkenes and conjugated enynes could be readily obtained by the method in mild conditions.
- Wang, Tongqiang,Hu, Yuanyuan,Zhang, Songlin
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supporting information; experimental part
p. 2312 - 2315
(2010/07/09)
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- Ru-mediated selective addition reactions of carboxylic acids to internal and terminal alkynes
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This study examined the nucleophilic addition of trichloroacetic acid to internal alkynes using RuCHPhCl2(PCy3)(IPr) (IPr: [1,3-Bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazo-2-ylidene]). This reaction was performed in good yield
- Karabulut, Solmaz,?ztürk, Bengi ?zgün,Imamo?lu, Yavuz
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experimental part
p. 2161 - 2166
(2010/09/15)
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- Novel, highly efficient and selective ruthenium catalysts for the synthesis of vinyl esters from carboxylic acids and alkynes
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An efficient and highly selective synthesis of vinyl esters was developed that employed carboxylic acids and terminal alkynes as reagents, and novel tethered (η1:η6-phosphanoarene)ruthenium complexes as catalyst precursors. With thes
- Nicks, Francois,Aznar, Rosario,Sainz, Daniel,Muller, Guillermo,Demonceau, Albert
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supporting information; scheme or table
p. 5020 - 5027
(2010/02/27)
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- Palladhim-catalyzed decarboxylative sp-sp2 cross-coupling reactions of aryl and vinyl halides and triflates with α,β-ynoic acids using silver oxide
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Palladium-catalyzed decarboxylative sp-sp2 cross-coupling reactions of aryl and vinyl halides and triflates with α,β-ynoic acids using silver oxide have been developed. A variety of α,β-ynoic acids were readily decarboxylated in the presence of
- Kim, Hyunseok,Lee, Phil Ho
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scheme or table
p. 2827 - 2832
(2010/03/26)
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