544-12-7Relevant articles and documents
Galvanic synthesis of AgPd bimetallic catalysts from Ag clusters dispersed in a silica matrix
Alyari, Maryam,Gangishetty, Mahesh,Scott, Robert W. J.,Sudheeshkumar, V.
, p. 8421 - 8428 (2020/12/30)
While bottom-up synthetic strategies for the formation of near-monodisperse clusters have attracted much attention, top-down synthetic strategies in which metals are dispersed into clusters can also be viable. In this study, we follow up previous work that showed the formation of Ag clusters dispersed in a silica matrix by breaking up larger triangular Ag nanoparticles upon calcination in air. AgPd bimetallic catalysts were synthesized via a galvanic replacement reaction of these thermally activated Ag clusters in a silica matrix. The galvanic reaction of the Ag clusters with Pd(ii) salts was monitored by in situ XANES spectroscopy. Interestingly, extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS) studies suggested that the majority of the Ag atoms are located on the surface of the resulting clusters and Pd atoms are in the core region. The catalytic activity for 3-hexyne-1-ol hydrogenation was investigated and the AgPd?SiO2 catalysts showed superior selectivity for the selective hydrogenation to 3-hexene-1-ol.
USE OF A RUTHENIUM CATALYST COMPRISING A TETRADENTATE LIGAND FOR HYDROGENATION OF ESTERS AND/OR FORMATION OF ESTERS AND A RUTHENIUM COMPLEX COMPRISING SAID TETRADENTATE LIGAND
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Page/Page column 33, (2019/08/20)
The present invention relates to the use of a transition metal catalyst TMC1, which comprises a transition metal M selected from metals of groups 7, 8, 9 and 10 of the periodic table of elements according to IUPAC and a tetradentate ligand of formula I wherein R1 are identical or different and are each an organic radical having from 1 to 40 carbon atoms, and R2 are identical or different and are each an organic radical having from 1 to 40 carbon atoms, as catalyst in processes for formation of compounds comprising at least one carboxylic acid ester functional group -O-C(=O)- starting from at least one primary alcohol and/or hydrogenation of compounds comprising at least one carboxylic acid ester functional group -O-C(=O)-. The present invention further relates to a process for hydrogenation of a compound comprising at least one carboxylic acid ester functional group -O-C(=O)-, to a process for the formation of a compound comprising at least one carboxylic acid ester functional group -O-C(=O)- by dehydrogenase coupling of at least one primary alcohol with a second alcoholic OH-group, to a transition metal complex comprising the tetradentate ligand of formula I and to a process for preparing said transition metal complex.
Study of Precatalyst Degradation Leading to the Discovery of a New Ru0 Precatalyst for Hydrogenation and Dehydrogenation
Anaby, Aviel,Schelwies, Mathias,Schwaben, Jonas,Rominger, Frank,Hashmi, A. Stephen K.,Schaub, Thomas
supporting information, p. 2193 - 2201 (2018/07/25)
The complex Ru-MACHO (1) is a widely used precatalyst for hydrogenation and dehydrogenation reactions under basic conditions. In an attempt to identify the active catalyst form, 1 was reacted with a strong base. The formation of previously unreported species was observed by NMR and mass spectrometry. This observation indicated that complex 1 quickly degraded under basic conditions when no substrate was present. X-ray crystallography enabled the identification of three complexes as products of this degradation of complex 1. These complexes suggested degradation pathways which included ligand cleavage and reassembly, along with reduction of the ruthenium atom. One of the decomposition products, the Ru0 complex [Ru(N(CH2CH2PPh2)3)CO] (5), was prepared independently and studied. 5 was found to be active, entirely additive-free, in the acceptorless dehydrogenation of aliphatic alcohols to esters. The hydrogenation of esters catalyzed by 5 was also demonstrated under base-free conditions with methanol as an additive. Protic substrates were shown to add reversibly to complex 5, generating RuII-hydrido species, thus presenting a rare example of reversible oxidative addition from Ru0 to RuII and reductive elimination from RuII to Ru0.
Chiral Selenide-Catalyzed Enantioselective Construction of Saturated Trifluoromethylthiolated Azaheterocycles
Luo, Jie,Liu, Yannan,Zhao, Xiaodan
supporting information, p. 3434 - 3437 (2017/07/15)
An indane-based, bifunctional, chiral selenide catalyst has been developed. The new catalyst is efficient for the enantioselective synthesis of saturated azaheterocycles possessing a trifluoromethylthio group. The desired products were obtained in good yields with high diastereo- and enantioselectivities.
Selective Cobalt-Catalyzed Reduction of Terminal Alkenes and Alkynes Using (EtO)2Si(Me)H as a Stoichiometric Reductant
Raya, Balaram,Biswas, Souvagya,Rajanbabu
, p. 6318 - 6323 (2016/09/09)
While attempting to effect Co-catalyzed hydrosilylation of β-vinyl trimethylsilyl enol ethers, we discovered that, depending on the silane, solvent, and the method of generation of the reduced cobalt catalyst, a highly efficient and selective reduction or hydrosilylation of an alkene can be achieved. This paper deals with this reduction reaction, which has not been reported before in spite of the huge research activity in this area. The reaction, which uses the air-stable [2,6-bis(aryliminoyl)pyridine)]CoCl2 activated by 2 equiv of NaEt3BH as the catalyst (0.001-0.05 equiv) and (EtO)2SiMeH as the hydrogen source, is best run at ambient temperature in toluene and is highly selective for the reduction of simple unsubstituted 1-alkenes and the terminal double bonds in 1,3- and 1,4-dienes, β-vinyl ketones, and silyloxy dienes. The reaction is tolerant of various functional groups such as bromide, alcohol, amine, carbonyl, di- or trisubstituted double bonds, and water. Highly selective reduction of a terminal alkyne to either an alkene or alkane can be accomplished by using stoichiometric amounts of the silane. Preliminary mechanistic studies indicate that the reaction is stoichiometric in the silane and both hydrogens in the product come from the silane.
Comparison of “on water” and solventless procedures in the rhodium-catalyzed hydroformylation of diolefins, alkynes, and unsaturated alcohols
Alsalahi,Trzeciak
, p. 41 - 48 (2016/07/06)
Catalytic systems containing Rh(acac)(CO)2 or Rh/PAA (PAA?=?polyacrylic acid) and hydrophobic phosphine (PPh3) were used in the hydroformylation of diolefins, alkynes, and unsaturated alcohols under solventless and “on water” conditions. The total yield of dialdehydes obtained from 1,5-hexadiene and 1,7-octadiene reached 99%, and regioselectivity towards linear dialdehydes was higher in the “on water” system. The tandem hydroformylation-hydrogenation of phenylacetylene led to the formation of saturated aldehydes (3-phenylpropanal and 2-phenylpropanal) at 98% conversion with a good regioselectivity towards the linear aldehyde in the “on water” reaction. In contrast, solventless conditions appeared better in the hydroformylation of 1-propen-3-ol. 4-Hydroxybutanal, formed in this reaction with an excellent selectivity, was next transformed to tetrahydrofuran-2-ol via a ring-closure process. Cyclic products were also obtained in hydroformylation of 1-buten-3-ol. In reaction of undec-1-ol and 2-allylphenol linear aldehydes were formed with the yield 69–87%. The hydroformylation of 3-buten-1-ol performed under “on water” conditions showed very good regioselectivity towards a linear aldehyde, 5-hydroxypentanal. Further cyclization of the aldehyde to tetrahydropyran-2-ol was observed.
Continuous flow hydrogenation reactions by Pd catalysts onto hybrid ZrO2/PVA materials
Liguori, Francesca,Barbaro, Pierluigi,Sawa, Haruo
, p. 58 - 65 (2017/03/10)
Palladium nanoparticles of 3.2?±?0.9?nm size were generated within 12–18 mesh pellets of hybrid zirconia/polyvinyl alcohol matrix, to afford a 0.03–0.1% Pd loading (w/w). The material was used in the catalytic, continuous flow hydrogenation reaction of multiple C[dbnd]C and C[tbnd]C bonds and nitrobenzene, showing good selectivity at full conversion and excellent resistance over prolonged time-on-stream under room temperature and 1–2?bar H2gas. No metal leaching in solution was detected as well as no additives nor regeneration steps were needed for use in hydrophilic solvents.
Ni-In intermetallic nanocrystals as efficient catalysts toward unsaturated aldehydes hydrogenation
Li, Changming,Chen, Yudi,Zhang, Shitong,Xu, Simin,Zhou, Junyao,Wang, Fei,Wei, Min,Evans, David G.,Duan, Xue
, p. 3888 - 3896 (2013/10/22)
The chemoselective hydrogenation of unsaturated carbonyl compounds is one of the most important and challenging chemical processes in the fine chemical synthesis field, where intermetallic compounds (IMCs) have attracted extensive interest as efficient catalysts. In this work, we demonstrate the preparation of several Ni-In IMCs (Ni3In, Ni2In, NiIn, and Ni 2In3) with a tunable particle size via the utilization of layered double hydroxides (LDHs) precursors that exhibit largely enhanced catalytic activity and selectivity toward the hydrogenation of α,β-unsaturated aldehydes. H2-TPR and semi-in situ XRD measurements reveal a coreduction process in the topotactic transformation of NiIn-LDHs materials to Ni-In IMCs. The catalytic behavior toward various unsaturated carbonyl compounds (e.g., furfural, 1-phenyltanol, crotonaldehyde, and 2-hexenal) can be improved by the modulation of the Ni/In ratio and the particle size of these Ni-In IMCs. For instance, a yield of 99% for the hydrogenation of furfural to furfuryl alcohol was obtained over supported Ni2In catalyst (particle size 5.1 nm, 110 C, 3 MP, 2 h). The XAFS characterization and DFT calculation further reveal the electron transfer and active-site isolation in Ni-In IMCs, accounting for the largely enhanced hydrogenation selectivity. The control over the activity and selectivity of Ni-In IMCs catalysts makes them promising candidates for the chemoselective hydrogenation of unsaturated carbonyl compounds.
Characterization and catalytic-hydrogenation behavior of SiO 2-embedded nanoscopic Pd, Au, and Pd-Au alloy colloids
Parvulescu, Vasile I.,Parvulescu, Viorica,Endruschat, Uwe,Filoti, George,Wagner, Friedrich E.,Kübel, Christian,Richards, Ryan
, p. 2343 - 2357 (2008/02/03)
Colloids embedded in a silica sol-gel matrix were prepared by using fully alloyed Pd-Au colloids, and pure Pd and Au colloids stabilized with tetraalkylammonium bromide following a modified sol-gel procedure with tetrahydrofuran (THF) as the solvent. Tetraethoxysilicate (TEOS) was used as the precursor for the silica support. The molar composition of the sol was TEOS/THF/H2O/HCl = 1:3.5:4:0.05 for the bimetallic Pd-Au and TEOS/THF/H2O/HCl = 1:4.5:4:0.02 for Pd and Au monometallic systems. After refluxing. the colloid was added as a 4.5 wt % solution in THF for Pd-Au. 10.2 wt % solution in THF for Pd and 8.4 wt % solution in THF for Au at room temperature. The gelation was carried out with vigorous stirring (4 days) under an Ar atmosphere. Following these procedures, bimetallic Pd-Au-SiCK catalysts with 0.6 and 1 wt % metal, and monometallic Pd- and Au-SiO2 catalysts with 1 wt% metal were prepared. These materials were further treated following four different routes: 1) by simple drying, 2) in which the dried catalysts were calcined in air at 723 K and then reduced at the same temperature, 3) in which they were directly reduced in hydrogen at 723 K, and 4) in which the surfactant was extracted using an ethanol-heptane azeotropic mixture. The catalysts were characterized by nitrogen adsorption-desorption isotherms at 77 K, H2 chemisorption measurements, solid-state 1H, 13C 29SiCP/MAS-NMR spectroscopy, powder X-ray diffraction (XRD), small angle X-ray scattering (SAXS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and 197Au M?ssbauer spectroscopy. The physical characterization by a combination of these techniques has shown that the size and the structural characteristics of the Pd-Au colloid precursor are preserved when embedded in an SiO2 matrix. Catalytic tests were carried out in selective hydrogenation of 3-hexyn-1-ol, cinnamaldehyde, and styrene. These data showed evidence that alloying Pd with Au in bimetallic colloids leads to enhanced activity and most importantly to improved selectivity. Also, the combination of the two metals resulted in catalysts that were very stable against poisoning, as was evidenced for the hydrogenation of styrene in the presence of thiophene.
Process for α,β-dihydroxyalkenes and derivatives
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Page 10, (2008/06/13)
Disclosed is a process wherein a first olefin selected from certain α,β-dihydroxyalkenes and 4-(alkenyl)ethylenecarbonates is reacted with a second olefin reactant to produce an olefin metathesis product. When the first olefin reactant is an optically enriched or enantiomerically pure α,β-dihydroxyalkene, cross metathesis reactions produce products possessing the same optical purity. The α,β-dihydroxyalkenes and the 4-(alkenyl)ethylene carbonates may be converted to hydrogenated products, and the 4-(alkenyl)ethylenecarbonates may be decarboxylated to provide the corresponding epoxides. The products of the disclosure may be used as monomers for the preparation of specialty polyesters and as intermediates in the manufacture pharmaceuticals and other chemicals.
