- Tethered Silanoxyiodination of Alkenes
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We present the first examples of tethered silanoxyiodination reactions of allylic alcohols. The products are useful silanediol organoiodide synthons and are formed with high regioselectivity and diastereocontrol. The reaction is scalable greater than 10-fold without loss of yield or selectivity. Furthermore, the products are starting materials for further transformations, including deiodination, C-N bond installation, epoxide synthesis, and desilylation. DFT calculations provide a basis for understanding the exquisite 6-endo selectivity of this silanoxyiodination reaction and show that the observed products are both kinetically and thermodynamically preferred.
- Dhokale, Ranjeet A.,Seidl, Frederick J.,Shinde, Anand H.,Mague, Joel T.,Sathyamoorthi, Shyam
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- Discovery of a new series of monoamine reuptake inhibitors, the 1-amino-3-(1H-indol-1-yl)-3-phenylpropan-2-ols
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A novel series of monoamine reuptake inhibitors, the 1-amino-3-(1H-indol-1-yl)-3-phenylpropan-2-ols, have been discovered by combining virtual and focused screening efforts with design techniques. Synthesis of the two diastereomeric isomers of the molecule followed by chiral resolution of each enantiomer revealed the (2R,3S)-isomer to be a potent norepinephrine reuptake inhibitor (IC50 = 28 nM) with excellent selectivity over the dopamine transporter and 13-fold selectivity over the serotonin transporter.
- Kim, Callain Y.,Mahaney, Paige E.,McConnell, Oliver,Zhang, Yingru,Manas, Eric,Ho, Douglas M.,Deecher, Darlene C.,Trybulski, Eugene J.
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- Enantiocomplementary Epoxidation Reactions Catalyzed by an Engineered Cofactor-Independent Non-natural Peroxygenase
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Peroxygenases are heme-dependent enzymes that use peroxide-borne oxygen to catalyze a wide range of oxyfunctionalization reactions. Herein, we report the engineering of an unusual cofactor-independent peroxygenase based on a promiscuous tautomerase that accepts different hydroperoxides (t-BuOOH and H2O2) to accomplish enantiocomplementary epoxidations of various α,β-unsaturated aldehydes (citral and substituted cinnamaldehydes), providing access to both enantiomers of the corresponding α,β-epoxy-aldehydes. High conversions (up to 98 %), high enantioselectivity (up to 98 % ee), and good product yields (50–80 %) were achieved. The reactions likely proceed via a reactive enzyme-bound iminium ion intermediate, allowing tweaking of the enzyme's activity and selectivity by protein engineering. Our results underscore the potential of catalytic promiscuity for the engineering of new cofactor-independent oxidative enzymes.
- Crotti, Michele,Kataja, Kim M.,Poelarends, Gerrit J.,Saravanan, Thangavelu,Xu, Guangcai
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p. 10374 - 10378
(2020/04/23)
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- Three- and two-site heteropolyoxotungstate anions as catalysts for the epoxidation of allylic alcohols by H2O2 under biphasic conditions: Reactivity and kinetic studies of the [Ni3(OH2)3(B-PW9O34){WO5(H2O)}]7?, [Co3(OH2)6(A-PW9O34)2]12?, and [M4(OH2)2(B-PW9O34)2]10? anions, where M?=?Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)
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The trimetallic phosphopolyoxotungstate anions [Ni3(OH2)3(B-PW9O34){WO5(H2O)}]7? and [Co3(OH2)6(A-PW9O34)2]12? have been studied as epoxidation catalysts for oxygen transfer from 30% H2O2 to a range of allylic alcohols under biphasic conditions (1,2-dichloroethane/H2O) at 15 °C. The reaction mechanism involves coordination of an allylic alcohol at an M(II) site in each case, prior to transfer of a peroxy oxygen from an adjacent W(O2) site. The latter is formed from a terminal W = O unit by reaction with H2O2. Evidence of W(O2) formation was obtained through IR studies. The W(O2) group forms the epoxide by transfer of an oxygen atom to the C[dbnd]C bond of the coordinated allylic alcohol. Kinetic studies using 3-methyl-2-buten-1-ol as the allylic alcohol substrate have been modelled with all three metal sites catalytically active. The reaction involves an autocatalysis mechanism involving an induction period, which can be rationalised by proposing not only coordination of the allylic alcohol to M(II), but also the product hydroxy epoxide, both through their –OH groups. The autocatalysis is generated by formation of the W(O2) group adjacent to a coordinated hydroxy epoxide, which competes with coordination of allylic alcohol. The mechanism requires some twenty-one steps involving just the generic steps listed above, with all three metal sites catalytically active. Temperature-dependent kinetic studies and subsequent Eyring analyses have shown that the Co(II)-containing catalyst is the most active of the two. Analogous studies of the epoxidation of 3-methyl-2-buten-1-ol by the two-site [M4(OH2)2(B-PW9O34)2]10? ions as catalysts, where M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II), at 15 °C gave an order of reactivity of Cu(II) > Ni(II) > Zn(II), Co(II), Mn(II), which mostly mimics the natural order of stability constants (the Irving-Williams series), suggesting that the formation of the allylic alcohol complexes play a dominant role in this series of related complex anions, with greater replacement of water by allylic alcohol leading to greater reactivity.
- Abram, Paulus Hengky,Burns, Robert C.,Li, Lichun
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- Borylation and rearrangement of alkynyloxiranes: A stereospecific route to substituted α-enynes
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1,3-Enynes are important building blocks in organic synthesis and also constitute the key motif in various bioactive natural products and functional materials. However, synthetic approaches to stereodefined substituted 1,3-enynes remain a challenge, as they are limited to Wittig and cross-coupling reactions. Herein, stereodefined 1,3-enynes, including tetrasubstituted ones, were straightforwardly synthesized from cis or trans-alkynylated oxiranes in good to excellent yields by a one-pot cascade process. The procedure relies on oxirane deprotonation, borylation and a stereospecific rearrangement of the so-formed alkynyloxiranyl borates. This stereospecific process overall transfers the cis or trans-stereochemistry of the starting alkynyloxiranes to the resulting 1,3-enynes.
- Fuentespina, Ruben Pomar,De La Cruz, José Angel Garcia,Durin, Gabriel,Mamane, Victor,Weibel, Jean-Marc,Pale, Patrick
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supporting information
p. 1416 - 1424
(2019/07/10)
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- Efficient and selective oxidation of alcohols to carbonyl compounds at room temperature by a ruthenium complex catalyst and hydrogen peroxide
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In this study, convenient and selective oxidation of alcohols using aqueous hydrogen peroxide to yield carbonyl compounds was studied. Using the ruthenium-(4-methylphenyl-2,6-bispydinyl) pyridinedicarboxylate complex [Ru(mpbp)(pydic)] as a catalyst, primary and secondary alcohols were oxidized to aldehydes and ketones at room temperature with a satisfactory yield and excellent selectivity. The influence of various reaction parameters, such as solvent, catalyst and oxidant amount on both the activity and selectivity was also evaluated. Kinetic studies showed that the oxidation of alcohol was first order in terms of the substrate and hydrogen peroxide, and was second order in terms of the catalyst. A plausible mechanism involving ruthenium-oxo species with electrophilic character was proposed based on the in situ UV-vis spectroscopy studies and Hammett plots.
- Wang, Jie-Xiang,Zhou, Xian-Tai,Han, Qi,Guo, Xiao-Xuan,Liu, Xiao-Hui,Xue, Can,Ji, Hong-Bing
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p. 19415 - 19421
(2019/12/24)
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- SO2F2-Mediated Epoxidation of Olefins with Hydrogen Peroxide
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An inexpensive, mild, and highly efficient epoxidation protocol has been developed involving bubbling SO2F2 gas into a solution of olefin, 30% aqueous hydrogen peroxide, and 4 N aqueous potassium carbonate in 1,4-dioxane at room temperature for 1 h with the formation of the corresponding epoxides in good to excellent yields. The novel SO2F2/H2O2/K2CO3 epoxidizing system is suitable to a variety of olefinic substrates including electron-rich and electron-deficient ones.
- Ai, Chengmei,Zhu, Fuyuan,Wang, Yanmei,Yan, Zhaohua,Lin, Sen
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p. 11928 - 11934
(2019/10/02)
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- Enantioselective Access to Chiral Cyclic Sulfamidates Through Iridium-Catalyzed Asymmetric Hydrogenation
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The Iridium-catalyzed asymmetric hydrogenation of cyclic sulfamidate imines was successfully developed with N-methylated ZhaoPhos L2 as the ligand. A variety of chiral cyclic sulfamidates were obtained with excellent results (up to 99% yield, 99% ee). Furthermore, this asymmetric hydrogenation can be employed as the key reaction step to prepare the important intermediates in organic synthesis. (Figure presented.).
- Liu, Yuanhua,Huang, Yi,Yi, Zhiyuan,Liu, Gongyi,Dong, Xiu-Qin,Zhang, Xumu
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supporting information
p. 1582 - 1586
(2019/02/19)
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- Towards Mechanistic Understanding of Liquid-Phase Cinnamyl Alcohol Oxidation with tert-Butyl Hydroperoxide over Noble-Metal-Free LaCo1–xFexO3 Perovskites
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Noble-metal-free perovskite oxides are promising and well-known catalysts for high-temperature gas-phase oxidation reactions, but their application in selective oxidation reactions in the liquid phase has rarely been studied. We report the liquid-phase oxidation of cinnamyl alcohol over spray-flame synthesized LaCo1–xFexO3 perovskite nanoparticles with tert-butyl hydroperoxide (TBHP) as the oxidizing agent under mild reaction conditions. The catalysts were characterized by XRD, BET, EDS and elemental analysis. LaCo0.8Fe0.2O3 showed the best catalytic properties indicating a synergistic effect between cobalt and iron. The catalysts were found to be stable against metal leaching as proven by hot filtration, and the observed slight deactivation is presumably due to segregation as determined by EDS. Kinetic studies revealed an apparent activation energy of 63.6 kJ mol?1. Combining kinetic findings with TBHP decomposition as well as control experiments revealed a complex reaction network.
- Waffel, Daniel,Alkan, Baris,Fu, Qi,Chen, Yen-Ting,Schmidt, Stefan,Schulz, Christof,Wiggers, Hartmut,Muhler, Martin,Peng, Baoxiang
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p. 1155 - 1163
(2019/09/06)
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- Catalytic oxidation of alcohols with novel non-heme N4-tetradentate manganese(ii) complexes
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We report the preparation and characterisation of a series of novel non-heme N4-tetradentate Mn(OTf)2 complexes of the type, [(L)MnOTf2], where L = R,R and S,S enantiomers of BPMCN, its 6-methyl and 6-bromo derivatives as well as the novel ligand BMIMCN (BPMCN = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)-(R,R/S,S)-1,2-diaminocyclohexane, BMIMCN = N,N′-dimethyl-N,N′-bis(1-methyl-2-imidazolemethyl)-(R,R/S,S)-1,2-diaminocyclohexane). Solid state structural analysis of the BMIMCN-ligated Mn-triflate complexes (R,R-C4 and S,S-C4) revealed opposite helicity but identical metal site accessibility. This feature was exploited in the catalytic oxidation of primary and secondary alcohols, with hydrogen peroxide as oxidant and acetic acid as co-catalyst. Complexes R,R-C4 and S,S-C4 displayed the highest activity in benzyl alcohol oxidation, attributed to the electron-donating property of the BMIMCN ligand. Complex S,S-C4, displayed high activity for a variety of primary alcohol substrates, but the reaction suffered from reduced selectivity and side-reactions due to the presence of acetic acid. In contrast, secondary alcohol substrates could be oxidised to the corresponding ketone products in excellent isolated yields under mild reaction conditions and short reaction times.
- Vermaak, Vincent,Young, Desmond A.,Swarts, Andrew J.
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supporting information
p. 16534 - 16542
(2018/12/05)
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- Oxygen bridged Homobinuclear Mn(II) compounds with Anthranilic acid: Theoretical calculations, oxidation and catalase activity
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Two new homobinuclear manganese compounds with mixed ligands, [Mn2(μ1,1–2-NH2C6H4COO)2(phen)4](ClO4)2(CH3OH) (1), and [Mn2(μ1,3–2-NH2C6H4COO)2(bipy)4](ClO4)2 (2) (NH2C6H4COOH?=?anthranilic acid, bipy?=?2,2′-bipyridine, phen?=?1,10- phenanthroline) were synthesized and thoroughly characterized by elemental analysis, IR, UV and single crystal X-ray crystallography. X-ray structure analysis shows that in the mono- and bidentate carboxylate bridged compounds, Mn–Mn distances of 1 and 2 are 3,461??, and 4,639??, respectively. The energy of the compounds was determined with a DFT (Density Functional Theory) calculation on B3LYP/6-31G(d,p) optimized geometry by using the B3LYP/6-31G(d,p) basis set. These compounds acts as biomimetic catalyst and show catalase-like activity for the hydrogen peroxide dismutation at room temperature in different solvents with remarkable activity (TOF, Turnover frequency?=?mol of subst./(mol of cat. × time)) up to 12640?h?1 with 1, and 17910?h?1 with 2 in Tris–HCl buffer). Moreover, the catalytic activity of 1 and 2 has been studied for oxidation of alcohols (cinnamyl alcohol, benzyl alcohol, cyclohexanol, 1-octanol and 1-heptanol) and alkenes (cyclohexene, styrene, ethyl benzene, 1-octene and 1-hexene) in a homogeneous catalytic system consisting t-butylhydroperoxide (TBHP) as an oxidant in acetonitrile. Both compounds exhibited very high activity in the oxidation of cyclohexene to cyclohexanone (~80% selectivity, ~99% conversion in 1?h, TOF?=?243?h?1 and 226?h?1) and cinnamyl alcohol to cinnamaldehyde (~64% selectivity) as the main product with very high TOF value (9180?h?1 and 13040?h?1 in the first minute of reaction) (~100% conversion in 0.5?h) with TBHP at 70?°C in acetonitrile, for 1 and 2, respectively.
- Su, Esra,Guven, Alaettin,Kani, Ibrahim
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- Chiral Manganese Aminopyridine Complexes: the Versatile Catalysts of Chemo- and Stereoselective Oxidations with H2O2
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In the last decade, manganese(II) complexes with N-donor tetradentate aminopyridine ligands emerged as efficient catalysts of enantioselective epoxidation of olefins and direct selective oxidation of C?H groups in complex organic molecules, with environmentally benign oxidant hydrogen peroxide. In this personal account, we summarize the progress of these catalysts with regard to ligands design, structure-reactivity correlations, evaluation of the substrate scope, as well as mechanistic studies, shedding light on the nature of active sites and the mechanisms of selective oxygenations. Several practically promising catalytic syntheses with the aid of Mn aminopyridine catalysts are exemplified.
- Ottenbacher, Roman V.,Talsi, Evgenii P.,Bryliakov, Konstantin P.
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- An Isolable and Bench-Stable Epoxidizing Reagent Based on Triazine: Triazox
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A new triazine-based oxidizing reagent, 2-hydroperoxy-4,6-diphenyl-1,3,5-triazine (Triazox), has been developed. The reagent can be synthesized from inexpensive starting materials and is a bench-stable solid that is isolable in pure form. Epoxidation of alkenes possessing acid-sensitive functionalities using Triazox proceeded in good to excellent yields. The accompanying nonacidic triazinone coproduct can be easily removed by filtration. These features indicate that Triazox is a practically useful oxidizing reagent.
- Yamada, Kohei,Igarashi, Yuki,Betsuyaku, Tatsuki,Kitamura, Masanori,Hirata, Koki,Hioki, Kazuhito,Kunishima, Munetaka
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supporting information
p. 2015 - 2019
(2018/04/16)
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- 1,1,2,2-Tetrahydroperoxy-1,2-Diphenylethane: An efficient and high oxygen content oxidant in various oxidative reactions
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Several oxidative approaches namely thiocyanation of aromatic compounds, epoxidation of alkenes, amidation of aromatic aldehydes, epoxidation of α β-unsaturated ketones, oxidation of sulfides to sulfoxides and sulfones, bayer-villeger reaction, bromination and iodation of aniline and phenol derivatives oxidative esterification, oxidation of pyridines and oxidation of secondary, allylic and benzyllic alcohols were carried out using 1,1,2,2-Tetrahydroperoxy-1,2-Diphenylethane as the potential solid oxidant which can be stored for several months without any loss in its activity. All of the procedures were accomplished via mild reaction conditions and the products were afforded in high yields and short reaction times.
- Khosravi, Kaveh,Naserifar, Shirin
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supporting information
p. 6584 - 6592
(2018/10/05)
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- Identifying catalytically active mononuclear peroxoniobate anion of ionic liquids in the epoxidation of olefins
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The organic carboxylic acid coordinated monomeric peroxoniobate-based ionic liquids (ILs) [TBA][NbO(OH)2(R)] (TBA = tetrabutylammonium; R = lactic acid (LA), glycolic acid (GLY), malic acid (MA)) were prepared and fully characterized by elemental analysis, NMR, IR, Raman, TGA, 93Nb NMR, and HRMS. These IL catalysts exhibited not only high catalytic activity for the epoxidation of olefins under very mild reaction conditions, as the turnover frequency of [TBA][NbO(OH)2(LA)] reached up to 110 h-1, but also satisfactory recyclability in the epoxidation by using only 1 equiv of hydrogen peroxide as an oxidant. Meanwhile, this work revealed that the ILs underwent structural transformation from [NbO(OH)2(R)]- to [Nb(O-O)2(R)]- (R = LA, GLY, MA) in the presence of H2O2 by a subsequent activity evaluation, characterization, and first-principles calculations. Moreover, the organic carboxylic acid coordinated monomeric peroxoniobate-based ILs were investigated using density functional theory (DFT) calculations, which identified that [Nb(O-O)2LA]- was more advantageous than [Nb(O-O)2(OOH)2]- for the epoxidation of olefins. Due to the coordination between the α-hydroxy acids and the monomeric peroxoniobate anions, the functionalized ILs can efficiently catalyze the epoxidation of a wide range of olefins and allylic alcohols under very mild conditions. Additionally, the effect of solvents on the reaction is illustrated. It was found that methanol can lower the epoxidation barriers by forming a hydrogen bond with a peroxo ligand attached to the niobium center.
- Ma, Wenbao,Yuan, Haiyang,Wang, Haifeng,Zhou, Qingqing,Kong, Kang,Li, Difan,Yao, Yefeng,Hou, Zhenshan
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p. 4645 - 4659
(2018/05/08)
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- Arylruthenium(III) Porphyrin-Catalyzed C-H Oxidation and Epoxidation at Room Temperature and [RuV(Por)(O)(Ph)] Intermediate by Spectroscopic Analysis and Density Functional Theory Calculations
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The development of highly active and selective metal catalysts for efficient oxidation of hydrocarbons and identification of the reactive intermediates in the oxidation catalysis are long-standing challenges. In the rapid hydrocarbon oxidation catalyzed by ruthenium(IV) and -(III) porphyrins, the putative Ru(V)-oxo intermediates remain elusive. Herein we report that arylruthenium(III) porphyrins are highly active catalysts for hydrocarbon oxidation. Using catalyst [RuIII(TDCPP)(Ph)(OEt2)] (H2TDCPP = 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin), the oxidation of C-H bonds of various hydrocarbons with oxidant m-CPBA at room temperature gave alcohols/ketones in up to 99% yield within 1 h; use of [nBu4N]IO4 as a mild alternative oxidant avoided formation of lactone from cyclic ketone in C-H oxidation, and the catalytic epoxidation with up to 99% yield and high selectivity (no aldehydes as side product) was accomplished within 5 min. UV-vis, electrospray ionization-mass spectrometry, resonance Raman, electron paramagnetic resonance, and kinetic measurements and density functional theory calculations lend evidence for the formation of Ru(V)-oxo intermediate [RuV(TDCPP)(O)(Ph)].
- Shing, Ka-Pan,Cao, Bei,Liu, Yungen,Lee, Hung Kay,Li, Ming-De,Phillips, David Lee,Chang, Xiao-Yong,Che, Chi-Ming
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supporting information
p. 7032 - 7042
(2018/06/12)
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- A carboxylate-bridged Mn(II) compound with 6-methylanthranilate/bipy: oxidation of alcohols/alkenes and catalase-like activity
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A novel manganese compound, [Mn2(μ1,3-6-CH3-2-NH2C6H4COO)2(bipy)4](ClO4)2 (bipy?=?2,2′-bipyridine), was synthesized and used as a catalyst precursor in the oxidation of alkenes and primary alcohols to corresponding aldehydes, ketones, and acids. The six-coordinate compound has a binuclear structure in which two Mn(II) ions adopt a syn-anti μ1,3-bridging mode with two carboxylate groups and two chelated bipy ligands. The compound exhibits good activity in the oxidation of cyclohexene to 2-cyclohexene-1-one as the major product (93% conv. in 3?h, 79.3% selectivity) and of cinnamyl alcohol to cinnamaldehyde as the major product with 46% selectivity (100% conv. in 1.5?h) with tert-butyl hydroperoxide (TBHP) in acetonitrile at 70?°C. Furthermore, the catalase-like activity of the compound was studied in different solvents (acetonitrile, methanol, Tris-HCl buffer; TOF?=?29,910?h?1 in Tris-HCl buffer).
- Kilic, Yalcin,Bolat, Serkan,Kani, Ibrahim
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p. 2293 - 2303
(2018/05/14)
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- Zinc-Mediated Efficient and Selective Reduction of Carbonyl Compounds
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We herein describe for the first time that an optimized combination of Zn and NH4Cl can be used for the selective reduction of aldehydes and ketones to the corresponding alcohols. The aldehyde and keto groups are selectively reduced in the presence of azide, cyano, epoxy, ester, and carbon–carbon double-bond functional groups. A broad functional-group compatibility, chemoselective reduction of aldehydes in the presence of ketones, and selective reduction of isatins at the C3 carbonyl group are the highlights of the present method.
- Mandal, Tirtha,Jana, Snehasish,Dash, Jyotirmayee
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p. 4972 - 4983
(2017/09/13)
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- Metallophthalocyanine intercalated layered double hydroxides as an efficient catalyst for the selective epoxidation of olefin with oxygen
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Varied metallophthalocyanine intercalated layered double hydroxides (LDHs) as bifunctional hybrid catalysts for selective epoxidation have been prepared and characterized. Systematic characterizations suggested the successful intercalation of the metallophthalocyanines into the interlayer of ZnAl LDHs. The synthesized hybrid exhibited excellent catalytic activity in the selective epoxidation of various olefins through O2/isobutaldehyde system. The basicity of the hybrid benefits to the selectivity of epoxide, and the bifunctional roles of the catalyst in the reaction have been discussed and verified by a series of controlled experiments. On the basis of obtained results, a probable mechanism of the epoxidation by the hybrid has been proposed and detailedly investigated. Under the catalysis of metallophthalocyanines intercalated LDHs in the presence of O2/isobutaldehyde, the production of epoxide undergoes two reaction paths. And two types of intermediates, namely acylperoxy radical and peroxyacid, are formed in the reaction, and the former is predominant.
- Zhou, Weiyou,Zhou, Jiacheng,Chen, Yong,Cui, Aijun,Sun, Fu'an,He, Mingyang,Xu, Zhixiang,Chen, Qun
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p. 191 - 200
(2017/06/09)
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- Peroxotantalate-Based Ionic Liquid Catalyzed Epoxidation of Allylic Alcohols with Hydrogen Peroxide
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The efficient and environmentally benign epoxidation of allylic alcohols has been attained by using new kinds of monomeric peroxotantalate anion-functionalized ionic liquids (ILs=[P4,4,4,n]3[Ta(O)3(η-O2)], P4,4,4,n=quaternary phosphonium cation, n=4, 8, and 14), which have been developed and their structures determined accordingly. This work revealed the parent anions of the ILs underwent structural transformation in the presence of H2O2. The formed active species exhibited excellent catalytic activity, with a turnover frequency for [P4,4,4,4]3[Ta(O)3(η-O2)] of up to 285 h?1, and satisfactory recyclability in the epoxidation of various allylic alcohols under very mild conditions by using only one equivalent of hydrogen peroxide as an oxidant. NMR studies showed the reaction was facilitated through a hydrogen-bonding mechanism, in which the peroxo group (O–O) of the peroxotantalate anion served as the hydrogen-bond acceptor and hydroxyl group in the allylic alcohols served as the hydrogen-bond donor. This work demonstrates that simple monomeric peroxotantalates can catalyze epoxidation of allylic alcohols efficiently.
- Ma, Wenbao,Chen, Chen,Kong, Kang,Dong, Qifeng,Li, Kun,Yuan, Mingming,Li, Difan,Hou, Zhenshan
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p. 7287 - 7296
(2017/05/31)
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- One-pot epoxidation of alkenes using aerobic photoperoxidation of toluenes
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We developed an aerobic photooxidative synthesis of peroxybenzoic acids from toluenes using anthraquinone-2-carboxylic acid (AQN-2-CO2H) as a photocatalyst. We also found a one-pot epoxidation reaction of alkenes using 4-tert-butylperoxybenzoic acid produced in situ by aerobic photooxidative synthesis.
- Taguchi, Miyabi,Nagasawa, Yoshitomo,Yamaguchi, Eiji,Tada, Norihiro,Miura, Tsuyoshi,Itoh, Akichika
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supporting information
p. 230 - 232
(2015/12/31)
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- Highly Efficient Epoxidation of Allylic Alcohols with Hydrogen Peroxide Catalyzed by Peroxoniobate-Based Ionic Liquids
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This work reports new kinds of monomeric peroxoniobate anion functionalized ionic liquids (ILs) designated as [A+][Nb=O(O-O)(OH)2] (A+ = tetrapropylammonium, tetrabutylammonium, or tetrahexylammonium cation), which have been prepared and characterized by elemental analysis, HRMS, NMR, IR, TGA, etc. With hydrogen peroxide as an oxidant, these ILs exhibited excellent catalytic activity and recyclability in the epoxidation of various allylic alcohols under solvent-free and ice bath conditions. Interestingly, subsequent activity tests and catalyst characterization together with first-principles calculations indicated that the parent [Nb=O(O-O)(OH)2]- anion has been oxidized into the anion [Nb(O-O)2(OOH)2]- in the presence of H2O2, which constitutes the real catalytically active species during the reaction; this anion has higher activity in comparison to the analogous peroxotungstate anion. Moreover, the epoxidation process of the substrate (allylic alcohol) catalyzed by [Nb(O-O)2(OOH)2]- was explored at the atomic level by virtue of DFT (density functional theory) calculations, identifying that it is more favorable to occur through a hydrogen bond mechanism, in which the peroxo group of [Nb(O-O)2(OOH)2]- serves as the adsorption site to anchor the substrate OH group by forming a hydrogen bond, while OOH as the active oxygen species attacks the C=C bond in substrates to produce the corresponding epoxide. This is the first example of the highly efficient epoxidation of allylic alcohols using a peroxoniobate anion as a catalyst.
- Chen, Chen,Yuan, Haiyang,Wang, Haifeng,Yao, Yefeng,Ma, Wenbao,Chen, Jizhong,Hou, Zhenshan
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p. 3354 - 3364
(2016/07/06)
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- Asymmetric epoxidation of α,β-unsaturated aldehydes catalyzed by a spiro-pyrrolidine-derived organocatalyst
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The asymmetric epoxidation of α,β-unsaturated aldehydes, catalyzed by a spiro-pyrrolidine (SPD)-derived organocatalyst, has been accomplished with good diastereoselectivities (up to dr >20:1) and with high to excellent enantioselectivities (up to 99% ee).
- Xu, Ming-Hui,Tu, Yong-Qiang,Tian, Jin-Miao,Zhang, Fu-Min,Wang, Shao-Hua,Zhang, Shi-Heng,Zhang, Xiao-Ming
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p. 294 - 300
(2017/03/01)
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- Diastereoselective synthesis of 3-acetoxy-4-(3-aryloxiran-2-yl)azetidin-2-ones and their transformation into 3,4-oxolane-fused bicyclic β-lactams
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cis-3-Acetoxy-4-(3-aryloxiran-2-yl)azetidin-2-ones were prepared through a Staudinger [2+2]-cyclocondensation between acetoxyketene and the appropriate epoxyimines in a highly diastereoselective way. Subsequent potassium carbonate-mediated acetate hydrolysis, followed by intramolecular ring closure through epoxide ring opening, afforded stereodefined 3-aryl-4-hydroxy-2-oxa-6-azabicyclo[3.2.0]heptan-7-ones as a novel class of C-fused bicyclic β-lactams. Selective benzylic oxidation of bicyclic N-(4-methoxybenzyl)-β-lactams with potassium persulfate and potassium dihydrogen phosphate provided the corresponding N-aroyl derivatives as interesting leads for further β-lactamase inhibitor development.
- Piens, Nicola,De Craene, Sven,Franceus, Jorick,Mollet, Karen,Van Hecke, Kristof,Desmet, Tom,D'Hooghe, Matthias
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p. 11279 - 11288
(2016/12/07)
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- Effective catalytic oxidation of alcohols and alkenes with monomeric versus dimeric manganese(II) catalysts and t-BuOOH
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Two new Mn(II) complexes, [Mn(C6H5COO)(H2O)(phen)2](ClO4)(CH3OH) (1) and [Mn2(μ-C6H5COO)2(bipy)4]?2(ClO4) (2) (phen = 1,10-phenanthroline; bipy = 2,2′-bipyridine), were synthesized and characterized using UV–visible and infrared spectroscopies and single-crystal X-ray diffraction analyses. Complexes 1 and 2 have six-coordinate octahedral geometry around the Mn(II) centre. Complex 1 is a monomer and consists of a deprotonated monodentate benzoate ligand together with two neutral bidentate amine ligands (phen) and a water molecule. Complex 2 has a dinuclear structure in which two Mn(II) ions share two carboxylate groups, adopting a two-atom bridging mode, and two chelated bipy ligands. Both complexes catalyse the oxidation of alcohols and alkenes in a homogeneous catalytic system consisting of the Mn(II) complex and tert-butyl hydroperoxide (TBHP) in acetonitrile. The system yields good to quantitative conversions of various alkenes and alcohols, such as styrene, ethylbenzene and cyclohexene to their corresponding ketones, and primary alcohols and 1-octanol, 1-heptanol, cyclohexanol, benzyl alcohols and cinnamyl alcohol to their corresponding aldehydes and carboxylic acids. Complexes 1 and 2 exhibit very high activity in the oxidation of cyclohexene to cyclohexanone (ca 80% selectivity) as the main product (ca 94% conversion in 1 h) and of cinnamyl alcohol to cinnamaldehyde (ca 64% selectivity) as the main product (ca 100% conversion in 0.5 h) with TBHP at 70°C in acetonitrile. In addition, optimum reaction conditions were also determined for benzyl alcohol with complexes 1 and 2 and TBHP.
- Kani, Ibrahim,Bolat, Serkan
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p. 713 - 721
(2016/07/19)
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- Selective photocatalytic oxidation of alcohols to corresponding aldehydes in solvent-free conditions using porphyrin sensitizers
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Abstract: In this work, selective and aerobic photooxidation of a range of aromatic, aliphatic and α,β-unsaturated alcohols to corresponding carbonyl compounds has been performed with tetraphenylporphyrin (H2TPP), ClFeTPP and ZnTPP as sensitizers using visible light and in the presence of molecular oxygen in solvent-free conditions. The conversion rates for alcohols oxidations were in the order of free-base porphyrin (H2TPP)?>?metalloporphyrin (ClFeTPP) and (ZnTPP). This method has a wide range of applications, remarkable conversion and product yield in reasonable time, does not include cumbersome work-up, exhibits chemoselectivity, and proceeds under mild reaction conditions. As the matter of oxidation of cycloheptanol and cyclooctanol using H2TPP as photosensitizer, the TON reached up to 1686 and 2464, respectively and selectivity more than 99?%. Graphical abstract: [Figure not available: see fulltext.]
- Mehrabi-Kalajahi, Seyed Saeed,Hajimohammadi, Mahdi,Safari, Nasser
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p. 1069 - 1076
(2016/05/02)
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- Highly efficient transformation of alcohol to carbonyl compounds under a hybrid bifunctional catalyst originated from metalloporphyrins and hydrotalcite
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The development of a highly active and selective catalytic system that is economical, environmentally benign, and easily recoverable is highly desirable. Bifunctional hybrid catalysts originated from metalloporphyrins (MTSPP; M = Co, Fe, and Mn), and hydrotalcite have been synthesized, characterized, and investigated in the aerobic oxidation of alcohols in the presence of isobutyraldehyde. The designed catalysts exhibited excellent activity, broad applicable scope, and good stability in the oxidation. The effect of surface basicity on the catalytic performance has been studied in detail. The research results showed that as well as protecting the metalloporphyrin molecule, the surface basicity of hydrotalcite also contributed to improving the catalytic activity and the selectivity of aldehyde, and a synergistic effect was observed in the catalytic system. A proposed mechanism for the reaction involving the formation of high-valence cobalt-oxo porphyrin intermediate was postulated based on catalytic results and Hammett and H218O experiments.
- Zhou, Wei-You,Tian, Peng,Sun, Fu'An,He, Ming-Yang,Chen, Qun
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p. 105 - 116
(2016/01/26)
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- Asymmetric epoxidation of allylic alcohols catalyzed by vanadium-binaphthylbishydroxamic acid complex
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A vanadium-binaphthylbishydroxamic acid (BBHA) complex-catalyzed asymmetric epoxidation of allylic alcohols is described. The optically active binaphthyl-based ligands BBHA 2a and 2b were synthesized from (S)-1,1'-binaphthyl-2,2'dicarboxylic acid and N-substituted-O-trimethylsilyl (TMS)-protected hydroxylamines via a one-pot, three-step procedure. The epoxidations of 2,3,3-trisubstituted allylic alcohols using the vanadium complex of 2a were easily performed in toluene with a TBHP water solution to afford (2R)-epoxy alcohols in good to excellent enantioselectivities.
- Noji, Masahiro,Kobayashi, Toshihiro,Uechi, Yuria,Kikuchi, Asami,Kondo, Hisako,Sugiyama, Shigeo,Ishii, Keitaro
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supporting information
p. 3203 - 3210
(2015/03/30)
-
- Immobilized V-MIL-101 on modified Fe3O4 nanoparticles as heterogeneous catalyst for epoxidation of allyl alcohols and alkenes
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As a new heterogeneous catalyst, Fe3O4 nanoparticles were prepared and modified with sodium silicate and (3-aminopropyl) trimethoxysilane (APTMS) followed by complexation with V-MIL-101 and designated as Fe3O4@SiO2@APTMS@VMIL-101. It was characterized using FTIR, TEM, and VSM techniques. The Fe3O4@SiO2@APTMS@VMIL-101 was found to successfully catalyze the epoxidation of allyl alcohols and alkenes with tert-butylhydroperoxide (TBHP) in moderate to high yields. The epoxidation of trans-stilbene, norbornen, cyclooctene, geraniol, trans-2-hexene-1ol and 1-octene-3-ol with 100% selectivity is promising. Investigation of the stability and reusability of Fe3O4@SiO2@APTMS@V-MIL-101 revealed the heterogeneity character of the catalyst with no desorption during the course of epoxidation reactions. High yields, clean reactions, ease of catalyst separation and recyclability of the solid catalyst are some advantages of this method.
- Farzaneh, Faezeh,Sadeghi, Yasaman
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p. 275 - 281
(2015/03/03)
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- Function-oriented investigations of a peptide-based catalyst that mediates enantioselective allylic alcohol epoxidation.
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We detail an investigation of a peptide-based catalyst (6) that is effective for the site- (>100 - 1 - 1) and enantioselective epoxidation (86% ee) of farnesol. Studies of the substrate scope exhibited by the catalyst are included, along with an exploration of optimized reaction conditions. Mechanistic studies are reported, including relative rate determinations for the catalyst and propionic acid, a historical perspective, truncation studies, and modeling using NMR data. Our compiled data advances our understanding of the inner workings of a catalyst that was identified through combinatorial means.
- Abascal, Nadia C.,Lichtor, Phillip A.,Giuliano, Michael W.,Miller, Scott J.
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p. 4504 - 4511
(2015/02/19)
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- Unusually Broad Substrate Profile of Self-Sufficient Cytochrome P450 Monooxygenase CYP116B4 from Labrenzia aggregata
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A new member of the CYP116B subfamily - P450LaMO - was discovered in Labrenzia aggregata by genomic data mining. It was successfully overexpressed in Escherichia coli, purified, and subsequently characterized spectroscopically, and its catalytic properties were assessed. Substrate profiling of the P450LaMO revealed that it was a versatile catalyst, exhibiting hydroxylation and epoxidation activities as well as O-dealkylation and asymmetric sulfoxidation activities. Diverse compounds, including alkylbenzenes, aromatic bicyclic molecules, and terpenoids, were shown to be hydroxylated by P450LaMO. Such diverse catalytic activities are uncommon for the bacterial P450s, and the P450LaMO -mediated stereoselective hydroxylation of inactivated C - H bonds - ubiquitous and relatively unreactive in organic molecules - is particularly unusual. The self-sufficient nature of P450LaMO, coupled with its broad substrate range, highlights it as an ideal template for directed evolution towards various applications.
- Yin, Yue-Cai,Yu, Hui-Lei,Luan, Zheng-Jiao,Li, Ren-Jie,Ouyang, Peng-Fei,Liu, Jing,Xu, Jian-He
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p. 2443 - 2449
(2015/03/03)
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- Unusually Broad Substrate Profile of Self-Sufficient Cytochrome P450 Monooxygenase CYP116B4 from Labrenzia aggregata
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A new member of the CYP116B subfamily - P450LaMO - was discovered in Labrenzia aggregata by genomic data mining. It was successfully overexpressed in Escherichia coli, purified, and subsequently characterized spectroscopically, and its catalytic properties were assessed. Substrate profiling of the P450LaMO revealed that it was a versatile catalyst, exhibiting hydroxylation and epoxidation activities as well as O-dealkylation and asymmetric sulfoxidation activities. Diverse compounds, including alkylbenzenes, aromatic bicyclic molecules, and terpenoids, were shown to be hydroxylated by P450LaMO. Such diverse catalytic activities are uncommon for the bacterial P450s, and the P450LaMO -mediated stereoselective hydroxylation of inactivated C-H bonds - ubiquitous and relatively unreactive in organic molecules - is particularly unusual. The self-sufficient nature of P450LaMO, coupled with its broad substrate range, highlights it as an ideal template for directed evolution towards various applications.
- Yin, Yue-Cai,Yu, Hui-Lei,Luan, Zheng-Jiao,Li, Ren-Jie,Ouyang, Peng-Fei,Liu, Jing,Xu, Jian-He
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p. 2443 - 2449
(2015/08/24)
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- Cis-2,6-Bis-(methanolate)-piperidine oxovanadium(V) complexes as catalysts for oxidative alkenol cyclization by tert-butyl hydroperoxide
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cis-2,6-Bis-(methanolate)-piperidine oxovanadium(V) complexes are Lewis acids able to catalyze oxidative cyclization of alkenols by tert-butyl hydroperoxide (TBHP). Terminal dimethyl-substituted (prenyl-type) 4-pentenols bearing an alkyl or a phenyl group in position 1 afford under such conditions 2,5-cis-derivatives of 2-(tetrahydrofuran-2-yl)-2-propanol as major and tetrahydropyran-3-ols as minor products (four examples). Oxidizing 1-phenyl-6-methylhept-5-en-1-ol yields a 75/25-mixture of the derived 2-(tetrahydropyran-2-yl)-2-propanol and an oxepan-3-ol, whereas 2-propenols give epoxides in up to 94% yield. Epoxidizing geraniol by TBHP in the presence of a vanadium catalyst prepared from (2S,6R)-2-diphenylmethanol-6- hydroxymethylpiperidine occurs enantioselectively. Highfield shifts of vanadium-51 resonances upon adding alkyl hydroperoxides to solutions of cis-2,6-bis-(methanolate)-piperidine vanadium(V) complexes point to vanadium(V) tert-butyl peroxy complex formation as key step for activating peroxides.
- D?nges, Maike,Amberg, Matthias,Stapf, Georg,Kelm, Harald,Bergstr??er, Uwe,Hartung, Jens
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p. 120 - 134
(2014/07/08)
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- Synthesis and structure-activity relationship study of substituted caffeate esters as antinociceptive agents modulating the TREK-1 channel
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The TWIK-related K+ channel, TREK-1, has recently emerged as an attractive therapeutic target for the development of a novel class of analgesic drugs. It has been reported that TREK-1 -/- mice were more sensitive than wild-type mice to painful stimuli, suggesting that activation of TREK-1 could result in pain inhibition. Here we report the synthesis of a series of substituted caffeate esters (12a-u) based on the hit compound CDC 2 (cinnamyl 3,4-dihydroxyl-α-cyanocinnamate). These analogs were evaluated for their ability to modulate TREK-1 channel by electrophysiology and for their in vivo antinociceptive activity (acetic acid induced-writhing assay) leading to the identification a series of novel molecules able to activate TREK-1 and displaying potent analgesic activity in vivo.
- Rodrigues, Nuno,Bennis, Khalil,Vivier, Delphine,Pereira, Vanessa,Chatelain, Franck C.,Chapuy, Eric,Deokar, Hemantkumar,Busserolles, Jér?me,Lesage, Florian,Eschalier, Alain,Ducki, Sylvie
-
supporting information
p. 391 - 402
(2014/03/21)
-
- 2,2,2-Trifluoroacetophenone: An organocatalyst for an environmentally friendly epoxidation of alkenes
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A cheap, mild, fast, and environmentally friendly oxidation of olefins to the corresponding epoxides is reported using polyfluoroalkyl ketones as efficient organocatalysts. Namely, 2,2,2-trifluoroacetophenone was identified as an improved organocatalyst for the epoxidation of alkenes. Various olefins, mono-, di-, and trisubstituted, are epoxidized chemoselectively in high to quantitative yields utilizing 2-5 mol % catalyst loading and H2O 2 as the green oxidant.
- Limnios, Dimitris,Kokotos, Christoforos G.
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p. 4270 - 4276
(2014/06/09)
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- Niobium peroxide-catalyzed selective epoxidation of allylic alcohols
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Modified niobium peroxides were prepared and used for catalyzing the epoxidation of allylic alcohols with hydrogen peroxide in the absence of any other solvent under ice bath conditions. Niobium peroxides modified with ionic liquid-type 1-dodecyl- 3-methylimidazolium hydroxide or conventional tetradecyl trimethyl ammonium hydroxide surfactants demonstrated excellent yields (80-99%) for the epoxidation of allylic alcohols to their epoxides even if the reaction was performed without any other solvent at 0°C for 0.5 h. The catalyst characterization demonstrated that the surfactant molecules were anchored on the surface of the niobium catalyst by weak noncovalent interactions. Compared with niobium peroxides, the modified amphiphilic catalysts allowed easier accessibility to hydrophobic substrates and thus demonstrated high reaction rate and excellent recyclability for the epoxidation under mild conditions.
- Chen, Chen,Zhao, Xiuge,Chen, Jizhong,Hua, Li,Zhang, Ran,Guo, Li,Song, Baoning,Gan, Huimei,Hou, Zhenshan
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p. 3231 - 3238
(2015/02/19)
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- Bioresolution production of (2R,3S)-Ethyl-3-phenylglycidate for chemoenzymatic synthesis of the taxol C-13 side chain by galactomyces geotrichum ZJUTZQ200, a new epoxide-hydrolase-producing strain
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A newly isolated Galactomyces geotrichum ZJUTZQ200 strain containing an epoxide hydrolase was used to resolve racemic ethyl 3-phenylglycidate (rac-EPG) for producing (2R,3S)-ethyl-3-phenylglycidate ((2R,3S)-EPG). G. geotrichum ZJUTZQ200 was verified to be able to afford high enantioselectivity in whole cell catalyzed synthesis of this chiral phenylglycidate synthon. After the optimization of the enzymatic production and bioresolution conditions, (2R,3S)-EPG was afforded with high enantioselectivity (e.e.S > 99%, E > 49) after a 8 h reaction. The co-solvents, pH buffer solutions and substrate/cell ratio were found to have significant influences on the bioresolution properties of G. geotrichum ZJUTZQ200. Based on the bioresolution product (2R,3S)-EPG, taxol's side chain ethyl (2R,3S)-3-benzoylamino-2-hydroxy- 3-phenylpropionate was successfully synthesized by a chemoenzymatic route with high enantioselectivity (e.e.S > 95%).
- Wei, Chun,Ling, Jinlong,Shen, Honglei,Zhu, Qing
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p. 8067 - 8079
(2014/07/08)
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- New one-pot procedure for the synthesis of diprotected amino alcohols from unprotected vinyl aziridines
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An unprecedented one-pot reaction that allows the synthesis of diprotected amino alcohols from unprotected vinyl aziridines is reported. The results demonstrate the possibility to use various acyl chlorides in order to obtain differently functionalised fragments. Mechanistic insights are given.
- Righi, Giuliana,Bovicelli, Paolo,Tirotta, Ilaria
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p. 6439 - 6442
(2013/11/19)
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- Determination of the stereochemistry of C-2' and C-3' positions of taxine NA-1 (2'-hydroxytaxine II) by the asymmetric synthesis of the reductive degradation product of its side chain moiety
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The reductive degradation of taxine NA-1 (2'-hydroxytaxine II) with n-Bu4NBH4 gave taxinine A and (-)-3-dimethylamino-3- phenylpropane-1,2-diol (1) in addition to 11,12-dihydrotaxinine A. The relative stereochemistry of (-)-1 was identical with syn-3-dimethylamino-3-phenylpropane- 1,2-diol, (±)-1b, which was synthesized from cis-2,3-epoxy-3- phenylpropan-1-ol, (±)-7. The absolute configuration of (-)-1 was certified by comparison of the specific optical rotation and the spectroscopic data of (-)-1 with those of (+)-1b and (-)-1b, which were enantioselectively synthesized by Sharpless asymmetric epoxidation reaction of cis-cinnamyl alcohol (6), respectively. As the result, the relative and absolute configuration of (-)-1 was same with that of (-)-1b possessing (2R, 3S) configuration. Thus, the absolute configuration of the side chain of taxine NA-1 (2'-hydroxytaxine II) at C-2' and C-3' positions was determined to be (2'R, 3'S).
- Tang, Wanxia,Minato, Hiroshi,Ando, Mariko,Ando, Masayoshi
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experimental part
p. 1697 - 1710
(2012/09/22)
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- Peroxometalates immobilized on magnetically recoverable catalysts for epoxidation
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Magnetically separable catalysts were prepared and employed for the epoxidation of olefins with hydrogen peroxide. In all cases the magnetic core was firstly covered with a silica layer to prevent iron ion-initiated decomposition of hydrogen peroxide. The catalytic active species, an ionic liquid-type peroxotungstate, was then immobilized either by hydrogen bonding (catalyst 1) or by covalent SiO linkage (catalyst 2). In addition to a thorough characterization by FT-IR, XRD, NMR, DRIFT, XPS, and TEM, the catalytic potential was evaluated in the epoxidation of a variety of olefins as well as allylic alcohols. Both catalysts showed essentially a constant activity after at least ten consecutive cycles. On the basis of the research above, a new type of magnetically separable catalyst was constructed by immobilization of lacunary-type phosphotungstate by hydrogen bonding between the sulfonate anion and silanol group on the surface of the core-shell magnetic nanoparticles. After the detailed characterization, the catalyst was used in the epoxidation of a variety of olefins and allylic alcohols and was found to possess high activity, selectivity towards epoxides, and a constant activity after at least ten catalytic recycles without solvent.
- Qiao, Yunxiang,Li, Huan,Hua, Li,Orzechowski, Lars,Yan, Kai,Feng, Bo,Pan, Zhenyan,Theyssen, Nils,Leitner, Walter,Hou, Zhenshan
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p. 1128 - 1138
(2013/03/13)
-
- Rapid aerobic oxidation of alcohols to carbonyl compounds with dioxygen using metallodeuteroporphyrin dimethyl esters as catalysts in the presence of isobutylaldehyde
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A facile biomimetic method for rapid oxidation of alcohols to carbonyl compounds using dioxygen as the primary oxidant catalyzed by metallodeuteroporphyrin dimethyl ester [M(DPDME)] in acetonitrile as the reaction solvent and isobutylaldehyde as cocatalyst has been investigated. Among the M(DPDME) catalysts, where M = Fe(III), Co(II), Mn(III), Ni(II), Cu(II), and Zn(II), cobalt porphyrin was found to be the most active and effective catalyst. The catalytic system was widely used in the oxidation of various alcohols and especially exhibited excellent activity for oxidation of aromatic alcohols under mild conditions. Moreover, M(DPDME) was prepared from an improved facile method by chemical modification of natural hemin and an alternative mechanism for the aerobic oxidation of alcohols has been proposed and discussed.
- Sun, Chengguo,Hu, Bingcheng,Liu, Zuliang
-
experimental part
p. 295 - 303
(2012/07/28)
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- Synthesis of novel magnetic chitosan supported protonated peroxotungstate and its catalytic performance for oxidation
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A novel magnetically recoverable catalyst in which protonated peroxotungstate was immobilized into a network of cross-linked chitosan with a superparamagnetic Fe3O4 core (Fe3O 4-CS/HWO) was prepared, characterized and used in oxidation reactions. With H2O2 as oxidant, a wide range of substrates including olefins, sulfides, amines and allylic alcohols could be oxidized selectively, exhibiting a relatively high utilization percentage of H2O2. Due to the existence of peroxotungstate as well as the magnetic core, both improved catalytic performance and facilitated separation were achieved for the reaction process. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012.
- Zhu, Jie,Wang, Peng Cheng,Lu, Ming
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p. 2587 - 2592
(2013/02/22)
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- Highly efficient oxidative cleavage of carbon-carbon double bond over meso-tetraphenyl cobalt porphyrin catalyst in the presence of molecular oxygen
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Highly efficient and selective carbon-carbon double bond aerobic cleavage of olefins catalyzed by metalloporphyrins was investigated, and carbonyl compounds and epoxide were produced as the main products. CoTPP (cobalt meso-tetraphenyl porphyrin) showed excellent activity for the oxidative cleavage of carbon-carbon double bond by using styrene as model compound, in which the TOF (turnover frequency) and selectivity toward benzaldehyde was obtained with 2×104 h-1 and 86%, respectively.
- Zhou, Xiantai,Ji, Hongbing
-
p. 2103 - 2108,6
(2020/09/09)
-
- Synthesis of arylnaphthalene lignan scaffold by gold-catalyzed intramolecular sequential electrophilic addition and benzannulation
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An intramolecular approach to generate compounds containing an arylnaphthalene lignan scaffold in high yields is presented. It involves a sequential intramolecular electrophilic attack of carbonyl on arylalkyne followed by benzannulation catalyzed by gold salt. AuCl3 in combination with AgSbF6 works better to effect this transformation. Selected products have been converted into arylnaphthalene lactone natural products such as justicidin E, taiwanin C, and retrojusticidin B (Figure presented).
- Gudla, Vanajakshi,Balamurugan, Rengarajan
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experimental part
p. 9919 - 9933
(2012/01/15)
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- Gold-catalysed activation of epoxides: Application in the synthesis of bicyclic ketals
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Gold-catalysed generation of diol equivalents from epoxides and their intramolecular reaction with Ca≡C bonds to generate bicyclic ketals is presented. This reaction essentially involves the formation of an acetonide, which subsequently cyclises on the alkyne intramolecularly under gold catalysis conditions. This method could be extended to make optically pure bicyclic ketals. Deuterium incorporation experiments were carried out to ascertain the mechanism of the reaction. Sequential activation of epoxide and alkyne moieties by a gold catalyst in acetone as solvent has been achieved. This strategyhas been employed to synthesise bicyclic ketals from epoxy alkynes. Copyright
- Balamurugan, Rengarajan,Kothapalli, Raveendra Babu,Thota, Ganesh Kumar
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supporting information; experimental part
p. 1557 - 1569
(2011/04/25)
-
- A concise enantioselective synthesis of (+)-goniodiol and (+)-8-methoxygoniodiol via Co-catalyzed HKR of anti-(2SR, 3RS)-3-methoxy-3- phenyl-1, 2-epoxypropane
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A short, enantioselective synthesis of (+)-goniodiol and (+)-8-methoxygoniodiol, cytotoxic styryllactones, has been achieved in high optical purities (99% ee). The strategy employs Co-catalyzed HKR of racemic anti-(2SR, 3RS)-3-methoxy-3-phenyl-1, 2-epoxypropane and Lewis acid-mediated diastereoselective allylation of aldehyde as chiral inducing key reactions.
- Kiran, I.N. Chaithanya,Reddy, R. Santhosh,Suryavanshi, Gurunath,Sudalai, Arumugam
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scheme or table
p. 438 - 440
(2011/03/18)
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- A simple, iron-catalyzed, pyridine-assisted hydrogen peroxide epoxidation system
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A simple and inexpensive system comprised of H2O 2-pyridine-FeCl3 · 6H2O for the catalysis of olefin epoxidation was established. Intriguingly, the reactivity of this system greatly depends on the amounts of pyridine. Various substrates, including aromatic and aliphatic olefins, were epoxidized by this simple system in moderate to excellent yields.
- Jiao, Mingyu,Matsunaga, Hirofumi,Ishizuka, Tadao
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scheme or table
p. 799 - 801
(2011/07/29)
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- Transition metal catalyzed oxidation of Alcell lignin, soda lignin, and lignin model compounds in ionic liquids
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Lignin is a component of lignocellulosic biomass from which important aromatic compounds can potentially be obtained. In the present work, Alcell and soda lignin were dissolved in the ionic liquid 1-ethyl-3-methylimidazolium diethylphosphate (EMIM DEP) and subsequently oxidized using several transition metal catalysts and molecular oxygen under mild conditions. CoCl 2·6H2O in EMIM DEP proved particularly effective for the oxidation. The catalyst rapidly oxidized benzyl and other alcohol functionalities in lignin, but left phenolic functionality and 5-5′, β-O-4 and phenylcoumaran linkages intact, as determined by analysis of various lignin model compounds and ATR-IR spectroscopy. The catalyst system oxidized the alcohol functionality contained in cinnamyl alcohol to form cinnamaldehyde or cinnamic acid or disrupted the double bond to form benzoic acid or an epoxide. The benzyl functionality in veratryl alcohol, a simple non-phenolic lignin model compound, was selectively oxidized to form veratraldehyde at a maximum turnover frequency of 1440 h-1, compared to 10-15 h-1 reported for earlier systems. Phenolic functional groups contained in guaiacol, syringol, and vanillyl alcohol remained intact, although the benzyl alcohol group in the latter was oxidized to form vanillin. Incorporation of strongly bound tetradentate ligands to the catalyst yielded reduced activity relative to those derived from simple metal salts in EMIM DEP. The influence of reaction conditions, such as temperature, oxygen pressure and NaOH loading, were also investigated. The system represents a potential method in a biorefinery scheme to increase the oxygen functionality in lignin prior to depolymerization or additional functionalization of already depolymerized lignin. The Royal Society of Chemistry 2010.
- Zakzeski, Joseph,Jongerius, Anna L.,Weckhuysen, Bert M.
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experimental part
p. 1225 - 1236
(2010/10/05)
-
- Oxidation catalysis of Nb(salan) complexes: Asymmetric epoxidation of allylic alcohols using aqueous hydrogen peroxide as an oxidant
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Several optically active Nb(salan) complexes were synthesized, and their oxidation catalysis was examined. A dimeric μ-oxo Nb(salan) complex that was prepared from Nb(OiPr)5 and a salan ligand was found to catalyze the asymmetric epoxidation of allylic alcohols using a urea-hydrogen peroxide adduct as an oxidant with good enantioselectivity. However, subsequent studies of the time course of this epoxidation and of the relationship between the ee of the ligand and the ee of the product indicated that the μ-oxo dimer dissociates into a monomeric species prior to epoxidation. Moreover, monomeric Nb(salan) complexes prepared in situ from Nb(OiPr)5 and salan ligands followed by water treatment were found to catalyze the epoxidation of allylic alcohols better using aqueous hydrogen peroxide in CHCl3/brine or toluene/brine solution with high enantioselectivity ranging from 83 to 95% ee, except for the reaction of cinnamyl alcohol that showed a moderate ee of 74%. This is the first example of the highly enantioselective epoxidation of allylic alcohols using aqueous hydrogen peroxide as an oxidant.
- Egami, Hiromichi,Oguma, Takuya,Katsuki, Tsutomu
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scheme or table
p. 5886 - 5895
(2010/07/05)
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- Indium-promoted chemo- and diastereoselective allylation of α,β-epoxy ketones with potassium allyltrifluoroborate
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A practical method for the chemo- and diastereoselective allylation of α,β-epoxy ketones has been developed by using the convenient air and moisture stable reagent potassium allyltrifluoroborate. Indium metal was found to promote addition in stoichiometric or catalytic amounts, to afford α,β-epoxyhomoallylic tertiary alcohols in high yields and diastereoselectivities, without competing ring-scission of the epoxide.
- Nowrouzi, Farhad,Janetzko, John,Batey, Robert A.
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supporting information; experimental part
p. 5490 - 5493
(2011/02/27)
-
- Synthesis and catalytic epoxidation potential of oxodiperoxo molybdenum(VI) complexes with 2-hydroxybenzohydroxamate and 2-hydroxybenzoate: The crystal structure of PPh4[MoO(O2)2(HBA)]
-
(PPh4)2[MoO(O2)2(SHAH)] ·H2O and PPh4[MoO-(O2)2(HBA)] (SHAH3 = 2-hydroxybenzohydroxamic acid and HBAH = 2-hydroxybenzoic acid) have been synthesized and characterized by physico-chemical and spectroscopic methods. In addition, the second complex has been structurally characterized by single-crystal X-ray diffraction analysis. We have compared the catalytic activities of these two new complexes, together with the previously reported PPh4[MoO(O2)2(BZ)] (BZH = benzoic acid), with respect to the epoxidation of alkenes. The hydroxamate complex is the most efficient catalyst among the three complexes, showing excellent catalytic activity for the substrates cyclohexene, cyclooctene, cinnamyl alcohol, pent-4-en-1-ol and hex-1-ene. Springer Science+Business Media B.V. 2010.
- Gharah, Narottam,Chattopadhyay, Basab,Maiti, Swarup K.,Mukherjee, Monika
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experimental part
p. 531 - 539
(2011/11/12)
-