1576-95-0Relevant academic research and scientific papers
Piperazine-promoted gold-catalyzed hydrogenation: The influence of capping ligands
Barbosa, Eduardo C. M.,Camargo, Pedro H. C.,Fiorio, Jhonatan L.,Hashmi, A. Stephen K.,Kikuchi, Danielle K.,Rossi, Liane M.,Rudolph, Matthias
, p. 1996 - 2003 (2020/04/22)
Gold nanoparticles (NPs) combined with Lewis bases, such as piperazine, were found to perform selective hydrogenation reactions via the heterolytic cleavage of H2. Since gold nanoparticles can be prepared by many different methodologies and using different capping ligands, in this study, we investigated the influence of capping ligands adsorbed on gold surfaces on the formation of the gold-ligand interface. Citrate (Citr), poly(vinyl alcohol) (PVA), polyvinylpyrrolidone (PVP), and oleylamine (Oley)-stabilized Au NPs were not activated by piperazine for the hydrogenation of alkynes, but the catalytic activity was greatly enhanced after removing the capping ligands from the gold surface by calcination at 400 °C and the subsequent adsorption of piperazine. Therefore, the capping ligand can limit the catalytic activity if not carefully removed, demonstrating the need of a cleaner surface for a ligand-metal cooperative effect in the activation of H2 for selective semihydrogenation of various alkynes under mild reaction conditions.
Accessing Frustrated Lewis Pair Chemistry through Robust Gold@N-Doped Carbon for Selective Hydrogenation of Alkynes
Fiorio, Jhonatan Luiz,Gon?alves, Renato Vitalino,Teixeira-Neto, Erico,Ortu?o, Manuel A.,López, Núria,Rossi, Liane Marcia
, p. 3516 - 3524 (2018/04/14)
Pyrolysis of Au(OAc)3 in the presence of 1,10-phenanthroline over TiO2 furnishes a highly active and selective Au nanoparticle (NP) catalyst embedded in a nitrogen-doped carbon support, Au@N-doped carbon/TiO2 catalyst. Parameters such as pyrolysis temperature, type of support, and nitrogen ligands as well as Au/ligand molar ratios were systematically investigated. Highly selective hydrogenation of numerous structurally diverse alkynes proceeded in moderate to excellent yield under mild conditions. The high selectivity toward the industrially important alkene substrates, functional group tolerance, and the high recyclability makes the catalytic system unique. Both high activity and selectivity are correlated with a frustrated Lewis pairs interface formed by the combination of gold and nitrogen atoms of N-doped carbon that, according to density functional theory calculations, can serve as a basic site to promote the heterolytic activation of H2 under very mild conditions. This "fully heterogeneous" and recyclable gold catalyst makes the selective hydrogenation process environmentally and economically attractive.
Copper-catalyzed enantioselective allylic alkylation of terminal alkyne pronucleophiles
Harada, Ayumi,Makida, Yusuke,Sato, Tatsunori,Ohmiya, Hirohisa,Sawamura, Masaya
supporting information, p. 13932 - 13939 (2015/02/05)
The copper-catalyzed enantioselective allylic alkylation of terminal alkynes with primary allylic phosphates was developed by the use of a new chiral N-heterocyclic carbene ligand bearing a phenolic hydroxy group at the ortho position of one of the two N-aryl groups. This reaction occurred with excellent γ-branch regioselectivity and high enantioselectivity, forming a controlled stereogenic center at the allylic/propargylic position. Various terminal alkynes, including silyl, aliphatic, and aromatic alkynes, could be used directly without premetalation of the C(sp)-H bond. On the basis of the results of experiments using an isomeric secondary allylic phosphate, which gave a branched product through an α-selective substitution reaction with retention of configuration, a reaction pathway involving 1,3-allylic migration of Cu in a ([σ + π]-allyl)copper(III) species is proposed.
Highly active and selective semihydrogenation of alkynes with the palladium nanoparticles-tetrabutylammonium borohydride catalyst system
Hori, Junichi,Murata, Kunihiko,Sugai, Toshiki,Shinohara, Hisanori,Noyori, Ryoji,Arai, Noriyoshi,Kurono, Nobuhito,Ohkuma, Takeshi
supporting information; experimental part, p. 3143 - 3149 (2010/04/06)
Palladium nanoparticles are prepared from palladium(II) acetate and 2 equivalents of potassium tert-butoxide in the presence of 4-octyne. The palladium nanoparticles-tetrabutylammonium borohydride system shows excellent catalytic activity and selectivity in the semihydrogenation of alkynes to the [(Z)-]alkenes. The hydrogenation of 4-octyne is conducted with the catalyst system at a substrate-to-palladium molar ratio of 10,000-200,000 under 8 atm of hydrogen to give (Z)-4-octene in > 99% yield. Isomerization and over-reduction of the Z-alkene are very slow even after consumption of the alkyne.
Selective liquid-phase semihydrogenation of functionalized acetylenes and propargylic alcohols with silica-supported bimetallic palladium-copper catalysts
Spee,Boersma,Meijer,Slagt,Van Koten,Geus
, p. 1647 - 1656 (2007/10/03)
Silica-supported, bimetallic palladium-copper catalysts were prepared in solution under mild conditions by reacting lithium di(4-tolyl)cuprate with palladium acetate in the presence of silica particles. Small bimetallic palladium-copper particles were deposited on the silica surface as confirmed with TEM-EDAX and EXAFS. The new material has been applied as catalyst in the liquid-phase semihydrogenation of mono- and disubstituted alkynes and showed high selectivity toward the cis-alkenes. The influence of addition of quinoline or potassium hydroxide to the semihydrogenation reaction mixture and the effects of exposure of the catalyst to air before use have been investigated. Silica-supported, bimetallic palladium-copper catalysts were prepared in solution under mild conditions by reacting lithium di(4-tolyl)cuprate with palladium acetate in the presence of silica particles. Small bimetallic palladium-copper particles were deposited on the silica surface as confirmed with TEM-EDAX and EXAFS. The new material has been applied as catalyst in the liquid-phase semihydrogenation of mono- and disubstituted alkynes and showed high selectivity toward the cis-alkenes. The influence of addition of quinoline or potassium hydroxide to the semihydrogenation reaction mixture and the effects of exposure of the catalyst to air before use have been investigated.
Palladium on pumice: New catalysts for the stereoselective semihydrogenation of alkynes to (Z)-alkenes
Gruttadauria, Michelangelo,Liotta, Leonarda F.,Noto, Renato,Deganello, Giulio
, p. 2015 - 2017 (2007/10/03)
High selectivities (93-99%) and excellent stereoselectivities (>99%) in the semihydrogenation of C-C triple bonds were achieved using palladium on pumice with a metal loading of 0.5, 1.5 or 3.0% wt as catalyst. The reactions were carried out in ethanol or tetrahydrofuran with only 2.5% of ethylenediamine allowing a self-terminating semihydrogenation independently on the C-C triple bond.
COMPOUNDS WITH HERBAL ODOR. V. UNBRANCHED PRIMARY (Z)-ALKENOLS
Vasil'ev, A. A.,Cherkaev, G. V.,Nikitina, M. A.
, p. 735 - 739 (2007/10/02)
The similarity between the odor of alkenols (Z)-CH3-(CH2)n(H=CH(CH2)mOH and the odor of leaf alcohol (m=2, n=1), taken as standard, gradually weakened with change in the m and/or n values and is determined by the number of carbon atoms in the molecules.
NEW STEREOCONTROLLED APPROACH TO THE INSECT SEX PHEROMONE SERRICORNIN
Szurdoki, F.,Novak, L.,Baitz-Gacs, Eszter,Szantay, Cs.
, p. 303 - 309 (2007/10/02)
The (Z)-allylic alcohol 1 was subjected to Sharpless asymmetric epoxidation to give the key intermediate 2.Ring opening of the epoxide 2 afforded the diol 3, which was then converted to serricornin 4, the sex pheromone of the cigarette beetle (Lasioderma serricorne F.) by routine transformations.
Syntheses of Jasmone, Jasmonic Acid and some Analogues from Alkyne-cobalt Complexes via the Khand Reaction.
Billington, David C.,Bladon, Peter,Helps, I. Malcolm,Pauson, Peter L.,Thomson, William,Willison, Debra
, p. 2601 - 2623 (2007/10/02)
The Khand reactions of the hexacarbonyldicobalt complexes of 2-octyne and of Z-oct-5-en-2-yne with ethylene lead directly to jasmone and dihydrojasmone. 2-Pentyl- and Z-2-pentenylcyclopent-2-en-1-one, known intermediates in the synthesis of jasmonic and dihydrojasmonic acid or their esters, have been obtained similarly from 1-heptyne and hept-4-en-1-yne respectively.These and related cyclopentenones have been converted into new analogues of methyl jasmonate, of interest as potential plant growth regulators.
ENANTIOSPECIFIC SYNTHESIS OF THE SPIROACETAL MOIETIES OF AVERMECTINS A1b, B1b, A1a, B1a, A2b, B2b, A2a, AND B2a AND MILBEMYCINS α7 AND α8
Baker, Raymond,Head, John C.,Swain, Christopher J.
, p. 85 - 98 (2007/10/02)
Three differently substituted unsaturated spiroacetals, two of which form part of the structure of avermectins A1b, B1b, A1a, and B1a, have been prepared by reaction of the appropriately substituted and chiral lithium acetylide with dibenzyl protected (4S,6S)-4-hydroxy-6-hydroxymethyltetrahydropyran-2-one followed by partial hydrogenation and acid-catalysed cyclisation.The preparation of the chiral hydroxyacetylene derivatives is described.Hydration of the double bond via the chlorohydrin followed by tributyltin hydride reduction led to formation of the spiroacetal moiety found in avermectins A2b, B2b, A2a, and B2a.Epoxidation of one of the unsaturated spiroacetals and subsequent treatment with perchloric acid afforded a diaxial spiroacetal diol from the major epoxide.A protocol for the selective acylation of the diol has been developed which involves selective deprotection of the corresponding dimethyl t-butylsilylated diol under acid-catalysed conditions followed by acylation with the appropriate chiral acid chloride.Desilylation then gave the spiroacetal moiety found in milbemycins α7 and α8.The acyl chloride has been prepared by alkylation of a chiral oxazolidone with subsequent hydrolytic removal of the chiral auxiliary and reaction with oxalyl chloride.
