Metal oxide-triazole hybrids as heterogeneous or reaction-induced self-separating catalysts

Amarante, Tatiana R.,Neves, Patrícia,Valente, Anabela A.,Paz, Filipe A. Almeida,Pillinger, Martyn,Gon?alves, Isabel S.

, p. 354 - 367 (2016)

The hybrid metal oxide-triazole materials [MoO3(trz)0.5] (1) and [W2O6(trz)] (2) (trz?=?1,2,4-triazole) have been hydrothermally synthesized and characterized by different techniques (TGA, SEM, 1H and 13C MAS NMR, FT-IR spectroscopy, and structure determination by Rietveld analysis of high resolution synchrotron powder XRD data). Materials 1 and 2 display distinct behaviors when applied as catalysts for oxidation reactions with alcohol, aldehyde, olefin and sulfide substrates, and are more effective with hydrogen peroxide as the oxidant than with tert-butylhydroperoxide. The MoVI hybrid 1 transforms into soluble active species during cis-cyclooctene epoxidation with H2O2. When consumption of H2O2 reaches completion, spontaneous reassembly of the 2-dimensional molybdenum oxide network of 1 takes place and the hybrid precipitates as a microcrystalline solid that can be easily separated and recycled. Reaction-induced self-separation behavior occurs with 1, H2O2 and other substrates such as methyl oleate and methylphenylsulfide. The WVI hybrid 2 behaves differently, preserving its structural features throughout the heterogeneous catalytic process.

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Wallace et al.

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Amphiphilic dipyridinium-phosphotungstate as an efficient and recyclable catalyst for triphasic fatty ester epoxidation and oxidative cleavage with hydrogen peroxide

De La Garza, Luis Carlos,De Oliveira Vigier, Karine,Chatel, Gregory,Moores, Audrey

, p. 2855 - 2862 (2017)

A novel amphiphilic dipyridinium peroxophosphotungstate ion pair was developed as a selective and recyclable catalyst for the triphasic epoxidation of fatty acids and esters with hydrogen peroxide. The synthesis of the catalyst was studied extensively by solid and liquid phase 31P nuclear magnetic resonance (NMR). The oxidation of vegetable oils is of prime importance for the production of lubricants, plasticizers, polymer stabilizers and other olefinic compounds. Based on the oxidizing activity of peroxophosphotungstates, we designed a lipophilic phase transfer agent that renders the active complex insoluble in the reaction media, without having to support it on a matrix. This affords a catalyst combining the activity of homogeneous catalysts and the recyclability of heterogeneous systems. We show that this catalyst is able to fully epoxidize methyl oleate with excellent selectivity, with a turnover frequency of 149 at 60 °C, and can be easily recycled, to reach a record turn over number of 1868. A larger scale experiment on 13 grams and a scope including linoleic and ricinoleic acids were also demonstrated. The catalyst also shows excellent activity and selectivity for the oxidative cleavage of methyl oleate and the oxidation of small olefins.

Selective dihydroxylation of methyl oleate to methyl-9,10-dihydroxystearate in the presence of a recyclable tungsten based catalyst and hydrogen peroxide

Araji, Nahla,Chatel, Gregory,Moores, Audrey,Jér?me, Fran?ois,De Oliveira Vigier, Karine

, p. 11507 - 11512 (2020)

The dihydroxylation of fatty methyl esters is of prime importance for the synthesis of surfactants and lubricants. The conversion of methyl oleate (MO) to 98percent yield of methyl-9,10-dihydroxystearate (MDHS) was performed in the presence of H2O2 and H3PW12O40 catalyst in the absence of a phase transfer agent. The study of the effect of hydrogen peroxide concentration revealed that significant catalytic activity was only achieved for an optimal amount of H2O2. A mechanism for this reaction was proposed where hydrogen peroxide reacts with H3PW12O40 to produce peroxo-phosphotungstate anions, which directly dihydroxylate MO. The recyclability of the catalyst was also studied. To this aim, a recyclable form of the heteropolyacid was synthesized using Cs cations (Cs2.3H0.7PW12O40). This catalyst was recycled up to three cycles without significant loss in catalytic performances. This journal is

Triazolyl, Imidazolyl, and Carboxylic Acid Moieties in the Design of Molybdenum Trioxide Hybrids: Photophysical and Catalytic Behavior

Lysenko, Andrey B.,Senchyk, Ganna A.,Domasevitch, Konstantin V.,Kobalz, Merten,Krautscheid, Harald,Cichos, Jakub,Karbowiak, Miroslaw,Neves, Patrícia,Valente, Anabela A.,Gon?alves, Isabel S.

, p. 4380 - 4394 (2017)

Three organic ligands bearing 1,2,4-triazolyl donor moieties, (S)-4-(1-phenylpropyl)-1,2,4-triazole (trethbz), 4-(1,2,4-triazol-4-yl)benzoic acid (trPhCO2H), and 3-(1H-imidazol-4-yl)-2-(1,2,4-triazol-4-yl)propionic acid (trhis), were prepared to evaluate their coordination behavior in the development of molybdenum(VI) oxide organic hybrids. Four compounds, [Mo2O6(trethbz)2]·H2O (1), [Mo4O12(trPhCO2H)2]·0.5H2O (2a), [Mo4O12(trPhCO2H)2]·H2O (2b), and [Mo8O25(trhis)2(trhisH)2]·2H2O (3), were synthesized and characterized. The monofunctional tr-ligand resulted in the formation of a zigzag chain [Mo2O6(trethbz)2] built up from cis-{MoO4N2} octahedra united through common μ2-O vertices. Employing the heterodonor ligand with tr/-CO2H functions afforded either layer or ribbon structures of corner- or edge-sharing {MoO5N} polyhedra (2a or 2b) stapled by tr-links in axial positions, whereas -CO2H groups remained uncoordinated. The presence of the im-heterocycle as an extra function in trhis facilitated formation of zwitterionic molecules with a protonated imidazolium group (imH+) and a negatively charged -CO2- group, whereas the tr-fragment was left neutral. Under the acidic hydrothermal conditions used, the organic ligand binds to molybdenum atoms either through [N-N]-tr or through both [N-N]-tr and μ2-CO2- units, which occur in protonated bidentate or zwitterionic tetradentate forms (trhisH+ and trhis, respectively). This leads to a new zigzag subtopological motif (3) of negatively charged polyoxomolybdate {Mo8O25}n2n- consisting of corner- and edge-sharing cis-{MoO4N2} and {MoO6} octahedra, while the tetradentate zwitterrionic trhis species connect these chains into a 2D net. Electronic spectra of the compounds showed optical gaps consistent with semiconducting behavior. The compounds were investigated as epoxidation catalysts via the model reactions of achiral and prochiral olefins (cis-cyclooctene and trans-β-methylstyrene) with tert-butylhydroperoxide. The best-performing catalyst (1) was explored for the epoxidation of other olefins, including biomass-derived methyl oleate, methyl linoleate, and prochiral dl-limonene.

Synthesis of Imidazoles from Fatty 1,2-Diketones

Bouchakour, Mansouria,Daaou, Mortada,Duguet, Nicolas

, p. 1647 - 1652 (2021)

Unsaturated vegetable oils and their corresponding fatty acid derivatives constitute interesting renewable platforms for the preparation of heterocycles, notably through the formation of oxygenated intermediates. In this work, fatty imidazoles were prepared from the corresponding 1,2-diketones through Debus-Radziszewski reaction. The reaction was optimized under microwave irradiation using a 1,2-diketone derived from methyl oleate and ammonium acetate as a nitrogen source. Using benzaldehyde as a model substrate, the reaction occurs at 180 °C for 5 min and the desired imidazole was formed in 96 % GC yield. A range of aldehydes was tested under the optimized conditions and the corresponding imidazoles were obtained in 33–99 % isolated yields (20 examples).

Spongy titanosilicate promotes the catalytic performance and reusability of WO3 in oxidative cleavage of methyl oleate

Huang, Zuoxin,Lin, Min,Peng, Xinxin,Shu, Xingtian,Xia, Changjiu,Xin, Shihao,Zhang, Yao,Zheng, Aiguo,Zhu, Bin

, p. 5135 - 5144 (2022/02/25)

A tungsten containing catalyst catalyzed oxidative cleavage of methyl oleate (MO) by employing H2O2 as an oxidant and is known as an efficient approach for preparing high value-added chemicals, however, the tungsten leaching problem remains unresolved. In this work, a binary catalyst consisting of tungsten oxide (WO3) and spongy titanosilicate (STS) zeolite is proposed for MO oxidative cleavage. The function of STS in this catalyst is investigated. On the one hand, STS converts MO to 9,10-epoxystearate (MES), which further forms nonyl aldehyde (NA) and methyl azelaaldehydate (MAA) with the catalysis of WO3. In this way, MO oxidation and hydrolysis that generates unwanted diol product 9,10-dihydroxystearate (MDS) decreases obviously. On the other hand, STS decomposes peroxide and promotes the conversion of soluble peroxotungstate to insoluble polytungstate. Meanwhile, these tungsten species are allowed to precipitate on its surface instead of remaining in the liquid phase owing to its relative large specific area. Therefore, tungsten leaching can be reduced from 37.0% to 1.2%. Due to the cooperation of WO3 and STS, 94.4% MO conversion and oxidative cleavage product selectivity of 63.1% are achieved, and the WO3-STS binary catalyst maintains excellent catalytic performance for 8 recycling reactions.

A Colorimetric Method for Quantifying Cis and Trans Alkenes Using an Indicator Displacement Assay

Valenzuela, Stephanie A.,Crory, Hannah S. N.,Yao, Chao-Yi,Howard, James R.,Saucedo, Gabriel,de Silva, A. Prasanna,Anslyn, Eric V.

supporting information, p. 13819 - 13823 (2021/05/17)

A colorimetric indicator displacement assay (IDA) amenable to high-throughput experimentation was developed to determine the percentage of cis and trans alkenes. Using 96-well plates two steps are performed: a reaction plate for dihydroxylation of the alkenes followed by an IDA screening plate consisting of an indicator and a boronic acid. The dihydroxylation generates either erythro or threo vicinal diols from cis or trans alkenes, depending upon their syn- or anti-addition mechanisms. Threo diols preferentially associate with the boronic acid due to the creation of more stable boronate esters, thus displacing the indicator to a greater extent. The generality of the protocol was demonstrated using seven sets of cis and trans alkenes. Blind mixtures of cis and trans alkenes were made, resulting in an average error of ±2 % in the percentage of cis or trans alkenes, and implementing E2 and Wittig reactions gave errors of ±3 %. Furthermore, we developed variants of the IDA for which the color may be tuned to optimize the response for the human eye.