- Selective Isomerization via Transient Thermodynamic Control: Dynamic Epimerization of trans to cis Diols
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Traditional approaches to stereoselective synthesis require high levels of enantio- and diastereocontrol in every step that forms a new stereocenter. Here, we report an alternative approach, in which the stereochemistry of organic substrates is selectivel
- Macmillan, David W. C.,Oswood, Christian J.
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- A Change from Kinetic to Thermodynamic Control Enables trans-Selective Stereochemical Editing of Vicinal Diols
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Here, we report the selective, catalytic isomerization of cis-1,2-diols to trans-diequatorial-1,2-diols. The method employs triphenylsilanethiol (Ph3SiSH) as a catalyst and proceeds under mild conditions in the presence of a photoredox catalyst and under
- Gu, Xin,Wendlandt, Alison E.,Zhang, Yu-An
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supporting information
p. 599 - 605
(2022/01/03)
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- Photo-Induced Dihydroxylation of Alkenes with Diacetyl, Oxygen, and Water
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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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- Hydrodealkenylative C(sp3)–C(sp2) bond fragmentation
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Chemical synthesis typically relies on reactions that generate complexity through elaboration of simple starting materials. Less common are deconstructive strategies toward complexity—particularly those involving carbon-carbon bond scission. Here, we introduce one such transformation: the hydrodealkenylative cleavage of C(sp3)–C(sp2) bonds, conducted below room temperature, using ozone, an iron salt, and a hydrogen atom donor. These reactions are performed in nonanhydrous solvents and open to the air; reach completion within 30 minutes; and deliver their products in high yields, even on decagram scales. We have used this broadly functionality tolerant transformation to produce desirable synthetic intermediates, many of which are optically active, from abundantly available terpenes and terpenoid-derived precursors. We have also applied it in the formal total syntheses of complex molecules.
- Smaligo, Andrew J.,Swain, Manisha,Quintana, Jason C.,Tan, Mikayla F.,Kim, Danielle A.,Kwon, Ohyun
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p. 681 - 685
(2019/06/11)
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- Pyrazine dicarboxylate-bridged arsenotungstate: Synthesis, characterization, and catalytic activities in epoxidation of olefins and oxidation of alcohols
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A praseodymium(iii)-containing arsenotungstate K16H15Li7[Pr2(H2O)3(pzdc)As3W29O103]2·38H2O (1) (pzdc = pyrazine-2,3-dicarboxylic acid) was synthesized by a conventional aqueous solution method and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), and single crystal X-ray diffraction. Structural analysis revealed that compound 1 was constructed by two identical subunits {Pr2(H2O)3(AsW9O33)3W2O4} bridged together by two pzdc ligands. In addition, compound 1 could act as an efficient catalyst for the epoxidation of olefins and oxidation of alcohols with hydrogen peroxide (H2O2) as the oxidant. In particular, the turnover frequency (TOF) in the oxidation of 1-phenylethanol reached up to 10170 h-1, which is higher than that of previously reported catalysts.
- Ma, Xinyi,He, Peipei,Xu, Baijie,Lu, Jingkun,Wan, Rong,Wu, Hechen,Wang, Yuan,Ma, Pengtao,Niu, Jingyang,Wang, Jingping
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supporting information
p. 12956 - 12963
(2019/09/07)
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- Amine Catalysis for the Organocatalytic Diboration of Challenging Alkenes
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The generation of in situ sp2–sp3diboron adducts has revolutionised the synthesis of organoboranes. Organocatalytic diboration reactions have represented a milestone in terms of unpredictable reactivity of these adducts. However, current methodologies have limitations in terms of substrate scope, selectivity and functional group tolerance. Here a new methodology based on the use of simple amines as catalyst is reported. This methodology provides a completely selective transformation overcoming current substrate scope and functional/protecting group limitations. Mechanistic studies have been included in this report.
- Farre, Albert,Soares, Kaline,Briggs, Rachel A.,Balanta, Angelica,Benoit, David M.,Bonet, Amadeu
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p. 17552 - 17556
(2016/11/28)
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- Selective transition-metal-free vicinal cis-dihydroxylation of saturated hydrocarbons
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A transition-metal-free cis-dihydroxylation of saturated hydrocarbons under ambient reaction conditions has been developed. The described approach allows a direct and selective synthesis of vicinal diols. The new reaction thereby proceeds via radical iodination and a sequence of oxidation steps. A broad scope of one-pot dual C(sp3)-H bond functionalization for the selective synthesis of vicinal syn-diols was demonstrated.
- Bering, Luis,Antonchick, Andrey P.
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p. 452 - 457
(2016/12/30)
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- Osmium impregnated on magnetite as a heterogeneous catalyst for the syn-dihydroxylation of alkenes
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A new catalyst derived from osmium has been prepared, fully characterized and tested in the dihydroxylation of alkenes. The catalyst was prepared by wet impregnation methodology of OsCl3·3H2O on a commercial micro-magnetite surface. The catalyst allowed the reaction with one of the lowest osmium loadings for a heterogeneous catalyst and was selective for the monodihydroxylation of 1,5-dienes. Moreover, the catalyst was easily removed from the reaction medium by the simple use of a magnet. The selectivity of catalyst is very high with conversions up to 99%. Preliminary kinetics studies showed a first-order reaction rate with respect to the catalyst.
- Cano, Rafael,Pérez, Juana M.,Ramón, Diego J.
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p. 177 - 182
(2014/01/06)
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- Osmium(III) and osmium(V) complexes bearing a macrocyclic ligand: A simple and efficient catalytic system for cis-dihydroxylation of alkenes with hydrogen peroxide
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A simple protocol that uses [OsIII(OH)(H2O)(L-N 4Me2)](PF6)2 (1; L-N 4Me2=N,N′-dimethyl-2,11-diaza[3.3](2,6) pyridinophane) as a catalyst and H2O2 as a terminal oxidant for efficient cis-1,2-dihydroxylation of alkenes is presented. Unfunctionalized (or aliphatic) alkenes and alkenes/styrenes containing electron-withdrawing groups are selectively oxidized to the corresponding vicinal diols in good to excellent yields (46-99 %). In the catalytic reactions, the stoichiometry of alkene:H2O2 is 1:1, and thus the oxidant efficiency is very high. For the dihydroxylation of cyclohexene, the catalytic amount of 1 can be reduced to 0.01 mol % to achieve a very high turnover number of 5500. The active oxidant is identified as the Os V(O)(OH) species (2), which is formed via the hydroperoxide adduct, an OsIII(OOH) species. The active oxidant 2 is successfully isolated and crystallographically characterized. The wizard of Os: A simple protocol that uses [OsIII(OH)(H2O)(L-N4Me 2)](PF6)2 (1) and H2O2 for efficient cis-1,2-dihydroxylation of alkenes is presented. Unfunctionalized (or aliphatic) alkenes and alkenes/styrenes containing electron-withdrawing groups were converted into the corresponding vicinal diols in good to excellent yields. It has been confirmed that the OsV(O)(OH) species (2) is the active oxidant, which is formed via the hydroperoxide adduct A. Copyright
- Sugimoto, Hideki,Ashikari, Kenji,Itoh, Shinobu
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p. 2154 - 2160
(2013/09/23)
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- Stereo- and regioselectivity in the P450-catalyzed oxidative tandem difunctionalization of 1-methylcyclohexene
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The selective partial oxidation of small non-functionalized molecules using biocatalysis based on P450 monooxygenases is known to be difficult due to the expected poor regio- and stereoselectivity, but in this study it was nevertheless attempted. 1-Methyl
- Roiban, Gheorghe-Doru,Agudo, Rubén,Reetz, Manfred T.
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p. 5306 - 5311
(2013/07/05)
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- Stereoselective selenium catalyzed dihydroxylation and hydroxymethoxylation of alkenes
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The selenium atom of the selenocysteine plays a crucial role in the reduction of peroxides. Herein we showed that, in the absence of a thiol cofactor, the same aminoacid efficiently catalyzed the dihydroxylation of carbon-carbon double bonds leading to the stereoselective formation of 1,2-diols at room temperature and in on water conditions. Alternatively, in the presence of methanol, the corresponding β-methoxyalcohol can be prepared. The stereoselectivity of the reaction will be discussed and NMR evidences of the actual catalyst are here reported.
- Santi, Claudio,Di Lorenzo, Rosalia,Tidei, Caterina,Bagnoli, Luana,Wirth, Thomas
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p. 10530 - 10535,6
(2012/12/12)
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- An osmium(III)/osmium(V) redox couple generating OsV(O)(OH) center for cis -1,2-dihydroxylation of alkenes with H2O2: Os complex with a nitrogen-based tetradentate ligand
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For the synthesis of the 1,2-diols, cis-1,2-dihydroxylation of alkenes catalyzed by osmium(VIII) tetroxide (OsO4) is a powerful method. However, OsO4 is quite toxic due to its highly volatile and sublimable nature. Thus, the development of alternative catalysts for cis-1,2-dihydroxylation of alkenes is highly challenging. Our approach involves the use of a nitrogen-based tetradentate ligand, tris(2-pyridylmethyl)amine (tpa), for an osmium center to develop a new osmium catalyst and hydrogen peroxide (H2O2) as a cheap and environmentally benign oxidant. The new Os-tpa complex acts as a very efficient turnover catalyst for syn-selective dihydroxylation of various alkenes (turnover number ~1000) in aqueous media, and H2O2 oxidant is formally incorporated into the products quantitatively (100% atom efficiency). The reaction intermediates involved in the catalytic cycle have been isolated and characterized crystallographically as [OsIII(OH)(H 2O)(tpa)]2+ and [OsV(O)(OH)(tpa)]2+ complexes. The observed syn-selectivity, structural characteristics of the intermediates, and kinetic studies have suggested a concerted [3 + 2]-cycloaddition mechanism between [OsV(O)(OH)(tpa)]2+ and alkenes, which is strongly supported by DFT calculations.
- Sugimoto, Hideki,Kitayama, Kazuhiro,Mori, Seiji,Itoh, Shinobu
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p. 19270 - 19280
(2013/01/15)
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- Bronsted acid-catalyzed dihydroxylation of olefins in aqueous medium
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The trans-dihydroxylation of olefins occurs efficiently by aqueous hydrogen peroxide catalyzed by p-toluenesulfonic acid at 50°C, allowing the catalyst reuse and an outstanding substrate functional group tolerance such as tert-butoxycarbonylamino (BocNH), benzyloxycarbonylamino (CbzNH), benzyloxy (OBn), tosyloxy (OTs), hindered ketal, (2-trimethylsilyl)ethoxymethoxy (OSEM), benzylamino (NBz), benzyloxy (OBz) and free amino acid. Copyright
- Rosatella, Andreia A.,Afonso, Carlos A.M.
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supporting information; experimental part
p. 2920 - 2926
(2012/01/03)
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- Manipulating the Expression Rate and Enantioselectivity of an Epoxide Hydrolase by Using Directed Evolution
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We describe here a strategy to improve the expression efficiency and enantioselectivity of Aspergillus niger epoxide hydrolase (ANEH) by directed evolution. Based on a blue-colony screening system using the LacZα (β-galactosidase α peptide) complementation solubility reporter, several ANEH variants out of 15000 transformants from a random-mutagenesis library were identified that show improved recombinant expression in E. coli. Among them, Pro221Ser was subsequently used as a template for iterative saturation mutagenesis (ISM) at sites around the ANEH binding pocket. Following four rounds of ISM, a highly enantioselective mutant was identified that catalyzes the hydrolytic kinetic resolution of racemic glycidyl phenyl ether with a selectivity factor of E=160 in favor of the (S)-diol compared to WT ANEH characterized by E=4.6. Expression of this mutant is 50 times higher than that of WT ANEH. It also serves as an excellent stereoselective catalyst in the hydrolytic kinetic resolution and desymmetrization of several other structurally diverse epoxides. Copyright
- Reetz, Manfred T.,Zheng, Huabao
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experimental part
p. 1529 - 1535
(2012/05/31)
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- Manipulating the stereoselectivity of limonene epoxide hydrolase by directed evolution based on iterative saturation mutagenesis
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Limonene epoxide hydrolase from Rhodococcus erythropolis DCL 14 (LEH) is known to be an exceptional epoxide hydrolase (EH) because it has an unusual secondary structure and catalyzes the hydrolysis of epoxides by a rare one-step mechanism in contrast to the usual two-step sequence. From a synthetic organic viewpoint it is unfortunate that LEH shows acceptable stereoselectivity essentially only in the hydrolysis of the natural substrate limonene epoxide, which means that this EH cannot be exploited as a catalyst in asymmetric transformations of other substrates. In the present study, directed evolution using iterative saturation mutagenesis (ISM) has been tested as a means to engineer LEH mutants showing broad substrate scope with high stereoselectivity. By grouping individual residues aligning the binding pocket correctly into randomization sites and performing saturation mutagenesis iteratively using a reduced amino acid alphabet, mutants were obtained which catalyze the desymmetrization of cyclopentene-oxide with stereoselective formation of either the (R,R)- or the (S,S)-diol on an optional basis. The mutants prove to be excellent catalysts for the desymmetrization of other meso-epoxides and for the hydrolytic kinetic resolution of racemic substrates, without performing new mutagenesis experiments. Since less than 5000 tranformants had to be screened for achieving these results, this study contributes to the generalization of ISM as a fast and reliable method for protein engineering. In order to explain some of the stereoselective consequences of the observed mutations, a simple model based on molecular dynamics simulations has been proposed.
- Zheng, Huabao,Reetz, Manfred T.
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supporting information; experimental part
p. 15744 - 15751
(2011/02/21)
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- Manganese catalyzed cis-dihydroxylation of electron deficient alkenes with H2O2
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A practical method for the multigram scale selective cis-dihydroxylation of electron deficient alkenes such as diethyl fumarate and N-alkyl and N-aryl-maleimides using H2O2 is described. High turnovers (>1000) can be achieved with this efficient manganese based catalyst system, prepared in situ from a manganese salt, pyridine-2-carboxylic acid, a ketone and a base, under ambient conditions. Under optimized conditions, for diethyl fumarate at least 1000 turnovers could be achieved with only 1.5 equiv. of H2O2 with d/l-diethyl tartrate (cis-diol product) as the sole product. For electron rich alkenes, such as cis-cyclooctene, this catalyst provides for efficient epoxidation.
- Saisaha, Pattama,Pijper, Dirk,Van Summeren, Ruben P.,Hoen, Rob,Smit, Christian,De Boer, Johannes W.,Hage, Ronald,Alsters, Paul L.,Feringa, Ben L.,Browne, Wesley R.
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supporting information; experimental part
p. 4444 - 4450
(2010/11/05)
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- Fluorinated acid amplifiers for EUV lithography
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(Chemical Equation Presented) Five new compounds were synthesized for use as acid amplifiers in EUV (13.5 nm) photoresists. Four compounds act as acid amplifiers and decompose by autocatalytic kinetics to generate fluorinated sulfonic acids, essential for the simultaneous improvement of resolution, sensitivity, and line edge roughness (LER) in EUV photoresists. The decomposition rates were studied using 19F NMR in the presence and absence of 1.2 equiv of tri-tertbutylpyridine. Three acid amplifiers decomposed 490, 1360, and 1430 times faster without base than with base. Preliminary lithographic evaluations show that cis-1-methyl-2-(4-(trifluoromethyl) phenylsulfonyloxy)cyclohexyl acetate simultaneously improves the resolution, LER, and sensitivity of an EUV photoresist. Copyright
- Kruger, Seth,Revuru, Sri,Higgins, Craig,Gibbons, Sarah,Freedman, Daniel A.,Yueh, Wang,Younkin, Todd R.,Brainard, Robert L.
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supporting information; experimental part
p. 9862 - 9863
(2009/12/06)
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- Sharpless asymmetric dihydroxylation of olefins in water-surfactant media with recycling of the catalytic system by membrane nanofiltration
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This paper presents a new and more sustainable alternative approach for the Sharpless catalytic asymmetric dihydroxylation (AD) of olefins using a water/surfactant systemas reaction media. The AD reaction was performed using several cationic and anionic surfactants allowing yields and enantiomeric excesses higher or comparable with the conventional systems (using organic mixtures). The use of this water/surfactant medium offers the additional advantage of performing the reactions without the need of a slow addition of olefins. Asymmetric dihydroxylation of 1-hexene in a 1.5 mM sodium cholate aqueous solution, using N-methylmorpholine N-oxide (NMO) as co-oxidant was selected as model systemto evaluate the feasibility of recycling the Sharpless catalytic systemby nanofiltration. The reaction media was processed by nanofiltration, the product was isolated in the permeate, whereas the catalytic systemand surfactant were retained by the membrane and recycled through six successive reactions, improving the catalyst turn-over number. The experimental results were compared with the ones calculated on the basis of mass balances, membrane rejections to product and reaction yields.
- Branco, Luis C.,Ferreira, Frederico Castelo,Santos, Jose L.,Crespo, Joao G.,Afonso, Carlos A. M.
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supporting information; experimental part
p. 2086 - 2098
(2009/09/07)
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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
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experimental part
p. 956 - 960
(2009/04/06)
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- RuCl3/CeCl3/NaIO4: A new bimetallic oxidation system for the mild and efficient dihydroxylation of unreactive olefins
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(Chemical Equation Presented) The catalytic dihydroxylation of olefins represents a unique synthetic tool for the generation of two C,O-bonds with defined relative configuration. Whereas OsO4 has been established as a very general dihydroxylati
- Plietker, Bernd,Niggemann, Meike
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p. 2402 - 2405
(2007/10/03)
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- A new synthesis of cis-diol from alkene using iodine-ammonium cerium(IV) nitrate
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The reaction mixtures of 5α-cholest-2-ene with iodine-ammonium cerium(IV) nitrate [CAN(IV)] were converted with potassium hydroxide in methanol-water to give the more hindered 2β,3β-diol in high yield. Cyclohexene and cycloheptene similarly reacted to the corresponding cis-diols in good yield. It was found that this reaction intermediate proceeds to give trans-iodoacetate via trans-iodonitrate. This new synthetic method provided several advantages over the Prevost reaction. Georg Thieme Verlag Stuttgart.
- Horiuchi, C. Akira,Dan, Gong,Sakamoto, Masaki,Suda, Kazuhiko,Usui, Shigeru,Sakamoto, Okihiko,Kitoh, Shinya,Watanabe, Satoshi,Utsukihara, Takamitsu,Nozaki, Sukekatsu
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p. 2861 - 2864
(2007/10/03)
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- Studies on the asymmetric dihydroxylation of advanced bryostatin C-ring segments
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The asymmetric dihydroxylation reaction of early stage and advanced Bryostatin C-ring precursors was evaluated. For homoallylic ethers and alcohols, several AD ligands were investigated including a novel class of quinidine-alkynes.
- Seidel, Martin C.,Smits, René,Stark, Christian B. W.,Frackenpohl, Jens,Gaertzen, Oliver,Hoffmann, H. Martin R.
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p. 1391 - 1398
(2007/10/03)
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- Efficient photocatalytic oxidation of cycloalkenes by dihydroxo(tetraphenylporphyrinato)-antimony supported on silica gel under visible light irradiation
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In order to develop a photocatalyst operating under visible light irradiation, silica gel-supported dihydroxo(tetraphenylporphyrinato)antimony (V) complex, [SbTPP(OH)2]+/SiO2, was prepared. The photocatalytic oxidation of cycloalkenes with oxygen molecule was performed on [SbTPP(OH)2]+/SiO2 particles under irradiation of fluorescent light. The photocatalytic oxidation of cycloalkenes gave the corresponding cis-1,2-epoxycycloalkane, 2-cycloalkene-1-ol, and trans-1,2-cycloalkanediol.
- Shiragami, Tsutomu,Makise, Ryu-Ichi,Inokuchi, Yousuke,Matsumoto, Jin,Inoue, Haruo,Yasuda, Masahide
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p. 736 - 737
(2007/10/03)
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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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- 2,3,5-TRISUBSTITUTED PYRIDINES AS INHIBITORS OF CYCLOOXYGENASE-2
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The invention encompasses the novel compound of Formula (I) as well as a method of treating cyclooxygenase-2 mediated diseases comprising administration to a patient in need of such treatment of a non-toxic therapeutically effective amount of a compound of Formula (I). The invention also encompasses certain pharmaceutical compositions for treatment of cyclooxygenase-2 mediated diseases comprising compounds of Formula (I).
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- Zn(II)-catalyzed thiolysis of oxiranes in water under neutral conditions
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Thiolysis of a variety of 1,2-epoxides in water at 30 °C and pH 7.0 is strongly accelerated by ZnCl2 (10 mol %) except when amino- and carboxythiophenol are used. The aqueous medium and the catalyst were recovered and reused in various runs wit
- Fringuelli, Francesco,Pizzo, Ferdinando,Tortoioli, Simone,Vaccaro, Luigi
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p. 8248 - 8251
(2007/10/03)
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- Method for the asymmetric dihydroxylation of olefins, using osmium catalysts
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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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- 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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- Niobium pentachloride catalysed ring opening of epoxides
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Epoxide ring opening is a frequently required transformation in Organic Synthesis. In this paper we describe the application of NbCl5 for this purpose using three different substrates. Chlorohydrins, 1,2-diols, products containing solvent resid
- Gomes Constantino, Mauricio,Lacerda Jr., Valdemar,Arag?o, Valquiria
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p. 770 - 776
(2007/10/03)
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- Directive effect of the 2- and 3-axial hydroxy groups that appeared in the complex metal hydride reduction of cyclohexanones
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A directive effect of the 2-axial hydroxy group appeared in the LiAlH4, NaBH4, and Zn(BH4)2 reduction of cyclohexanone, while the 3-axial hydroxy group exhibited a steric hindrance. The distance between the carbonyl carbon and the hydroxy group interacting with the hydride reagent was responsible for such a difference. In the reduction of Na[B(OAc)3H], the 2- and 3-axial hydroxycyclohexanones gave the products obtained by the hydride approaching from the side of the hydroxy group. The key point of the stereoselectivity was the formation of Na[B(OAc)2(OR)H, which was more reactive than the parent hydride, by exchanging the acetate ion with the alkoxide. Although the reduction was performed under the condition that the hydride/substrate ratio was 1, the conversion of the hydroxy ketone to an alcohol were 4, NaBH4, and Zn(BH4)2 reductions in tetrahydrofuran. The conversions in the NaBH4 reduction in ethanol were > 90%.
- Senda,Kikuchi,Inui,Itoh
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p. 237 - 242
(2007/10/03)
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- Asymmetric synthesis of (S)-1-methyl-2-cyclohexen-1-ol, a constituent of the aggregation pheromone of Dendroctonus pseudotsugae
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1-Methyl-2-cyclohexen-1-ol has been prepared by a three step synthesis from 1-methylcyclohexene, in greater than 94% e.e., via a 'merged substitution-elimination reaction' between NaSePh and 2-methyl-2- hydroxycyclohexyl p-toluenesulphonate. (C) 2000 Elsevier Science Ltd.
- Hamon, David P. G.,Tuck, Kellie L.
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p. 4829 - 4835
(2007/10/03)
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- Acid-catalyzed enzymatic hydrolysis of 1-methylcyclohexene oxide
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Limonene-1,2-epoxide hydrolase from Rhodococcus erythropolis DCL14, an enzyme involved in the limonene metabolism of this microorganism, catalyzes the enantioselective hydrolysis of 1-methylcyclohexene oxide. (1R,2S)-1- Methylcyclohexene oxide was the preferred substrate and it was mainly hydrolyzed to (1S,2S)-1-methylcyclohexane-1,2-diol, while (1S,2R)-1- methylcyclohexene oxide was converted more slowly and mainly yielded (1R,2R)- 1-methylcyclohexane-1,2-diol. The reaction proceeded with a high regioselectivity (C1:C2, 85:15). H218O-labelling experiments confirmed that the nucleophile was mainly incorporated at the most substituted carbon atom, suggesting that limonene-1,2-epoxide hydrolase uses an acid-catalyzed enzyme mechanism.
- Van Der Werf, Mariet J.,De Bont, Jan A. M.,Swarts, Henk J.
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p. 4225 - 4230
(2007/10/03)
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- Aqueous permanganate oxidations of cycloalkenes to cis-glycols and cis to trans conversions
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A series of cis-glycols including 1,2-cyclopentanediol, 1-methyl-1,2-cyclopentanediol, 1,2-dimethyl-1,2-cyclopentanediol, 1,2-cyclohexanediol, 1-methyl-1,2-cyclohexanediol, 1,2-dimethyl-1,2-cydohexanediol, 1,2-cycloheptanediol, 1,2-cyclooctanediol, exo,exo-bicyclo[2.2.1]heptane-2,3-diol, and bicyclo[2.2.2]octane-2,3-diol have been prepared by permanganate oxidations of cycloalkenes using a turbulent stirring technique. Conditions for the reactions, methods of purification, and yields are presented. Both hydroxide ion and an aqueous environment are highly essential to the formation of glycols. Excessive solvent decreases yields. A procedure for converting certain cis- to trans-glycols is given. A preparation for very pure Δ9,10-octalin is included.
- Taylor, Jay E.,Janini, Thomas E.,Elmer, Otto C.
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p. 147 - 150
(2013/09/08)
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- Non-dehydrative pinacol rearrangement using a Lewis acid-trialkyl orthoester combined system
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An efficient pinacol rearrangement mediated by trialkyl orthoformate has been developed. The reactions of various types of diols with a catalytic amount of a Lewis acid in the presence of an orthoester afforded the rearranged product in good yields via a cyclic orthoester intermediate. This combined system is applicable not only to cyclic and acyclic tri- and tetra- substituted diols but also to the diols having acid-sensitive acetals.
- Kita, Yasuyuki,Yoshida, Yutaka,Mihara, Sachiko,Furukawa, Akihiro,Higuchi, Kazuhiro,Fang, Dai-Fei,Fujioka, Hiromichi
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p. 14689 - 14704
(2007/10/03)
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- Synthesis of Stereoisomeric 1-Oxaspiro[2.5]octan-4-ols and 1-Oxaspiro[2.5]octan-4-yl Acetates and Their Reactions with Amines and Alcohols
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cis- and trans-1-Oxaspiro[2.5]octan-4-ols at a ratio of 2:1 were synthesized by epoxidation of 2-methylenecyclohexanol with peroxyacetic acid, whereas epoxidation of 2-methylenecyclohexyl acetate gave cis- and trans-1-oxaspiro[2.5]octan-4-yl acetates at a ratio of 2.6:1. Opening of the oxirane ring under the action of amines and alcohols occurs regioselectively with formation of products of nucleophilic addition at the methylene group. The reaction of cis-1-oxaspiro[2.5]octan-4-ol with methanol in the presence of p-toluenesulfonic acid yields a mixture of products due to addition of the alcohol both at the methylene group and at the spiro atom.
- Prishchepenko,Zhavnerko,Katash
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p. 298 - 302
(2007/10/03)
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- Chemoenzymic resolution and deracemisation of (±)-1-methyl-1,2- epoxycyclohexane: The synthesis of (1-S, 2-S)-1-methylcyclohexane-1,2-diol
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Corynebacterium C12 epoxide hydrolase transforms (±)-1-methyl-1,2-epoxy-cyclohexane 1 to the (1-S, 2-S)-1-methylcyclohexane-1,2-diol 2 leaving the (1-S, 2-R)-epoxide 3 unchanged. The diol 2 is converted to the (1-R, 2-S)-epoxide 4 by sulfonation-ring closure. A one pot combination of Corynebacterium C12 epoxide hydrolase and acid catalysed ring opening converts (±)-1-methyl-1,2-epoxycyclohexane 1 to (1-S, 2-S)-1-methylcyclohexane-1,2-diol 2.
- Archer, Ian V. J.,Leak, David J.,Widdowson, David A.
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p. 8819 - 8822
(2007/10/03)
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- ONE-POT TWO-STEP SYNTHESIS OF 1,2-DIOL
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Diols can be prepared by hydroxilation of alkenes with m-chloroperoxybenzoic acid in water.The process occurs with high yield and complete anti stereospecificity.
- Fringuelli, F.,Germani, R.,Pizzo, F.,Savelli, G.
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p. 1939 - 1944
(2007/10/02)
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- Asymmetric Synthesis Using Chiral Acetals: Studies on the Nucleophilic Addition of Organometallics to Chiral α-Keto Acetals in Cyclic Systems
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Four chiral cyclic α-keto acetals (3a-d) were prepared through transacetalization of the α-hydroxydimethyl acetals with (-)-(2S,3S)-1,4-dimethoxy-2,3-butanediol or (-)-(2R,3R)-2,3-butanediol and reacted with organometallic reagents (Grignard reagents and organolithium reagents).The reactions of the α-keto acetals (3a, 3b) derived from 1 and (-)-(2S,3S)-1,4-dimethoxy-2,3-butanediol with Grignard reagents proceeded in a highly diastereoselective manner.Keywords-Asymmetric synthesis; diastereoselective nucleophilic addition; chiral cyclic α-keto-acetal; (-)-(2S,3S)-1,4-dimethoxy-2,3-butanediol; (-)-(2R,3R)-2,3-butanediol; Grignard reagent; organolithium reagent
- Tamura, Yasumitsu,Annoura, Hirokazu,Kondo, Hiroshi,Fuji, Masahiro,Yoshida, Takayuki,Fujioka, Hiromichi
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p. 2305 - 2313
(2007/10/02)
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- Diethoxytriphenylphosphorane: A Mild, Regioselective Cyclodehydrating Reagent for Conversion of Diols to Cyclic Ethers. Stereochemistry, Synthetic Utility, and Scope
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Diethoxytriphenylphosphorane, Ph3P(OEt)2, prepared by reaction of triphenylphosphine and diethyl peroxide, is a "hydrolytically active" dioxyphosphorane which promotes mild cyclodehydration (40-110 deg C) of diols to cyclic ethers in neutral media.The regioselectivity in the closure of (S)-(+)-propane-1,2-diol and (R)-(-)-pentane-1,4-diol with Ph3P(OEt)2 is high (81-82 percent) while the cyclodehydration of (S)-(+)-phenylethane-1,2-diol gives racemized (+/-)-styrene oxide.Simple 1,2-, 1,4-, and 1,5-diols afford good yields of the cyclic ethers but 1,3-propanediol and 1,6-hexanediol give mainly 3-ethoxy-1-propanol and 6-ethoxy-1-hexanol, respectively with Ph3P(OEt)2.Tri- and tetra-substituted 1,2-diols afford the relatively stable 1,3,2-dioxaphospholanes (or ?-dioxyphosphoranes) in the presence of Ph3P(OEt)2, and, depending on conditions, the 1,3,2-dioxaphospholanes are selectively converted to epoxides, ketones or allylic alcohols.The carbonyl compounds arise from 1,2-hydride and 1,2-methyl migrations; the allylic alcohols are derived from thermolytic eliminations. trans-1,2-Cyclohexanediols afford essentially quantitative yields (>95 percent) of the cyclohexene oxides while cis-1,2-cyclohexanediol gives the stable 1,3,2-dioxaphospholane with Ph3P(OEt)2 which decomposes under thermal conditions to cyclohexanone (90 percent).Ph3P(OEt)2 is extremely useful for conversion of "sensitive" 1,2-diols to acidic and /or thermally labile epoxides as demonstrated by the quantitative conversion of 9,10-dihydro-trans-9,10-phenanthrenediol to 9,10-dihydrophenanthrene oxide and 2α,10-pinanediol to 2α,10-epoxypinane.
- Robinson, Philip L.,Barry, Carey N.,Kelly, Jeffery W.,Evans, Slayton A.
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p. 5210 - 5219
(2007/10/02)
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- ORGANIC SELENOXIDES AS OXIDANTS IN OSMIUM TETROXIDE CATALYZED OXIDATION OF OLEFINS TO GLYCOLS
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Olefins are catalytically oxidized to glycols by osmium tetroxide in the presence of organic selenoxide cooxidants.Glycols were obtained in good yields from mono-, di-, and tetrasubstituted olefins.
- Abatjoglou, A. G.,Bryant, D. R.
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p. 2051 - 2054
(2007/10/02)
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