- Osmium-catalyzed dihydroxylation of alkenes by H2O2 in room temperature ionic liquid co-catalyzed by VO(acac)2 or MeReO3
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Room temperature ionic liquid [bmim]PF6 was used to immobilize a bimetallic catalytic system for H2O2-based dihydroxylation of alkenes. Osmium tetroxide was used as the substrate-selective catalyst with either VO(acac)2 or MeReO 3 as co-catalyst. The latter serve as an electron transfer mediator (ETM) and activates H2O2. For an increased efficiency N-methylmorpholine is required as an additional ETM in most cases. A range of alkenes were dihydroxylated using this robust bimetallic system and it was demonstrated that for some of the alkenes the catalytic system can be recycled and used up to five times.
- Johansson, Mikael,Lindén, Auri A.,B?ckvall, Jan-E.
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- Direct, high-yielding, one-step synthesis of vic-diols from aryl alkynes
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An unprecedented, high yielding, direct, one-step synthesis of vic-diols from alkynes has been developed via metal-free, open-to-air dihydroboration with ammonia borane. The electronics of the alkyne and the reaction stoichiometry are critical for obtaining optimal yields of the 1,2-diol.
- Ramachandran, P. Veeraraghavan,Drolet, Michael P.
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supporting information
p. 967 - 970
(2018/02/14)
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- Formation of persulphate from sodium sulphite and molecular oxygen catalysed by H5PV2Mo10O40-aerobic epoxidation and hydrolysis
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The H5PV2Mo10O40 polyoxometalate catalysed the electron transfer oxidation of sulphite to yield a sulphite radical, SO3- that upon addition of O2 yielded a peroxosulphate species efficient for the H5PV2Mo10O40 catalysed epoxidation of alkenes. The acidic polyoxometalate further catalysed hydrolysis of the epoxide to give vicinal diols in high yields. This journal is
- Rubinstein, Amir,Carmeli, Raanan,Neumann, Ronny
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p. 13247 - 13249
(2015/05/20)
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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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- The acid accelerated ruthenium-catalysed dihydroxylation. Scope and limitations
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Recently, we discovered a significant rate acceleration in RuO 4-catalysed dihydroxylations of olefins by addition of Broensted-acids resulting in a reduction of the catalyst loading to only 0.5 mol%. The present paper gives a full account on the optimisation protocol that led to the discovery of the beneficial influence of protic acids. A strong focus is set on the detailed description of the influence of different reaction parameters on both reactivity and selectivity. In the second part an intense investigation of scope and limitations will be presented. The results provided in this manuscript might lead to a deeper understanding of competing processes that influence the selectivity in RuO4-catalysed dihydroxylations.
- Plietker, Bernd,Niggemann, Meike,Pollrich, Anja
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p. 1116 - 1124
(2007/10/03)
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- An improved protocol for the RuO4-catalyzed dihydroxylation of olefins
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(Matrix Presented) Dihydroxylation under ruthenium catalysis provides an easy access to syn-diols, although overoxidation is a common side reaction. Furthermore, the high catalyst loadings offset the lower price of ruthenium compared to osmium. In this paper, we present an improved protocol for the RuO4-catalyzed syn-dihydroxylation using only 0.5 mol % catalyst under acidic conditions. A variety of olefins can be hydroxylated in good to excellent yields with only minor formation of side products.
- Plietker, Bernd,Niggemann, Meike
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p. 3353 - 3356
(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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- Osmium-Catalyzed Dihydroxylation of Olefins in Acidic Media: Old Process, New Tricks
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A screen of over 500 diversely functionalized additives in osmium-catalyzed dihydroxylation has uncovered that electron-deficient olefins are converted into the corresponding diols much more efficiently when the pH of the reaction medium is maintained on the acidic side. Further studies have identified citric acid as the additive of choice, for it allows preparation of very pure diols in yields generally exceeding 90%. As described here, a much wider range of olefin classes can now be successfully dihydroxylated. The process is experimentally simple, in most cases involving little more than dissolving the reactants in water or a waler/tertbutyl alcohol mixture, stirring them, and filtering off the pure diol product.
- Dupau, Philippe,Epple, Robert,Thomas, Allen A.,Fokin, Valery V.,Sharpless, K. Barry
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p. 421 - 433
(2007/10/03)
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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
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p. 2197 - 2199
(2007/10/03)
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- Efficient diastereoselective pinacol coupling reaction of aliphatic and aromatic aldehydes by using newly utilized low valent titanium bromide and iodide species
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Reductive coupling reaction of aromatic and aliphatic aldehydes proceeded under mild conditions to give the corresponding pinacols in moderate to high yields and DL-diastereoselectivities by using combinations of either low valent titanium(II) bromide and copper or titanium(IV) iodide and copper in a mixed solvent of dichloromethane and pivalonitrile. In the case of using titanium(IV) iodide and copper, pinacols were obtained in good to high yields with moderate to high diastereoselectivities irrespective of the number of substitutuents at α-position of aliphatic aldehydes.
- Mukaiyama, Teruaki,Yoshimura, Naritoshi,Igarashi, Koji,Kagayama, Akifumi
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p. 2499 - 2506
(2007/10/03)
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- Osmium-catalyzed asymmetric dihydroxylation of olefins by H2O2 using a biomimetic flavin-based coupled catalytic system
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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
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p. 1365 - 1371
(2007/10/03)
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- Efficient diastereoselective pinacol reaction of aliphatic and aromatic aldehydes by combined use of newly utilized titanium(II) bromide and copper
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Newly utilized low-valent titanium reductant, titanium(II) bromide, was conveniently prepared by treating titanium(IV) bromide with hexamethyldisilane. The pinacol reaction of aromatic and aliphatic aldehydes including primary aldehydes proceeded smoothly in dichloromethane-pivalonitrile at temperatures ranging from -23 to 0 °C by the combined use of soluble titanium(II) bromide and copper to give 1,2-diols in good to high yields with good to high dl-selectivities.
- Mukaiyama, Teruaki,Kagayama, Akifumi,Igarashi, Koji
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p. 336 - 337
(2007/10/03)
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- Dichlorotin oxide-catalyzed new direct functionalization of olefins: Synthesis of trans β-azidohydrins and 1,2-diols
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We have succeeded in developing direct syntheses of trans β- azidohydrins and trans 1,2-diol derivatives from olefins catalyzed by dichlorotin oxide. The regioselectivity of these reactions with tri- substituted olefins is high (10:1 in the synthesis of 1,2-diol derivatives) to excellent (>99:1 in the synthesis of azidohydrins). It has been found that these reactions do not proceed via epoxides. (C) 2000 Elsevier Science Ltd.
- Sakurada, Isao,Yamasaki, Shingo,Kanai, Motomu,Shibasaki, Masakatsu
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p. 2415 - 2418
(2007/10/03)
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- Epoxydation diastereoselective d'alcools allyliques monofluores
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Epoxidation of fluoroallylic alcohols with VO(acac)2 or Ti(OiPr)4 + TBHP results in high diastereoselectivity (90-95percent).Epoxidation with m-CPBA gives the erythro isomer as the major component, as opposed to the hydrocarbon series.The ring opening of epoxy alcohols by nucleophiles is easy.
- Dubuffet, Thierry,Bidon, Corinne,Sauvetre, Raymond,Normant, Jean-F.
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p. 173 - 185
(2007/10/02)
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- Regioselective Nucleophilic Opening of erythro- and threo-2,3-Epoxy- Alcohols
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The epoxide opening reactions of erythro and threo epoxy alcohols with a variety of nucleophiles, both in the presence and absence of Ti(OiPr)4, were examined.In general, opening of threo epoxy alcohols proceeded faster and with higher selectivity than the same reaction with the corresponding erythro isomers.
- Kirshenbaum, Kenneth S.,Sharpless, K. Barry
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- PHOTOCHEMICAL REACTION OF ALCOHOLS-I IRRADIATION OF ALIPHATIC ALCOHOLS
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The UV irradiation of aliphatic alcohols gave α-glycols as the principal products.The values of the dl-α-glycol to meso-α-glycol ratios obtained in each example were analyzed.The stereochemical course of the formation of α-glycols, their conformations and configurations were established on basis of 1H NMR data.
- Balsells, R. Erra,Frasca, A. R.
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p. 245 - 255
(2007/10/02)
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