- Selective Catalytic Isomerization of β-Pinene Oxide to Perillyl Alcohol Enhanced by Protic Tetraimidazolium Nitrate
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A series of tetraimidazolium salts with different anions was prepared and applied in the isomerization of β-pinene oxide. After examining the activity of different catalysts, a remarkable enhancement of the selectivity of perillyl alcohol (47 %) was obtained over [PEimi][HNO3]4 under mild reaction conditions and using DMSO as the solvent. Furthermore, noncovalent interactions between solvent molecules and the catalyst were found by FT-IR spectroscopy and confirmed by computational chemistry. The homogeneous catalyst showed excellent stability and was reused up to six times without significant loss.
- Li, Hui,Liu, Jian,Zhao, Juan,He, Huiting,Jiang, Dabo,Kirk, Steven Robert,Xu, Qiong,Liu, Xianxiang,Yin, Dulin
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- New sustainable synthetic routes to cyclic oxyterpenes using the ecocatalyst toolbox
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Cyclic oxyterpenes are natural products that are mostly used as fragrances, flavours and drugs by the cosmetic, food and pharmaceutical industries. However, only a few cyclic oxyterpenes are accessible via chemical syntheses, which are far from being ecofriendly. We report here the synthesis of six cyclic oxyterpenes derived from ?-pinene while respecting the principles of green and sustainable chemistry. Only natural or biosourced catalysts were used in mild conditions that were optimised for each synthesis. A new generation of ecocatalysts, derived from Mn-rich water lettuce, was prepared via green processes, characterised by MP-AES, XRPD and TEM analyses, and tested in catalysis. The epoxidation of ?-pinene led to the platform molecule, ?-pinene oxide, with a good yield, illustrating the efficacy of the new generation of ecocatalysts. The opening ?-pinene oxide was investigated in green conditions and led to new and regioselective syntheses of myrtenol, 7-hydroxy-α-terpineol and perillyl alcohol. Successive oxidations of perillyl alcohol could be performed using no hazardous oxidant and were controlled using the new generation of ecocatalysts generating perillaldehyde and cuminaldehyde.
- Bihanic, Camille,Grison, Claude,Lasbleiz, Arthur,Le Blainvaux, Pierre,Petit, Eddy,Regnier, Morgan
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- Preparation of α-terpineol and perillyl alcohol using zeolites beta
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The preparation of α-terpineol by direct hydration of limonene catalyzed by zeolites beta was studied. The same catalyst was used to prepare perillyl alcohol by isomerization of β-pinene oxide in the presence of water. The aim was to optimize the reaction conditions to achieve high conversions of starting material and high selectivity to the desired products. In the case of limonene, it was found that the highest selectivity to α-terpineol was 88% with conversion of 36% under the conditions: 50?wt% of catalyst beta 25, 10% aqueous acetic acid (10?mL) (volume ratio limonene:H2O = 1:4.5), temperature 50?°C, after 24?h. In the case of β-pinene oxide, it was found that the highest selectivity to perillyl alcohol, which was 36% at total conversion, was obtained in the reaction under the following conditions: dimethyl?sulfoxide as solvent (volume ratio β-pinene oxide:DMSO = 1:5), catalyst beta 25 without calcination (15?wt%), demineralized water (molar ratio β-pinene oxide:H2O = 1:8), temperature 70?°C, 3?h. The present study shows that the studied reactions are suitable for the selective preparation of chosen compounds.
- ?erveny, Libor,Vysko?ilová, Eli?ka,Zítová, Kate?ina
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p. 4297 - 4310
(2021/07/26)
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- Design, synthesis and application of pinenyl chiral olefin and carbene ligand
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The invention discloses design, synthesis and application of pinenyl chiral olefin and carbene ligands. According to the carbene ligand, pinene or 9-anthraceneformaldehyde is taken as a chiral source,a corresponding bromide is obtained through a two-step reaction, then benzimidazole is taken as an initial raw material, reacts with one molecule of bromide and then reacts with the other molecule ofbromide to form a salt, and corresponding pinenyl chiral olefin and carbene ligands are obtained; the carbene ligand is used as a chiral catalyst to perform asymmetric 1, 4-addition reaction, and hasfavorable selectivity.
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Paragraph 0045; 0050-0052
(2020/11/10)
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- Homogeneous Lewis and Br?nsted acids as catalysts for β-pinene oxide rearrangement to prepare myrtenol and myrtanal
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Myrtenol and myrtanal find their utilization as fine chemicals or intermediates for the synthesis of food additive myrtanol. β-Pinene oxide rearrangement was studied using homogeneous Lewis and Br?nsted acids as catalysts for the production of these compounds. The composition of reaction products depended on the type of active sites. Lewis active sites favoured the formation of myrtanal while in presence of Br?nsted active sites undesirable perillyl aldehyde and perillyl alcohol were formed to a high extent. Optimal reaction conditions for myrtenol and myrtanal preparation were found. With 5 mol.% of anhydrous SnCl2 as Lewis acid catalysts and 1,4-dioxane as the solvent β-pinene oxide achieved total conversion with 95% selectivity to desired products.
- Cerveny, Libor,Fidlerova, Barbora,Paterova, Iva,Vavra, Michal,Vyskocilova, Eliska
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- Selective Allylic Oxidation of Terpenic Olefins Using Co-Ag Supported on SiO2 as a Novel, Efficient, and Recyclable Catalyst
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Co-Ag supported on the SiO2 catalyst was synthesized by the sol-gel method and characterized using XRD, FT-IR, TG-DTG, BET, CV, and SEM/EDX analysis. The catalytic performance of the resulting catalyst was examined by the oxidation of mono and sesquiterpenic olefins using hydrogen peroxide and tert-butyl peroxide as oxidant agents. Various parameters such as catalyst amount, temperature, and solvents have been studied. The Co-Ag supported on the SiO2 catalyst showed a high activity, selectivity, and recyclability for the selected oxidation reaction.
- Aberkouks, Abderrazak,Mekkaoui, Ayoub Abdelkader,Ait Ali, Mustapha,El Firdoussi, Larbi,El Houssame, Soufiane
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- 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
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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.
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p. 223 - 237
(2016/12/09)
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- Solvent and additive-free selective aerobic allylic hydroxylation of β-pinene catalyzed by metalloporphyrins
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Metallodeuteroporphyrins (MDPs) were employed as the catalysts for aerobic oxidation of β-pinene in absence of solvents and additives. Allylic hydroxylation products were found to be the main products from this protocol. The catalytic activity of MDPs with different metal nuclei and the influences of technological conditions on this reaction were investigated. This catalytic system has bright application prospect since only eco-friendly and readily available dioxygen were needed.
- Xu, Shi-Chao,Zhu, Shou-Ji,Bi, Liang-Wu,Chen, Yu-Xiang,Wang, Jing,Lu, Yan-Ju,Gu, Yan,Zhao, Zhen-Dong
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p. 575 - 578
(2017/06/19)
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- Beta-pinene selective hydroxylation oxidation method and product thereof
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The invention discloses a beta-pinene selective hydroxylation oxidation method and a product thereof. The beta-pinene selective hydroxylation oxidation method uses ordinary-pressure oxygen or oxygen-enriched air as an oxidant, uses metal porphyrin or their solid carriers as a catalyst and is performed in the absence of an additional solvent or a co-oxidation reducer, and the beta-pinene hydroxylation oxidation product is obtained by means of the method in a high-selectivity mode. Main oxidation products include pinocarveol, 2,10-epoxy pinane and myrtenol, wherein the overall selectivity of the hydroxylation oxidation products 1 and 3 is above 90%. The usage amount of the catalyst used in method is small, a reaction process is simple, the temperature is low, the initiation rate is high, the selectivity is good, homogeneous catalysis can be achieved, and heterogeneous catalysis can also be performed after immobilization.
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Paragraph 0032; 033; 0334;
(2016/10/10)
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- Biologically Inspired and Magnetically Recoverable Copper Porphyrinic Catalysts: A Greener Approach for Oxidation of Hydrocarbons with Molecular Oxygen
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An efficient synthetic method for magnetically recoverable hybrid copper porphyrinic nanomaterials is reported. These functionalized magnetic materials prove to be efficient bioinspired oxidation catalysts of olefins and thiols, using molecular oxygen as oxidant, in total absence of reductants and solvents, with the highest TON (turnover number) yet achieved for this reaction (≈200 000). A comparative study between homogeneous and heterogeneous oxidation of cyclohexene is discussed, revealing the heterogeneous system to be the most promising concerning stability and reusability of the catalysts. The full characterization of the magnetic hybrid porphyrinic nanomaterials, by transmission electron microscopy, flame atomic absorption spectrometry, thermogravimetry, N2 sorption, and infrared spectroscopy, is also described.
- Henriques, César A.,Fernandes, Auguste,Rossi, Liane M.,Ribeiro, M. Filipa,Calvete, Mário J. F.,Pereira, Mariette M.
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p. 3359 - 3368
(2016/06/06)
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- Comparison of enzymatic and acid hydrolysis of bound flavor compounds in model system and grapes
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Four synthesized terpenyl-β-D-glycopyranosides (geranyl, neryl, citronellyl, myrtenyl) were subjected to enzymatic (AR 2000, pH 5.5) and acid (citric buffer, pH 2.5) hydrolysis. Decrease of glycosides was measured by HPLC and the volatiles released - by comprehensive gas chromatography-mass spectrometry (GC x GC-ToF-MS). Enzymatic hydrolysis performed for 21 h yielded 100% degree of hydrolysis for all glycosides but citronellyl (97%). Degree of acid hydrolysis was highly dependent on type of aglycone and the conditions. The highest degree was achieved for geraniol, followed by citronellol and nerol. Myrtenylo-β-D-glycopyranoside was the most resistant glycoside to hydrolysis. Acid hydrolysis degree was also related to temperature/time combination, the highest being for 100 °C and 2 h. In a result of enzymatic hydrolysis 85-91% of total peak areas was terpene aglycone, whereas for acid hydrolysis the area of released terpene aglycone did not exceed 1.3% of total peak area indicating almost complete decomposition/transformation of terpenyl aglycone.
- Dziadas, Mariusz,Jeleń, Henryk H.
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p. 412 - 418
(2015/06/17)
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- Continuous flow photooxygenation of monoterpenes
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Photooxygenation of monoterpenes was conducted in two continuous flow reactors. The first, suitable for lab-scale research, had a maximum yield of 99.9%, and the second, focused on industrial applications, showed a daily output that was 270.0-fold higher than that in batch systems. The use of sunlight instead of an LED lamp gave 68.28% conversion.
- Park, Chan Yi,Kim, Young Joon,Lim, Hyo Jin,Park, Jeong Hyeon,Kim, Mi Jin,Seo, Seung Woo,Park, Chan Pil
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p. 4233 - 4237
(2015/02/19)
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- Fast and selective iron-catalyzed transfer hydrogenations of aldehydes
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An efficient iron-based catalyst system consisting of Fe(BF)4$6H2O and P(CH2CH2PPh2)3 [tetraphos, (PP3)] is presented for the highly selective transfer hydrogenation of aromatic, aliphatic, and a,b-unsaturated aldehydes. A wide range of substrates including aldehydes with other reducible functional groups gave the corresponding alcohols in good yields. Formic acid is applied as a cheap, environmentally benign and easy to handle hydrogen source. Notable features of the presented methodology are the fast reactions under mild conditions. Advantageously compared to most transfer hydrogenations, no stoichiometric amounts of base additives are required.
- Wienh?fer, Gerrit,Westerhaus, Felix A.,Junge, Kathrin,Beller, Matthias
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p. 156 - 159
(2013/10/01)
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- β-pinene oxidation by hydrogen peroxide catalyzed by modified niobium-MCM
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Although solid niobium has a high surface area, its high Lewis and Br?nsted acidity is a drawback that always compromises its catalytic performance in oxidation reactions. In this work, treating the niobium catalyst with hydrogen peroxide circumvents this disadvantage and results in a significant increase in the selectivity of the oxidation of β-pinene. In addition, the efficiency of the niobium catalysts supported on MCM was investigated. Nb-MCM//H2O2 and Nb-MCM were the most active catalysts. Good selectivity of up to 85% at a 93-97% substrate conversion has been achieved. The catalyst can easily be recovered and reused several times without loss in activity.
- Coelho, Jakelyne V.,Oliveira, Luiz C.A.,Moura, Flavia C.C.,De Souza, Patterson P.,Silva, Cesar Augusto,Batista, Kenia Barros,Silva, Márcio José Da
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experimental part
p. 215 - 220
(2012/06/29)
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- Solvent-free chromium catalyzed aerobic oxidation of biomass-based alkenes as a route to valuable fragrance compounds
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Chromium containing mesoporous molecular sieves MCM-41 were shown to be an efficient heterogeneous catalyst for the liquid-phase aerobic oxidation of various monoterpenic alkenes under mild solvent-free conditions. The material was prepared through a direct hydrothermal method and characterized by ICP-AES, N2 adsorption-desorption, TEM, XRD, SAXS, and H2-TPR techniques. Characterizations suggest that chromium introduced in MCM-41 is essentially incorporated in the silica framework, with no extraframework chromium oxides being detected. Various oxygenated monoterpenoids important for the flavor and fragrance industry were obtained with high combined selectivities (75-92%) at 30-40% substrate conversions. The oxidation of β-pinene led almost exclusively to allylic mono-oxygenated derivatives, whereas limonene and α-pinene gave both epoxides and allylic oxidation products. The catalyst undergoes no metal leaching and can be easily recovered and re-used. A silica-included chromium catalyst prepared through a conventional sol-gel method showed activity comparable with that of Cr-MCM-41; however, selectivity was much lower.
- Robles-Dutenhefner, Patricia A.,Brand?o, Bruno B.N.S.,De Sousa, Líniker F.,Gusevskaya, Elena V.
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experimental part
p. 172 - 178
(2012/02/05)
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- Selective photosensitized oxidation and its catalytic regulation of monoterpene with molecular oxygen in different reaction media
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The photo-catalytic oxidation of α-pinene, β-pinene and limonene with molecular oxygen sensitized by tetrachlorotetraiodo-fluorescein sodium salt (RB) has been studied in different reaction media under green light irradiation. Simple and efficient photosensitized oxidation equipment was employed successfully to improve the efficiency of the photosensitized reaction. The results indicate that the photosensitized oxidation products can be directly obtained without after-treatment by reductive reagent. Furthermore, it was found that the product distributions are remarkably affected by reaction media, and that N,N-dimethylformamide (DMF) can regulate the selectivity to products. In particular, the good selectivity (85%) to the main product (myrtenal) and the excellent conversion (99%) were obtained in the absence of any other catalysts when DMF was used as reaction solvent in the photosensitized oxidation of β-pinene. Moreover, the possible photosensitized oxidation reaction mechanism in different media was suggested in the present work.
- You, Kuiyi,Yin, Dulin,Mao, Liqiu,Liu, Pingle,Luo, He'An
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experimental part
p. 321 - 325
(2011/10/13)
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- Design of a bio-inspired imidazole-based iron catalyst for epoxidation of olefins: Mechanistic insights
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A novel defined iron catalyst for the epoxidation of aromatic and aliphatic olefins with hydrogen peroxide as the terminal oxidant is described. Our catalyst approach is based on bio-inspired both alkyl- and aryl-substituted imidazoles in combination with cheap and abundant iron trichloride hexahydrate. Heterocycles similar to imidazole can be used as ligands in this epoxidation system, too. The novel system is stable towards air and water. It is shown that the mechanism depends strongly on the used ligands and substrates. In the presence of radical scavengers no carbon-centered radical could be detected.
- Schr?der, Kristin,Junge, Kathrin,Spannenberg, Anke,Beller, Matthias
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experimental part
p. 364 - 370
(2011/01/04)
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- Biomass to chemicals: Rearrangement of β-pinene epoxide into myrtanal with well-defined single-site substituted molecular sieves as reusable solid Lewis-acid catalysts
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The epoxide rearrangement of β-pinene oxide into myrtanal was studied in the presence of solid Lewisacid catalysts. Different metals such as Zr, Sn, Ti, Nb, Ta, Al, and Ga have been incorporated within network positions of zeolite Beta by isomorphous substitution. The materials have been characterized by powdered X-ray diffraction (XRD), IR spectroscopy and by in situ IR spectroscopy on adsorbed molecules (cyclohexanone and pyridine). Among the studied catalysts Zr-Beta gave the best selectivity (up to 94%) in acetonitrile as solvent at practically complete conversion. In this epoxide rearrangement the solvent has to be selected to balance the competitive adsorption of the product. Product desorption is enhanced with acetonitrile which results in a selectivity increase with only a small penalty on the rate of reaction. Zr-Beta has been reused in the batch mode and in a fixed-bed reactor for several times and analysis of the reused catalyst indicated that Zr-Beta is a robust catalyst for the epoxide rearrangement. Leaching of the metal or crystal degradation has not been detected.
- De La Torre, Olalla,Renz, Michael,Corma, Avelino
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experimental part
p. 165 - 171
(2011/10/02)
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- Iron-catalyzed epoxidation of aromatic olefins and 1,3-dienes
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The combination of iron(III) chloride, pyridine-2,6-dicarboxylic acid and formamidine ligands allows for the epoxidation of styrenes and conjugated dienes in excellent chemoselectivity and yields.
- Schroeder, Kristin,Enthaler, Stephan,Join, Benoit,Junge, Kathrin,Beller, Matthias
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scheme or table
p. 1771 - 1778
(2010/09/11)
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- Cobalt- and manganese-substituted ferrites as efficient single-site heterogeneous catalysts for aerobic oxidation of monoterpenic alkenes under solvent-free conditions
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Cobalt- and manganese-substituted ferrites were used as heterogeneous catalysts for liquid-phase aerobic oxidation of various monoterpenic alkenes. The materials were prepared by co-precipitation and characterized by Moessbauer spectroscopy, powder X-ray diffractometry, magnetization measurements, and elemental analysis. The results show that isomorphic substitution of iron in the ferrite crystalline structure occurred preferentially at octahedral positions and strongly affected its catalytic properties in the oxidation of monoterpenes. Various valuable oxygenated monoterpenic compounds were obtained with high combined selectivities (75-95%) at ca. 40% substrate conversions. Oxidations of β-pinene and 3-carene led almost exclusively to allylic mono-oxygenated derivatives, whereas limonene and α-pinene gave both epoxides and allylic products. The use of inexpensive catalyst and oxidant, solvent-free conditions, and high final product concentrations (ca. 40 wt%) are significant practical advantages of this environmentally friendly process. The catalysts undergo no metal leaching and can be easily recovered by the application of an external magnet and reused.
- Menini, Luciano,Pereira, Marcio C.,Parreira, Luciana A.,Fabris, Jose D.,Gusevskaya, Elena V.
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p. 355 - 364
(2008/09/18)
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- Palladium catalyzed oxidation of monoterpenes: NMR study of palladium(II)-monoterpene interactions
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Reactions of the monoterpenes β-pinene, limonene and myrcene with Pd(II) complexes in acetic acid solutions were studied by 1H NMR spectroscopy. Various π-allyl palladium complexes were detected in situ and their interaction with CuCl2 has been investigated. The results clarify the mechanism of allylic oxidation of these substrates mediated by Pd(II)/Cu(II)-based catalytic systems. Originally introduced to regenerate reduced palladium species, CuCl2 has been shown to play an important role in the formation and/or decomposition of key reaction intermediates - π-allyl palladium complexes. β-Pinene and myrcene readily react with Pd(OAc)2 giving corresponding π-allyls, with two complexes acyclic and cyclic being formed from myrcene. On the other hand, the formation of π-allyl complexes from limonene occurs at a significant rate only in the presence of CuCl2. NMR observations, including selective paramagnetic enhancement of spin-lattice relaxation, indicate that π-allyl palladium intermediates specifically interact with Cu(II) ions in the reaction solutions. Such interaction probably involves Cu(II) bonding to Pd(II) via bridging ligands, and seems to be responsible for the accelerative effect of CuCl 2 in the palladium catalyzed oxidation of the monoterpenes. Indeed, most of these reactions do not occur at all in the absence of CuCl2.
- Gon?alves, José Ailton,Da Silva, Márcio José,Piló-Veloso, Dorila,Howarth, Oliver W.,Gusevskaya, Elena V.
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p. 2996 - 3003
(2007/10/03)
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- Generation of singlet oxygen from ozone catalysed by phosphinoferrocenes
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A novel chemical source of singlet oxygen based on the conversion of ozone by 1,1′-bis(triphenylphosphino)ferrocene as catalyst was developed into a feasible method for a preperative scale. This is, to our best knowledge, the first application of substituted ferrocenes as oxidation catalysts. Springer-Verlag 2004.
- Jary, Walther G.,Ganglberger, Thorsten,Poechlauer, Peter,Falk, Heinz
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p. 537 - 541
(2007/10/03)
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- Juvenile hormone analogues active on mosquitoes: Synthesis and biological activity of hydrocarbon juvenoids with a pinene and substituted cyclohexane ring in the terminal position
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1-(2-Pinen-10-yl)-3,7-dimethyl-2(E), 6-octadiene 1, 1-(2'- isopropyl -5'-methylcyclohexyl)-3,7-dimethyl-2(E),6-octadiene 2 and their analogues have been prepared. These compounds have been tested on Culex pipiens quinquefasciatus Say for their juvenile hormone (JH) activity.
- Kalra,Kad
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- A facile route to acyclic substituted α,β-unsaturated aldehydes: The allene claisen rearrangement
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(equation presented) Sigmatropic rearrangement of allenyl ethers furnishes α,β-unsaturated aldehydes in good yield.
- Parsons, Philip J.,Thomson, Peter,Taylor, Andrew,Sparks, Timothy
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p. 571 - 572
(2007/10/03)
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- Photocatalytic Activation of Oxygen by Iron(III) Porphyrins
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Photochemical charge transfer excitation of tetraphenyl(porphyrinato)iron(III) complexes yields tetraphenyl-(porphyrinato)iron(II) which is able to coordinate molecular oxygen under formation of oxo-[tetraphenyl(porphyrinato)]-iron(IV). Based on this photochemical reaction pathway photocatalytic oxygenation of α-pinene and other alkenes can be initiated. Iron(III) complexes of tetramesitylporphyrin, tetrakis-(pentafluorophenyl)porphyrin, octa-β-bromo-tetrakis-(pentafluorophenyl)porphyrin, and octa-β-chloro-tetrakis-(pentafluorophenyl)porphyrin were investigated photochemically with the aim to improve the low photochemical efficiency of tetraphenyl(porphyrinato)iron(III). The influence of substituents on the porphyrin ligand on the photochemical behavior of the corresponding iron(III) complexes is measured mainly by means of temperature dependent UV/Vis spectroscopy. Both, the yield of oxygenation products formed photocatalytically with α-pinene and the product distribution (allylic alcohols versus epoxide) depend on the design of the porphyrin ligands coordinated with iron(III).
- Hennig, Horst,Luppa, Doritt
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p. 757 - 767
(2007/10/03)
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- Pinane-Type Tridentate Reagents for Enantioselective Reactions: Reduction of Ketones and Addition of Diethylzinc to Aldehydes
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The reduction of aryl and alkenyl methyl ketones using lithium aluminum hydride modified with (1R,2S,3S,5A)-(+)-10-anilino-3-ethoxy-2-hydroxypinane (10b) afforded chiral secondary alcohols in 83-96% chemical yields and 50-91% ee with dominance of R enantiomers. The reduction of acetophenone in the presence of lithium iodide gave the alcohol product with higher ee. On the other hand, the addition reaction of diethylzinc to benzaldehyde using the pinane-based diols 5-9 as promoters gave 1-phenylpropanol in favor of the S enantiomer up to 88% ee. Using the pinane-based alcohols 10a-e as promoters, the R enantiomer was obtained as the major product. The addition reactions of diethylzinc to various substituted benzaldehydes, employing the diol ligands 5c and 8e, afforded predominantly the corresponding (S)-alcohols. The chiral modifiers 5-10 were prepared from (1R)-(-)-myrtenol and were readily recovered (>90%) after the asymmetric reactions. In this study, LAH reduction and Et2Zn addition are complementary methods for the preparation of optically active secondary alcohols. The ligand 10-butylanilino-2,3-dihydroxypinane 5c promoted the Et2Zn additions effectively, whereas the modifier 10-anilino-3-ethoxy-2-hydroxypinane 10b induced the LAH reductions in a highly enantioselective manner.
- Cherng, Yie-Jia,Fang, Jim-Min,Lu, Ta-Jung
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p. 3207 - 3212
(2007/10/03)
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- Facile deprotection of trimethylsilyl ethers with modified borohydride agents; 1-benzyl-4-aza-1-azoniabicyclo[2.2.2]octane tetrahydroborate (BAAOTB) versus tetrabutylammonium tetrahydroborate(TBATB)
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Deprotection structurally different trimethylsilyl ethers with the modified borohydride agents BAAOTB and TBATB to their corresponding alcohols in reflexing t-BuOH is described. Both BAAOTB and TBATB are efficient reagents for this purpose. BAAOTB seems to be more selective than TBATB.
- Firouzabadi,Afsharifar
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p. 1065 - 1073
(2007/10/03)
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- Cobalt catalyzed oxidation of cyclic alkenes with molecular oxygen: Allylic oxidation versus double bond attack
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Cobalt (II) Schiff's base complex 1 and 2 exhibit a remarkable chemoselectivity during oxidation of cyclic alkenes with molecular oxygen in the presence of 2-methylpropanal. Catalyst 1 encourages the oxidation of double bond to give epoxide as the major product whereas catalyst 2 promotes mainly the allylic oxidation leading to allylic alcohols or enones.
- Madhava Reddy,Punniyamurthy,Iqbal, Javed
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p. 159 - 162
(2007/10/02)
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- Aminoborohydrides. 4. The Synthesis and Characterization of Lithium Aminoborohydrides: A New Class of Powerful, Selective, Air-Stable Reducing Agents
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Lithium aminoborohydrides (LiABH3) are a new class of powerful yet selective reducing agents that reproduce, in air, virtually all of the transformations for which lithium aluminum hydrides is now used.LiABH3's can be readily prepared as solids or generated in situ, are nonpyrophoric, and liberate hydrogen only slowly with protic solvents above pH 4.LiABH3's can be handled in dry air as easily as sodium borohydride and retain their chemical activity for at least 6 month when stored under nitrogen or dry air at 25 deg C.LiABH3's can be synthesized from any primary or secondary amine, thus allowing control of the steric and electronic environment of these reagents.
- Fisher, Gary B.,Fuller, Joseph C.,Harrison, John,Alvarez, Salvador G.,Burkhardt, Elizabeth R.,et al.
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p. 6378 - 6385
(2007/10/02)
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- Reduction of α,β-unsaturated carbonyl compounds with sodium borohydride in the diethyl ether/methanol/pentafluorophenol solvent system. Use of N,N,N',N'-tetramethylethylenediamine and 1-hexene as borane scavengers
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Pentafluorophenol acts as an efficient proton source for sodium borohydride reductions in diethyl ether containing methanol.This system allows for the regioselective reduction of α,β-unsaturated carbonyl compounds to the corresponding allylic alcohols in high yield.Use of either 1-hexene or N,N,N',N'-tetramethylethylenediamine as borane scavengers moderately improved the regioselectivity of this reaction.Fortunately, sodium trispentafluorophenoxyborohydride, generated in situ, gave regiospecific 1,2-reduction of α,β-unsaturated carbonyl compounds.
- Fuller, Joseph C.,Williamson, Stanley M.,Singaram, Bakthan
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p. 265 - 268
(2007/10/02)
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- Novel allylic oxidation reagents
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Pentafluorobenzeneseleninic acid and 2-(N-oxido)pyridineseleninic anhydride were prepared and used efficiently in the oxidation of alcohols and in the allylic oxidation of alkenes.
- Barton, Derek H. R.,Wang, Tie-Lin
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p. 5149 - 5152
(2007/10/02)
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- Aminoborohydrides. 2. Regiospecific reductions of α,β-unsaturated carbonyl compounds with lithium pyrrolidinoborohydride. A facile conversion of α,β-unsaturated aldehydes and ketones to the corresponding allylic alcohols in high purity
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Lithium aminoborohydrides (LiABH3), obtained by the reaction of n-BuLi with amine-boranes, are powerful reducing agents for the reduction α,β-unsaturated aldehydes and ketones to the corresponding allylic alcohols. Thus, lithium pyrrolidinoborohydride (LiPyrrBH3) and reduces cinnamaldehyde and cyclohexenone to give exclusively cinnamyl alcohol and 2-cyclohexen-1-ol respectively. This 1,2-reduction appears to be general and ester groups are tolerated. The yield of allylic alcohols from this procedure is essentially quantitative.
- Fuller, Joseph C.,Stangeland, Eric L.,Goralski, Christian T.,Singaram, Bakthan
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p. 257 - 260
(2007/10/02)
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- Carbon-Carbon Bond Scission during the Reactions of Allylic Hydroperoxides with some Transition Metal Compounds. Result Relevant to a Recent Proposal
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The proposal that 4-exo closure of an allylic peroxyl radical can account for the titled reactions of pinocarveyl hydroperoxide has been considered in the light of literature data, along with the results of reactions carried out with a range of alternative copper and iron reagents and with the previously examinated reagents in the presence or absence of suitable traps: an acid-catalysed pathway is proposed to account for the observed scission reaction.
- Courtneidge, John L.
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p. 381 - 383
(2007/10/02)
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- Photooxygenation of olefins in the presence of titanium(IV) catalyst: A convenient 'one-pot' synthesis of epoxy alcohols
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The photooxygenation of olefins in the presence of transition-metal complexes derived from Ti, V, and Mo constitutes a convenient and efficient 'one-pot' synthesis of epoxy alcohols. First, singlet oxygen transforms the olefin via an ene reaction into its allylic hydroperoxide, and subsequently, the allylic hydroperoxide is converted via transition-metal-catalyzed oxygen transfer into its epoxy alcohol. From the point of view of the olefinic substrate, the oxygen transfer is intermolecular, one allylic hydroperoxide molecule serving as oxygen donor and the other as oxygen acceptor in the form of its allylic alcohol, the transition metal playing the role of a template for both as in the Sharpless epoxidation. Unlike the latter process, the hydroperoxide donor and the allylic alcohol acceptor are generated in situ and continually consumed via a novel oxygen-transfer chain sequence.
- Adam,Braun,Griesbeck,Lucchini,Staab,Will
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p. 203 - 212
(2007/10/02)
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- UNSOLVATED MAGNESIUM DIISOPROPYLAMIDE (MDA) IN ORGANIC SYNTHESIS. THE REDUCTION OF ALDEHYDES AND KETONES TO ALCOHOLS.
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A solution of unsolvated magnesium diisopropylamide in cyclohexane has been found to reduce aldehydes and ketones to the corresponding alcohols in good yield.
- Sanchez, Ramiro,Scott, William
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p. 139 - 142
(2007/10/02)
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- Calcium in Liquid Ammonia for the Reduction of Benzyl Ethers. Mechanistic Clues Derived from Chemoselectivity Studies
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Extremely high selectivity was provided by calcium in liquid ammonia in the cleavage of the benzylic carbon-oxygen bond in benzyl ethers containing various other functionalities.Results of controlled experiments indicate that the selectivities offered by the Ca -> Ca+ + e- and the Ca+ -> Ca2+ + e- processes are 4.6 and 47 times greater, respectively, than that afforded by the Li -> Li+ + e- process.
- Hwu, Jih Ru,Chua, Vincent,Schroeder, Jean E.,Barrans, Richard E.,Khoudary, Kevin P.,et al.
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p. 4731 - 4733
(2007/10/02)
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- THE ALLYLIC REARRANGEMENT OF HYDROPEROXIDES : THE ALLYLPEROXYL RADICAL
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The free-radical rearrangement of pinocarveyl hydroperoxide (1) or myrtenyl hydroperoxide (2) in hexane produces an equilibrium mixture of both hydroperoxides.The absence of carbon skeletal rearrangement suggests that the intermediate radical involved in hydroperoxide isomerization has its unpaired electron localized elsewhere than the α-carbon atom.The failure of oxygen to react with pinocarveyl, myrtenyl, and acyclic hydroperoxides (8) and (9) during the allylic rearrangement supports this suggestion.The kinetics of the rearrangement of 1-isopropyl-2-methylallyl hydroperoxide (8) is compatible with a mechanism in wich the intermediate is a common allylperoxyl radical produced directly from either allylic isomer.
- Brill, William F.
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p. 621 - 628
(2007/10/02)
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- AN EFFICIENT DEPROTECTIVE METHOD FOR ALLYLIC ALCOHOLS PROTECTED AS METHOXYETHOXYMETHYL (MEM) AND METHOXYMETHYL (MOM) ETHERS
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Methoxyethoxymethyl ethers (MEM) and methoxymethyl ethers (MOM) of allylic alcohols are readily cleaved by pyridinium paratoluenesulfonate (PPTS) in 2-butanone or t-butyl alcohol.This procedure is also efficient for deprotection of benzylic and aliphatic alcohols.
- Monti, H.,Leandri, G.,Klos-Ringuet, M.,Corriol, C.
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p. 1021 - 1026
(2007/10/02)
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