- Palladium Nanoparticles by Electrospinning from Poly(acrylonitrile-co-acrylic acid)-PdCl2 Solutions. Relations between Preparation Conditions, Particle Size, and Catalytic Activity
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Catalytic palladium (Pd) nanoparticles on electrospun copolymers of acrylonitrile and acrylic acid (PAN-AA) mats were produced via reduction of PdCl2 with hydrazine. Fiber mats were electrospun from homogeneous solutions of PAN-AA and PdCl2 in dimethylformamide (DMF). Pd cations were reduced to Pd metals when fiber mats were treated in an aqueous hydrazine solution at room temperature. Pd atoms nucleate and form small crystallites whose sizes were estimated from the peak broadening of X-ray diffraction peaks. Two to four crystallites adhere together and form agglomerates. Agglomerate sizes and fiber diameters were determined by scanning and transmission electron microscopy. Spherical Pd nanoparticles were dispersed homogeneously on the electrospun nanofibers, The effects of copolymer composition and amount of PdCl2 on particle size were investigated. Pd particle size mainly depends on the amount of acrylic acid functional groups and PdCl2 concentration in the spinning solution. Increasing acrylic acid concentration on polymer chains leads to larger Pd nanoparticles. In addition, Pd particle size becomes larger with increasing PdCl2 concentration in the spinning solution. Hence, it is possible to tune the number density and the size of metal nanoparticles. The catalytic activity of the Pd nanoparticles in electrospun mats was determined by selective hydrogenation of dehydrolinalool (3,7-dimethyloct-6-ene-l-yne-3-ol, DHL) in toluene at 90°C. Electrospun fibers with Pd particles have 4.5 times higher catalytic activity than the current PoVAl2O3 catalyst.
- Demir, Mustafa M.,Gulgun, Mehmet A.,Menceloglu, Yusuf Z.,Erman, Burak,Abramchuk, Sergei S.,Makhaeva, Elena E.,Khokhlov, Alexei R.,Matveeva, Valentina G.,Sulman, Mikhail G.
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- Rethinking Basic Concepts-Hydrogenation of Alkenes Catalyzed by Bench-Stable Alkyl Mn(I) Complexes
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An efficient additive-free manganese-catalyzed hydrogenation of alkenes to alkanes with molecular hydrogen is described. This reaction is atom economic, implementing an inexpensive, earth-abundant nonprecious metal catalyst. The most efficient precatalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid hydrogenolysis to form the active 16e Mn(I) hydride catalyst [Mn(dippe)(CO)2(H)]. A range of mono- A nd disubstituted alkenes were efficiently converted into alkanes in good to excellent yields. The hydrogenation of 1-alkenes and 1,1-disubstituted alkenes proceeds at 25 °C, while 1,2-disubstituted alkenes require a reaction temperature of 60 °C. In all cases, a catalyst loading of 2 mol % and a hydrogen pressure of 50 bar were applied. A mechanism based on DFT calculations is presented, which is supported by preliminary experimental studies.
- Weber, Stefan,St?ger, Berthold,Veiros, Luis F.,Kirchner, Karl
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p. 9715 - 9720
(2019/10/14)
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- Regio- and Chemoselective Hydrogenation of Dienes to Monoenes Governed by a Well-Structured Bimetallic Surface
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Unprecedented surface chemistry, governed by specific atomic arrangements and the steric effect of ordered alloys, is reported. Rh-based ordered alloys supported on SiO2 (RhxMy/SiO2, M = Bi, Cu, Fe, Ga, In, Pb, Sn, and Zn) were prepared and tested as catalysts for selective hydrogenation of trans-1,4-hexadiene to trans-2-hexene. RhBi/SiO2 exhibited excellent regioselectivity for the terminal C=C bond and chemoselective hydrogenation to the monoene, not to the overhydrogenated alkane, resulting in a high trans-2-hexene yield. Various asymmetric dienes, including terpenoids, were converted into the corresponding inner monoenes in high yields. This is the first example of a regio- and chemoselective hydrogenation of dienes using heterogeneous catalysts. Kinetic studies and density functional theory calculations revealed the origin of the high selectivity: (1) one-dimensionally aligned Rh arrays geometrically limit hydrogen diffusion and attack to alkenyl carbons from one direction and (2) adsorption of the inner C=C moiety to Rh is inhibited by steric repulsion from the large Bi atoms. The combination of these effects preferentially hydrogenates the terminal C=C bond and prevents overhydrogenation to the alkane.
- Miyazaki, Masayoshi,Furukawa, Shinya,Komatsu, Takayuki
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p. 18231 - 18239
(2017/12/27)
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- Palladium nanoparticles in situ generated in metal-organic films for catalytic applications
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Palladium nanoparticles were first in situ generated in metal-organic films for catalytic applications. Layer-by-layer assembly of metal-organic films consisting of rigid-rod chromophores connected by terminal pyridine moieties to palladium centers on solid substrates was presented. Bipyridyl and polypyridyl ligands were used as building blocks to explore the influence of different ligand structures on catalytic properties. Metal-organic films were characterized by UV-Vis spectra, atomic force microscopy (AFM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results show that the deposition mechanism of metal-organic films is perfect layer-by-layer self-assembling with complete surface coverage and regular growth. Moreover, the catalytic activity toward the hydrogenation of olefin was investigated. Based on XPS and TEM, the catalytic activity toward the hydrogenation of olefin was ascribed to the in situ formation of Pd nanoparticles from Pd ions in metal-organic films. This film material is an active catalyst for the hydrogenation of olefin under mild conditions. Furthermore, catalytic results indicated that monodentate bipyridyl ligands exhibited superior catalytic activity than tridentate polypyridyl ligands. Catalytic activity is related to the loading amount of catalysts and permeability. More importantly, this study points toward the potential application of metal-organic films as heterogeneous catalysts with easy separation and good recyclability. This journal is the Partner Organisations 2014.
- Gao, Shuiying,Cao, Minna,Li, Weijin,Cao, Rong
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p. 12185 - 12193
(2014/08/05)
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- Selective reduction of dienes/polyenes using sodium borohydride/catalytic ruthenium(III) in various liquid amide aqueous mixtures
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An efficient method to effect selective reduction of several structurally diverse dienes and an unsymmetrical triene is reported. The reduction is facile at 0 °C in a liquid amide aqueous solution containing sodium borohydride in the presence of 15 mol % ruthenium(III) chloride. The chemoselectivity of the reaction is controlled by proper choice of the liquid amide solvent.
- Babler, James H.,Ziemke, David W.,Hamer, Robert M.
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p. 1754 - 1757
(2013/04/10)
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- Iron(III) chloride-catalysed aerobic reduction of olefins using aqueous hydrazine at ambient temperature
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A chemoselective reduction of olefins and acetylenes is demonstrated by employing catalytic amounts of ferric chloride hexahydrate (FeCl 3·6 H2O) and aqueous hydrazine (NH 2NH2·H2O) as hydrogen source at room temperature. The reduction is chemoselective and tolerates a variety of reducible functional groups. Unlike other metal-catalysed reduction methods, the present method employs a minimum amount of aqueous hydrazine (1.5-2 equiv.). Also, the scope of this method is demonstrated in the synthesis of ibuprofen in aqueous medium. Copyright
- Lamani, Manjunath,Ravikumara, Guralamata S.,Prabhu, Kandikere Ramaiah
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supporting information; experimental part
p. 1437 - 1442
(2012/07/03)
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- Guanidine catalyzed aerobic reduction: A selective aerobic hydrogenation of olefins using aqueous hydrazine
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An efficient aerobic reduction of olefins, internal as well as terminal, is developed using guanidine as an organocatalyst. A remarkable chemoselectivity in reduction has been demonstrated in the presence of a variety of functional groups and protective groups and a selective reduction of a terminal olefin in the presence of an internal olefin is revealed.
- Lamani, Manjunath,Guralamata, Ravikumara Siddappa,Prabhu, Kandikere Ramaiah
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supporting information; experimental part
p. 6583 - 6585
(2012/07/14)
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- Aerobic reduction of olefins by in situ generation of diimide with synthetic flavin catalysts
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A versatile reducing agent, diimide, can be generated efficiently by the aerobic oxidation of hydrazine with neutral and cationic synthetic flavin catalysts 1 and 2. This technique provides a convenient and safe method for the aerobic reduction of olefins, which proceeds with 1 equiv of hydrazine under an atmosphere of O2 or air. The synthetic advantage over the conventional gas-based method has been illustrated through high hydrazine efficiency, easy and safe handling, and characteristic chemoselectivity. Vitamin B2 derivative 6 acts as a highly practical, robust catalyst for this purpose because of its high availability and recyclability. Association complexes of 1b with dendritic 2,5-bis(acylamino)pyridine 15 exhibit unprecedented catalytic activities, with the reduction of aromatic and hydroxy olefins proceeding significantly faster when a higher-generation dendrimer is used as a host pair for the association catalysts. Contrasting retardation is observed upon similar treatment of non-aromatic or non-hydroxy olefins with the dendrimer catalysts. Control experiments and kinetic studies revealed that these catalytic reactions include two independent, anaerobic and aerobic, processes for the generation of diimide from hydrazine. Positive and negative dendrimer effects on the catalytic reactions have been ascribed to the specific inclusion of hydrazine and olefinic substrates into the enzyme-like reaction cavities of the association complex catalysts. Copyright
- Imada, Yasushi,Iida, Hiroki,Kitagawa, Takahiro,Naota, Takeshi
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supporting information; experimental part
p. 5908 - 5920
(2011/07/07)
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- Neutral flavins: Green and robust organocatalysts for aerobic hydrogenation of olefins
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"Chemical Equation Presented" Various olefins can be hydrogenated quantitatively with neutral flavin 2 catalysts in the presence of 1 -2 equiv of hydrazine under 1 atm of O2. Vitamin B2 derivative 2g acts as a highly efficient and robust catalyst for the present environmentally benign process producing water and nitrogen gas as the only waste products
- Imada, Yasushi,Kitagawa, Takahiro,Ohno, Takashi,Iida, Hiroki,Naota, Takeshi
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supporting information; experimental part
p. 32 - 35
(2010/03/04)
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- Reduction of carbon-carbon double bonds using organocatalytically generated diimide
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(Chemical Equation Presented) An efficient method has been developed for the reduction of carbon-carbon double bonds with diimide, catalytically generated in situ from hydrazine hydrate. The employed catalyst is prepared in one step from riboflavin (vitamin B2). Reactions are carried out in air and are a valuable alternative when metal-catalyzed hydrogenations are problematic.
- Smit, Christian,Fraaije, Marco W.,Minnaard, Adriaan J.
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supporting information; experimental part
p. 9482 - 9485
(2009/04/06)
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- Homogeneous electro-mediated reduction of unsaturated compounds using Ni and Fe as mediators in DMF
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The homogeneous electro-mediated reduction (HEMR) of several organic compounds (cyclohexene, cyclohexanone, acetophenone, benzaldehyde, styrene, linalool, 1,3-cyclohexadiene, citral, trans-4-phenyl-3-buten-2-one, and piperine) was carried out using Fe2+, Ni2+, and [NiII(bpy)]Br2 (bpy=2,2′-bipyridine) as electron mediators. An electrochemical system composed of sacrificial anode (Fe, Ni or Zn), nickel cathode, NaI (0.2 M) as supporting electrolyte in DMF and an undivided cell, was used. A constant current ≤100 mA was applied with a maximum cell potential of 2.0 V. Non-conjugated olefins are not reactive, but ketones may be easily reduced to the respective alcohol. In the case of conjugated olefins and ketones, [NiII(bpy)]Br2 or Ni2+ mediator presented good reactivity and selectivity in most cases. Fe2+ more efficiently mediates the reduction of carbonyl containing systems. Preliminary electroanalytical studies indicate the complexation of the organic substrate by Fe2+ and Ni2+ ions and [NiII(bpy)]Br2 complex.
- da Silva, Aderivaldo P.,Mota, Saulo D.C.,Bieber, Lothar W.,Navarro, Marcelo
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p. 5435 - 5440
(2007/10/03)
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- Semiochemicals of the scarabaeinae. VII: Identification and synthesis of ead-active constituents of abdominal sex attracting secretion of the male dung beetle, Kheper subaeneus
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Using gas chromatography with flame ionization detection (FID) and electroantennographic detection (EAD) in parallel, butanoic acid, skatole, and (E)-2,6-dimethyl-6-octen-2-ol were identified as constituents of the abdominal sex-attracting secretion of the male dung beetle, Kheper subaeneus, which reproducibly elicited EAD responses in male and female antennae. This is the first report of the occurrence of (E)-2,6-dimethyl-6-octen-2-ol as a natural product, for which the name (E)-subaeneol is proposed. In some experiments, a few other constituents of the secretion also gave reproducible responses in specific male and female antennae but did not elicit responses when the analyses were repeated with other antennae. The major volatile constituent of the secretion, identified as (S)-(+)-2,6-dimethyl-5-heptenoic acid, is one of these EAD-active compounds. Both this compound and (E)-2,6-dimethyl-6-octen-2-ol were synthesized from authentic starting materials for comparison with the natural products.
- Burger,Petersen,Weber,Munro
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p. 2527 - 2539
(2007/10/03)
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- Total synthesis of korormicin
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Recently, we have assigned the (5S,3′R,9′S,10′R) stereochemistry to planar korormicin (1) on the basis of the specific rotations of the four possible diastereoisomers [i.e., (5S,3′R,9′S,10′R), (5S,3′S,9′S,10′R), (5S,3′S,9′R,10′S), and (5S,3′R,9′R,10′S) isomers], which were prepared by a total synthesis. In this article, we describe the synthetic aspects in detail. The intermediates in the synthesis are enamino lactone (5S)-4 and both enantiomers of acid 5 and of boronate ester 7. Lactone (5S)-4 and boronate 7 with (9′S,10′R) and (9′R,10′S) chiralities were prepared through asymmetric dihydroxylation of olefins 11 and 30, respectively, with AD-mix-α or -β. Compounds (3′R)- and (3′S)-5 were prepared by kinetic resolution of rac-19 with asymmetric epoxidation. Condensation of (5S)-4 and (3′R)- or (3′S)-5 with DCC in the presence of DMAP and PPTS furnished the advanced intermediate 6 with (5S,3′R) and (5S,3′S) chiralities in good yields. Addition of PPTS was important to prevent formation of acyl urea 24. A nickel-catalyzed coupling reaction between 6 and 8 [prepared in situ from (9′S,10′R)- or (9′R, 10′S)-7 and MeLi] produced 9, which upon deprotection with Bu4NF furnished the four diastereoisomers of korormicin (1).
- Kobayashi, Yuichi,Yoshida, Shinya,Nakayama, Yuji
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p. 1873 - 1881
(2007/10/03)
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- A General Approach to the Synthesis of Butanolides: Synthesis of the Sex Pheromone of the Japanese Beetle
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A variety of substituted γ-hydroxy olefins 1 have been converted to butanolides 4 in very high yield in a three-step sequence involving bromoetherification, elimination, and oxidative cleavage.The key step in the overall transformation is the highly selective oxidative cleavage of enol ethers 3 with PCC under very mild reaction conditions.Application of this methodology has been exemplified in the synthesis of the Japanese beetle pheromone.
- Baskaran, Sundarababu,Islam, Imadul,Chandrasekaran, Srinivasan
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p. 891 - 895
(2007/10/02)
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- p-Anisyloxymethyl Group, a Novel Oxidatively Removable Acetal Type OH-Protecting Group
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Protection of various types of alcohols with p-anisyloxymethyl (p-AOM) chloride gave the corresponding p-AOM ethers which were deprotected with ceric ammonium nitrate efficiently.Chemoselective removal either of p-AOM group or of tetrahydropyranyl group is also reported.
- Masaki, Yukio,Iwata, Ikuhiro,Mukai, Isao,Oda, Hirohisa,Nagashima, Hiromu
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p. 659 - 662
(2007/10/02)
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- Studies on organolanthanide complexes. XVIII. The reduction and isomerization of olefins with tricyclopentadienyllanthanides/sodium hydride
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Reduction of 1-hexene with Cp3Ln/NaH (Cp=cyclopentadienyl, Ln=rare earth metals) in THF at 45 deg C, after hydrolysis, gives hexane.The reducing activity of Cp3Ln depends strongly upon the ionic radius of the trivalent rare earth ion.The activity and selectivity of early rare earths for 1-hexene reduction are higher than those of heavy rare earths.The Cp3Ln/NaH systems can be used to regioselectively reduce dienes which contain a terminal carbon-carbon double bond as well as an internal one with high yield.Selectivity is 100percent.Moreover, the Cp3Ln/NaH systems are able to catalyze the hydrogenation of olefins.When Cp3Ln/NaH is used as catalyst, 1-hexene was isomerized at 45 deg C to cis-2-hexene and to trans-2-hexene in excellent yields.In contrast to reducing activity, the catalytic activity of heavy rare earths in the isomerization reaction is higher than that of the early earths.Hence, Cp3Sm/NaN and Cp3Y/NaH are new reducing agents and catalysts for 1-hexene reduction and isomerization, respectively.
- Qian, Changtao,Ge, Yuanwen,Deng, Daoli,Gu, Yongjie,Zhang, Caihua
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p. 175 - 184
(2007/10/02)
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- CATALYTIC HYDROGENATION OF DEHYDROLINALOOL AND DEHYDROLINALYL ACETATE
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Catalytic hydrogenation of dehydrolinalool and of dehydrolinalyl acetate has been studied in the liquid phase under atmospheric pressure at 20 deg C with the aim to obtain selectively linalool and linalyl acetate.High selectivities have been obtained with the palladium on CaCO3 catalyst which was partially poisoned by lead.
- Cerveny, Libor,Kuncova, Marcela,Ruzicka, Vlastimil
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p. 1258 - 1261
(2007/10/02)
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- Process for producing linalool
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Linalool is produced by a hydrogenation of O-linalyl-N,N-dimethyl hydroxylamine having the formula STR1 wherein Me represents methyl group and the reference numerals 1 to 10 represent 1 to 10 carbon positions under a hydrogen partial pressure of lower than 30 Kg/cm2 in the presence of a catalyst of a combination of Ni or Co component with a modifying component selected from the group consisting of Al, Ge, Sn, As, Sb, S, Se and Cr.
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- Process for synthesizing ethylenic compounds
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The invention relates to a process for the preparation of ethylenic compounds and to certain novel ethylenic compounds produced by the process. The process comprises the reaction of an appropriate carbonyl compound with a sulphone to obtain an alcohol sulphone which is then reduced to obtain the desired ethylenic compound.
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