4501-58-0Relevant articles and documents
Organocatalytic epoxidation and allylic oxidation of alkenes by molecular oxygen
Orfanidou, Maria,Petsi, Marina,Zografos, Alexandros L.
supporting information, p. 9172 - 9178 (2021/11/30)
Pyrrole-proline diketopiperazine (DKP) acts as an efficient mediator for the reduction of dioxygen by Hantzsch ester under mild conditions to allow the aerobic metal-free epoxidation of electron-rich alkenes. Mechanistic crossovers are underlined, explaining the dual role of Hantzsch ester as a reductant/promoter of the DKP catalyst and a simultaneous competitor for the epoxidation of alkenes when HFIP is used as a solvent. Expansion of this protocol to the synthesis of allylic alcohols was achieved by adding a catalytic amount of selenium dioxide as an additive, revealing a superior method to the classical application of t-BuOOH as a selenium dioxide oxidant.
A recyclable cobalt(iii)-ammonia complex catalyst for catalytic epoxidation of olefins with air as the oxidant
Wang, Chenlong,Zhan, Hongju,Lu, Xinhuan,Jing, Run,Zhang, Haifu,Yang, Lu,Li, Xixi,Yue, Fanfan,Zhou, Dan,Xia, Qinghua
supporting information, p. 2147 - 2156 (2021/02/06)
[Co(NH3)6]Cl3and other ammonia complexes with different external anions or metal ions were synthesized to catalyze the epoxidation of α-pinene. The synthesized complexes were characterized using XRD, SEM, TGA, FTIR and UV spectra. With air as the oxidant, [Co(NH3)6]Cl3exhibited excellent catalytic activity for the epoxidation of α-pinene among the prepared complexes. The conversion of α-pinene reached 97.4%, with 98.3% selectivity of epoxide when using a small amount of cumene hydroperoxide (CHP) as the initiator. The results revealed that a single Co(iii) system can also catalyze the epoxidation process in the absence of Co(ii), even showing better catalytic performance than single Co(ii). Recycling experiments showed that there was no significant drop in activity after 10 cycles, demonstrating that it is a stable and efficient heterogeneous catalyst for the epoxidation of α-pinene. The excellent recycling performance may be attributed to the stability of the coordination complex itself.
Tailoring Lewis/Br?nsted acid properties of MOF nodesviahydrothermal and solvothermal synthesis: simple approach with exceptional catalytic implications
Bohigues, Benjamin,Boronat, Mercedes,Corma, Avelino,Lopes, Christian W.,Meira, Débora M.,Moliner, Manuel,Rojas-Buzo, Sergio
, p. 10106 - 10115 (2021/08/04)
The Lewis/Br?nsted catalytic properties of the Metal-Organic Framework (MOF) nodes can be tuned by simply controlling the solvent employed in the synthetic procedure. In this work, we demonstrate that Hf-MOF-808 can be prepared from a material with a higher amount of Br?nsted acid sites,viamodulated hydrothermal synthesis, to a material with a higher proportion of unsaturated Hf Lewis acid sites,viamodulated solvothermal synthesis. The Lewis/Br?nsted acid properties of the resultant metallic clusters have been studied by different characterization techniques, including XAS, FTIR and NMR spectroscopies, combined with a DFT study. The different nature of the Hf-MOF-808 materials allows their application as selective catalysts in different target reactions requiring Lewis, Br?nsted or Lewis-Br?nsted acid pairs.
Development of rapid and selective epoxidation of α-pinene using single-step addition of H2O2in an organic solvent-free process
Eze, Valentine C.,Harvey, Adam P.,López Fernández, Ana María,Mukhtar Gunam Resul, Mohamad Faiz,Rehman, Abdul
, p. 33027 - 33035 (2021/12/07)
This study reports substantial improvement in the process for oxidising α-pinene, using environmentally friendly H2O2 at high atom economy (～93%) and selectivity to α-pinene oxide (100%). The epoxidation of α-pinene with H2O2 was catalysed by tungsten-based polyoxometalates without any solvent. The variables in the screening parameters were temperatures (30-70 °C), oxidant amount (100-200 mol%), acid concentrations (0.02-0.09 M) and solvent types (i.e., 1,2-dichloroethane, toluene, p-cymene and acetonitrile). Screening the process parameters revealed that almost 100% selective epoxidation of α-pinene to α-pinene oxide was possible with negligible side product formation within a short reaction time (～20 min), using process conditions of a 50 °C temperature in the absence of solvent and α-pinene/H2O2/catalyst molar ratio of 5?:?1?:?0.01. A kinetic investigation showed that the reaction was first-order for α-pinene and catalyst concentration, and a fractional order (～0.5) for H2O2 concentration. The activation energy (Ea) for the epoxidation of α-pinene was ～35 kJ mol-1. The advantages of the epoxidation reported here are that the reaction could be performed isothermally in an organic solvent-free environment to enhance the reaction rate, achieving nearly 100% selectivity to α-pinene oxide.
Engineering a Highly Defective Stable UiO-66 with Tunable Lewis-Br?nsted Acidity: The Role of the Hemilabile Linker
De Geyter, Nathalie,De Vos, Dirk E.,Feng, Xiao,Hajek, Julianna,Hoffman, Alexander E. J.,Jena, Himanshu Sekhar,Leus, Karen,Leyssens, Karen,Marquez, Carlos,Meynen, Vera,Morent, Rino,Van Der Voort, Pascal,Van Speybroeck, Veronique,Veerapandian, Savita K. P.,Wang, Guangbo
, p. 3174 - 3183 (2020/03/10)
The stability of metal-organic frameworks (MOFs) typically decreases with an increasing number of defects, limiting the number of defects that can be created and limiting catalytic and other applications. Herein, we use a hemilabile (Hl) linker to create up to a maximum of six defects per cluster in UiO-66. We synthesized hemilabile UiO-66 (Hl-UiO-66) using benzene dicarboxylate (BDC) as linker and 4-sulfonatobenzoate (PSBA) as the hemilabile linker. The PSBA acts not only as a modulator to create defects but also as a coligand that enhances the stability of the resulting defective framework. Furthermore, upon a postsynthetic treatment in H2SO4, the average number of defects increases to the optimum of six missing BDC linkers per cluster (three per formula unit), leaving the Zr-nodes on average sixfold coordinated. Remarkably, the thermal stability of the materials further increases upon this treatment. Periodic density functional theory calculations confirm that the hemilabile ligands strengthen this highly defective structure by several stabilizing interactions. Finally, the catalytic activity of the obtained materials is evaluated in the acid-catalyzed isomerization of α-pinene oxide. This reaction is particularly sensitive to the Br?nsted or Lewis acid sites in the catalyst. In comparison to the pristine UiO-66, which mainly possesses Br?nsted acid sites, the Hl-UiO-66 and the postsynthetically treated Hl-UiO-66 structures exhibited a higher Lewis acidity and an enhanced activity and selectivity. This is further explored by CD3CN spectroscopic sorption experiments. We have shown that by tuning the number of defects in UiO-66 using PSBA as the hemilabile linker, one can achieve highly defective and stable MOFs and easily control the Br?nsted to Lewis acid ratio in the materials and thus their catalytic activity and selectivity.
Heteropoly acid catalysts in upgrading of biorenewables: Synthesis of para-menthenic fragrance compounds from α-pinene oxide
Ribeiro, Cláudio J.A.,Pereira, Matheus M.,Kozhevnikova, Elena F.,Kozhevnikov, Ivan V.,Gusevskaya, Elena V.,da Silva Rocha, Kelly A.
, p. 166 - 170 (2019/01/04)
The isomerization of α-pinene oxide in the presence of Cs2.5H0.5PW12O40 (CsPW) heteropolysalt as solid acid catalyst is reported. The reactions were performed in various solvents, which allowed to obtain trans-carveol, trans-sobrerol and pinol in 60–80% yield each, which exceed the yields reported so far. The CsPW catalyst could be recovered and reused without loss of its activity and selectivity.
A Cu-Doped ZIF-8 metal organic framework as a heterogeneous solid catalyst for aerobic oxidation of benzylic hydrocarbons
Nagarjun, Nagarathinam,Dhakshinamoorthy, Amarajothi
, p. 18702 - 18712 (2019/12/09)
Mixed-metal metal organic frameworks have received considerable attention in recent years and it has been shown that the activity of the parent metal organic framework (MOF) is often enhanced upon doping with external metal ions within the framework. In this context, Cu2+ ions with different loadings were incorporated within the ZIF-8 framework to obtain a series of Cu-doped ZIF-8 materials and their activity was examined in the aerobic oxidation of hydrocarbons. The as-synthesized Cu-doped solids were characterized by powder X-ray diffraction (XRD), ultraviolet diffuse reflectance spectroscopy (UV-DRS), scanning electron microscopy (SEM), Fourier Transform infrared (FT-IR), electron paramagnetic resonance (EPR) and inductively coupled plasma (ICP) analysis. The experimental results revealed that the activity of Cu-doped ZIF-8 is much higher than that of the parent ZIF-8 in all the tested substrates at 120 °C. Furthermore, the activity of the Cu-doped ZIF-8 with the highest Cu loading was eight fold higher than that of the parent ZIF-8 in the aerobic oxidation of cyclooctane (1) at 120 °C with more than 80% selectivity to the corresponding cyclooctanol/cyclooctanone (ol/one) mixture. Cu-doped ZIF-8 was reused two times with no significant drop in its activity under identical conditions. Furthermore, comparison of the two times reused solid with that of the fresh solid by powder XRD and SEM analysis revealed identical structural integrity and morphology, respectively during the oxidation reactions.
Tin-containing zeolitic material having an MWW-type framework structure
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Page/Page column 33, (2018/06/19)
A process for preparing a tin-containing zeolitic material having an MWW-type framework structure comprising providing a zeolitic material having an MWW-type framework structure having vacant tetrahedral framework sites, providing a tin-ion source in solid form, and incorporating tin into the zeolitic material via solid-state ion exchange.
Synthesis of Fencholenic Aldehyde from α-pinene Epoxide on Modified Clays
Sidorenko, A. Yu.,Ignatovich, Zh. V.,Ermolinskaya,Kravtsova,Baranovskii,Koroleva,Agabekov
, p. 893 - 897 (2018/09/27)
The conditions for isomerization of α-pinene epoxide (2,3-epoxypinane) on modified clays that gave comparatively high contents (33.0%) of fencholenic (iso-campholenic) aldehyde in the product mixture were determined. An effective method for isolating it w
Zeolite Y encaged Ru(III) and Fe(III) complexes for oxidation of styrene, cyclohexene, limonene, and α-pinene: An eye-catching impact of H2SO4 on product selectivity
Godhani, Dinesh R.,Nakum, Haresh D.,Parmar, Digvijaysinh K.,Mehta, Jignasu P.,Desai, Nisheeth C.
, p. 223 - 237 (2016/12/09)
A novel Ru(III) and Fe(III) complexes of ligands 1 and/or 2 {where 1 = 2,2'-((1E,1'E)-((azanediylbis(ethane-2,1-diyl))bis(azanylylidene))bis(methanylylidene))diphenol and 2 = 2,2'-((1E,1'E)-((azanediylbis(ethane-2,1-diyl))bis(azanylylidene))bis(methanylylidene)) bis(4-nitrophenol)} have been synthesized as ‘neat’ and zeolite Y encapsulated complexes. These catalysts are characterized by various analytical tools such as FTIR, UV–vis, elemental analysis, ICP-AES, molar conductivity, 1H- and 13C NMR, TGA, SEM, AAS, BET, magnetic susceptibility and powder XRD to endorse the complex formation, absence of peripheral redundant ligands and complexes, conservation of zeolite Y morphology and crystallinity, and the encapsulation of complexes without devastation in the zeolite Y framework. Out of these synthesized catalysts, 5Y is found to be a potent candidate for styrene (Conv. 76.1%, TOF: 2130 h?1), cyclohexene (Conv. 84.4%, TOF: 2351 h?1), limonene (Conv. 81.6%, TOF: 2273 h?1), and α-pinene (Conv. 72.6%, TOF: 2023 h?1) oxidation with high selectivity of respective allylic products excluding the styrene oxidation, which undergoes epoxidation only. The addition of H2SO4 in an identical reaction catalyzed by 5Y not only surge the conversion up to 100% in a short time span with high TOF but also increase the selectivity of respective epoxidation products. This switchover in the selectivities could be credited to the presence of H2SO4 that facilitates the heterolytic [sbnd]O[sbnd]O[sbnd] bond cleavage of metal hydroperoxide and stimulates the epoxidation over allylic oxidation. Furthermore, the results establish that the heterogeneous systems are effortlessly recovered and reused without ample drop in the activity and selectivity.
