- A recyclable cobalt(iii)-ammonia complex catalyst for catalytic epoxidation of olefins with air as the oxidant
-
[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.
- 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)
-
- Tailoring Lewis/Br?nsted acid properties of MOF nodesviahydrothermal and solvothermal synthesis: simple approach with exceptional catalytic implications
-
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.
- Bohigues, Benjamin,Boronat, Mercedes,Corma, Avelino,Lopes, Christian W.,Meira, Débora M.,Moliner, Manuel,Rojas-Buzo, Sergio
-
p. 10106 - 10115
(2021/08/04)
-
- Organocatalytic epoxidation and allylic oxidation of alkenes by molecular oxygen
-
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.
- Orfanidou, Maria,Petsi, Marina,Zografos, Alexandros L.
-
supporting information
p. 9172 - 9178
(2021/11/30)
-
- Development of rapid and selective epoxidation of α-pinene using single-step addition of H2O2in an organic solvent-free process
-
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.
- Eze, Valentine C.,Harvey, Adam P.,López Fernández, Ana María,Mukhtar Gunam Resul, Mohamad Faiz,Rehman, Abdul
-
p. 33027 - 33035
(2021/12/07)
-
- Engineering a Highly Defective Stable UiO-66 with Tunable Lewis-Br?nsted Acidity: The Role of the Hemilabile Linker
-
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.
- 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)
-
- Heteropoly acid catalysts in upgrading of biorenewables: Synthesis of para-menthenic fragrance compounds from α-pinene oxide
-
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.
- 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)
-
- A Cu-Doped ZIF-8 metal organic framework as a heterogeneous solid catalyst for aerobic oxidation of benzylic hydrocarbons
-
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.
- Nagarjun, Nagarathinam,Dhakshinamoorthy, Amarajothi
-
p. 18702 - 18712
(2019/12/09)
-
- Tin-containing zeolitic material having an MWW-type framework structure
-
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.
- -
-
Page/Page column 33
(2018/06/19)
-
- Synthesis of Fencholenic Aldehyde from α-pinene Epoxide on Modified Clays
-
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
- Sidorenko, A. Yu.,Ignatovich, Zh. V.,Ermolinskaya,Kravtsova,Baranovskii,Koroleva,Agabekov
-
p. 893 - 897
(2018/09/27)
-
- 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
-
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.
- Godhani, Dinesh R.,Nakum, Haresh D.,Parmar, Digvijaysinh K.,Mehta, Jignasu P.,Desai, Nisheeth C.
-
p. 223 - 237
(2016/12/09)
-
- Rhenium complex-catalyzed Meinwald rearrangement reactions of oxiranes
-
The Meinwald rearrangement reaction of oxiranes to the corresponding carbonyl compounds is efficiently catalyzed by the ReBr(CO)5 complex.
- Umeda, Rui,Muraki, Masahito,Nakamura, Yuudai,Tanaka, Tomoyuki,Kamiguchi, Kyohei,Nishiyama, Yutaka
-
p. 2393 - 2395
(2017/05/29)
-
- PROCESS FOR THE PREPARATION OF POLYSANTOL-TYPE COMPOUNDS
-
The present invention relates to the field of organic synthesis and more specifically it concerns a novel compound of formula (I) which could be used as a novel intermediate in the process for the preparation of compound of formula (III).
- -
-
Page/Page column 11
(2018/01/17)
-
- Synthesis of bimetallic Zr(Ti)-naphthalendicarboxylate MOFs and their properties as Lewis acid catalysis
-
Bimetallic Zr(Ti)-NDC based metal-organic frameworks (MOFs) have been prepared by incorporation of titanium(iv) into zirconium(iv)-NDC-MOFs (UiO family). The resulting materials maintain thermal (up to 500 °C), chemical and structural stability with respect to parent Zr-MOFs as can be deduced from XRD, N2 adsorption, FTIR and thermal analysis. The materials have been studied in Lewis acid catalyzed reactions, such as, domino Meerwein-Ponndorf-Verley (MPV) reduction-etherification of p-methoxybenzaldehyde with butanol, isomerization of α-pinene oxide and cyclization of citronellal.
- Rasero-Almansa, Antonia M.,Iglesias, Marta,Sánchez, Félix
-
p. 106790 - 106797
(2016/11/23)
-
- Efficient epoxide isomerization within a self-assembled hexameric organic capsule
-
The isomerization of epoxides to the corresponding carbonyl compounds is efficiently catalyzed by the supramolecular organic nano-capsule formed by the self-assembly of six resorcin[4]arene units. The capsule provides a combination of weak Br?nsted acidity and a suitable nano-environment that favors the metal-free isomerization reaction.
- Caneva, Thomas,Sperni, Laura,Strukul, Giorgio,Scarso, Alessandro
-
p. 83505 - 83509
(2016/11/01)
-
- Chemical characterization of α-pinene secondary organic aerosol constituents using gas chromatography, liquid chromatography, and paper spray-based mass spectrometry techniques
-
Rationale: Despite ample research into the atmospheric oxidation of α-pinene, an important precursor to biogenic secondary organic aerosol formation, the identification of its reaction products, specifically organic nitrates, which impact atmospheric NOx concentrations, is still incomplete. This negatively impacts our understanding of α-pinene oxidation chemistry and its relation to air quality. Methods: Photochemical chamber experiments were conducted in conjunction with mass spectrometric techniques, including gas chromatography/mass spectrometry (GC/MS), high-performance liquid chromatography/time-of-flight (HPLC/TOF), and paper spray ionization MS, to investigate products from the OH radical initiated oxidation of α-pinene under high NOx conditions. Results: Over 30 compounds were tentatively identified, including those newly detected from photochemical chamber studies of α-pinene oxidation, pinocamphenol, fencholenic aldehyde, and α-pinene-derived nitrate isomers. α-Pinene-derived hydroxynitrate isomers were successfully detected using chromatographic methods, demonstrating, for the first time, the identification of individual first-generation organic nitrate products derived from α-pinene. The application of paper spray ionization to particle-phase compounds collected on filters represents a novel method for the direct analysis of filter samples at ambient pressure and temperature. Conclusions: The use of HPLC/TOF and paper spray ionization methods to identify previously unobserved α-pinene-derived products helps lower the uncertainty in α-pinene oxidation chemistry and provides new platforms that can be used to identify and quantify important atmospheric compounds that relate to air quality in a complex sample matrix, such as ambient aerosol particles. Additionally, the use of paper spray ionization for direct filter analysis is a fast, relatively inexpensive sample preparation technique that can be used to reduce sample manipulation from solvent-induced reactions. Copyright
- Rindelaub, Joel D.,Shepson, Paul B.,Wiley, Joshua S.,Cooper, Bruce R.
-
p. 1627 - 1638
(2016/09/08)
-
- Synthesis and analgesic activity of new compounds combining azaadamantane and monoterpene moieties
-
Synthesis of new compounds that combine the diazaadamantane and monoterpenoid moieties was carried out based on the reaction between dimethylbispidinone and monoterpene-derived aldehydes. Investigation of the analgesic activity of the obtained products revealed that compound 5a synthesized from (-)-myrtenal had a higher efficacy compared with the reference drug, diclofenac sodium, in the acetic acid-induced writhing and hot plate tests. Compound 5a exhibits a low acute toxicity and does not cause damage to the gastric mucosa, and its analgesic effect is, at least partially, mediated by the cannabinoid system involving CB1 receptors.
- Ponomarev, Konstantin,Pavlova, Alla,Suslov, Evgeniy,Ardashov, Oleg,Korchagina, Dina,Nefedov, Andrej,Tolstikova, Tat'Yana,Volcho, Konstantin,Salakhutdinov, Nariman
-
p. 4146 - 4156
(2015/11/02)
-
- Nanoporous alumino- and borosilicate-mediated Meinwald rearrangement of epoxides
-
Nanoporous alumino- and borosilicate materials, produced using an evaporation-induced self-assembly approach (EISA), efficiently catalyse the Meinwald rearrangement of epoxides in dimethyl carbonate (DMC) to produce the corresponding carbonyl compounds in high yield and excellent selectivity.
- Davies, Thomas E.,Kondrat, Simon A.,Nowicka, Ewa,Kean, Joseline L.,Harris, Christopher M.,Socci, Joseph M.,Apperley, David C.,Taylor, Stuart H.,Graham, Andrew E.
-
-
- Ring-opening of epoxides promoted by organomolybdenum complexes of the type [(η5-C5H4R)Mo(CO)2(η3-C3H5)] and [(η5-C5H5)Mo(CO)3(CH2R)]
-
The cyclopentadienyl molybdenum carbonyl complexes [(η5-C5H4R)Mo(CO)2(η3-C3H5)] and [(η5-C5H5)Mo(CO)3(CH2R)] (R = H, COOH) have been shown to promote acid-catalysed reactions in liquid phase, under moderate conditions. The catalytic alcoholysis of styrene oxide with ethanol at 35 °C gave 2-ethoxy-2-phenylethanol in 100% yield within 30 min for the dicarbonyl complexes and 3-6 h for the tricarbonyl complexes. Steady catalytic performances were observed in consecutive runs with the same catalytic solution, suggesting fairly good catalytic stability. In the second acid-catalysed reaction studied, the isomerization of α-pinene oxide at 55 °C gave campholenic aldehyde and trans-carveol in a total yield of up to 86% at 100% conversion. Chemoselectivity is shown to be solvent dependent.
- Bruno, Sofia M.,Gomes, Ana C.,Abrantes, Marta,Valente, Anabela A.,Pillinger, Martyn,Gon?alves, Isabel S.
-
p. 179 - 183
(2015/10/19)
-
- Different acidity and additive effects of zirconium metal-organic frameworks as catalysts for cyanosilylation
-
The Zr(iv) metal-organic framework with 1,4-benzenedicarboxylate (UiO-66) in different forms was studied as a solid catalyst for carbonyl cyanosilylation. The anhydrous material (UiO-66-A) obtained after calcination has open Lewis-acid sites and acts as a heterogeneous and size selective catalyst for the reaction of aldehydes and trimethylsilylcyanide (TMSCN). Notably, it was found that the as-synthesized hydrous form (UiO-66-H) shows comparable activity to UiO-66-A, so UiO-66 can be used as a catalyst for cyanosilylation with no need of high-temperature activation. With a number of intentionally designed control experiments, we demonstrated that the acetic acid enclosed in UiO-66-H during synthesis serves as a Bronsted acid to promote the reaction, though acetic acid is inactive by itself. The different acidity between UiO-66-H and UiO-66-A was confirmed by using the isomerization of α-pinene oxide as a probe reaction. Both UiO-66-H and UiO-66-A are recyclable without significant degradation in framework integrity and catalytic activity. In addition, it was unexpectedly found that pyridine, which is inactive alone, acts as co-catalyst, rather than a Lewis acid poison, to dramatically accelerate the catalytic reaction over UiO-66-H or UiO-66-A. A synergistic mechanism was suggested, in which the Lewis or Bronsted acid activates the aldehyde substrate while pyridine acts as a Lewis base to activate TMSCN.
- Xi, Fu-Gui,Yang, Yang,Liu, Hui,Yao, Hong-Fei,Gao, En-Qing
-
p. 79216 - 79223
(2015/10/05)
-
- Catalytic isomerisation of α-pinene oxide in the presence of ETS-10 supported ferrocenium ions
-
Ferrocenium ions, [Fc]+, have been immobilised in the microporous titanosilicate ETS-10 by ion exchange of Na+/K+ ions under hydrothermal conditions. The resultant hybrid inorganic-organometallic (ETS-10/[Fc]+) material was characterised by elemental analysis, diffuse reflectance UV-Vis spectroscopy, FT-IR spectroscopy, powder X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The ETS-10/[Fc]+ sample was tested as a catalyst for the isomerisation of α-pinene oxide (PinOx) at 35 C. With α, α, α-trifluorotoluene (TFT) as solvent, campholenic aldehyde (CPA) was the main product formed in 38% yield at 100% conversion and 30 min reaction. Other reaction products included trans-carveol, iso-pinocamphone and trans-pinocarveol. The same PinOx conversion and CPA yield could be reached within 1 min reaction time by increasing the reaction temperature (to 55 °C) and the Fe:PinOx molar ratio. Other solvents (hexane, CH3CN, toluene) led to poorer results than TFT. Characterisation of the used catalyst, together with an analysis of the catalytic activity of the liquid phase obtained after contact of ETS-10/[Fc]+ with TFT, indicated that the ETS-10/[Fc]+ sample was resistant toward leaching of iron-containing active species. When the recovered solid was reused in a second batch run, catalytic activity was lower than in the first run, while selectivity to CPA was higher.
- Bruno, Sofia M.,Gomes, Ana C.,Coelho, Ana C.,Brand?o, Paula,Valente, Anabela A.,Pillinger, Martyn,Gon?alves, Isabel S.
-
-
- H- and Fe-modified zeolite beta catalysts for preparation of trans-carveol from α-pinene oxide
-
The isomerisation of α-pinene oxide has been intensively investigated for selective preparation of campholenic aldehyde, a compound used in the synthesis of fragrances. Selective preparation of another product of α-pinene oxide rearrangement, trans-carveol, still remains a challenging task. Trans-carveol is a highly valuable compound used in perfume bases, food flavour compositions and as an active pharmaceutical substance in chemoprevention of mammary carcinogenesis. In the present work zeolite beta with different SiO2/Al2O3 molar ratios was modified by iron, characterised and tested per se and in the modified form for trans-carveol preparation from α-pinene oxide. The isomerisation reaction was carried out in a polar basic solvent N,N-dimethylacetamide at 140 °C. The activities and selectivities of the catalysts were correlated with their acid properties and with the iron content.
- Stekrova,Kumar,Díaz,M?ki-Arvela,Murzin, D. Yu.
-
p. 237 - 245
(2015/02/19)
-
- Biomass toward fine chemical products: Oxidation of α-pinene over sieves nanostructured modified with vanadium
-
Vanadium-containing molecular sieves (V-M(x)) were synthetized and applied as heterogeneous catalysts for the liquid phase oxidation of α-pinene with hydrogen peroxide at 70°C. It has been found that the vanadium content in V-M(x) materials affected the conversion of α-pinene and product distribution. The turnover numbers increased strongly with the decreasing of V content probably caused by a high V dispersion. The major products were verbenone, trans-sobrerol and campholenic aldehyde. The acid-base properties of V-M(x) affected the distribution of products formed via the isomerization of α-pinene oxide over Lewis acid sites to campholenic aldehyde while Br?nsted acid sites brought about the formation of 1,2 pinanediol and trans-sobrerol by hydrolysis and by the opening of oxirane ring. The increase in V content in V-M(x) led to the increase in campholenic aldehyde, 1,2 pinanediol, trans- sobrerol and over oxidation products. Moreover, the effect of several solvents on the reaction oxidation was studied. The results showed that the highest α-pinene conversions are obtained in the following order: acetonitrile > ethanol > isoamyl alcohol > methyl ethyl ketone. Thus, using aprotic solvents, the catalytic activity was increased and the formation of alkyl glycol ethers as by-product was not observed.
- Cánepa, Analía L.,Chanquía, Corina M.,Vaschetti, Virginia M.,Eimer, Griselda A.,Casuscelli, Sandra G.
-
-
- H- and Fe-modified zeolite beta catalysts for preparation of trans-carveol from α-pinene oxide
-
The isomerisation of a-pinene oxide has been intensively investigated for selective preparation of campholenic aldehyde, a compound used in the synthesis of fragrances. Selective preparation of another product of α-pinene oxide rearrangement, trans-carveol, still remains a challenging task. Trans-carveol is a highly valuable compound used in perfume bases, food flavour compositions and as an active pharmaceutical substance in chemoprevention of mammary carcinogenesis. In the present work zeolite beta with different SiO2/Al2O3 molar ratios was modified by iron, characterised and tested per se and in the modified form for trans-carveol preparation from a-pinene oxide. The isomerisation reaction was carried out in a polar basic solvent N, N-dimethylacetamide at 140 °C. The activities and selectivities of the catalysts were correlated with their acid properties and with the iron content.
- Stekrova,Kumar,Daz,M?ki-Arvela,Murzin
-
p. 237 - 245
(2015/03/14)
-
- A chiral two-dimensional coordination polymer based on CuII and (S)-4,4′-bis(4-carboxyphenyl)-2,2′-bis(diphenylphosphinoyl)-1, 1′-binaphthyl: Synthesis, structure, and magnetic and optical properties
-
The functionalized binaphthyl derivative (S)-4,4′-bis(4- carboxyphenyl)-2,2′-bis(diphenylphosphinoyl)-1,1′-binaphthyl (H 2L) was employed as linker in the synthesis of the chiral Cu II-based two-dimensional network {[Cu2(L) 2(dmf)2]·H2O·9 dmf}n (1). Single-crystal X-ray analysis showed a two-dimensional structure with a copper paddle wheel as secondary building unit. One dmf molecule is additionally axially coordinated to each Cu cation. A lamellar structure results consisting of alternating [Cu2(L)2(dmf)2]n and solvent (dmf, H2O) layers. According to DTA/TG measurements the coordinated dmf molecules are released at about 320 °C, followed by decomposition around 460 °C. Magnetic susceptibility measurements on 1 indicate strong antiferromagnetic coupling between the two metal centers in Cu2(L)2(dmf)2. Compound 1 exhibits ligand-based luminescence, assigned to the S1 → S0 transition of the aromatic units. Moreover, the emission spectrum of 1 is blueshifted in comparison to H2L, due to different dihedral angles within the respective structures. Activated 1 (heating to 300 °C under vacuum for 3 h) showed low activity in the catalytic cyanosilylation of benzaldehyde (up to 27.1% conversion) and the isomerization of α-pinene oxide to campholenic aldehyde (up to 15.5% conversion).
- Lestari, Witri Wahyu,L?nnecke, Peter,Streit, Huayna Cerqueira,Schleife, Frederik,Wickleder, Claudia,Hey-Hawkins, Evamarie
-
p. 392 - 398
(2014/08/05)
-
- Isomerization of α-pinene oxide using Fe-supported catalysts: Selective synthesis of campholenic aldehyde
-
α-Pinene oxide, an oxygenated derivative of α-pinene, can be converted into various valuable substances useful as flavour, fragrance and pharmaceutical compounds. Campholenic aldehyde is one of the most desired products of α-pinene oxide isomerization being a valuable intermediate for the production of sandalwood-like fragrances. Iron modified zeolites Beta-75 and ZSM-5, mesoporous material MCM-41, silica and alumina were prepared by two methods (impregnation and solid-state ion exchange) and tested for selective preparation of campholenic aldehyde by isomerization of α-pinene oxide. The characterization of tested catalyst was carried out using scanning electron microscope analysis, nitrogen adsorption measurements, pyridine adsorption-desorption with FTIR, X-ray absorption spectroscopy measurements, XPS-analysis, 29Si MAS NMR and 27Al MAS NMR and X-ray diffraction. The isomerization of α-pinene oxide was carried out in toluene as a solvent at 70 C. The main properties influencing the activity and the selectivity are the acidic and structural properties of the tested catalysts. The highest selectivity of 66% was achieved at complete conversion of α-pinene oxide with Fe-MCM-41.
- Stekrova, Martina,Kumar, Narendra,Aho, Atte,Sinev, Ilia,Grünert, Wolfgang,Dahl, Johnny,Roine, Jorma,Arzumanov, Sergey S.,M?ki-Arvela, P?ivi,Murzin, Dmitry Yu.
-
p. 162 - 176
(2014/01/06)
-
- Isomerization of bicyclic terpene epoxides into allylic alcohols without changing of the initial structure
-
A novel method of (1S,2R,3R,5R)-6,6-dimethyl-4-methylenebicyclo[3.1.1] heptane-2,3-diol synthesis, which is a valuable intermediate in the synthesis of a perspective potent anti-Parkinson drugs, in the presence of TiO2 was proposed. Catalytic activity of TiO2 in the bicyclic terpene epoxides isomerization to corresponding allylic alcohols without changing of the initial structure was demonstrated, contrary to titania-supported Au catalysts which promoted rearrangement with predominant formation of a cyclopentene α-hydroxy ketone.
- Demidova, Yu.S.,Ardashov,Simakova,Simakova,Volcho,Salakhutdinov,Murzin, D.Yu.
-
p. 162 - 166
(2014/06/09)
-
- Niobium-containing hydroxyapatites as amphoteric catalysts: Synthesis, properties, and activity
-
We present here a new class of Nb-containing catalysts offering both acid and base functionalities thanks to the hydroxyapatite (HAP) structure, which acts as a host matrix for guest niobium species. Incorporation of Nb has led to samples with strengthened amphoteric properties with a prevalence of acid or basic sites depending on the synthesis procedure. Nb-containing HAP samples (12-14 wt % of Nb) have been synthesized by coprecipitation in water and in alcoholic solutions and by impregnation starting from different precursors. The intrinsic and effective acid and base properties have been measured, and a series of mass and surface characterizations have been performed to determine the Nb content, its oxidation state as well as its morphologic, structural, and electronic properties. The performances of the samples have been studied in several reactions of liquid-solid heterogeneous catalysis in batch or fixed tubular reactors working in the recirculation mode on the basis of the known catalytic features of Nb, including hydrolysis, acid-catalyzed isomerization, and selective oxidation reactions.
- Carniti, Paolo,Gervasini, Antonella,Tiozzo, Cristina,Guidotti, Matteo
-
p. 469 - 479
(2014/03/21)
-
- Application of an indenyl molybdenum dicarbonyl complex in the isomerisation of α-pinene oxide to campholenic aldehyde
-
The complex [{(η5-Ind)Mo(CO)2(μ-Cl)} 2] (1) has been tested for the industrially relevant catalytic isomerisation of α-pinene oxide (PinOx) to campholenic aldehyde (CPA) in the liquid phase. PinOx conversion and CPA selectivity are strongly influenced by the solvent employed. Complete conversion of PinOx was achieved within 1 min at 55 °C or 30 min at 35 °C using 1,2-dichloroethane as solvent, giving CPA in 68% yield. Other products included trans-carveol, iso-pinocamphone and trans-pinocarveol. The stability of 1 under the reaction conditions used was investigated by using FT-IR spectroscopy and electrospray ionisation mass spectrometry (ESI-MS) to characterise recovered solids. In the presence of air/moisture 1 undergoes oxidative decarbonylation upon dissolution to give oxomolybdenum species that are proposed to include a tetranuclear oxomolybdenum(v) complex. Conversely, ESI-MS studies of 1 dissolved in dry acetonitrile show mononuclear species of the type [IndMo(CO)2(CH 3CN)n]+. The crystal structure of the ring-slipped dicarbonyl complex [(η3-Ind)Mo(CO) 2Cl(CH3CN)2] (2) (obtained after dissolution of 1 in acetonitrile) is reported. the Partner Organisations 2014.
- Bruno, Sofia M.,Gomes, Ana C.,Gamelas, Carla A.,Abrantes, Marta,Oliveira, M. Concei??o,Valente, Anabela A.,Almeida Paz, Filipe A.,Pillinger, Martyn,Rom?o, Carlos C.,Gon?alves, Isabel S.
-
p. 3172 - 3180
(2014/07/07)
-
- Photocatalytic degradation of water taste and odour compounds in the presence of polyoxometalates and TiO2: Intermediates and degradation pathways
-
Geosmin (GSM) and 2-methylisoborneol (MIB) are produced by several species of cyanobacteria and actinomycetes. These compounds can taint water and fish causing undesirable taste and odours. Studies have shown that GSM/MIB are resistant in standard water treatments. Polyoxometalates (POM) are efficient photocatalysts in the degradation and mineralization of a great variety of organic pollutants, presenting similar behaviour with the widely published titanium dioxide (TiO2). Photocatalytic degradation of GSM and MIB under UV-A light in the presence of a characteristic POM photocatalyst, SiW 12O404-, in aqueous solution has been studied and compared with the photodegradation by TiO2 suspensions. GSM and MIB are effectively degraded in the presence of both photocatalysts. Addition of OH radical scavengers (KBr and tertiary butyl alcohol, TBA) retards the photodegradation rates of both compounds, suggesting that photodegradation mechanism takes place via OH radicals. Intermediates identified using GC-MS in the case of GSM and MIB, are mainly identical in the presence of both photocatalysts, also suggesting a common reaction mechanism. Possible photocatalytic degradation pathway for both GSM and MIB is proposed.
- Fotiou, Theodora,Triantis, Theodoros M.,Kaloudis, Triantafyllos,Papaconstantinou, Elias,Hiskia, Anastasia
-
-
- Catalytic olefin epoxidation with a carboxylic acid-functionalized cyclopentadienyl molybdenum tricarbonyl complex Dedicated to Prof. Maria José Calhorda on the occasion of her 65th birthday and in recognition of her outstanding contributions to the field of computational organometallic chemistry.
-
The complex CpMo(CO)3CH2COOH (1) (Cp = η5-C5H5) has been examined as a precatalyst for the epoxidation of cis-cyclooctene and α-pinene using tert-butylhydroperoxide (TBHP) as oxidant. A high turnover frequency of ca. 600 mol molMo-1 h-1 was achieved in the epoxidation of cyclooctene, giving the epoxide as the only reaction product. With α-pinene as substrate, the added-value products α-pinene oxide and campholenic aldehyde were obtained. Two different approaches to facilitate catalyst recovery and reuse were explored: (1) use of an ionic liquid (IL) as solvent, and (2) intercalation of 1 in a Zn,Al layered double hydroxide (LDH) by a direct synthesis (coprecipitation) route. Characterization of the LDH by powder X-ray diffraction, thermogravimetric analysis, FT-IR and 13C CP MAS NMR spectroscopies showed that the CpMo(CO)3CH 2COO- anions intercalate in a bilayer arrangement, resulting in an interlayer spacing of 20.7 A?. In the epoxidation of cyclooctene, catalytic activity in the first batch run was very high for the catalyst/IL mixture and moderate for the LDH. Characterization of the LDH after catalysis indicated that nearly complete oxidative decarbonylation of supported complexes had occurred (by reaction with TBHP), resulting in the presence of immobilized oxomolybdenum species. However, catalytic activities for both the recovered LDH and catalyst/IL decreased in consecutive runs, due in part to progressive removal of active species during either the catalytic reaction (for the LDH) or the solvent extraction/work-up (for the catalyst/IL mixture).
- Gomes, Ana C.,Bruno, Sofia M.,Abrantes, Marta,Magalh?es, Clara I.R.,Gon?alves, Isabel S.,Valente, Anabela A.,Pillinger, Martyn
-
p. 205 - 211
(2014/05/06)
-
- Isomerization of α-pinene oxide in the presence of methyltrioxorhenium(VII)
-
The catalytic performance of methyltrioxorhenium(VII) (MTO) has been investigated for the first time in the isomerization of α-pinene oxide (PinOx) into campholenic aldehyde (CPA). The high isomerization activity of MTO is coupled with high selectivity to CPA: CPA yield of up to 87% (100% conversion) was obtained by using α,α,α-trifluorotoluene as solvent at 15 C. Catalyst recycling is possible in a relatively simple fashion by using MTO coupled to an appropriate ionic liquid. The catalytic application of MTO in the isomerization of PinOx versus the integrated epoxidation- isomerization process of the conversion of α-pinene into CPA is discussed.
- Bruno, Sofia M.,Pillinger, Martyn,Kühn, Fritz E.,Gon?alves, Isabel S.,Valente, Anabela A.
-
-
- 3-methyl-6-(prop-1-en-2-yl)cyclohex-3-ene-1,2-diol: The importance of functional groups for antiparkinsonian activity
-
Compounds with different sets of three of the four functional groups of (1R,2R,6S)-3-methyl-6-(prop-1-en-2-yl)cyclohex-3-ene-1,2-diol 1 possessing high antiparkinsonian activity were synthesized. The synthesized compounds were tested for the antiparkinsonian activity in vivo on a mouse model with MPTP neurotoxin. A pronounced antiparkinsonian effect of 1 can only be achieved if it contains all the four functional groups (two hydroxy groups and two double bonds). The 2-hydroxy group or the 3,4-double bond is not required for stimulating the exploratory activity of the animals.
- Ardashov, Oleg V.,Pavlova, Alla V.,Korchagina, Dina V.,Volcho, Konstantin P.,Tolstikova, Tat'yana G.,Salakhutdinov, Nariman F.
-
p. 731 - 739
(2013/09/23)
-
- Hot water-promoted SN1 solvolysis reactions of allylic and benzylic alcohols
-
During the studies of hydrolysis of epoxides in water, we found that the hydrolysis of (-)-α-pinene oxide at 20 °C gave enantiomerically pure trans-(-)-sobrerol, whereas the same reaction in water heated at reflux unexpectedly gave a racemic mixture of trans- and cis-sobrerol (trans/cis=6:4). We have examined this remarkable difference in detail and found that hot water, whose behavior is quite different compared with room- or high-temperature water, could promote SN1 solvolysis reactions of allylic alcohols and thus caused the racemization of trans-(-)-sobrerol. The effect of reaction temperature, the addition of organic co-solvent, and the concentration of the solute on the rate of the racemization of trans-(-)-sobrerol were further examined to understand the role that hot water played in the reaction. It was proposed that the catalytic effects of hot water are owing to its mild acidic characteristic, thermal activation, high ionizing power, and better solubility of organic reactant. Further investigation showed that the racemization of other chiral allylic/benzylic alcohols could efficiently proceed in hot water.
- Xu, Zhao-Bing,Qu, Jin
-
p. 314 - 323
(2013/03/13)
-
- Vanadium-containing nickel phosphate molecular sieves as catalysts for α-pinene oxidation with molecular oxygen: A study of the effect of vanadium content on activity and selectivity
-
Vanadium-containing nickel phosphate molecular sieves (V-VSB-5) were applied as heterogeneous catalysts for the liquid phase oxidation of α-pinene with molecular oxygen at 60 °C. It has been found that the vanadium content in V-VSB-5 materials affects the
- Timofeeva, M. N.,Panchenko, V. N.,Prosvirin, I. P.,Hasan, Zubair,Jhung, Sung Hwa
-
p. 328 - 334,7
(2020/07/30)
-
- Nanosized sulfated zinc ferrite as catalyst for the synthesis of nopol and other fine chemicals
-
A nanosized highly ordered mesoporous zinc ferrite (ZnFe2O 4; ZF) was synthesized via co-precipitation method, further sulfated with ammonium sulfate solution to obtain sulfated ZF (SZF) and have been used for the synthesis of nopol by Prins condensation of β-pinene and paraformaldehyde. The NH3-TPD and pyridine sorption DRIFT-IR studies revealed the significant enhancement in Lewis acidic sites of the zinc ferrite on sulfatation. The influence of various reaction parameters such as reaction temperature, effect of substrate stoichiometry and catalyst loading has been investigated. It gave 70% conversion of β-pinene with 88% selectivity to nopol. The spent catalyst was regenerated and reused successfully up to four cycles with slight loss in catalytic activity. The nanosized SZF catalyst was found to be highly active towards several other commercially important acid catalyzed reactions such as isomerization, acetalization and aldol condensation.
- Jadhav, Sumit V.,Jinka, Krishna Mohan,Bajaj, Hari C.
-
-
- Acid/vanadium-containing saponite for the conversion of propene into coke: Potential flame-retardant filler for nanocomposite materials
-
Vanadium-containing saponite samples were synthesized in a one-pot synthetic procedure with the aim of preparing samples for potential application as fillers for polymeric composites. These vanadium-modified materials were prepared from an acid support by adopting a synthetic strategy that allowed us to introduce isolated structural V species (H/V-SAP). The physicochemical properties of these materials were investigated by XRD analysis and by DR-UV/Vis and FTIR spectroscopy of CO that was adsorbed at 100 K; these data were compared to those of a V-modified saponite material that did not contain any Bronsted acid sites (Na/V-SAP). The surface-acid properties of both samples (together with the fully acidic H-SAP material and the Na-SAP solid) were studied in the catalytic isomerization of α-pinene oxide. The V-containing solids were tested in the oxidative dehydrogenation reaction of propene to evaluate their potential use as flame-retardant fillers for polymer composites. The effect of tuning the presence of Lewis/Bronsted acid sites was carefully studied. The V-containing saponite sample that contained a marked presence of Bronsted acid sites showed the most interesting performance in the oxidative dehydrogenation (ODH) reactions because they produced coke, even at 773 K. The catalytic data presented herein indicate that the H/V-SAP material is potentially active as a flame-retardant filler. In questo lavoro e stato sintetizzata tramite metodologia one-pot una saponite contenente in struttura vanadio, di interesse come additivo per compositi polimerici. La metodologia di sintesi adottata ha permesso di ottenere un solido acido contenente siti di vanadio strutturale isolati (H/V-SAP). Le proprieta chimico-fisiche di tale materiale sono state studiate tramite XRD, DR-UV-Vis e FT-IR di CO adsorbito a 100 K e confrontate con quelle di una V-saponite priva di acidita di Bronsted (Na/V-SAP). Le proprieta acide di entrambi i materiali (e di saponiti acidi H-SAP e sodica Na-SAP) sono state investigate sottoponendo i campioni ad un test catalitico di isomerizzazione dell' ossido di α-pinene. I campioni contenenti vanadio sono stati infine testati come catalizzatori per la reazione di deidrogenazione ossidativa del propene, con l'obiettivo di valutarne i loro potenziale uso come additivi ritardanti di fiamma per compositi polimerici. La saponite contenente vanadio strutturale e caratterizzata da una marcata acidita di Bronsted ha mostrato le migliori prestazioni catalitiche, producendo prodotti carboniosi anche ad alte temperature di esercizio (773 K). I dati catalitici qui mostrati indicano che il campione H/V-SAP e potenzialmente attivo come ritardante di fiamma per compositi polimerici. A hard day's saponite: An acid/vanadium-containing saponite (H/V-SAP) was synthesized and its physicochemical properties were compared to those of a V-modified saponite material that did not contain acid sites. Both samples were tested in the oxidative dehydrogenation (ODH) reaction of propene to study the capability of the samples to form coke species. H/V-SAP was the most interesting catalyst for the production of coke. Copyright
- Ostinelli, Luca,Recchia, Sandro,Bisio, Chiara,Carniato, Fabio,Marchese, Leonardo,Guidotti, Matteo,Psaro, Rinaldo
-
p. 2394 - 2402,9
(2020/08/24)
-
- Influence of the Br?nsted and Lewis acid sites on the catalytic activity and selectivity of Fe/MCM-41 system
-
The system Fe2O3/MCM-41, with high iron dispersion, was synthesized in order to introduce Lewis acid sites into the MCM-41 structure. Two calcination atmospheres (inert and oxidant) were used to produce iron nanoclusters with different structural properties. Besides, a silylation treatment was realized on both solids with the aim of neutralizing the Br?nsted acidity associated with the MCM-41 silanol groups. The samples were characterized by atomic absorption spectroscopy, X-ray diffraction at low angles, N2 adsorption, temperature-programmed reduction, Fourier transform infrared spectroscopy, nuclear magnetic resonance of 29Si, and M?ssbauer spectroscopy. The influence of the structural changes of the nanoclusters and the effect of the simultaneous presence of Lewis and Br?nsted acid sites were evaluated studying the product distribution from the α-pinene oxide isomerization reaction. It was determined that the Br?nsted acidity of the Fe/MCM-41 system has not the sufficient acid strength to modify the product distribution which is mainly governed by the Lewis sites.
- Fellenz,Bengoa,Marchetti,Gervasini
-
scheme or table
p. 187 - 196
(2012/10/08)
-
- Ti-POSS covalently immobilized onto mesoporous silica: A model for active sites in heterogeneous catalytic epoxidation
-
A functionalized Ti-containing polyhedral oligomeric silsesquioxane was anchored on the surface of an ordered SBA-15 and a non-ordered amorphous mesoporous silica. The physico-chemical characterization of the textural, thermal and electronic properties of the final anchored materials led to the evaluation of the distribution of Ti-POSS moieties on the silica surface, of the oxidation state and of the coordination geometry of the titanium centres. It was discovered that Ti-POSS are accommodated mainly as dinuclear dimeric species on the external surface of ordered mesoporous silica or in the large mesopores of non-ordered silica supports. Epoxidation tests on unsaturated terpenes (limonene, carveol and α-pinene) with TBHP as oxidant were performed to monitor the activity and accessibility of Ti(IV) sites in the anchored samples and compared with conventional titanocene-grafted Ti/SBA-15 and Ti/SiO 2 systems. The different chemoselectivity recorded over anchored catalysts, with respect to the grafted ones, can be a potential diagnostic tool to shed light on the mechanism or the molecular intermediates occurring at the surface during the oxidation reaction.
- Carniato, Fabio,Bisio, Chiara,Sordelli, Laura,Gavrilova, Elena,Guidotti, Matteo
-
experimental part
p. 244 - 251
(2012/04/10)
-
- H2O2 based α-pinene oxidation over Ti-MCM-41. A kinetic study
-
α-Pinene oxidation with hydrogen peroxide using Ti-MCM-41, prepared by hydrothermal synthesis, with a Ti content of 1.12 wt.% was studied. The major products of reaction observed were: verbenone, verbenol and campholenic aldehyde which are used in the pha
- Cánepa, Analía L.,Herrero, Eduardo R.,Crivello, Mónica E.,Eimer, Griselda A.,Casuscelli, Sandra G.
-
experimental part
p. 1 - 7
(2011/10/09)
-
- Isomerization of α-pinene oxide over cerium and tin catalysts: Selective synthesis of trans-carveol and trans-sobrerol
-
A remarkable effect of the solvent nature on the acid catalyzed transformation of α-pinene oxide allowed direction of the reaction to either trans-carveol or trans-sobrerol. Each of these highly valuable compounds was obtained in nearly 70% yield using an appropriate polar solvent, whose basicity affected strongly the product distribution. In acetone, a weakly basic solvent, the reaction over heterogeneous sol-gel Sn/SiO2 or Ce/SiO2 catalysts gave mainly trans-sobrerol. No leaching of active components occurs under the reaction conditions and the catalysts can be recovered and reused. On the other hand, in more basic solvent, i.e., dimethylacetamide, the reaction was essentially directed to trans-carveol. Due to the leaching problems with Sn/SiO2 and Ce/SiO2 materials, the synthesis of trans-carveol was performed under homogeneous conditions using CeCl3 or SnCl2 as catalysts with a catalyst turnover number up to ca. 1200. The method represents one of the few examples of the synthesis of isomers from α-pinene oxide, other than campholenic aldehyde, with a sufficient for practical usage selectivity.
- Costa, Vinícius V.,Da Silva Rocha, Kelly A.,De Sousa, Líniker F.,Robles-Dutenhefner, Patricia A.,Gusevskaya, Elena V.
-
experimental part
p. 69 - 74
(2011/10/05)
-
- Copper(II) tetrafluroborate-promoted Meinwald rearrangement reactions of epoxides
-
Epoxides undergo a highly efficient Meinwald rearrangement in the presence of catalytic quantities of copper(II) tetrafluoroborate to give carbonyl compounds in high yields and with excellent selectivity. The low toxicity and ease of handling of this reagent make it an attractive alternative to the more corrosive or costly Lewis acids frequently employed.
- Robinson, Mathew W.C.,Pillinger, Kathryn S.,Mabbett, Ian,Timms, David A.,Graham, Andrew E.
-
scheme or table
p. 8377 - 8382
(2010/11/19)
-
- Studies towards the taming of the 'carbocation' in the regioselective ring opening of epoxides to allylic alcohols
-
Regioselective isomerisation of epoxides to allylic alcohols can be achieved using p-toluenesulfonic acid in the presence of 1,3- dimethylimidazolidin-2-one. Georg Thieme Verlag Stuttgart.
- Chapman, Helen A.,Herbal, Karim,Motherwell, William B.
-
experimental part
p. 595 - 598
(2010/09/15)
-
- The thermolysis of α-pinene and verbenone epoxides in supercritical solvents
-
Thermal transformations of α-pinene and verbenone epoxides were studied in supercritical solvents with complex compositions, including CO 2, lower alcohols (ethanol and isopropanol), and water, over the temperature and pressure ranges 387-575 K and 135-215 atm. The main product from α-pinene epoxide in a supercritical solvent containing water was campholenic aldehyde and pinocamphone; the total content of these products in the reaction mixture was 80%. Suggestions concerning the mechanism of the thermal isomerization of α-pinene epoxide depending on the acidity of supercritical solvents were made. The direction of verbenone epoxide transformations was independent of the presence of water in the mixture. The main identified products were ketoalcohols with para-menthane and camphane frameworks.
- Anikeev,Il'Ina,Volcho,Ermakova,Salakhutdinov
-
scheme or table
p. 1112 - 1117
(2011/01/05)
-
- Simple preparation and application of TEMPO-coated Fe3O 4 superparamagnetic nanoparticles for selective oxidation of alcohols
-
The organic oxidant TEMPO (2,2,4,4-tetramethylpiperdine-1-oxyl) was immobilized on iron oxide (Fe3O4) superparamagnetic nanoparticles by employing strong metal-oxide chelating phosphonates and azide/alkyne "click" chemistry. This simple preparation yields recyclable TEMPO-coated nanoparticles with good TEMPO loadings. They have excellent magnetic response and efficiently catalyze the oxidation of a wide range of primary and secondary alcohols to aldehydes, ketones, and lactones under either aerobic acidic MnII/CuII oxidizing Minisci conditions, or basic NaOCl Anelli conditions. The nanoparticles could be recycled more than 20 times under the Minisci conditions and up to eight times under the Anelli conditions with good to excellent substrate conversions and product selectivities. Immobilization of the catalyst through a phosphonate linkage allows the particles to withstand acidic oxidizing environments with minimal catalyst leaching. Clicking TEMPO to the phosphonate prior to phosphonate immobilization, rather than after, ensures the clicked catalyst is the only species on the particle surface. This facilitates quantification of the catalyst loading. The stability of the phosphonate linker and simplicity of this catalyst immobilization method make this an attractive approach for tethering catalysts to oxide supports, creating magnetically separable catalysts that can be used under neutral or acidic conditions. Recycling to a different TEMPO: An extremely simple and economic synthesis of a recyclable 2,2,4,4-tetramethylpiperdine-1-oxyl(TEMPO)-coated superparamagnetic catalyst is described. The catalyst shows excellent performance in the rapid oxidation of primary and secondary benzylic and aliphatic alcohols by using oxygen and MnII/CuII or biphasic NaOCl/KBr conditions.
- Tucker-Schwartz, Alexander K.,Garrell, Robin L.
-
experimental part
p. 12718 - 12726
(2011/02/21)
-
- Epoxide ring-opening and Meinwald rearrangement reactions of epoxides catalyzed by mesoporous aluminosilicates
-
Mesoporous aluminosilicates efficiently catalyze the ring-opening of epoxides to produce β-alkoxyalcohols in high yields under extremely mild reaction conditions. These materials also catalyze the corresponding Meinwald rearrangement in non-nucleophilic solvents to give aldehydes which can be trapped in situ to provide the corresponding acetals in an efficient tandem process. The Royal Society of Chemistry 2009.
- Robinson, Mathew W. C.,Davies, A. Matthew,Buckle, Richard,Mabbett, Ian,Taylor, Stuart H.,Graham, Andrew E.
-
experimental part
p. 2559 - 2564
(2009/10/30)
-
- Phosphotungstic acid as a versatile catalyst for the synthesis of fragrance compounds by α-pinene oxide isomerization: Solvent-induced chemoselectivity
-
The remarkable effect of the solvent on the catalytic performance of H 3PW12O40, the strongest heteropoly acid in the Keggin series, allows direction of the transformations of α-pinene oxide (1) to either campholenic aldehyde (2), trans-carveol (3), trans-sobrerol (4a), or pinol (5). Each of these expensive fragrance compounds was obtained in good to excellent yields by using an appropriate solvent. Solvent polarity and basicity strongly affect the reaction pathways: nonpolar nonbasic solvents favor the formation of aldehyde 2; polar basic solvents favor the formation of alcohol 3; whereas in polar weakly basic solvents, the major products are compounds 4a and 5. On the other hand, in 1,4-dioxane, which is a nonpolar basic solvent, both aldehyde 2 and alcohol 3 are formed in comparable amounts. The use of very low catalyst loading (0.005-1 mol%) and the possibility of catalyst recovery and recycling without neutralization are significant advantages of this simple, environmentally benign, and low-cost method. This method represents the first example of the synthesis of isomers from α-pinene oxide, other than campholenic aldehyde, with a selectivity that is sufficient for practical usage.
- Da Silva Rocha, Kelly A.,Hoehne, Juliana L.,Gusevskaya, Elena V.
-
body text
p. 6166 - 6172
(2009/06/17)
-
- Aerobic oxidations of α-pinene over cobalt-substituted polyoxometalate supported on amino-modified mesoporous silicates
-
Co-containing polyoxometalate [Bu4N]4H[PW11Co(H2O)O39] (Co-POM) was supported on various NH2-modified mesoporous silicate matrixes (SBA-15, MCF, and SiO2-xerogel). The catalysts
- Maksimchuk,Melgunov,Chesalov,Mrowiec-Bialon,Jarzebski,Kholdeeva
-
p. 241 - 248
(2008/02/13)
-
- Opening of epoxide rings catalyzed by niobium pentachloride
-
The behavior of several epoxides when treated with NbCl5 was studied. In general, the studied epoxides reacted rapidly with NbCl5, giving, in most cases, more than one product (chlorohydrins, products containing solvent residues, as well as rearrangement products). A detailed study was performed to verify the effects of the temperature (rt, 0°C, or -78°C) and of the NbCl5 molar concentration on the composition of the products, yield, and time required for the reactions. Copyright Taylor & Francis Group, LLC.
- Constantino, Mauricio Gomes,Lacerda Jr., Valdemar,Invernize, Paulo Roberto,Filho, Luiz Carlos Da Silva,Da Silva, Gil Valdo Jose
-
p. 3529 - 3539
(2008/03/13)
-
- Highly efficient Meinwald rearrangement reactions of epoxides catalyzed by copper tetrafluoroborate
-
Epoxides undergo a highly efficient and selective rearrangement in the presence of catalytic quantities of copper tetrafluoroborate to give carbonyl compounds in excellent yields. The low toxicity and ease of handling of this reagent make it an attractive alternative to the more corrosive Lewis acids frequently employed.
- Robinson, Mathew W.C.,Pillinger, Kathryn S.,Graham, Andrew E.
-
p. 5919 - 5921
(2007/10/03)
-
