451-40-1Relevant articles and documents
Hydration of Alkynes Catalyzed by L-Au-X under Solvent- and Acid-Free Conditions: New Insights into an Efficient, General, and Green Methodology
Gatto, Mattia,Del Zotto, Alessandro,Segato, Jacopo,Zuccaccia, Daniele
, p. 4685 - 4691 (2018)
L-Au-X [L = 1,3-bis(2,6-di-isopropylphenyl)-imidazol-2-ylidene {NHCiPr}, tris(3,5-bis(trifluoromethyl)phenyl)phosphine {PArF}, bis(imino)acenaphtene-1,3-bis(2,6-di-isopropylphenyl)dihydroimidazol-2-ylidene {BIAN}, 1,3-bis(2,6-di-isopropyl-phenyl)dihydroimidazol-2-ylidene {NHCCH2}, bis(tert-butylamino)methylidene {NAC}, 2-(di-tert-butylphosphino)biphenyl {JohnPhos}, tricyclohexylphosphine {PCy3}, triphenylphosphine {PPh3}, tris(2,4-di-tert-butylphenyl)phosphite {POR3}; X- = Cl-, OTf-, OTs-] catalysts were tested in the hydration of alkynes in neat and acid-free conditions. The overall catalytic evidence confirms that not only the counterion as previously observed by us but also the ligand play a crucial role. As a matter of fact, only complexes bearing NHC ligands showed appreciable catalytic activity. A complete rationalization of the ligand and counterion effects enabled us to develop a highly efficient methodology for the hydration of inactive diphenylacetylene in solvent-, silver-, and acid-free conditions. Thus, it was possible to reduce the catalyst loading to 0.01 mol % (with respect to diphenylacetylene) leading, to the best of our knowledge, to the highest TON (3400) and TOF (435 h-1) values found at 120 °C. The favorable catalytic conditions allowed us to reach for the first time very low E-factor (0.03) and high EMY (77) values for this substrate.
Reactivity and Crystal Structure of 10,11-Dihydro-10,11-epoxy-5H-dibenzocycloheptene. A Comparison with cis-Stilbene Oxide
Bellucci, Giuseppe,Chiappe, Cinzia,Marioni, F.,Spagna, Riccardo
, p. 2147 - 2151 (1990)
The kinetics and product distributions for the HClO4 catalysed hydrolysis of 10,11-dihydro-10,11-epoxy-5H-dibenzocycloheptene 1 and of cis-stilbene oxide 6 in tetrahydrofuran-water (8:2), have been investigated by HPLC.The former epoxide gives 9,10-dihydroanthracene-9-carbaldehyde 4 and the trans- and cis-10,11-dihydro-5H-dibenzocycloheptene-10,11-diols 2 and 3, in the ratio 6:6:1. cis-Stilbene oxide reacts with a rate constant ca. ten times lower, giving mostly (+/-)-1,2-diphenylethane-1,2-diol.These differences can be explained by the crystal structure of 1, which shows considerable ring strain due to the enlargement of the bond angles at C(10) and C(11).This structure also suggests an explanation for the much lower rate of the microsomal epoxide hydrolase catalysed hydration of 1 relative to 6.
ELECTRON-TRANSFER CHAIN ISOMERIZATION OF EPOXIDES INDUCED BY ONE-ELECTRON OXIDIZING AGENTS
Lopez, Luigi,Troisi, Luigino
, p. 3097 - 3100 (1989)
One electron oxidizing agents have been employed to achieve the isomerization of epoxides to ketones.The reactions most likely proceed via a radical cation chain electron-transfer mechanism.
Improving process efficiency of gold-catalyzed hydration of alkynes: Merging catalysis with membrane separation
A. C. A. Bayrakdar, Tahani,Nahra, Fady,Zugazua, Oihane,Eykens, Lies,Ormerod, Dominic,Nolan, Steven P.
, p. 2598 - 2604 (2020)
In this report, we investigate the integration of a membrane separation protocol in line with the gold-catalyzed hydration of alkynes. The catalytic reaction is optimised towards that end and subsequently merged with membrane technology via the development of an organic solvent nanofiltration (OSN) procedure. The protocol is investigated over both ceramic and polymeric membranes. Several gold catalysts were screened in the hydration of diphenylacetylene 1, and high rejection was observed in all cases using Borsig-type polymeric membranes. Catalyst recycling was also achieved up to 4 times using [Au(OTf)(IPr)] (3). In addition, the retained catalyst in the last catalytic cycle was analyzed and readily converted into [Au(Cl)(IPr)] (synthetic precursor to 3), using a straightforward treatment. The sustainability of the process was improved by using a green solvent, 2-methyltetrahydrofuran (Me-THF), and by reducing the amount of solvent used via the implementation of a second membrane.
PMO-Immobilized AuI–NHC Complexes: Heterogeneous Catalysts for Sustainable Processes
De Canck, Els,Nahra, Fady,Bevernaege, Kevin,Vanden Broeck, Sofie,Ouwehand, Judith,Maes, Diederick,Nolan, Steven P.,Van Der Voort, Pascal
, p. 430 - 436 (2018)
A stable periodic mesoporous organosilica (PMO) with accessible sulfonic acid functionalities is prepared via a one-pot-synthesis and is used as solid support for highly active catalysts, consisting of gold(I)-N-heterocyclic carbene (NHC) complexes. The gold complexes are successfully immobilized on the nanoporous hybrid material via a straightforward acid–base reaction with the corresponding [Au(OH)(NHC)] synthon. This catalyst design strategy results in a boomerang-type catalyst, allowing the active species to detach from the surface to perform the catalysis and then to recombine with the solid after all the starting material is consumed. This boomerang behavior is assessed in the hydration of alkynes. The tested catalysts were found to be active in the latter reaction, and after an acidic work-up, the IPr*-based gold catalyst can be recovered and then reused several times without any loss in efficiency.
Investigation of axial ligand effects on catalytic activity of manganese porphyrin, evidence for the importance of hydrogen bonding in cytochrome-P450 model reactions
Mesbahi, Elnaz,Safari, Nasser,Gheidi, Mahin
, p. 354 - 365 (2014)
Various nitrogenous bases, such as imidazoles, pyridines and amines were employed as axial ligands in epoxidation reaction of cyclooctene bytetra-n-butylammonium hydrogen monopersulfate (n-Bu4NHSO5), in the presence of Mn(III)-tetrakis(2,3-dimethoxyphenyl)porphyrin-acetate (T(2,3-OMeP)PorMnOAc). T(2,3-OMeP)PorMnOAc is a fairly stable catalyst, with the ability of producing hydrogen bonding. High epoxidation yield of 85 ± 6% was obtained in the presence of imidazole axial ligand with 100% selectivity in 30 min. Higher conversion of around 100% was obtained by pyridine axial base, while selectivity was reduced to 69%. Further epoxidation reactions were also performed using Mn(III)-Tetrakis(2,3-dihydroxyphenyl)porphyrin-acetate (T(2,3-OHP)PorMnOAc) as catalyst. In addition to the usual electronic and steric effects, it is proposed that the catalytic activity depends on the existence and kind of hydrogen bonding between the axial base and the ortho-methoxy or hydroxy groups on the phenyl rings of manganese porphyrin. The cis to trans ratio of cis-stilbene oxide formed by imidazole and pyridine axial bases were obtained as 7.5 and 2.5 respectively. In addition GC-Ms and UV-vis studies were employed to find the nature of active species and product formation. Our DFT calculations disclosed that pyridine hydrogen bonding with moiety of the macrocycle rings strongly affects the relative energies of S/Q spin states in [T(2,3-OMeP)PorMnV(O)(Py)]+, in that it results in the longer Mn-O bond and reactivity toward substrates.
ABOUT THE MECHANISM OF THE PHOTOLYSIS OF BENZOYLTRIETHYLGERMANE, Et3GeCOPh
Taraban, M. B.,Maryasova, V. I.,Leshina, T. V.,Rybin, L. I.,Gendin, D. V.,Vyazankin, N. S.
, p. 347 - 356 (1987)
The detailed mechanism of the photolysis of benzoyltriethylgerman Et3GeCOPh in various media has been studied using the chemically induced dynamic nuclear polarization method (1 H CIDNP).It has been shown that in all cases the photolytic decomposition lea
Synthesis, reactivity and catalytic activity of Au-PAd3complexes
Voloshkin, Vladislav A.,Saab, Marina,Van Hecke, Kristof,Lau, Sii Hong,Carrow, Bradley P.,Nolan, Steven P.
, p. 13872 - 13879 (2020)
Tri(1-adamantyl)phosphine (PAd3) possesses unique steric and electronic properties positioning it at the border between tertiary phosphines and N-heterocyclic carbenes (NHC). Novel Au-PAd3complexes were synthesized from the known [Au(PAd3)Cl]. We have optimised reaction conditions for the synthesis of this useful synthon in order to circumvent the formation of the [Au(PAd3)2]Cl. [Au(PAd3)Cl] was used to access a number of derivatives and some were deployed as catalysts. The hydration of alkynes was targeted to gauge the reactivity of Au-PAd3complexes and permit comparison with NHC and tertiary phosphine congeners.
Synthesis and characterization of gold(I) complexes of dibenzotropylidene-functionalized NHC ligands (Trop-NHCs)
Brill, Marcel,Collado, Alba,Cordes, David B.,Slawin, Alexandra M. Z.,Vogt, Matthias,Grützmacher, Hansj?rg,Nolan, Steven P.
, p. 263 - 274 (2015)
Gold(I) complexes of dibenzotropylidene-functionalized N-heterocyclic carbene ligands (Trop-NHCs) have been prepared in order to investigate their structural features and to reveal possible interactions of the olefin unit with the metal center. The precursor imidazolium chloride salts (R-1) were generated in a single step using N-substituted imidazoles (R = H, Me, DiPP, Ad) and 1 or 2 equiv of Trop-Cl, generating unsymmetrical and symmetrical NHC-olefin hybrids. The structural parameters of the ligands were determined by synthesis and X-ray diffraction analysis of their corresponding gold(I) chloride complexes, revealing highly flexible steric demands of the Trop unit. Conversion of these complexes with halide-abstracting reagents such as AgNTf2 and NaBArF24 cleanly gave neutral, NTf2-coordinated complexes of the type [(NHC)Au(NTf2)] (R-3) and the cationic bis-NHC-coordinated complexes [(NHC)2Au]BArF24 (R-4), respectively. The Gagosz-type complexes R-3 were further tested in the hydration of diphenylacetylene, showing a clear trend in activity depending on the ligand's sensitivity to hydrolysis.
Chiral α-hydroxy acid-coadsorbed TiO2 photocatalysts for asymmetric induction in hydrogenation of aromatic ketones
Kohtani, Shigeru,Kawashima, Akira,Masuda, Fumie,Sumi, Momono,Kitagawa, Yuichi,Yoshioka, Eito,Hasegawa, Yasuchika,Miyabe, Hideto
, p. 12610 - 12613 (2018)
Modification of titanium dioxide (TiO2) photocatalysts with chiral reagents was evaluated by the hydrogenation of aromatic ketones. The strong adsorption of chiral mandelic acid (R)-MA on TiO2 was confirmed by comparing the inhibitio
