- Photo-Induced Dihydroxylation of Alkenes with Diacetyl, Oxygen, and Water
-
Herein reported is a photo-induced production of vicinal diols from alkenes under mild reaction conditions. The present dihydroxylation method using diacetyl (= butane-2,3-dione), oxygen, and water dispenses with toxic reagents and intractable waste generation.
- Masuda, Yusuke,Ikeshita, Daichi,Murakami, Masahiro
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- Racemic or enantioselective osmium-catalyzed dihydroxylation of olefins under near-neutral conditions
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K3Fe(CN)6 and NaIO4 serve as catalytic co-oxidants for osmium-catalyzed dihydroxylations that are performed under near-neutral conditions with K2S2O8 as the stoichiometric oxidant and Na2HPO4 as the base. By using either quinuclidine or hydroquinidine 1,4-phthalazinediyl ether [(DHQD)2Phal], good yields of racemic or enantioenriched diols are obtained. This simple, biphasic procedure offers advantages over other neutral dihydroxylation protocols that use N-methylmorpholine oxide as the stoichiometric oxidant, by suppressing the secondary catalytic cycle that leads to reduced enantioselectivities. The utility of the procedure, which is nicely suited for base-labile starting materials or products, is demonstrated by performing the dihydroxylation in the presence of an aliphatic aldehyde moiety.
- Blumberg, Shawn,Martin, Stephen F.
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- Enantioselective Dihydroxylation of Alkenes Catalyzed by 1,4-Bis(9-O-dihydroquinidinyl)phthalazine-Modified Binaphthyl–Osmium Nanoparticles
-
A series of unprecedented binaphthyl–osmium nanoparticles (OsNPs) with chiral modifiers were applied in the heterogeneous asymmetric dihydroxylation of alkenes. A remarkable size effect of the OsNPs, depending on the density of the covalent organic shells, on the reactivity and enantioselectivity of the dihydroxylation reaction was revealed. Successful recycling of the OsNPs was also demonstrated and high reaction efficiency and enantioselectivity were maintained.
- Zhu, Jie,Sun, Xiao-Tao,Wang, Xiao-Dong,Wu, Lei
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p. 1788 - 1792
(2018/04/30)
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- Bronsted Acid Mediated Direct α-Hydroxylation of Cyclic α-Branched Ketones
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We report a Bronsted acid mediated direct α-hydroxylation of cyclic α-branched ketones via a tandem aminoxylation/N-O bond-cleavage process. Nitrosobenzene is used as the oxidant and subsequently promotes the liberation of the free alcohol. The desired pr
- Shevchenko, Grigory A.,Dehn, Stefanie,List, Benjamin
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supporting information
p. 2298 - 2300
(2018/10/20)
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- Green Organocatalytic Dihydroxylation of Alkenes
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An inexpensive, green, metal-free one-pot procedure for the dihydroxylation of alkenes is described. H2O2 and 2,2,2-trifluoroacetophenone were employed as the oxidant and organocatalyst, respectively, in this highly sustainable protocol in which a variety of homoallylic alcohols, aminoalkenes, and simple alkenes were converted into the corresponding polyalcohols in good to excellent yields. This process takes advantage of an epoxidation reaction followed by an acidic treatment in which water participates in the ring opening of the in situ prepared epoxide to lead to the desired product.
- Theodorou, Alexis,Triandafillidi, Ierasia,Kokotos, Christoforos G.
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p. 1502 - 1509
(2017/04/01)
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- Osmium on chelate resin: Nonvolatile catalyst for the synthesis of DIOLS from alkenes
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Osmium tetraoxide (OsO4) was immobilized on a commercially available chelate resin DIAION CR11 (CR11) just by simply immersing it in a methanol solution of OsO4 at room temperature. The resulting purple solid, 5% Os/CR11, indicated no volatility, and effectively catalyzed the oxidation of various alkenes to the corresponding diols.
- Monguchi, Yasunari,Wakayama, Fumika,Takada, Hitoshi,Sawama, Yoshinari,Sajiki, Hironao
-
supporting information
p. 700 - 704
(2015/03/14)
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- Novel biphenyl organocatalysts for iminium ion-catalyzed asymmetric epoxidation
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Two novel chiral biphenyl iminium salts derived from L-acetonamine, containing electron-withdrawing 3,30-substituents on the biphenyl unit, have been prepared and tested as asymmetric catalysts for epoxidation of prochiral alkenes. The results are compared with those achieved using the corresponding unsubstituted system.
- Farah, Mohamed M.,Page, Philip C. Bulman,Buckley, Benjamin R.,Blacker, A. John,Elsegood, Mark R.J.
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p. 758 - 769
(2013/07/27)
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- Enantioselective titanium(III)-catalyzed reductive cyclization of ketonitriles
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Reduction, please! The title reaction affords ?-hydroxyketones, a common structural motif in biologically active natural products, in good yields and high enantioselectivities at room temperature. The commercially available ansa-titanocene 1 was found to be an efficient catalyst for this process, which presumably proceeds by addition of a ketyl radical to a nitrile.
- Streuff, Jan,Feurer, Markus,Bichovski, Plamen,Frey, Georg,Gellrich, Urs
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supporting information; experimental part
p. 8661 - 8664
(2012/09/21)
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- Synthesis and reaction of phthaloyl peroxide derivatives, potential organocatalysts for the stereospecific dihydroxylation of alkenes
-
To improve the synthesis and reactivity of phthaloyl peroxide derivatives a method has been developed using sodium percarbonate and phthaloyl chlorides. The reactions of the new phthaloyl peroxide derivatives with trans-stillbene as well as the improved reactivity of 3,4-dichlorophthaloyl peroxide with a variety of alkenes are reported.
- Yuan, Changxia,Axelrod, Abram,Varela, Michael,Danysh, Laura,Siegel, Dionicio
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supporting information; experimental part
p. 2540 - 2542
(2011/06/21)
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- The nature of the catalytically active species in olefin dioxygenation with PhI(OAc)2: Metal or proton?
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Evidence for the protiocatalytic nature of the diacetoxylation of alkenes using PhI(OAc)2 as oxidant is presented. Systematic studies into the catalytic activity in the presence of proton-trapping and metal-complexing agents indicate that protons act as catalysts in the reaction. Using triflic acid as catalyst, the selectivity and reaction rate of the conversion is similar or superior to most efficient metal-based catalysts. Metal cations, such as Pd(II) and Cu(II), may interact with the oxidant in the initiation phase of the catalytic transformation; however, 1 equiv of strong acid is produced in the first cycle which then functions as the active catalyst. Based on a kinetic study as well as in situ mass spectrometry, a mechanistic cycle for the proton-catalyzed reaction, which is consistent with all experimental data presented in this work, is proposed.
- Kang, Yan-Biao,Gade, Lutz H.
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supporting information; experimental part
p. 3658 - 3667
(2011/05/03)
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- Efficient diacetoxylation of alkenes via Pd(II)/Pd(IV) process with peracetic acid and acetic anhydride
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A palladium-catalyzed diacetoxylation of alkenes in the presence of peracetic acid and acetic anhydride was developed to produce diacetates efficiently and diastereoselectively. Due to its mild conditions, this method was suitable for a broad range of substrates encompassing conjugated and nonconjugated olefins.
- Park, Chan Pil,Lee, Joo Ho,Yoo, Kyung Soo,Jung, Kyung Woon
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supporting information; scheme or table
p. 2450 - 2452
(2010/07/05)
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- Homogeneous dihydroxylation of olefins catalyzed by a recyclable OsO42 - core dendrimer
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By employing an osmate (OsO42 -) core dendrimer as a catalyst, homogeneous dihydroxylation reactions proceeded rapidly, and the dendritic osmium catalyst was efficiently recycled by reprecipitation.
- Fujita, Ken-ichi,Ainoya, Taku,Tsuchimoto, Teruhisa,Yasuda, Hiroyuki
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experimental part
p. 808 - 810
(2010/03/26)
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- A recyclable dendritic osmium catalyst for homogeneous dihydroxylation of olefins
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A series of osmate (OsO42-) core dendrimers was prepared by an ion-exchange technique through the mixing of K 2OsO4 and a bis(quaternary ammonium bromide) core dendrimer, which consisted of poly(benzyl ether) dendron. By employing an osmate core dendrimer as a homogeneous catalyst, dihydroxylation reactions of olefins proceeded rapidly, and the dendritic osmium catalyst was recovered by reprecipitation and then reused. Furthermore, a dendritic effect on the recyclability of a catalyst was observed. In the case of asymmetric dihydroxylation reactions, the corresponding diol was obtained in a high chemical yield with a fair enantiomeric excess (ee). In this case, not only the dendritic osmium catalyst but also the chiral ligand could be recovered by reprecipitation and reused efficiently up to five times.
- Fujita, Ken-Ichi,Yamazaki, Manabu,Ainoya, Taku,Tsuchimoto, Teruhisa,Yasuda, Hiroyuki
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experimental part
p. 8536 - 8543
(2010/11/18)
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- Osmium-catalyzed asymmetric dihydroxylation by carbon dioxide-activated hydrogen peroxide and N-methylmorpholine
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An improved process has been developed for the osmium-catalyzed dihydroxylation of olefins via in situ formation of NMO from NMM using CO2 catalysis and H2O2. All olefins examined were selectively cis-dihydroxylated to their corresponding diols in good to excellent yields, and by the use of chiral ligands, high enantiomeric excesses were obtained.
- Balagam, Bharathi,Mitra, Ranjan,Richardson, David E.
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p. 1071 - 1075
(2008/09/18)
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- Diastereo and enantioselective synthesis of 1,2-diols promoted by electrophilic selenium reagents
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Here we report the first example in which the phenylseleno group is directly substituted by a hydroxy function. The reaction is promoted by the PhSeOSO3H generated "in situ" by oxidation of (PhSe)2 with (NH4)2S2O8 at reflux in a 3:1 mixture of MeCN-H2O. I
- Santi,Tiecco,Testaferri,Tomassini,Santoro,Bizzoca
-
experimental part
p. 956 - 960
(2009/04/06)
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- Highly stereoselective syn-ring opening of enantiopure epoxides with nitric oxide
-
Reaction of enantiopure epoxides (1) with NO occurred highly stereoselectively, affording syn-ring opened products, nitrates (2). The configuration of 2 was confirmed to be retained by determining the configuration of reduced products 1,2-glycols (4) from 2. A possible mechanism is suggested to trace out the syn-ring opening pathway.
- Wu, Wentao,Liu, Qiang,Shen, Yinglin,Li, Rui,Wu, Longmin
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p. 1653 - 1656
(2008/02/03)
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- Preparation, characterization and catalytic properties of polyaniline-supported metal complexes
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Polyaniline-supported Sc, In, Pd, Os and Re catalysts were prepared by using a simple protocol and the thus prepared catalysts were well characterized using FTIR, XPS, UV-Vis/DRS, TGA-DTA. All the catalysts were successfully employed in a wide range of organic transformations such as cyanation and allylation of carbonyl compound, Suzuki coupling of aryl halides and boronic acids, and, most importantly, in asymmetric dihydroxylation of olefins to afford optically active vicinal diols. All the catalysts were separated from the reaction mixture by simple filtration and reused with consistent activity for five cycles without noticeable leaching of metal from the support.
- Choudary, Boyapati M.,Roy, Moumita,Roy, Sarabindu,Kantam, M. Lakshmi,Sreedhar, Bojja,Kumar, Karasala Vijay
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p. 1734 - 1742
(2007/10/03)
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- Synthesis with improved yield and study on the analgesic effect of 2-methoxyphencyclidine
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Phencyclidine (1-(1-phenylcyclohexyl)piperidine, CAS 956-90-1, PCP) has shown analgesic effects. Some of Its derivatives have been synthesized and their biological properties were studied. Since a methoxy group has been added to the position 2 of the cyclohexane ring of PCP, the resulting compound is more polar than PCP. This compound was synthesized using an improved method with a higher yield. Its analgesic effect was studied using the tail-flick test on rats and was compared with that of ketamine (CAS 1867-66-9). The results showed that 2-methoxyphencyclidine increased tail-flick latencies as compared to the control group. The maximum analgesic effect of the compound occurred 5-10 min after its injection, while the effect of ketamine was observed 10-25 min after injection. ECV · Editio Cantor Verlag.
- Ahmadi, Abbas,Mahmoudi, Ali
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p. 346 - 350
(2007/10/03)
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- Filtration-free recyclable catalytic asymmetric dihydroxylation using a ligand immobilized on magnetic mesocellular mesoporous silica
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A new magnetic mesocellular mesoporous silica support featuring a 3D open-pore structure has been developed for highly efficient, filtration-free recycling of chiral ligands for catalytic asymmetric dihydroxylation. Reactions using the ligand immobilized on this magnetic silica system exhibited almost the same reactivity and enantioselectivity as those obtained in the homogeneous reaction. Magnetically recovered ligand could be recycled eight times with good to excellent conservation of reaction rates and enantioselectivities.
- Lee, Daewon,Lee, Jinwoo,Lee, Honggeun,Jin, Sunmi,Hyeon, Taeghwan,Kim, B. Moon
-
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- Osmium-catalyzed olefin dihydroxylation and aminohydroxylation in the second catalytic cycle
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Two catalytic cycles operate in the osmium-catalyzed olefin dihydroxylation and aminohydroxylation. Slow hydrolysis of the Os(VI) monoglycolate (or monoazaglycolate in aminohydroxylation) intermediate often results in the addition of another molecule of o
- Wu, Peng,Hilgraf, Robert,Fokin, Valery V.
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p. 1079 - 1085
(2007/10/03)
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- A novel microencapsulated osmium catalyst using cross-linked polystyrene as an efficient catalyst for asymmetric dihydroxylation of olefins in water
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A novel microencapsulated osmium catalyst (PSresin-MC Os) was developed using cross-linked polystyrene. The concept of this method may go beyond that of microencapsulation. The catalyst was successfully used in asymmetric dihydroxylation in water, and it was recovered quantitatively by simple filtration and reused several times without loss of activity. The shape of the catalyst was maintained even after several uses. Moreover, no leaching of the Os component was detected.
- Ishida, Tasuku,Akiyama, Ryo,Kobayashi, Shu
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p. 1189 - 1192
(2007/10/03)
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- Markedly enhanced recyclability of osmium catalyst in asymmetric dihydroxylation reactions by using macroporous resins bearing both residual vinyl groups and quaternary ammonium moieties
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Markedly enhanced recyclability of osmium catalyst in asymmetric dihydroxylation has been achieved by using osmylated macroporous resins bearing both residual vinyl groups and quaternary ammonium moiety. The Royal Society of Chemistry 2005.
- Kim, Kwang Jin,Choi, Han Young,Hwang, Soon Ho,Park, Yil Sung,Kwueon, Eun Kyung,Choi, Doo Seong,Song, Choong Eui
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p. 3337 - 3339
(2007/10/03)
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- Fluorous osmium tetraoxide (FOsO4): A recoverable and reusable catalyst for dihydroxylation of olefins
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A fluorous osmium catalyst was firstly developed. It had been effectively used as recoverable and reusable catalyst in the dihydroxylation of olefins.
- Huang, Yangen,Meng, Wei-Dong,Qing, Feng-Ling
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p. 1965 - 1968
(2007/10/03)
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- Microencapsulation of osmium tetroxide in polyurea
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(Matrix presented) Osmium tetroxide has been microencapsulated in a polyurea matrix using an in situ interfacial polymerization approach. These microcapsules have been effectively used as recoverable and reusable catalysts in the dihydroxylation of olefins.
- Ley, Steven V.,Ramarao, Chandrashekar,Lee, Ai-Lan,stergaard, Niels,Smith, Stephen C.,Shirley, Ian M.
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p. 185 - 187
(2007/10/03)
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- The synthesis of the anti-malarial natural product polysphorin and analogues using polymer-supported reagents and scavengers.
-
A general asymmetric route to both enantiomers of polysphorin has been developed. The route utilizes polymer-supported reagents, catalysts and scavengers to minimise the need for aqueous work-up and chromatography. This includes application of a method to scavenge 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and a "catch-and-release" procedure to extract the resultant diol following Sharpless asymmetric dihydroxylation. A novel enzymatic selective protection and investigations of a new asymmetric dihydroxylation using microencapsulated osmium tetroxide were also investigated during the course of this study.
- Lee, Ai-Lan,Ley, Steven V
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p. 3957 - 3966
(2007/10/03)
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- A trifunctional catalyst for one-pot synthesis of chiral diols via heck coupling-N-oxidation-asymmetric dihydroxylation: Application for the synthesis of diltiazem and taxol side chain
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A heterogeneous bifunctional catalyst composed of OsO42--WO42- and a trifunctional catalyst comprising PdCl42--OsO42-- WO42-, designed and prepared by an ion-exchange technique using layered double hydroxides (LDH) as an ion-exchanger and their homogeneous bifunctional analogue, K2OsO4-Na2WO4 and trifunctional analogue, Na2PdCl4-K2OsO4-K2 OSO4-NNa2WO4, devised for the first time are evaluated for the synthesis of chiral vicinal diols. These bifunctional and trifunctional catalysts perform asymmetric dihydroxylation-N-oxidation and Heck-asymmetric dihydroxylation-N-oxidation, respectively, in the presence of Sharpless chiral ligand, (DHQD)2PHAL in a single pot using H2O2 as a terminal oxidant to provide N-methylmorpholine oxide (NMO) in situ by the oxidation of N-methylmorpholine (NMM). The heterogeneous bifunctional catalyst supported on LDH (LDH-OsW) displays superior activity to afford diols with higher yields over the other heterogeneous catalysts developed by the ion exchange on quaternary ammonium salts covalently bound to resin (resin-OsW) and silica (silica-OsW) or homogeneous catalysts in the achiral dihydroxylation reactions. The LDH-OsW and its homogeneous analogue are found to be very efficient in performing a simultaneous asymmetric dihydroxylation (AD)-N-oxidation of a wide and varied range of aromatic, cyclic, and mono, di-, and trisubstituted olefins to obtain chiral vicinal diols with higher yields and ee's using H2O2. Further, the use of OsO42--WO42-- WO42- catalysts as such or in the supported form offers a simplified procedure for catalyst recycling, which shows consistent activity for a number of cycles. In this process, OsVI is recycled to OsVIII by a coupled electron transfer-mediator (ETM) system based on NMO-WO42- using H2O2, leading to a mild and selective electron transfer. The one-pot biomimic synthesis of chiral diols is mediated by a recyclable trifunctional heterogeneous catalyst (LDH-PdOsW) consisting of active palladium, tungsten, and osmium species embedded in a single matrix. This protocol, which provides prochiral olefins and NMO in situ by Heck coupling and N-oxidation of NMM, respectively, required for the AD, unfolds a low cost process. We extended the present method to the one-pot synthesis of trisubstituted chiral vicinal diols with moderate to excellent ee's by AD of trisubstituted olefins that are obtained by in situ Heck arylation of disubstituted olefins. The heterogeneous trifunctional catalysts offers chiral diols with unprecedented ee's and excellent yields in the AD of prochiral cinnamates, which are obtained in situ from acrylates and halobenzenes for the first time. The new variants such as LDH support and Et3N·HX inherently composed in the heterogeneous multicomponent system and slow addition of H202 facilitates the hydrolysis of osmium monogylcolate ester to subdue the formation of bisglycolate ester to achieve higher ee's. Without resorting to recrystallization, the chiral diols of cinnamates thus synthesized with 99% ee's and devoid of osmium contamination are directly put to use in the synthesis of diltiazem and Taxol side chain with an overall improved yield to demonstrate the synthetic utility of the trifunctional heterogeneous catalyst. The high binding ability of the heterogeneous osmium catalyst enables the use of equimolar ratio of ligand to osmium to give excellent ee's in AD in contrast to the homogeneous osmium system in which the excess molar quantities of the expensive chiral ligand to osmium are invariably used. Further, the XRD, FT-IR, UV-vis DRS, and XPS studies indicate the retention of the coordination geometries of the specific divalent anions anchored to LDH matrix in their monomeric form during the ion exchange and after the reaction.
- Choudary, Boyapati M.,Chowdari, Naidu S.,Madhi, Sateesh,Kantam, Mannepalli L.
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p. 1736 - 1746
(2007/10/03)
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- A new practical method for the osmium-catalyzed dihydroxylation of olefins using bleach as the terminal oxidant
-
A general procedure for the osmium-catalyzed dihydroxylation of various olefins using bleach as oxidant is reported for the first time. Aromatic and aliphatic olefins yield the corresponding cis-1,2-diols in the presence of dihydroquinine or dihydroquinidine derivatives (Sharpless ligands) with good to excellent chemo- and enantioselectivities under optimized pH conditions. In the presence of a small excess of bleach as reoxidant fast dihydroxylation takes place even at 0°C. Under optimum reaction conditions it is possible to dihydroxylate terminal aliphatic and aromatic olefins as well as internal olefins. The low price of the oxidant and the simple handling of bleach make this dihydroxylation variant attractive for further applications.
- Mehltretter, Gerald M.,Bhor, Santosh,Klawonn, Markus,D?bler, Christian,Sundermeier, Uta,Eckert, Markus,Militzer, Hans-Christian,Beller, Matthias
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p. 295 - 301
(2007/10/03)
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- MTO and OsO4: An efficient catalytic couple for mild H2O2-based asymmetric dihydroxylation of olefins
-
A novel and robust system for osmium-catalyzed asymmetric dihydroxylation of olefins by aqueous H2O2 with methyltrioxorhenium (MTO) as electron transfer mediator (ETM) has been developed. The MTO is catalyzing the H2O2 oxidation of the chiral ligand to its mono-N-oxide, which in turn reoxidizes OsVI to OsVIII. Thus the (DHQD)2PHAL plays a dual role serving as the chiral inductor as well as the tertiary amine generating the N-oxide required for the recycling of osmium. The present catalytic system gives vicinal diols in good isolated yields and high enantiomeric excess (up to 99 % ee).
- Jonsson, Sandra Y.,Adolfsson, Hans,Baeckvall, Jan-E.
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p. 2783 - 2788
(2007/10/03)
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- A Mechanistically Guided Design Leads to the Synthesis of an Efficient and Practical New Reagent for the Highly Enantioselective, Catalytic Dihydroxylation of Olefins
-
(Equation presented) The catalytic asymmetric dihydroxylation of olefins has been accomplished with high enantioselectivities using a proline-based catalyst. The pre-transition-state assembly for styrene is shown.
- Huang, Jinkun,Corey
-
p. 3455 - 3458
(2007/10/03)
-
- Method for the asymmetric dihydroxylation of olefins, using osmium catalysts
-
This invention relates to process for asymmetric dihydroxylation of olefins using osmium catalysts to obtain monofunctional, bifunctional, and/or polyfunctional chiral 1,2-diols of the formula (I) R1R2C(OH)—C(OH)R3R4??(I) where R1to R4are defined herein, by reacting an olefin of the formula (II) R1R2C═CR3R4??(II) where R1to R4are defined as for formula (I), with molecular oxygen in the presence of an osmium compound and a chiral amine ligand in water or a water-containing solvent mixture at a pH of from 8.5 to 13.
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-
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- OsO(4) in ionic liquid [Bmim]PF(6): a recyclable and reusable catalyst system for olefin dihydroxylation. remarkable effect of DMAP.
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[reaction: see text] The combination of the ionic liquid [bmim]PF(6) and DMAP provides a most simple and practical approach to the immobilization of OsO(4) as catalyst for olefin dihydroxylation. Both the catalyst and the ionic liquid can be repeatedly recycled and reused in the dihydroxylation of a variety of olefins with only a very slight drop in catalyst activity.
- Yao, Qingwei
-
p. 2197 - 2199
(2007/10/03)
-
- Silica Gel-Supported Cinchona Alkaloid-OsO4 Complex for Catalytic Heterogeneous Asymmetric Dihydroxylation of Olefins by H2O2 using a Titanium Silicalite-Based Coupled Catalytic System
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A triple catalytic system designed for asymmetric dihydroxylation of olefins, composed of NMM and two divergent heterogeneous catalysts, titanium silicalite and silica gel-supported 1,4-bis(9-O-dihydroquinidinyl)phthalazine [SGS-(DHQD)2 PHAL)]-OsO4 complex relays the transport of two electrons from olefin to H2O2 used as a terminal oxidant to provide chiral diols with good yields and high enantiomeric excesses in a single pot.
- Choudary, Boyapati M.,Chowdari, Naidu S.,Jyothi, Karangula,Madhi, Sateesh,Kantam, Mannepalli L.
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p. 503 - 506
(2007/10/03)
-
- Ruthenium-catalyzed oxidative cleavage of olefins to aldehydes
-
Three oxidation protocols have been developed to cleave olefins to carbonyl compounds with ruthenium trichloride as catalyst (3.5 mol %). These methods convert olefins that are not fully substituted to aldehydes rather than carboxylic acids. While aryl olefins were cleaved to aromatic aldehydes in excellent yields by using the system of RuCl3-Oxone-NaHCO3 in CH3CN-H2O (1.5:1), aliphatic olefins were converted into alkyl aldehydes with RuCl3-NaIO4 in 1,2-dichloroethane-H2O (1:1) in good to excellent yields. It is noteworthy that terminal aliphatic olefins were cleaved to the corresponding aldehydes in excellent yields by using RuCl3-NaIO4 in CH3CN-H2O (6:1).
- Yang,Zhang
-
p. 4814 - 4818
(2007/10/03)
-
- Osmium-catalyzed asymmetric dihydroxylation of olefins by H2O2 using a biomimetic flavin-based coupled catalytic system
-
Selective cis-dihydroxylation of olefins with the aid of a triple catalytic system using H2O2 as the terminal oxidant has been developed. In this process Os(VI) is recycled to Os(VIII) by a coupled electron-transfer-mediator system based on N-methylmorpholine and a biomimetic flavin, leading to a mild and selective electron transfer. Aliphatic, aromatic, and functionalized olefins were successfully cis-dihydroxylated, employing the triple catalytic system. The present biomimetic catalytic system works well in asymmetric dihydroxylation and gave optically active diols in good isolated yields and high enantiomeric excesses (up to 99% ee).
- Jonsson,Faernegardh,Baeckvall
-
p. 1365 - 1371
(2007/10/03)
-
- Catalytic asymmetric dihydroxylation of C,C double bonds with osmium tetroxide using selenoxides as co-oxidants
-
Asymmetric dihydroxylation of olefins has been achieved in good yields and ee's using potassium osmate dihydrate (K2OsO2(OH)4, the pre-oxidant), (DHQD)2PHAL (the chiral ligand), potassium carbonate (the base) and selenoxides (the co-oxidants). Both the yield and the ee proved to be pH dependent, the highest yield and ee being found at almost the same pH values. The rate of the reaction was found to be highly dependent upon the structure of the selenoxide used. Some representative examples involving aminoxides are presented for comparison.
- Krief,Castillo-Colaux
-
p. 501 - 504
(2007/10/03)
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- Catalytic asymmetric dihydroxylation using phenoxyethoxymethyl-polystyrene (PEM)-based novel microencapsulated osmium tetroxide (PEM-MC OsO4)
-
(Equation presented) A phenoxyethoxymethyl-polystyrene (PEM)-based novel polymer-supported osmium catalyst has been developed. The catalyst was readily prepared from PEM polymer based on a microencapsulation technique, and asymmetric dihydroxylation of olefins has been successfully performed using (DHQD)2PHAL as a chiral ligand and K3Fe(CN)6 as a cooxidant in H20/acetone. The catalyst was recovered quantitativery by simple filtration and reused without loss of activity several times.
- Kobayashi, Shu,Ishida, Tasuku,Akiyama, Ryo
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p. 2649 - 2651
(2007/10/03)
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- Osmium-catalyzed asymmetric dihydroxylation of olefins by H2O2; dual role of the cinchona alkaloid ligand
-
(matrix presented) A novel application of the cinchona alkaloid derivative (DHQD)2PHAL in the osmium-catalyzed asymmetric dihydroxylation of olefins is presented. In a triple catalytic system using H2O2 as the terminal oxidant, the alkaloid ligand has a dual function in providing stereocontrol in the addition step and, via its N-oxidized form, acting as reoxidant for the in situ generated osmium(VI). The formation of the N-oxide is catalyzed by a biomimetic flavin.
- Jonsson, Sandra Y.,Adolfsson, Hans,Baeckvall, Jan-E.
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p. 3463 - 3466
(2007/10/03)
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- Acid-catalyzed phenylcyclohexene oxide hydrolysis: Role of para-phenyl substituent on syn:anti hydration ratio
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Rate and product studies of the hydronium ion-catalyzed hydrolysis of 1- phenylcyclohexene oxide and its p-methoxy and p-methyl derivatives in 1:9 dioxane-water solutions were carried out under conditions in which the diol products are stable. It is shown that the cis:trans diol ratio from hydrolysis of this series of epoxides does not systematically increase with the electron-donating ability of the para-substituent, contrary to conclusions in the literature. The equilibrium constants and rates for acid- catalyzed approach to equilibration of cis- and trans-1-(p- methoxyphenyl)cyclohexane-1,2-diol and of cis- and trans-1-(p- methylphenyl)cyclohexane-1,2-diol were measured, and the cis-diol was determined to be the more stable isomer in each case. An intermediate in the acid-catalyzed hydrolysis of 1-(p-methoxyphenyl)cyclohexene oxide is trapped, after its rate-limiting formation, by azide ion. For a series of 1- arylcyclohexene oxides, results are interpreted in terms of a mechanism in which there is a discrete carbocation intermediate, and products are determined solely by the partitioning reactions of this intermediate, with the pathway leading to the more stable product being energetically favored.
- Doan, Lanxuan,Bradley, Kevin,Gerdes, Sonya,Whalen, Dale L.
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p. 6227 - 6234
(2007/10/03)
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- Atom-efficient oxidation of alkenes with molecular oxygen: Synthesis of diols
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Dihydroxylations of simple alkenes were carried out for the first time in excellent yields and selectivities with molecular oxygen as oxidant [(Eq. (a)]. Both oxygen atoms are used productively and are incorporated into the product in this transition metal catalyzed alkene oxidation.
- Doebler, Christian,Mehltretter, Gerald,Beller, Matthias
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p. 3026 - 3028
(2007/10/03)
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- The Effect of Reduced Osmium Amounts on the Asymmetric Dihydroxylation of 1-Arylcyclohexenes
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The amount of osmium required for satisfactory levels of conversion and asymmetric induction in the AD reaction of 1-arylcyclohexenes has been established.
- McIntosh, John M.,Kiser, E. Jay
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p. 1283 - 1284
(2007/10/03)
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- Enantioselective acylation of alcohols catalyzed by lipase QL from Alcaligenes sp.: A predictive active site model for lipase QL to identify the faster reacting enantiomer of an alcohol in this acylation
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Lipase QL-catalyzed acylation of secondary alcohols using isopropenyl acetate as the acylating agent in diisopropyl ether gave preferentially the corresponding acetate with an R configuration. On the basis of the results, a predictive active site model for lipase QL is proposed for identifying which enantiomer of a secondary alcohol reacts faster in this reaction.
- Naemura,Murata,Tanaka,Yano,Hirose,Tobe
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p. 1581 - 1584
(2007/10/03)
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- Enantioselective acylation of primary and secondary alcohols catalyzed by lipase QL from Alcaligenes sp.: A predictive active site model for lipase QL to identify which enantiomer of an alcohol reacts faster in this acylation
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Lipase QL (from Alcaligenes sp.)-catalyzed acylation of alcohols using isopropenyl acetate as the acylating agent in diisopropyl ether converted preferentially primary alcohols with an S configuration and secondary alcohols with an R configuration into the corresponding homochiral acetates. On the basis of observed enantiomer selectivities, a predictive active site model for lipase QL is proposed for identifying which enantiomer of a primary or a secondary alcohol reacts faster in this acylation. Copyright (C) 1996 Published by Elsevier Science Ltd.
- Naemura, Koichiro,Murata, Masaki,Tanaka, Rie,Yano, Masashi,Hirose, Keiji,Tobe, Yoshito
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p. 3285 - 3294
(2007/10/03)
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- Preparation and enantiomer recognition behaviour of azophenolic crown ethers containing cis-1-phenylcyclohexane-1,2-diol as the chiral subunit and 2,4-dinitrophenylazophenol as the chromophore
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Optically active azophenolic crown ethers 1 and 2 incorporating two cis-1-phenylcyclohexane-1,2-diol chiral subunits and a p-(2,4-dinitrophenylazo)phenol moiety as a chromophore have been prepared and the enantiomer recognitive coloration in complexation with chiral ethylamine and 2-aminoethanol derivatives has been examined. The observed enantiomer selectivities of crown ethers 1 and 2 have been interpreted on the basis of CPK molecular model examination of the diastereoisomeric complexes.
- Naemura, Koichiro,Ueno, Koji,Takeuchi, Sachiko,Hirose, Keiji,Tobe, Yoshito,Kaneda, Takahiro,Sakata, Yoshiteru
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p. 383 - 388
(2007/10/03)
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- Chemical and Electrochemical Asymmetric Dihydroxylation of Olefins in I2-K2CO3-K2OsO2(OH)4 and I2-K3PO4/K2HPO4-K2OsO2(OH)4 Systems with Sharpless' Ligand
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Iodine-assisted chemical and electrochemical asymmetric dihydroxylation of various olefins in I2-K2CO3-K2OsO2(OH)4 and I2-K3PO4/K2HPO4-K2OsO2(OH)4 systems with Sharpless' ligand provided the optically active glycols in excellent isolated yields and high enantiomeric excessses.Iodine (I2) was used stoichiometrically for the chemical dihydroxylation, and good results were obtained with nonconjugated olefins in contrast to the case of potassium ferricyanide as a co-oxidant.The potentialily of I2 as a co-oxidant under stoichiometric conditions has been proven to be effective as an oxidizing mediator in electrolysis systems.Iodine-assited asymmetric electro-dihydroxylation of olefins in either a t-BuOH/H2O(1/1)-K2CO3/(DHQD)2PHAL-(Pt) or t-BuOH/H2O(1/1)-K3PO4/K2HPO4/(DHQD)2PHAL-(Pt) system in the presence of potassium osmate in an undivided cell was investigated in detail.Irrespective of the substitution pattern, all the olefins afforded the diols in high yields and excellent enantiomeric excesses.A plausible mechanism is discussed on the basis of cyclic voltammograms as well as experimental observations.
- Torii, Sigeru,Liu, Ping,Bhuvaneswari, Narayanaswamy,Amatore, Christian,Jutand, Anny
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p. 3055 - 3060
(2007/10/03)
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- A Mechanistically Designed Mono-cinchona Alkaloid Is An Excellent Catalyst for the Enantioselective Dihydroxylation of Olefins
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On the basis of ideas recently advanced regarding the origin of enantioselectivity in the OsO4 promoted dihydroxylation of olefins catalyzed by bis-cinchona alkaloid derivatives such as 1, specifically strong evidence for reaction via transition state assembly 2, the mono-quinidine derivative 3 was selected as a promising catalytic ligand.The experimental observation of high enantioselectivity promoted by 3 provides additional evidence in favor of transition-state 2.
- Corey, E. J.,Noe, Mark C.,Grogan, Michael J.
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p. 6427 - 6430
(2007/10/02)
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- Heterogeneous catalytic asymmetric dihydroxylation of olefins: A new polymeric support and a process improvement
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A new polymeric support containing a derivative of quinine 4-chlorobenzoate and alcoholic pendent groups was found to give good enantioselectivity in many cases comparable to those obtained with the free alkaloid in homogeneous reaction conditions, providing also the known advantages of the heterogeneous process. Both aromatic and aliphatic olefins were screened, using either N-methylmorpholine-N-oxide (NMO) or potassium ferricyanide (K3Fe(CN)6) as secondary oxidants.
- Pini, Dario,Petri, Antonella,Salvadori, Piero
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p. 11321 - 11328
(2007/10/02)
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- An efficient synthesis of enantiomerically pure trans-2-phenylcyclohexanol
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Both enantiomers of trans-2-phenylcyclohexanol (3), Whitesell's auxiliary, have been prepared in a simple two step sequence featuring a catalytic asymmetric dihydroxylation followed by stereo selective hydrogenolysis.
- King, S. Bruce,Sharpless, K. Barry
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p. 5611 - 5612
(2007/10/02)
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