- Design and performance of a microstructured peek reactor for continuous poly-l-leucine-catalysed chalcone epoxidation
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The poly-L-leucine (PLL)-catalysed epoxidation of chalcone allows access to highly enantioselective chalcone epoxides. The reaction requires two steps, a deprotonation step where the oxidising reactive species is formed and an epoxidation step where the substrate is epoxidised. In this work, a microstructured SU-8/ PEEK plate flow reactor with a footprint of 110 mm × 85 mm and production rate of ~0.5 g/day was designed. The reactor consists of two micromixer-reactor sections in series. A staggered herringbone micromixer design was employed for efficient mixing, with channel width, height, and length of 0.2, 0.085, and 40 mm respectively. A mathematical model was used to aid the design, and its predictions were compared with experimental results. The deprotonation and epoxidation steps were performed in reaction channels with width and height of 2 and 0.33 mm, while lengths of 450 and 480 mm provided residence times for the two steps of 30 and 16 min, respectively. The effects of operating temperature, reactant and catalyst concentrations, and residence time on reaction performance were investigated. The base case condition (13.47 g/L PLL, 0.132 mol/L H2O2,0.0802 mol/L chalcone, 0.22 mol/L DBU) was found to be optimal, achieving a conversion of 86.7% and enantioselectivity of 87.6%. Comparison between model and experimental results provided insight into the reaction mechanism as well as reactor design. It showed quantitative and, in some cases, qualitative differences. These were attributed to the simplicity of the kinetic model, bubble formation from peroxide decomposition and their stagnation in the rectangular channels, and high viscosity of catalyst solution which may have affected mixing performance.
- Kee, Suet-Ping,Gavriilidis, Asterios
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- Chiral amplification by polypeptides and its relevance to prebiotic catalysis
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Polyleucine prepared from scalemic Leu-NCA monomers, shows high chiral amplification in the Julia-Colonna epoxidation of chalcone.
- Kelly, David H.,Meek, Alastair,Roberts, Stanley M.
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- Reaction in biphasic water/organic solvent system in the presence of surfactant: Inverse phase transfer catalysis versus interfacial catalysis
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Unexpected results obtained during the study of the influence of surfactant concentration on chalcone epoxidation by H2O2 in a water/heptane two-phase system in the presence of a surfactant (DTAB) led us to reconsider the catalytic mechanism of this reaction. Two stirring rates experiments, either low speed (i.e, 100 rpm) or high speed (i.e. 1200 rpm), lead us to discuss kinetic results on the basis of two competitive catalytic processes: an Inverse Phase Transfer Catalysis (IPTC) or an Interfacial Catalysis (IC).
- Boyer, Bernard,Hambardzoumian, Araik,Roque, Jean-Pierre,Beylerian, Norair
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- The effect of the primary structure of the polypeptide catalyst on the enantioselectivity of the Julia-Colonna asymmetric epoxidation of enones
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Epoxidation of chalcone (1), using basic hydrogen peroxide, catalysed by polypeptides with defined primary structures demonstrates that the residues in the chain near to the N-terminus determine the stereochemical outcome of the reaction.
- Bentley,Flood,Roberts,Skidmore,Smith,Smith
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- Juliá-Colonna asymmetric epoxidation in a continuously operated chemzyme membrane reactor
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Two novel soluble polymer-bound oligo-L-leucines 2 and 5, Which can be retained by a membrane reactor system, have been prepared and used as catalysts for the continuously operated asymmetric epoxidation of chalcone. The optimized batch reaction condition
- Tsogoeva, Svetlana B.,W?ltinger, Jens,Jost, Carsten,Reichert, Dietmar,Kühnle, Adolf,Krimmer, Hans-Peter,Drauz, Karlheinz
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- Design of a stabilized short helical peptide and its application to catalytic enantioselective epoxidation of (E)-chalcone
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Stabilized short helical heptapeptides containing a combination of an α-aminoisobutyric acid as a helical promoter and l/d-serine derivatives to produce cross-linked units were synthesized. The cyclic peptide R 3,7R-2, which had d-se
- Yamagata, Nanako,Demizu, Yosuke,Sato, Yukiko,Doi, Mitsunobu,Tanaka, Masakazu,Nagasawa, Kazuo,Okuda, Haruhiro,Kurihara, Masaaki
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- Highly enantioselective enone epoxidation catalyzed by short solid phase-bound peptides: dominant role of peptide helicity.
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The series of L-Leu 1-20-mers, peptides carrying 1-5 N-terminal Gly residues, and oligomers of (S)-beta(3)-Leu and (1R,2R)-2-aminocyclohexanecarboxylic acid were synthesized on TentaGel S NH(2). Five L-Leu residues were found sufficient to catalyze the Ju
- Berkessel,Gasch,Glaubitz,Koch
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- Asymmetric C-C Bond Forming Reactions by Chiral Crown Catalysts; Darzens Condensation and Nitroalkane Addition to the Double Bond
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A new, efficient crown ether 1 anellated to a sugar derivative has been prepared which shows significant asymmetric induction as phase transfer catalyst in the Michael addition of 2-nitropropane to chalcone (60% ee for the S antipode) and in the Darzens c
- Bakó, Péter,Sz?ll?sy, áron,Bombicz, Petra,T?ke, László
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- Reaction of a polycyclic diketone with lithiated methoxyallene: Synthesis of new functionalized cage compounds
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Syntheses of several new functionalized cage compounds are described. The key steps of the reaction sequence are addition of lithiated methoxyallene 2 to cage diketone 1, preparation of dehydrated intermediate 5, and its ozonolysis leading to diester 7. Alternatively, 5 could be hydrolyzed to provide cage compound 6 with a bisenone subunit. Via diol 9 chiral crown ether 11 could be prepared in low yield. A first stereoselective epoxidation of chalcone 12 with tert-butyl hydroperoxide in the presence of 11 gave the epoxide 13 in reasonable yield, but with a low level of enantioselectivity.
- Zimmer, Reinhold,Taszarek, Maurice,Schefzig, Luise,Reissig, Hans-Ulrich
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- Synthesis of d-mannitol-based crown ethers and their application as catalyst in asymmetric phase transfer reactions
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A few new d-mannitol-based monoaza-15-crown-5 type chiral lariat ethers and 18-crown-6 type macrocycles were synthesized. These crown compounds were used as phase transfer catalysts in asymmetric Michael addititons and in a Darzens condensation under mild conditions to afford the corresponding products in a few cases in good to excellent enantioselectivities. In the Michael addition of diethyl acetoxymalonate to trans-chalcone, in the addition of diethyl acetamidomalonate to ?-nitrostyrene, in the reaction of diethyl bromomalonate with benzylidene malononitriles, in the cyclopropanation reaction of diethyl bromomalonate and 2-benzylidene-1,3-indandione, and in the Darzens condensation of α-chloroacetophenone with benzaldehyde, maximum enantioselectivities of 39%, 65%, 99%, 56%, and 62%, respectively, were obtained in the presence of the d-mannitol-based macrocycles as the catalysts.
- Nemcsok, Tamás,Rapi, Zsolt,Keglevich, Gy?rgy,Grün, Alajos,Bakó, Péter
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- Theoretical and experimental investigations of the enantioselective epoxidation of olefins catalyzed by manganese complexes
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The enantioselective epoxidation of olefin by MnII(R,R-PMCP)(OTf)2, H2O2 and H2SO4 was explored by DFT calculations and experiments. Theoretical results suggest that [MnV(O)(R,R-PMCP)(SO4)]+ species with a triplet ground spin state serves as the active species for the olefin epoxidation. It can be generated by the H2SO4 assisted O-O heterolysis of MnIII(OOH) species. MnIII-persulfate is also involved in this system, but it cannot promote the olefin epoxidation directly, preferring instead to transform into MnV(O). Actually, the asymmetric epoxidation reactions with H2O2/H2SO4 or Oxone provide similar enantioselectivity in the presence of manganese catalyst. These observations further support the transformation of MnIII-persulfate to MnV(O) species.
- Lin, Jin,Sun, Wei,Tian, Jing,Wang, Fang,Wang, Yong,Zhang, Jisheng
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- Dimeric samarium(III) alkoxides bearing N2O2 tetradentate Schiff bases and their utility for the catalytic epoxidation of trans-chalcone
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Two anhydrous, dimeric samarium(III) complexes bearing a bulky μ-alkoxide (diphenylmethoxide) ligand and different "saturated" tetradentate Schiff bases {bis-5,5′-(1,3-propanediyldiimino)-2,2-dimethyl- 4-hexene-3-onato and bis-5,5′-(2,2-dimethyl-1,3-propanediyldiimino)-2,2- dimethyl-4-hexene-3-onato} were synthesized and fully characterized. The complexes differ only in alkyl substitution at the three-carbon amino linker between the ketoiminato halves, with one having a CH2 group and the other a C(CH3)2 substituent along the free-ligand idealized mirror plane. Both metal-containing molecules were isolated in high-yields from direct alcoholysis of the corresponding 5-coordinate, mononuclear complexes and their catalytic activity for the epoxidation of 1,3-diphenyl propenone (trans-chalcone), an α,β-unsaturated ketone, investigated.
- Schuetz, Steven A.,Bowman, Elizabeth A.,Silvernail, Carter M.,Day, Victor W.,Belot, John A.
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- Catalytic asymmetric epoxidation of chalcones under poly(ethylene glycol)-supported Cinchona ammonium salt catalyzed conditions
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Dimeric cinchonine, cinchonidine, and quinine have been anchored (via nitrogen) to long linear PEG chains to afford soluble polymer-supported chiral ammonium salts, which were employed as phase-transfer catalysts in the asymmetric epoxidation of chalcones
- Lv, Jian,Wang, Xin,Liu, Juyan,Zhang, Liping,Wang, Yongmei
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- Catalytic epoxidation of enones mediated by zinc alkylperoxide/ tert- buooh systems
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The epoxidation of enones by zinc alkylperoxides is a challenging task receiving considerable attention in contemporary research; however, until now no well-defined zinc alkylperoxide based systems have been described. Here, a new catalytic method of epoxidation of enones in the presence of zinc alkylperoxides supported by N,N-bidentate ligands and tert-butyl hydroperoxide is reported. A new dimeric zinc alkylperoxide complex supported by an aminotroponiminate ligand is also presented. The studied catalytic systems show high activity in the epoxidation of trans-chalcone, and in the case of a chiral catalyst with the (S,S)-N,N′-bis(1-phenylethyl)aminotroponiminate ligand a moderate enantioselectivity was achieved.
- Kubisiak, Marcin,Zelga, Karolina,Justyniak, Iwona,Tratkiewicz, Ewa,Pietrzak, Tomasz,Keeri, Abdul R.,Ochal, Zbigniew,Hartenstein, Larissa,Roesky, Peter W.,Lewinski, Janusz
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- Mechanistic Insights into the Enantioselective Epoxidation of Olefins by Bioinspired Manganese Complexes: Role of Carboxylic Acid and Nature of Active Oxidant
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Bioinspired manganese and iron complexes bearing nonporphyrinic tetradentate N4 ligands are highly efficient catalysts in asymmetric oxidation reactions by hydrogen peroxide (H2O2), in which carboxylic acid is employed as an essentia
- Du, Junyi,Miao, Chengxia,Xia, Chungu,Lee, Yong-Min,Nam, Wonwoo,Sun, Wei
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- Structure and catalytic activity of some soluble polyethylene glycol-peptide conjugates
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Soluble catalysts for the Juliá-Colonna asymmetric epoxidation reaction have been constructed in three different ways, using NH 2-PEG-OMe as the support system: suitable solvents have been identified and it is shown that the degree of helicity
- Kelly, David R.,Bui, Tam T. T.,Caroff, Eva,Drake, Alex F.,Roberts, Stanley M.
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- Inverse phase transfer catalysis versus interfacial catalysis. Effect of medium stirring in the epoxidation reaction of chalcone by hydrogen peroxide
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The epoxidation of chalcone by H2O2 has been investigated in a water-heptane two-phase system in the presence of a surfactant (dodecyltrimethylammonium bromide; DTAB) in order to analyse the role played by the rate and the type of stirring (magnetic and sonication). Under these conditions two catalytic processes have been proved to intervene: an inverse phase transfer catalysis (IPTC) or an interfacial catalysis (IC). This latter process appears to be very sensitive to stirring efficiency.
- Boyer, Bernard,Hambardzoumian, Araik,Roque, Jean-Pierre,Beylerian, Norair
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- Efficient asymmetric epoxidation of α,β-unsaturated ketones using a soluble triblock polyethylene glycol-polyamino acid catalyst
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Equation presented Polyethlene glycol (PEG)-bound poly-L-leucine acts as a THF-soluble catalyst for the Julia-Colonna asymmetric epoxidation of enones. Excellent enantioselectivities may be obtained even with short chain length polyleucine. FT-IR investigations have determined that the catalytically active polyleucine components of these copolymers have an α-helical structure.
- Flood, Robert W.,Geller, Thomas P.,Petty, Sarah A.,Roberts, Stanley M.,Skidmore, John,Volk, Martin
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- Synthesis of N-containing heterocycles via mechanochemical grinding and conventional techniques
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Mechano heterocyclic chemistry is a recent quickly growing technique draws the attention of hetrocyclic chemists towards the use of grindstone technique in a solvent free green efficient clean synthesis of many heterocyclic systems. α,β-Epoxy ketones were used as a unique scaffold for synthesis of stable hydroxyazoles. The key advantage of grinding technique over the conventional thermal technique includes its simple, solvent free conditions, as well as facile work up with high yield economy. It is also successful in achieving three of the green chemistry objectives of a solvent free, high atom economy, save energy thus combining the features of both economic and environmental advantages.
- Fahmy, Amin F.M.,El-Sayed, Amira A.,Hemdan, Magdy M.,Hassaballah, Aya I.,Mabied, Ahmed F.
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- First structurally authenticated zinc alkylperoxide: A model system for the epoxidation of enones
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β-Ketoimine ligands stabilize zinc compounds: The dimeric zinc alkylperoxide [{(LL)ZnOOEt}2] (where LE = HC{(CMe)(2,6-iPr 2C6H3N)}2) has been prepared and structurally characterized (see picture, Zn green, N blue, O red, C gray). This compound, which is formed by the insertion of dioxygen into the Zn-Et bond, is very active in the epoxidation of enones.
- Lewinski, Janusz,Ochal, Zbigniew,Bojarski, Emil,Tratkiewicz, Ewa,Justyniak, Iwona,Lipkowski, Janusz
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- Cooxidation of enones during reaction of superoxide with acidic aromatic amines
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Enones can be epoxidized by O2-. in the presence of various compounds having an acidic >NH group. Cyclic voltammetry and ESR study show that O2-. was disproportionated into H2O2 and O2 by these compounds. Furthermore, H2O2 was deprotonated by unreacted O2-. and HOO- was formed, which is widely known to be the effective oxidant in the epoxidation of enones. This confirms the strong basicity of O2-. in aprotic media, and we propose an alternative scheme for the Haber-Weiss reaction in the absence of metal ions.
- Takizawa,Nagano,Hirobe
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- The Julia-Colonna asymmetric epoxidation reaction of chalcone catalyzed by length defined oligo-L-leucine: Importance of the N-terminal functional group and helical structure of the catalyst in the asymmetric induction
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Catalysts, oligo-L-leucine, for the Julia-Colonna asymmetric epoxidation of chalcone with defined degrees of polymerization were prepared by a stepwise elongation method. The yield and enantioselectivity in the epoxidation increased with the degree of polymerization of the catalyst. The presence of an unprotected amine moiety at the N-terminus proved to be essential for high asymmetric induction. The IR characteristic absorption bands (the amide I region) of the catalysts suggested that helical structure in the catalyst is related to asymmetric induction.
- Takagi,Manabe,Shiraki,Yoneshige,Hiraga,Kojima,Ohkata
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- Enantioselective epoxidation of chalcone catalysed by the artificial enzyme poly-L-leucine: Kinetic mechanism
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An insight into the kinetics, mechanism and optimum reaction conditions of the Julia-Colonna enantioselective epoxidation has been gained using a soluble polyleucine catalyst (PLL), chalcone as the substrate, and hydrogen peroxide (HOO-) as the
- Carrea, Giacomo,Colonna, Stefano,Meek, Alastair D.,Ottolina, Gianluca,Roberts, Stanley M.
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- Electrospray-assisted laser desorption/ionization mass spectrometry for continuously monitoring the states of ongoing chemical reactions in organic or aqueous solution under ambient conditions
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Electrospray-assisted laser desorption/ionization (ELDI) combined with mass spectrometry allows chemical and biochemical compounds to be characterized directly from hydrophilic and hydrophobic organic solutions mixed with carbon powders under ambient conditions. Organic and inorganic compounds dissolved in polar or nonpolar solvent such as methanol, tetrahydrofuran, ethyl acetate, toluene, dichloromethane, or hexane can be detected using this ambient ionization technique without prior pretreatment. We have used this technique to monitor the progress in several ongoing reactions: the epoxidation of chalcone in ethanol, the chelation of ethylenediaminetetraacetic acid with copper and nickel ions in aqueous solution, the chelation of 1,10-phenanthroline with iron(II) in methanol, and the tryptic digestion of cytochrome c in aqueous solution. Liquid-ELDI analyses simply require irradiation of the surface of the sample solution with a pulsed ultraviolet laser; the laser energy is adsorbed by the carbon powder presuspended in the sample solution; the absorbed laser energy is then transferred to the surrounding solvent and to the analyte molecules in the solution, leading to their desorption; the desorbed gaseous analyte molecules are then postionized within an electrospray (ESI) plume to generate ESI-like analyte ions.
- Cheng, Chi-Yuan,Yuan, Cheng-Hui,Cheng, Sy-Chyi,Huang, Min-Zong,Chang, Hui-Chiu,Cheng, Tien-Lu,Yeh, Chen-Sheng,Shiea, Jentaie
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- Kinetics of chalcone oxidation by peroxide anion catalysed by poly-L-leucine
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An insight into the kinetics, mechanism and optimum reaction conditions of the Julia-Colonna epoxidation has been gained using a soluble polyleucine catalyst.
- Carrea, Giacomo,Colonna, Stefano,Meek, Alastair D.,Ottolina, Gianluca,Roberts, Stanley M.
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- Enantioselective epoxidation of chalcones and naphthoquinones mediated by (+)-norcamphor-derived hydroperoxide
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(+)-Norcamphor-derived hydroperoxide has been employed in the asymmetric epoxidation of electron poor alkenes such as trans-chalcones and naphthoquinones. Optimization of the reaction conditions required the employment of n-BuLi/THF at -20°C to achieve ees up to 58%. The epoxide of vitamin K3 has now been obtained with the best up to now reported value of enantioselectivity (51% ee).
- Lattanzi, Alessandra,Cocilova, Maria,Iannece, Patrizia,Scettri, Arrigo
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- Zinc-mediated asymmetric epoxidation of α-enones
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A new efficient method for the asymmetric epoxidation of α-enones with oxygen in the presence of diethylzinc and a chiral amino alcohol is presented. The epoxidation proceeds in moderate to excellent yields, complete diastereoselectivity and enantiomeric
- Enders, Dieter,Zhu, Jiqun,Kramps, Laurenz
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- High-Spin and Low-Spin Perferryl Intermediates in Fe(PDP)-Catalyzed Epoxidations
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Two bioinspired hydroxo-bridged diferric complexes 6 and 7 with N4-donor ligands of the PDP type (PDP=N,N′-bis(pyridin-2-ylmethyl)-2,2′-bipyrrolidine), differing by substituents at the pyridine rings (4-NMe2 in 7 vs. 3,5-Me2-4-OMe in 6), efficiently catalyze the enantioselective alkene epoxidation with H2O2 and peracetic acid in the presence of a carboxylic acid additive (up to 99 catalyst turnover numbers, TON, toward epoxide, up to 94 % ee). Catalyst systems based on complex 7 display the high-spin perferryl intermediate 7 aAA (S=3/2, g1, g2=3.69, g3=1.96), whereas catalyst systems based on complex 6 exhibit the low-spin perferryl intermediate 6 aAA (S=1/2, g1=2.07, g2=2.01, g3=1.96). The S=3/2 and the S=1/2 intermediates directly react with cyclohexene and cyclohexane at low temperatures (?40 °C and ?85 °C, respectively). The catalyst systems, exhibiting less reactive intermediate 7 aAA, demonstrate higher enantioselectivity (% ee) in the epoxidation of chalcone. The origin of the unprecedented high-spin state of the perferryl intermediate is discussed.
- Zima, Alexandra M.,Lyakin, Oleg Y.,Bryliakov, Konstantin P.,Talsi, Evgenii P.
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- Synthesis and a Catalytic Study of Diastereomeric Cationic Chiral-at-Cobalt Complexes Based on (R, R)-1,2-Diphenylethylenediamine
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Here we report the first synthesis of two diastereomeric cationic octahedral Co(III) complexes based on commercially available (R,R)-1,2-diphenylethylenediamine and salicylaldehyde. Both diastereoisomers with opposite chiralities at the metal center (Λ and Δconfigurations) were prepared. The new Co(III) complexes possessed both acidic hydrogen-bond donating (HBD) NH moieties and nucleophilic counteranions and operate as bifunctional chiral catalysts for the challenging kinetic resolution of terminal and disubstituted epoxides by the reaction with CO2 under mild conditions. The highest selectivity factor (s) of 2.8 for the trans-chalcone epoxide was achieved at low catalyst loading (2 mol %) in chlorobenzene, which is the best achieved result currently for this type of substrate.
- Emelyanov, Mikhail A.,Stoletova, Nadezhda V.,Smol'Yakov, Alexander F.,Il'In, Mikhail M.,Maleev, Victor I.,Larionov, Vladimir A.
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supporting information
p. 13960 - 13967
(2021/09/11)
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- Asymmetric Epoxidation of Enones Promoted by Dinuclear Magnesium Catalyst
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Asymmetric synthesis with cheaper and non-toxic alkaline earth metal catalysts is becoming an important and sustainable alternative to conventional catalytic methodologies mostly relying on precious metals. In spite of some sustainable methods for enantioselective epoxidation of enones, the development of a well-defined and efficient catalyst based on magnesium complexes for these reactions is still a challenging task. In this perspective, we present the application of chiral dinuclear magnesium complexes for asymmetric epoxidation of a broad range of electron-deficient enones. We demonstrate that the in situ generated magnesium-ProPhenol complex affords enantioenriched oxiranes in high yields and with excellent enantioselectivities (up to 99% ee). Our extensive study verifies the literature data in this area and provides a step forward to better understand the factors controlling the oxygenation process. Elaborated catalyst offers mild reaction conditions and a truly wide substrate scope. (Figure presented.).
- Jaszczewska-Adamczak, Joanna A.,Mlynarski, Jacek
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supporting information
p. 4247 - 4255
(2021/07/17)
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- Asymmetric epoxidation of α,β-unsaturated ketones catalyzed by rare-earth metal amides RE[N(SiMe3)2]3with chiral TADDOL ligands
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The catalytic asymmetric epoxidation of α,β-unsaturated ketones by tert-butylhydroperoxide (TBHP) has been well established using rare-earth metal amides RE[N(SiMe3)2]3 (RE = La(1), Nd(2), Sm(3), Y(4), Yb(5)) with chiral TADDOL ligands. It was found that
- Shan, Haiwen,Lu, Chengrong,Zhao, Bei,Yao, Yingming
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supporting information
p. 1043 - 1053
(2021/01/25)
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- Asymmetric epoxidation of α,β-unsaturated ketones via an amine-thiourea dual activation catalysis
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A simple asymmetric epoxidation method is developed to effectively synthesize chiral α-carbonyl epoxides through an amine-thiourea dual activation catalysis. In this method, TBHP, as an oxidant, determined the reaction rate, and the chiral amine-thiourea catalyst effectively controlled the stereoselectivity of the reaction, and KOH promoted deprotonation. 22 examples of α,β-unsaturated ketones with various substituent groups are smoothly converted into α-carbonyl epoxides with moderate to excellent enantiomeric excess.
- Zhang, Lu-Wen,Wang, Li,Ji, Nan,Dai, Si-Yang,He, Wei
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supporting information
(2021/03/15)
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- Efficient Aliphatic C-H Oxidation and C═C Epoxidation Catalyzed by Porous Organic Polymer-Supported Single-Site Manganese Catalysts
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Bioinspired manganese complexes have emerged over recent decades as attractive catalysts for a number of selective oxidation reactions. However, these catalysts still suffer from oxidative degradation. In the present study, we prepared a series of porous Mn-N4 catalysts in which the catalytic units are embedded in the skeleton of porous organic polymers (POPs). These POP-based manganese catalysts demonstrated high reactivity in the oxidation of aliphatic C-H bonds and the asymmetric epoxidation of olefins. Furthermore, these catalysts could be readily recycled and reused due to their heterogeneous nature. Morphological characterization revealed that the Mn-N4 complex was individually distributed over a porous polymer network. Remarkably, the nature of the single-site catalyst prevented oxidative degradation during the reaction. The present work has thus developed a successful approach for bioinspired single-site manganese catalysts in which the oxidation reaction is confined to a specific channel in an enzyme-like mode.
- Wang, Bingyang,Lin, Jin,Sun, Qiangsheng,Xia, Chungu,Sun, Wei
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p. 10964 - 10973
(2021/09/08)
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- Asymmetric Epoxidation of Olefins Catalyzed by Substituted Aminobenzimidazole Manganese Complexes Derived from L-Proline
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A family of manganese complexes [Mn(Rpeb)(OTf)2] (peb=1-(1-ethyl-1H-benzo[d]imidazol-2-yl)-N-((1-((1-ethyl-1H-benzo[d]imidazol-2-yl)methyl) pyrrolidin-2-yl)methyl)-N-methylmethanamine)) derived from L-proline has been synthesized and characterized, where R refers to the group at the diamine backbone. X-ray crystallographic analyses indicate that all the manganese complexes [Mn(Rpeb)(OTf)2] exhibit cis-α topology. These types of complexes are shown to catalyze the asymmetric epoxidation of olefins employing H2O2 as a terminal oxidant with up to 96% ee. Obviously, the R group of the diamine backbone can influence the catalytic activity and enantioselectivity in the asymmetric epoxidation of olefins. In particular, Mn(i-Prpeb)(OTf)2 bearing an isopropyl arm, cannot catalyze the epoxidation reaction with H2O2 as the oxidant. However, when PhI(OAc)2 is used as the oxidant instead, all the manganese complexes including Mn(i-Prpeb)(OTf)2 can promote the epoxidation reactions efficiently. Taken together, these results indicate that isopropyl substitution on the Rpeb ligand inhibits the formation of active Mn(V)-oxo species in the H2O2/carboxylic acid system via an acid-assisted pathway.
- Lin, Jin,Sun, Wei,Tian, Jing,Xia, Chungu,Zhang, Jisheng
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- Synthesis of methyl 4,6-di-o-ethyl-α-d-glucopyranoside-based azacrown ethers and their effects in asymmetric reactions
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Carbohydrate-based crown ethers have been reported to be able to generate asymmetric induction in certain reactions. Previously, it was proved that the monosaccharide unit, the anomeric substituent, and the sidearm could influence the catalytic activity of the monoaza-15-crown-5 macrocycles derived from sugars. In order to gain information about the effect of the flexibility, 4,6-di-O-ethyl-glucoside-based crown compounds were synthesized, and their efficiency was compared to the 4,6-O-benzylidene analogues. It was found that the absence of the two-ring annulation has a negative effect on the enantioselectivity in liquid-liquid two-phase reactions: in the Darzens condensation of 2-chloroacetophenone and in the epoxidation of chalcone. The same trend was observed in the solid-liquid phase Michael addition of diethyl acetamidomalonate. Surprisingly, in the solid-liquid phase cyclopropanation of benzylidenemalononitrile, one of the new catalysts was highly enantioselective (99% ee).
- Bagi, Péter,Bakó, Péter,Heged?s, László,Orbán, István,Rapi, Zsolt,Varga, Bertalan
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- One-pot cascade synthesis of α-diketones from aldehydes and ketones in water by using a bifunctional iron nanocomposite catalyst
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A new methodology for the synthesis of α-diketones was reportedviaa one-pot cascade process from aldehydes and ketones catalyzed by a bifunctional iron nanocomposite using H2O2as a green oxidant in water. The one-pot strategy showed excellent catalytic stability, comprehensive suitability of substrates and important practical utility for directly synthesizing biologically active and medicinally valuable N-heterocyclesviaan intermittent process.
- Song, Tao,Zhou, Xin,Wang, Xiaoxue,Xiao, Jianliang,Yang, Yong
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p. 1955 - 1959
(2021/03/26)
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- A high-yielding protocol for the synthesis of 4,5-diarylpyrimidin-2-amine derivatives from chalcones
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A novel, high yielding and versatile protocol was achieved for the synthesis of 4,5-diaryl-2-pyrimidinamine derivatives from chalcones. The synthesis was accomplished by converting the chalcones into 3-chloro-2,3-diaryl-2-propen-1-ones followed by subsequent reaction with amidine derivatives.
- Devaky, K. S.,George, Scholly Clair,Kooramatom Unni, Krishnaraj,Menon, Prasanth K.,Thomas, Sajesh P.
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- Peroxide- And transition metal-free electrochemical synthesis of α,β-epoxy ketones
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A novel electrochemical method for the synthesis of α,β-epoxy ketones is reported. With KI as the redox mediator, methyl ketones reacted with aldehydes under peroxide- and transition metal-free electrolytic conditions and afforded α,β-epoxy ketones in one pot (36 examples, 52-90% yield). This safe and environmental-friendly method has a broad substrate scope and can readily provide a variety of α,β-epoxy ketones in gram-scales for evaluation of their anti-cancer activities.
- Zhang, Mengxun,Chen, Tie,Fang, Shisong,Wu, Weihua,Wang, Xin,Wu, Haiqiang,Xiong, Yongai,Song, Jun,Li, Chenyang,He, Zhendan,Lee, Chi-Sing
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supporting information
p. 2481 - 2486
(2021/04/02)
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- Synthesis and characterization of 1,3,5-triarylpyrazol-4-ols and 3,5-diarylisoxazol-4-ols from chalcones and theoretical studies of the stability of pyrazol-4-ol toward acid dehydration
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The synthesis of diverse pyrazol-4-ol and isoxazole-4-ol heterocycles involving only 3 reaction steps is reported in this study. However, the synthesis of carboxamide pyrazol-4-ol has failed in the conditions used in the synthesis, acid methanol solution. The carboxamide pyrazol-4-ol decomposes via dehydration, forming the respective pyrazol. Theoretical calculations were used to elucidate the dehydration reaction. We have found a mechanism for acid-catalyzed dehydration that can explain the experimental observations. The calculated free energy profile for acid-catalyzed dehydration of the carboxamide pyrazol-4-ol and phenylpyrazole-4-ol point out that the latter is more stable in relation dehydration, with a dehydration rate 100 times smaller in acid methanol solution.
- Cipagauta Esquivel, Edna Carolina,Rufino, Virgínia Camila,Trindade Nogueira, Matheus Henrique,Carbonaro Souza, Ana Carolina,Pliego Júnior, Josefredo Rodriguez,Valle, Marcelo Siqueira
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- Highly Enantioselective Epoxidation of α,β-Unsaturated Ketones Using Amide-Based Cinchona Alkaloids as Hybrid Phase-Transfer Catalysts
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A series of 20 one chiral epoxides were obtained with excellent yields (up to 99%) and enantioselectivities (up to >99% ee) using hybrid amide-based Cinchona alkaloids. Our method is characterized by low catalyst loading (0.5 mol %) and short reaction times. Moreover, the epoxidation process can be carried out in 10 cycles, without further catalyst addition to the reaction mixture. This methodology significantly enhance the scale of the process using very low catalyst loading.
- Jurczak, Janusz,Majdecki, Maciej,Tyszka-Gumkowska, Agata
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supporting information
(2020/11/13)
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- Ligand regulation for manganese-catalyzed enantioselective epoxidation of olefins without acid
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A novel manganese catalyst bearing an l-proline-derived N4 ligand has been developed for enabling acid-free asymmetric epoxidation of olefins with tert-butyl hydroperoxide as the oxidant. A variety of olefins that are well-matched in size with the ligand
- Xu, Daqian,Sun, Qiangsheng,Lin, Jin,Sun, Wei
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p. 13101 - 13104
(2020/11/09)
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- Synthesis of xylal- and arabinal-based crown ethers and their application as asymmetric phase transfer catalysts
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New xylal- and arabinal-based monoaza-15-crown-5 ethers were synthesized starting from l- and d-xylose, and l- and d-arabinose, respectively. These monosaccharide-based chiral macrocycles were tested as phase transfer catalysts in a few asymmetric reactions. The xylal-based crown compounds proved to be efficient catalysts in a few liquid-liquid phase reactions. The epoxidation of trans-chalcone and the Darzens condensation of α-chloroacetophenone with benzaldehyde took place with complete diastereoselectivity and up to 77% ee and 58% ee, respectively. It was found that the substituents in the aromatic ring of the chalcone and the α-chloroacetophenone had an influence on the enantioselectivity. The highest ee values were obtained in the epoxidation of 4-chlorochalcone (81% ee) and in the reaction of a 2-naphthyl analogue (96% ee), while in the Darzens condensation of 4-phenyl-α-chloroacetophenone with benzaldehyde, a maximum ee of 91% was detected. The configuration of the monosaccharide unit in the crown ring influenced the absolute configuration of the epoxyketones synthesized.
- Nemcsok, Tamás,Rapi, Zsolt,Bagi, Péter,Keglevich, Gy?rgy,Bakó, Péter
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p. 107 - 119
(2019/11/16)
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- Selective oxidative hydroxylation of arylboronic acids by colloidal nanogold catalyzed in situ generation of H2O2 from alcohols under aerobic conditions
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Selective hydroxylation of arylboronic acids was achieved through PVP (polyvinylpyrrolidone)-stabilized nanogold catalyzed in situ generated H2O2 formed by the oxidation of an alcoholic solvent under aerobic conditions. The synthetic application of in situ generated H2O2 was investigated through aerobic epoxidation of (E)-chalcone.
- Sakurai, Hidehiro,Vinsen, Yuta Uetake
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p. 299 - 301
(2020/04/27)
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- N-Heterocyclic Carbene Catalyzed Synthesis of Trisubstituted Epoxides via Tandem Amidation/Epoxidation Sequence
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A tandem amidation/epoxidation sequence between various substituted chalcones and N,N-dimethylformamide (DMF) for the synthesis of trisubstituted epoxides employing N-heterocyclic carbene catalysis was developed. This reaction was performed under metal-free conditions in the presence of tert-butyl hydroperoxide (TBHP) as the oxidant. Trisubstituted epoxides bearing a ketone and an amide functionality (N,N-dimethyl formyl group) were synthesized starting from a wide range of chalcones in moderate to good yields with excellent diastereoselectivity.
- Devi, E. Sankari,Pavithra, Thangavel,Tamilselvi,Nagarajan, Subbiah,Sridharan, Vellaisamy,Maheswari, C. Uma
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p. 3576 - 3580
(2020/04/20)
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- Pyrenediones as versatile photocatalysts for oxygenation reactions with: In situ generation of hydrogen peroxide under visible light
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Pyrenediones (PYDs) are efficient photocatalysts for three oxygenation reactions: Epoxidation of electron deficient olefins, oxidative hydroxylation of organoborons, and oxidation of sulfides via in situ generation of H2O2 under visible light irradiation, using oxygen as a terminal oxidant and IPA as a solvent and a hydrogen donor.
- Zhang, Yuannian,Yang, Xin,Tang, Haidi,Liang, Dong,Wu, Jie,Huang, Dejian
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supporting information
p. 22 - 27
(2020/01/13)
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- Epoxidation of Alkenes with Molecular Oxygen as the Oxidant in the Presence of Nano-Al 2O 3
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The nano-Al 2O 3-promoted epoxidation of alkenes with molecular oxygen as the oxidant has been developed, providing an efficient route to a variety of epoxides in moderate to excellent yields. The environmentally friendly and efficient nano-Al 2O 3catalyst could be easily recovered and reused five times without significant loss of activity.
- Zhou, Xuan,Wang, Qiong,Xiong, Wenfang,Wang, Lu,Ye, Rongkai,Xiang, Ge,Qi, Chaorong,Hu, Jianqiang
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supporting information
p. 1789 - 1794
(2020/09/18)
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- Visible-light assisted of nano Ni/g-C3N4 with efficient photocatalytic activity and stability for selective aerobic C?H activation and epoxidation
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A selective, economical, and ecological protocol has been described for the oxidation of methyl arenes and their analogs to the corresponding carbonyl compounds and epoxidation reactions of alkenes with molecular oxygen (O2) or air as a green oxygen source, under mild reaction conditions. The nano Ni/g-C3N4 exhibited high photocatalytic activity, stability, and selectivity in the C?H activation of methyl arenes, methylene arenes, and epoxidation of various alkenes under visible- light irradiation without the use of an oxidizing agent and under base free conditions.
- Akrami, Zahra,Hosseini-Sarvari, Mona
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supporting information
(2020/10/13)
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- Mixed tetradentate NHC/1,2,3-triazole iron complexes bearing cis labile coordination sites as highly active catalysts in Lewis and Br?nsted acid mediated olefin epoxidation
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Two bio-inspired non-heme iron complexes bearing mixed tetradentate N-heterocyclic carbene/1,2,3-triazole ligands with cis labile coordination sites are reported. The compounds are studied in olefin epoxidation catalysis using H2O2 as oxidant. Sc(OTf)3, HClO4 and HOAc are applied as additives resulting in significant improvement of catalytic performance. Under optimized conditions the most active catalyst exhibits activities of 76,000 turnovers per hour, which is the highest reported value for an iron(II) catalyst. The complexes reveal comparably high stability and enable the challenging epoxidation of functionalized olefins. These results prove 1,2,3-triazoles to be promising and tunable ligands for iron catalyzed oxidation reactions.
- Dyckhoff, Florian,Jakob, Christian H. G.,Kühn, Fritz E.,Nguyen, Linda,Reich, Robert M.,Schlagintweit, Jonas F.
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p. 144 - 152
(2020/02/04)
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- Nucleophilic versus Electrophilic Activation of Hydrogen Peroxide over Zr-Based Metal-Organic Frameworks
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Zr-based metal-organic frameworks (Zr-MOF) UiO-66 and UiO-67 catalyze thioether oxidation in nonprotic solvents with unprecedentedly high selectivity toward corresponding sulfones (96-99% at ca. 50% sulfide conversion with only 1 equiv of H2O2). The reaction mechanism has been investigated using test substrates, kinetic, adsorption, isotopic (18O) labeling, and spectroscopic tools. The following facts point out a nucleophilic character of the peroxo species responsible for the superior formation of sulfones: (1) nucleophilic parameter XNu = 0.92 in the oxidation of thianthrene 5-oxide and its decrease upon addition of acid; (2) sulfone to sulfoxide ratio of 24 in the competitive oxidation of methyl phenyl sulfoxide and p-Br-methyl phenyl sulfide; (3) significantly lower initial rates of methyl phenyl sulfide oxidation relative to methyl phenyl sulfoxide (kS/kSO = 0.05); and (4) positive slope ρ = +0.42 of the Hammett plot for competitive oxidation of p-substituted aryl methyl sulfoxides. Nucleophilic activation of H2O2 on Zr-MOF is also manifested by their capability of catalyzing epoxidation of electron-deficient C═C bonds in α,β-unsaturated ketones accompanied by oxidation of acetonitrile solvent. Kinetic modeling on methyl phenyl sulfoxide oxidation coupled with adsorption studies supports a mechanism that involves the interaction of H2O2 with Zr sites with the formation of a nucleophilic oxidizing species and release of water followed by oxygen atom transfer from the nucleophilic oxidant to sulfoxide that competes with water for Zr sites. The nucleophilic peroxo species coexists with an electrophilic one, ZrOOH, capable of oxygen atom transfer to nucleophilic sulfides. The predominance of nucleophilic activation of H2O2 over electrophilic one is, most likely, ensured by the presence of weak basic sites in Zr-MOFs identified by FTIR spectroscopy of adsorbed CDCl3 and quantified by adsorption of isobutyric acid.
- Chesalov, Yuriy A.,Evtushok, Vasiliy Yu.,Glazneva, Tatyana S.,Ivanchikova, Irina D.,Kholdeeva, Oxana A.,Larionov, Kirill P.,Skobelev, Igor Y.,Zalomaeva, Olga V.
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- Neighbouring effects on catalytic epoxidation by Fe-cyclam in M2-PDIxCy complexes
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The unsymmetric PDIeCy ligand, featuring pyridinediimine and cylam sites, can be selectively metalated. Complementing the diiron compound, we have synthesized two heterobimetallic isomers, [ZnPDIFeCy(PDIeCy)(OTf)4] (3) and [FePDIZnCy(PDIeCy)(OTf)4] (4), and a dizinc complex, [Zn2(PDIeCy)(OTf)4] (5). Olefin epoxidation by the series of complexes was investigated. The M-PDI site influences the reactivity of the M-cyclam, resulting in increased activity toward enones. This journal is
- Hofmann, Andreas J.,Niederegger, Lukas,Hess, Corinna R.
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supporting information
p. 17642 - 17648
(2020/12/30)
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- Organocatalytic Enantioselective γ-Elimination: Applications in the Preparation of Chiral Peroxides and Epoxides
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An organocatalyzed enantioselective γ-elimination process has been achieved and applied in the kinetic resolution of peroxides to access chiral peroxides and epoxides. The reaction provided a pathway for the preparation of two useful synthetic and biologically important structural motifs through a single-step reaction. A range of substrates has been resolved with a selectivity factor up to 63. The obtained enantioenriched peroxides and epoxides allowed a series of transformations with retained optical purities.
- Chen, Zhili,Gong, Xiangnan,Hu, Fangli,Huang, Shengli,Jia, Shiqi,Qin, Wenling,Tan, Yu,Xu, Da,Yan, Hailong
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p. 1934 - 1940
(2020/03/24)
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- Lanthanide complexes combined with chiral salen ligands: Application in the enantioselective epoxidation reaction of α,β-unsaturated ketones
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Readily available lanthanide amides Ln[N(SiMe3)2]3 (Ln = Nd (1), Sm (2), Eu (3), Yb (4), La (5)), combined with chiral salen ligands H2La ((S,S)-N,N′-di-(3,5-disubstituted-salicylidene)-1,2-cyclohexan
- Xia, Xuexiu,Lu, Chengrong,Zhao, Bei,Yao, Yingming
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p. 13749 - 13756
(2019/05/16)
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- Synthesis of novel phase transfer catalysts derived from proline-mandelic acid/tartaric acid: their evaluation in enantioselective epoxidation and Darzen condensation
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Abstract : Herein, we have described the synthesis of novel chiral cyclic phase transfer catalysts (PTCs). These catalysts are synthesized from proline, mandelic acid and tartaric acid by using simple synthetic methods with competitive yields. These chira
- Mahajan, Deepak P,Godbole, Himanshu M,Singh, Girij P,Shenoy, Gautham G
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- Method for preparing epoxide by one-pot olefin aerobic epoxidation
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The invention relates to a method for preparing an epoxide by one-pot olefin aerobic epoxidation, and belongs to the technical field of organic synthesis. An olefin, an alkyl aromatic compound and analkali are added into a solvent, or an olefin, an alkyl aromatic compound and an alkali are directly mixed; the temperature is raised to 70-160 DEG C in an air or oxygen atmosphere; reacting is carried out for 1-48 hours; and the olefin is directly oxidized into the corresponding epoxide in the presence of the alkyl aromatic compound, the alkali and air (or oxygen), wherein the yield is up to 99%.In the reaction process, the generated alkyl peroxide is generated in situ and consumed in situ, so that the concentration of the alkyl peroxide is kept at a lower level; and generated alkyl peroxy free radicals can also react with the olefin to further generate the peroxide, and efficiency is improved. The method has the advantages of simple operation, mild conditions, low raw material cost andno need of special complex equipment, and has a good industrial application prospect.
- -
-
Paragraph 0018-0041
(2020/01/03)
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- Highly enantioselective epoxidation of olefins by H2O2 catalyzed by a non-heme Fe(ii) catalyst of a chiral tetradentate ligand
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The chiral tetradentate N4-donor ligand, 1-methyl-2-({(S)-2-[(S)-1-(1-methylbenzimidazol-2-yl methyl)pyrrolidin-2-yl]pyrrolidin-1-yl}methyl) benzimidazole (S,S-PDBzL), based on a chiral dipyrrolidine backbone, has been synthesized and its corresponding Fe(ii) complex has been prepared and characterized. The X-ray structure of the complex reveals that the Fe(ii) ion is in a distorted octahedral coordination environment with two cis-oriented coordination sites occupied by (labile) triflate anions. The ability of the iron complex to catalyze asymmetric epoxidation reactions of olefins with H2O2 was investigated, using 2-cyclohexen-1-one, 2-cyclopenten-1-one, cis-β-methylstyrene, isophorone, chalcones and tetralones as substrates. Different carboxylic acids were used as additives to enhance yields and enantioselectivities, and 2-ethylhexanoic acid was found to give the best results. The catalysis results indicate that the Fe(ii) complex is capable of effecting comparatively high enantioselectivities (>80%) in the epoxidation reactions.
- Mitra, Mainak,Cusso, Olaf,Bhat, Satish S.,Sun, Mingzhe,Cianfanelli, Marco,Costas, Miquel,Nordlander, Ebbe
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p. 6123 - 6131
(2019/05/16)
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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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- An efficient Darzens reaction promoted by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)
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An efficient DBU promoted Darzens reaction utilising α-haloketones containing an enolizable α′-hydrogen is reported. This method diastereoselectively afforded the corresponding α,β-epoxy ketones good to excellent yields in an one-pot reaction without using any transition metals or additives. Furthermore, haloketones without an α′-hydrogen are also applicable in this reaction.
- Luo, Juan,Hu, Lanfang,Zhang, Minghao,Tang
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supporting information
p. 1949 - 1951
(2019/07/03)
-
- Crown-ether-modified cyclic dipeptides as supramolecular chiral catalysts
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With the objective to develop supramolecular catalysts for useful chemical transformations, we report here a rapid and efficient solid-phase synthesis of novel cyclic dipeptides (crown-CDPs) with a diversity of L-DOPA derived crown ether substituents and
- Bérubé, Christopher,Voyer, Normand
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p. 184 - 195
(2017/10/26)
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- Papain-catalysed mechanochemical synthesis of oligopeptides by milling and twin-screw extrusion: Application in the Juliá-Colonna enantioselective epoxidation
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The oligomerisation of l-amino acids by papain was studied in a mixer ball mill and in a planetary ball mill. The biocatalyst proved stable under the ball milling conditions providing the corresponding oligopeptides in good to excellent yields and with a variable degree of polymerisation. Both parameters were found to be dependent on the reaction conditions and on the nature of the amino acid (specifically on its side-chain size and hydrophobicity). In addition, the chemoenzymatic oligomerisation was demonstrated by utilising twin-screw extrusion technology, which allowed for a scalable continuous process. Finally, the synthesised oligo(l-Leu) 2b proved to be active as a catalyst in the Juliá-Colonna enantioselective epoxidation of chalcone derivatives.
- Ardila-Fierro, Karen J.,Crawford, Deborah E.,K?rner, Andrea,James, Stuart L.,Bolm, Carsten,Hernández, José G.
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supporting information
p. 1262 - 1269
(2018/03/26)
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- Chiral calcium-catalyzed asymmetric epoxidation reactions using hydrogen peroxide as the terminal oxidant
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Asymmetric epoxidation reactions of chalcone derivatives catalyzed by chiral calcium complexes using hydrogen peroxide were developed. The epoxidation reactions proceeded smoothly to afford the desired products in good yields with good enantioselectivitie
- Yamashita, Yasuhiro,Macor, Joseph Alexander,Fushimi, Seiya,Tsubogo, Tetsu,Kobayashi, Shū
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p. 847 - 850
(2018/09/10)
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- Syntheses, Structures, and Catalytic Activities of the Anionic Heterobimetallic Rare-Earth Metal Complexes Supported by Pyrrolyl-Substituted 1,2-Diimino Ligands
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A series of the anionic heterobimetallic rare-earth metal complexes supported by trans- or chiral pyrrolyl-substituted 1,2-diimino ligands were synthesized in good yields via reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3
- Wang, Wei,Wang, Xiaojia,Zhou, Shuangliu,Xu, Xiaolong,Du, Jun,Zhang, Lijun,Mu, Xiaolong,Wei, Yun,Zhu, Xiancui,Wang, Shaowu
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supporting information
p. 10390 - 10400
(2018/08/28)
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- Synthesis of alkyl α- and β-d-glucopyranoside-based chiral crown ethers and their application as enantioselective phase-transfer catalysts
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Chiral monoaza-15-crown-5-type lariat ethers annelated to alkyl 4,6-O-benzylidene-α- and β-d-glucopyranosides have been synthesized. These macrocycles generated significant asymmetric induction as phase-transfer catalysts in a few two-phase reactions. The catalytic effect of the lariat ethers with methoxy, ethoxy, and i-propoxy substituents on C-1 of the sugar unit in both α and β positions was compared. In liquid–liquid two-phase reactions, the nature and position of the substituents did not have much effect. The α-anomers were somewhat more efficient in terms of enantioselectivity than the β forms. In asymmetric Darzens condensations, in the epoxidation of trans-chalcone, in the Michael addition of β-nitrostyrene and diethyl acetamidomalonate, and in the reaction of 2-benzylidene-1,3-indandione with diethyl bromomalonate, maximum enantioselectivities of 73, 94, 78, and 72%, respectively, were obtained in presence of glucopyranoside-based lariat ethers as catalysts.
- Pálv?lgyi, ádám,Rapi, Zsolt,Ozohanics, Olivér,Tóth, Gábor,Keglevich, Gy?rgy,Bakó, Péter
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p. 1627 - 1645
(2017/11/16)
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- Visible Light-Induced Aerobic Epoxidation of α,β-Unsaturated Ketones Mediated by Amidines
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An aerobic photoepoxidation of α,β-unsaturated ketones driven by visible light in the presence of tetramethylguanidine (3b), tetraphenylporphine (H2TPP), and molecular oxygen under mild conditions was revealed. The corresponding α,β-epoxy ketones were obtained in yields of up to 94% in 96 h. The reaction time was shortened to 4.6 h by flow synthesis. The mechanism related to singlet oxygen was supported by experiments and density functional theory (DFT) calculations.
- Wu, Yufeng,Zhou, Guangli,Meng, Qingwei,Tang, Xiaofei,Liu, Guangzhi,Yin, Hang,Zhao, Jingnan,Yang, Fan,Yu, Zongyi,Luo, Yi
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supporting information
p. 13051 - 13062
(2018/10/25)
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- Method for preparing epoxide through induction of visible light
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The invention belongs to the technical field of organic synthesis and provides a method for preparing an epoxide through induction of visible light. The method comprises the following step: under thecondition that the visible light and a photosensitizer exist, by taking oxygen or air as an oxygen source or an oxidizing agent and taking a synthesized amidine derivative as a catalyst, performing areaction at the temperature of -40-50 DEG C for 36h-192h, so that olefin is directly oxidized into the corresponding epoxide. The method is mild in reaction conditions, and the yield is as high as 94%or above, therefore, the method has good development value and application prospect.
- -
-
Paragraph 0036; 0038; 0040; 0042; 0044; 0046; 0048; 0050
(2018/08/04)
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- Visible-Light-Driven Epoxyacylation and Hydroacylation of Olefins Using Methylene Blue/Persulfate System in Water
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A visible-light-driven strategy for hydroacylation and epoxyacylation of olefins in water using methylene blue as photoredox catalyst and persulfate as oxidant is reported. In this unprecedented unified approach, two different transformations are accomplished using only one set of reagents. The method has a broad scope spanning a range of aromatic and aliphatic aldehydes as well as conjugated and nonconjugated olefins to deliver ketones and epoxyketones from abundant and inexpensive chemical feedstocks.
- De Souza, Gabriela F. P.,Bonacin, Juliano A.,Salles, Airton G.
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p. 8331 - 8340
(2018/07/21)
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- Interfacial supramolecular biomimetic epoxidation catalysed by cyclic dipeptides
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We synthesised a library of cis- and trans-cyclic dipeptides and evaluated their efficacy as catalysts in the asymmetric Weitz-Scheffer epoxidation of trans-chalcone. A thorough investigation relying on structure-activity studies and computational studies provided insights into the mechanism of the process. Our results revealed some structural features required for efficient conversion and for introduction of chirality into the product. The cyclic dipeptide acts as a catalyst by templating a supramolecular arrangement at the aqueous-organic interface required for efficient transformations to occur. Among all cyclic dipeptides investigated, cyclo(Leu-Leu) was the most efficient supramolecular catalyst.
- Bérubé, Christopher,Barbeau, Xavier,Cardinal, Sébastien,Boudreault, Pierre-Luc,Bouchard, Corinne,Delcey, Nicolas,Lagüe, Patrick,Voyer, Normand
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p. 330 - 349
(2017/03/15)
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- Bioinspired Manganese Complexes and Graphene Oxide Synergistically Catalyzed Asymmetric Epoxidation of Olefins with Aqueous Hydrogen Peroxide
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Bioinspired manganese complexes of N4ligands and graphene oxide (GO) synergistically catalyze the highly enantioselective epoxidation of olefins (up to 99% ee), which is a rare example with GO as a co-catalyst in asymmetric catalysis. GO as a new and key additive not only successfully functions in catalytic amounts, but also has a positive effect for improving the enantioselectivity of the asymmetric epoxidation compared with the traditional stoichiometric organic carboxylic acid method [e.g., chalcone, 95% ee (3.5 mg GO) vs. 84% ee (5 equiv., 75 mg acetic acid), ethyl cinnamate, 84% ee (3.5 mg GO) vs. 19% ee (5 equiv., 75 mg acetic acid)]. The X-ray photoelectron spectroscopy (XPS) spectra of GO before and after the reaction indicate that the intensities of C–O become stronger after the reaction, which may have a certain relationship with hydrogen peroxide (H2O2) and gives a reasonable rationale for the large consumption of H2O2. Also, part of the hydrogen peroxide was used for the oxidation of GO. (Figure presented.).
- Miao, Chengxia,Yan, Xingbin,Xu, Daqian,Xia, Chungu,Sun, Wei
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p. 476 - 484
(2017/02/10)
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- Asymmetric Epoxidation of Olefins with H2O2 Catalyzed by a Bioinspired Aminopyridine N4 Iron Complex
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An iron complex with a chiral aminopyridine N4 ligand bearing strong electron-donating and bulky morpholine groups on the ligand is synthesized and characterized. The iron complex serves to efficiently catalyze the asymmetric epoxidation of various olefins by employing aqueous hydrogen peroxide as the green oxidant, providing the corresponding epoxides in good to excellent yields and enantioselectivities (up to 93 % yield and 99.9 % ee). Owing to the introduction of morpholine functional groups on the ligand, the Fe-catalyzed reaction can proceed with a catalytic amount of the carboxylic acid partner (3 mol %).
- Wang, Wenfang,Sun, Qiangsheng,Xu, Daqian,Xia, Chungu,Sun, Wei
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p. 420 - 424
(2017/02/15)
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- Enantioselective Epoxidation of Electron-Deficient Alkenes Catalyzed by Manganese Complexes with Chiral N4 Ligands Derived from Rigid Chiral Diamines
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A series of tetradentate sp2N/sp3N hybrid chiral N4 ligands derived from rigid chiral diamines were synthesized, which enabled the first manganese-catalyzed enantioselective epoxidation of electron-deficient alkenes with hydrogen peroxide (H2O2) as an oxidant. The reaction furnishes enantiomerically pure epoxy amides, epoxy ketones as well as epoxy esters in good yields and excellent enantioselectivities (up to 99.9% ee) with lower catalyst loading. Preliminary studies on structure–activity relationship demonstrated that maintaining comparatively lower electron-donating ability of the sp3N and relatively higher electron-donating ability of sp2N of the N4 ligands is beneficial to getting higher activity and selectivity, thus providing us a new view to understand epoxidation with H2O2. (Figure presented.).
- Chen, Xiangning,Gao, Bao,Su, Yijin,Huang, Hanmin
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supporting information
p. 2535 - 2541
(2017/08/16)
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- Asymmetric Cascade Catalysis with Chiral Polyoxometalate-Based Frameworks: Sequential Direct Aldol and Epoxidation Reactions
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Catalytic asymmetric cascade reactions in which the substrates are transferred through well-choreographed consecutive independent steps by a single catalyst have received increasing interest. By incorporating a chiral organocatalyst pyrrolidine, an oxidat
- Han, Qiuxia,Li, Wenwen,Wang, Shugai,He, Jiachen,Du, Wei,Li, Mingxue
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p. 1801 - 1807
(2017/05/29)
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- Highly enantioselective asymmetric reactions involving zinc ions promoted by chiral aziridine alcohols
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Enantiomerically pure, chiral secondary and tertiary aziridine alcohols (including the aziridine analogue of ProPhenol—AziPhenol) have proven to be highly effective catalysts for enantioselective asymmetric reactions in the presence of zinc ions, including arylation of aromatic aldehydes, epoxidation of chalcone and addition of diethylzinc to aldehydes, leading to the desired chiral products in high chemical yields (up to 90%) and with ee's up to 90%. A higher catalytic activity of Prophenol-type bis(aziridine alcohol) in the aforementioned asymmetric transformations has been demonstrated.
- Jarzyński, Szymon,Utecht, Greta,Le?niak, Stanis?aw,Rachwalski, Micha?
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p. 1774 - 1779
(2017/11/16)
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- Revisiting the Juliá-Colonna enantioselective epoxidation: Supramolecular catalysis in water
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We describe an efficient epoxidation process leading to chiral epoxyketones using the reusable homo-oligopeptide poly-l-leucine (PLL) in pure water, without any organic co-solvent. A range of substituted epoxyketones can be accessed with good conversions and high enantioselectivities. Based on the experimental results and computational studies, we propose a mechanism that demonstrates the importance of both the α-helical structure and the presence of a hydrophobic groove of the homo-oligopeptide catalyst for reactivity and selectivity.
- Bérubé, Christopher,Barbeau, Xavier,Lagüe, Patrick,Voyer, Normand
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supporting information
p. 5099 - 5102
(2017/07/12)
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- Synthesis of enantiomerically pure 2-(N-aryl, N-alkyl-aminomethyl)aziridines: a new class of ligands for highly enantioselective asymmetric synthesis
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A simple and effective synthesis of enantiomerically pure 2-(N-aryl-, N-alkyl-aminomethyl)aziridines from (2S)-N-tritylaziridine-2-carboxylic acid methyl ester has been developed. Treating of this key ester with several primary and secondary amines in the presence of AlMe3 provided the corresponding chiral N-trityl-2-carboxamides, and their reduction performed with different reagents resulted in the formation of the expected 2-(aminomethyl)aziridines. The choice of reaction conditions allows to either keep or leave the trityl substituent in the product. Such 2-(aminoalkyl)aziridines have shown very high catalytic efficiency in the asymmetric arylation of aldehydes and in other testing asymmetric reactions. On the other hand, homochiral N-trityl-2-carboxamides are interesting building blocks for the synthesis of various biologically active compounds.
- Jarzyński, Szymon,Le?niak, Stanis?aw,Rachwalski, Micha?
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p. 1808 - 1816
(2017/11/17)
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- Facile epoxidation of α, β-unsaturated ketones with urea-2,2-dihydroperoxypropane as a new oxidant
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Abstract: Various aromatic α, β-unsaturated ketones were successfully transformed into their corresponding epoxides using urea-2,2-dihydroperoxypropane as the oxygen source for the first time. The reactions were carried out under mild alkaline conditions at room temperature in high yields and short reaction times. Graphical Abstract: [Figure not available: see fulltext.]
- Khosravi, Kaveh,Naserifar, Shirin
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p. 323 - 328
(2017/01/10)
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