- An effective procedure for the synthesis of acid-sensitive epoxides: Use of 1-methylimidazole as the additive on methyltrioxorhenium-catalyzed epoxidation of alkenes with hydrogen peroxide
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An effective method for suppression of ring opening and rearrangement of acid-sensitive epoxides during methyltrioxorhenium(MTO)-catalyzed epoxidation of alkenes with H2O2 by using 1-methylimidazole as a co-additive has been found. The combined use of 3-methylpyrazole and 1-methylimidazole as the additives has been found to be an effective procedure that affords excellent yields of acid-sensitive epoxides for MTO-catalyzed epoxidation.
- Yamazaki, Shigekazu
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- A further step to sustainable palladium catalyzed oxidation: Allylic oxidation of alkenes in green solvents
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The palladium catalyzed oxidation of alkenes with molecular oxygen is a synthetically important reaction which employs palladium catalysts in solution; therefore, a solvent plays a critical role for the process. In this study, we have tested several green solvents as a reaction medium for the allylic oxidation of a series of alkenes. Dimethylcarbonate, methyl isobutyl ketone, and propylene carbonate, solvents with impressive sustainability ranks and very scarcely exploited in palladium catalyzed oxidations, were proved to be excellent alternatives for the solvents conventionally employed in these processes, such as acetic acid. Palladium acetate alone or in the combination with p-benzoquinone efficiently operates as the catalyst for the oxidation of alkenes by dioxygen under 5–10 atm. For most substrates, the systems in green solvents showed better selectivity for allylic oxidation products as compared to pure acetic acid; moreover, the reactions in propylene carbonate solutions occurred even faster than in acetic acid.
- dos Santos Costa, Maíra,de Camargo Faria, Amanda,Mota, Rayssa L.V.,Gusevskaya, Elena V.
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- An ultrathin amino-acid based copper(II) coordination polymer nanosheet for efficient epoxidation of β-caryophyllene
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Natural amino acids are important building blocks for the construction of intriguing coordination polymers (CPs) because of their abundance, inexpensiveness and environmental benignness. Herein, two copper(II) CPs, namely, 2D CuIle-e nanosheet (e: ethanol) and 1D CuIle-m nanoshuttle (m: methanol), were fabricated from L-isoleucine (Ile) and well characterized with single-crystal x-ray diffraction, XPS spectra, TEM and AFM, etc. More importantly, two novel and stable catalytic nanosystems, i.e. CuIle-e/acetone/TBHP (tert-butyl hydroperoxide) and CuIle-e/THF/O2/TBHP, were thus conveniently built by using ultrathin 2D CuIle-e nanosheet (~ 2.3 nm) in suitable aprotic solvents. Under mild conditions, complete conversion of β-caryophyllene and good yields (86.1% or 87.2%) for β-caryophyllene epoxide were gained via CuIle-e/acetone/TBHP or CuIle-e/THF/O2 (1 atm)/TBHP (10.0 mol%), respectively. Notably, ultrathin CuIle-e nanosheet showed fairly satisfactory stability, which may open a unique window for the facile fabrication of new amino-acid based CP nanosystems with outstanding catalytic performances in actual applications.
- Fu, Zaihui,Huang, Hongmei,Mao, Liqiu,Mao, Wensheng,Shi, Lihan,Xiao, Yi,Yin, Dulin,Yu, Ningya,Zhang, Li,Zhao, Yaqian
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- Ionic liquid-mediated catalytic oxidation of β-caryophyllene by ultrathin 2D metal-organic framework nanosheets under 1 atm O2
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An ionic liquid (IL)-mediated facile method was established for the epoxidation of β-caryophyllene with molecular oxygen using ultrathin (~3?6 nm) 2D Cu-, Co- or Ce-based MOF nanosheets. Under the optimum conditions, high selectivity (92.4percent) and excellent yield (86.7percent) for β-caryophyllene epoxide were obtained over ultrathin (~5.5 nm) Cu-TCPP nanosheets (TCPP = tetrakis(4-carboxyphenyl)porphyrin) with the aid of [C12mim]Cl at 313 K and 1 atm O2. Notably, a small amount of [C12mim]Cl (1-dodecyl-3-methylimidazolium chloride, 5.0 mol percent) played pivotal roles in forming a favorable microenvironment in-situ, thus significantly improving the catalytic performances of above-mentioned Cu-TCPP nanosheets containing PVP stabilizer. Moreover, ultrathin Cu-TCPP nanosheets showed better stability during β-caryophyllene transformation in the presence of amphiphilic [C12mim]Cl, as supported by TEM and XRD analyses. Importantly, the addition of TBHP (tert-butyl hydroperoxide, 13.0 mol percent) initiator is also crucial for the aerobic oxidation of β-caryophyllene via Cu-TCPP nanosheets/[C12mim]Cl/TBHP/O2 nanosystem. Further insights into the synergistic effects and free radical mechanism were achieved by fluorescence, DRUV-Vis, UV-vis and XPS measurements.
- Li, Shiye,Shi, Lihan,Zhang, Li,Huang, Hongmei,Xiao, Yi,Mao, Liqiu,Tan, Rong,Fu, Zaihui,Yu, Ningya,Yin, Dulin
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- Electron transfer-initiated epoxidation and isomerization chain reactions of β-caryophyllene
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The abundant sesquiterpene b-caryophyllene can be epoxidized by molecular oxygen in the absence of any catalyst. In polar aprotic solvents, the reaction proceeds smoothly with epoxide selectivities exceeding 70%. A mechanistic study has been performed and the possible involvement of free radical, spin inversion, and electron transfer mechanisms is evaluated using experimental and computational methods. The experimental data-including a detailed reaction product analysis, studies on reaction parameters, solvent effects, additives and an electrochemical investigation-all support that the spontaneous epoxidation of b-caryophyllene constitutes a rare case of unsensitized electron transfer from an olefin to triplet oxygen under mild conditions (80 8C, 1 bar O2). As initiation of the oxygenation reaction, the formation of a caryophyllene-derived radical cation via electron transfer is proposed. This radical cation reacts with triplet oxygen to a dioxetane via a chain mechanism with chain lengths exceeding 100 under optimized conditions. The dioxetane then acts as an in situ-formed epoxidizing agent. Under nitrogen atmosphere, the presence of a one-electron acceptor leads to the selective isomerization of b -caryophyllene to isocaryophyllene. Observations indicate that this isomerization reaction is a novel and elegant synthetic pathway to isocaryophyllene.
- Steenackers, Bart,Campagnol, Nicol,Fransaer, Jan,Hermans, Ive,De Vos, Dirk
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p. 2146 - 2156
(2015/01/30)
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- 1-HYDROXY-OCTAHYDROAZULENES AS FRAGRANCES
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(3S,5R)-3,8-dimethyl-5-(prop-1-en-2-yl)-octahydroazulen-1-ols, their use as flavour or fragrance ingredient, and a process of their production by oxidation in the presence of laccase.
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Page/Page column 15-16
(2012/01/14)
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- Chromium(III) terephthalate metal organic framework (MIL-101): Hf-free synthesis, structure, polyoxometalate composites, and catalytic properties
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Hybrid materials of the metal-organic framework (MOF), chromium(III) terephthalate (MIL-101), and phosphotungstic acid (PTA) were synthesized in aqueous media in the absence of hydrofluoric acid. XRD analysis of the MIL101/PTA composites indicates the presence of ordered PTA assemblies residing in both the large cages and small pores of MIL-101, which suggests the formation of previously undocumented structures. The MIL101/PTA structure enables a PTA payload 1.5-2 times higher than previously achieved. The catalytic performance of the MIL101/PTA composites was assessed in the Baeyer condensation of benzaldehyde and 2-naphthol, in the three-component condensation of benzaldehyde, 2-naphthol, and acetamide, and in the epoxidation of caryophyllene by hydrogen peroxide. The catalytic efficiency was demonstrated by the high (over 80-90%) conversion of the reactants under microwave-assisted heating. In four consecutive reaction cycles, the catalyst recovery was in excess of 75%, whereas the product yields were maintained above 92%. The simplicity of preparation, exceptional stability, and reactivity of the novel composites indicate potential in utilization of these catalytic matrices in a multitude of catalytic reactions and engineering processes.
- Bromberg, Lev,Diao, Ying,Wu, Huimeng,Speakman, Scott A.,Hatton, T. Alan
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experimental part
p. 1664 - 1675
(2012/08/13)
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- An effective synthesis of acid-sensitive epoxides via oxidation of terpenes and styrenes using hydrogen peroxide under organic solvent-free conditions
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An efficient epoxidation process for various terpenes and styrenes using a hydrogen peroxide-tungsten catalytic system with organic solvent-and halide-free conditions was developed. In the presence of the catalytic system, Na 2WO4, PhP(O)(OH)2, and [Me(n-C 8H17)3N]HSO4, and under weak acidic conditions, hydrogen peroxide successfully epoxidized -pinene to -pinene oxide in 95% selectivity at 91% conversion, while the previously published conditions utilizing NH2CH2P(O)(OH)2 as a promoter provided no epoxide. Georg Thieme Verlag Stuttgart.
- Kon, Yoshihiro,Hachiya, Houjin,Ono, Yutaka,Matsumoto, Tomohiro,Sato, Kazuhiko
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experimental part
p. 1092 - 1098
(2011/05/14)
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- An effective catalytic epoxidation of terpenes with hydrogen peroxide under organic solvent-free conditions
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A catalytic system that operates well for the epoxidation of α-pinene, a very challenging substrate, at near-neutral pH and ambient temperature without organic solvent was developed. With hydrogen peroxide as a terminal oxidant, combination of Na2WO4, PhP(O)(OH) 2, and [Me(n-C8H17)3N]HSO 4 successfully catalyzed the epoxidation of α-pinene to give α-pinene oxide in 95% selectivity at 91% conversion, while the previously published conditions that use NH2CH2P(O)(OH)2 as a promoter provide no epoxide. The method is also well applicable to the epoxidation of the other acidsensitive terpenes. Georg Thieme Verlag Stuttgart.
- Kon, Yoshihiro,Ono, Yutaka,Matsumoto, Tomohiro,Sato, Kazuhiko
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scheme or table
p. 1095 - 1098
(2009/09/25)
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- REARRANGED CARYOPHYLLENES BY BIOTRANSFORMATION WITH CHAETOMIUM COCHLIODES
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Biotransformation of caryophyllene by Chaetomium cochliodes DSM 1909 (=ATCC 10195) leads to 4,5-epoxy-caryophyllene-7,12-diol as the main product.The hydroxylation of the geminal methyl groups is not very stereospecific, but as with Diploida gossypina the main product possesses the 11R-configuration.Side-reactions are ring contraction or formation of clovanes, probably via epoxide rearrangements.The use of mono- or diepoxy-caryophyllene as the substrate does not increase the yields significantly.Instead, diepoxy-caryophyllene gave a punctatin derivative.The same molecular framework, but with a different configuration, was observed among the fermentation products from Diplodia gossypina, which supports the assumption that a caryophyllane is the precursor of this class of antibiotics.
- Abraham, Wolf-Rainer,Ernst, Ludger,Arfmann, Hans-Adolf
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p. 757 - 763
(2007/10/02)
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- OXYMERCURATION-DEMERCURATION OF THE 4,5-EPOXIDES OF CARYOPHYLLENE AND ISOCARYOPHYLLENE
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The products from the transformations of the 4,5-epoxides of the sesquiterpene hydrocarbons caryophyllene and isocaryophyllene were studied under oxymercuration-demercuration conditions.Initially, the 4,5-epoxycaryophyllene isomers form the products from addition at the 8,13-double bond, in which intramolecular nucleophilic opening of the epoxide ring then occurs.In the case of epoxyisocaryophyllene the oxygen atom of the epoxide group takes part directly in nucleophilic attack on the intermediate mercurinium ion, formed at the 8,13-double bond.
- Tkachev, A. V.,Dubovenko, Zh. V.,Pentegova, V. A.
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p. 1593 - 1601
(2007/10/02)
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- EIGHT NEW XENIA DITERPENOIDS FROM THREE SOFT CORALS OF THE RED SEA
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Investigation of the terpenoid content of three soft corals from the Gulf of Eilat (THe Red Sea), Xenia macrospiculata, X. obscuronata and X. lilielae resulted in the isolation of 8 new diterpens.Two of the new compounds belong to the xeniolides (xenialactol-D (10a) and xeniolide-E (13)) and the other six (4,14-diepoxyxeniaphyllene (15), 4,5-epoxyxeniaphyllan-14,15-diol (17), 4,14-diepoxy-xeniaphyllenol-A (21a), xeniaphyllenol-B (23a), xeniaphyllenol-C (24a) and xeniaphyllantriol (25) are new xeniaphyllanes (prenylated caryophyllanes).The structure determination of the various compounds is based on chemical transformations as well as on the 1H and 13C NMR spectra.Several known caryophyllene derivatives have been synthesised for 13C NMR spectra and chemical comparisons.The 13C NMR has proven to be an excellent probe for structural and stereochemical determinations.
- Groweiss, Amiram,Kashman, Yoel
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p. 3385 - 3396
(2007/10/02)
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