- Reactions of the Trimethylsilyl Ion with 1,2-Cyclopentanediol Isomers in the Collision Region of a Triple Quadrupole Instrument
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Ion-molecule reactions with the trimethylsilyl ion were used to distinguish between cis- and trans-1,2-cyclopentanediol isomers.The ion kinetic energy of + was varied from 0 eV to 15 eV (center of mass frame of reference).At low ion kinetic energies (+.The cis-1,2-cyclopentanediol isomer favors decomposition of + to yield the hydrated trimethylsilyl ion + at m/z 91.For the trans isomer, the formation of the hydrated trimethylsilyl ion is an endethermic process with a definite threshold ion kinetic energy.
- Meyerhoffer, William J.,Bursey, Maurice M.
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- 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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supporting information
p. 93 - 98
(2022/01/03)
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- An Efficient Deprotection of 2,6-Bis(trifluoromethyl)phenylboronic Esters via Catalytic Protodeboronation Using Tetrabutyl ammonium Fluoride
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We herein describe an efficient deprotection of 2,6-bis(trifluoromethyl)phenylboronic esters, which serve as effective protective groups for 1,2- or 1,3-diols in various organic transformations, via protodeboronation by using a catalytic amount of tetrabutylammonium fluoride (TBAF).
- Makino, Kazuishi,Nojima, Shinya,Shimada, Naoyuki,Urata, Sari
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supporting information
p. 2300 - 2304
(2019/12/11)
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- One-Pot Enzymatic Synthesis of Cyclic Vicinal Diols from Aliphatic Dialdehydes via Intramolecular C?C Bond Formation and Carbonyl Reduction Using Pyruvate Decarboxylases and Alcohol Dehydrogenases
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An enzymatic cascade reaction was developed for one-pot enantioselective conversion of aliphatic dialdehydes to chiral vicinal diols using pyruvate decarboxylases (PDCs) and alcohol dehydrogenases (ADHs). The PDCs showed promiscuity in catalysing the cyclization of aliphatic dialdehydes through intramolecular stereoselective carbon-carbon bond formation. Consequently, 1,2-cyclopentanediols in three different stereoisomeric forms and 1,2-cyclohexanediols in two different stereoisomeric forms could be prepared with high conversion and stereoisomeric ratio from the respective initial substrates, glutaraldehyde and adipaldehyde. These cascade reactions represent a promising approach to the biocatalytic synthesis of important chiral vicinal diols. (Figure presented.).
- Zhang, Yan,Yao, Peiyuan,Cui, Yunfeng,Wu, Qiaqing,Zhu, Dunming
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supporting information
p. 4191 - 4196
(2018/09/25)
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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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- Facile and highly diastereoselective synthesis of syn- and cis-1,2-diol derivatives from protected α-hydroxy ketones
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An efficient method for the synthesis of monoprotected syn- or cis-1,2-diol derivatives by reduction of easily accessible α-(2,2,6,6-tetramethylpiperidinyloxy) ketones is reported. The α-(tetramethylpiperidinyloxy) group as the stereodirecting group induces in unhindered acyclic or cyclic ketones complete syn- or cis-diastereoselectivity, respectively, with L-Selectride. For more hindered derivatives, where L-Selectride becomes unreactive, LiAlH4 proved effective, essentially showing the same high selectivity. The diastereoselectivity of the reduction can be rationalized for acyclic ketones by the Felkin-Anh model, whereas for cyclic substrates, attack from the face opposite to the tetramethylpiperidinyloxy group predictably prevails with high selectivity regardless of the substitution pattern. The liberation of free diols was achieved by reductive N-O bond cleavage of the alkoxyamine unit. Monoprotected syn- and cis-1,2-diols were synthesized by reduction of ketones bearing the stereodirecting α-(2,2,6,6-tetramethylpiperidinyloxy) group. The latter induces syn- or cis-selectivity in unhindered acyclic or cyclic ketones with L-Selectride, whereas the smaller LiAlH4 induced excellent diastereoselectivity with hindered ketones. Free 1,2-diols were liberated by reductive N-O bond cleavage.
- Jahn, Emanuela,Smr?ek, Jakub,Pohl, Radek,Císa?ová, Ivana,Jones, Peter G.,Jahn, Ullrich
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p. 7785 - 7798
(2015/12/31)
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- A facile synthesis of vicinal cis-diols from olefins catalyzed by in situ generated MnxOy nanoaggregates
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A novel protocol for the practical and green synthesis of vicinal cis-diols from 10.0 mmol olefins by using 5.0 mmol KMnO4 as oxidant and 30.0 mmol H2O2 as co-oxidant is reported. The presented procedure is easy to carry out and enables the direct transformation of linear and cyclic alkenes to the corresponding vicinal cis-diols. The synthesis of vicinal cis-diols by dihydroxylation of olefins with a KMnO4/H2O2 system was catalyzed by in situ generated MnxOy nanoaggregates. The use of H2O2 as a co-oxidant is the key for the protocol to synthesize vicinal cis-diols in high yields, because it assists the oxidation of MnxOy nanoaggregates, which have an active role in the oxidation reaction medium.
- Dalmizrak, Di?dem,G?ksu, Haydar,Gültekin, Mehmet Serdar
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p. 20751 - 20755
(2015/03/18)
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- Carbon Dioxide as a Protecting Group: Highly Efficient and Selective Catalytic Access to Cyclic cis-Diol Scaffolds
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The efficient and highly selective formation of a wide range of (hetero)cyclic cis-diol scaffolds using aminotriphenolate-based metal catalysts is reported. The key intermediates are cyclic carbonates, which are obtained in high yield and with high levels of diastereo- and chemoselectivity from the parent oxirane precursors and carbon dioxide. Deprotection of the carbonate structures affords synthetically useful cis-diol scaffolds with different ring sizes that incorporate various functional groups. This atom-efficient method allows the simple construction of diol synthons using inexpensive and accessible precursors and green metal catalysts and showcases the use of CO2 as a temporary protecting group. Protective Carbon: Aminotriphenolate complexes of FeIII and AlIII are highly efficient and selective catalysts for the conversion of functional (multi)cyclic oxiranes into the corresponding cis carbonates. Basic hydrolysis of the latter provides a series of useful cyclic cis-diol scaffolds in high yield. In this process, CO2 acts as both a temporary protecting group and an oxygen donor.
- Laserna, Victor,Fiorani, Giulia,Whiteoak, Christopher J.,Martin, Eddy,Escudero-Adán, Eduardo,Kleij, Arjan W.
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p. 10416 - 10419
(2016/02/18)
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- Influence of temperature and pressure on cyclic carbonate synthesis catalyzed by bimetallic aluminum complexes and application to overall syn -bis-hydroxylation of alkenes
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The effect of moderate temperatures (22-100 °C) and pressures (1-10 bar) on the synthesis of cyclic carbonates from epoxides and carbon dioxide catalyzed by a combination of bimetallic aluminum complexes and tetrabutylammonium bromide is investigated. The combined bimetallic complex and tetrabutylammonium bromide catalyst system is shown to be an order of magnitude more active than the use of tetrabutylammonium bromide alone at all temperatures and pressures studied. At the higher temperatures and pressures used, disubstituted epoxides become substrates for the reaction and it is shown that reactions proceed with retention of the epoxide stereochemistry. This allowed a route for the overall syn-bis-hydroxylation of alkenes to be developed without the use of hazardous metal based reagents. At higher pressures it is also possible to use compressed air as the carbon dioxide source.
- Beattie, Christopher,North, Michael,Villuendas, Pedro,Young, Carl
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p. 419 - 426
(2013/03/13)
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- Dihydroxylation of olefins catalyzed by zeolite-confined osmium(0) nanoclusters: An efficient and reusable method for the preparation of 1,2-cis-diols
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Addressed herein is a novel, eco-friendly, recoverable, reusable and bottleable catalytic system developed for the dihydroxylation of various olefins yielding 1,2-cis-diols. In our protocol, zeolite-confined osmium(0) nanoclusters (zeolite-Os0) are used as reusable catalyst and H 2O2 served as a co-oxidant. Zeolite-Os0 are found to be highly efficient and selective catalysts for the dihydroxylation of a wide range olefins in an aqueous acetone mixture at room temperature. In all of the olefins surveyed, the catalytic dihydroxylation reaction proceeds smoothly and the corresponding 1,2-cis-diols are obtained in excellent chemical yield under the optimized conditions. The present heterogeneous catalyst system provides many advantages, such as being eco-friendly and industrially applicable over the traditional homogenous OsO4-NMO system for the dihydroxylation of olefins.
- Metin, Oender,Alp, Nurdan Alcan,Akbayrak, Serdar,Bier, Abdullah,Gueltekin, Mehmet Serdar,Oezkar, Saim,Bozkaya, Uur
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experimental part
p. 1488 - 1492
(2012/06/29)
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- Scaffolding catalysts: Highly enantioselective desymmetrization reactions
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Ex-changing places: A highly enantioselective desymmetrization of 1,2-diols has been developed in which the catalyst utilizes reversible covalent bonding to the substrate to achieve both high selectivity and rate acceleration (see scheme, PMP=pentalmethyl
- Sun, Xixi,Worthy, Amanda D.,Tan, Kian L.
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supporting information; experimental part
p. 8167 - 8171
(2011/10/18)
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- cis-Dihydroxylation of alkenes by a non-heme iron enzyme mimic
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Using the non-heme iron oxidase active site as a template, a peptidomimetic ligand has been designed, synthesized, and used to effect the dihydroxylation of alkene substrates. Fenton-type radical pathways are also observed. Georg Thieme Verlag Stuttgart.
- Barry, Sarah M.,Rutledge, Peter J.
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experimental part
p. 2172 - 2174
(2009/04/11)
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- A comparative study of the relative stability of representative chiral and achiral boronic esters employing transesterification
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A comparative study of the transesterification of five representative chiral and achiral boronic esters with various structurally modified diols was undertaken to qualitatively understand the factors influencing the relative stability of these boronic esters. Several factors such as chelation, conformation, steric bulk of the substituents, size of the heterocycle, and entropy influence the relative rate of transesterification as well as the stability of the boronic esters. Amongst these boronic esters, pinanediol phenylboronic ester was found to be the most stable boronic ester whereas DIPT boronic ester appeared to be thermodynamically the least stable one. The transesterification with sterically hindered diols was observed to be relatively slow, but afforded thermodynamically more stable boronic esters. Boronic esters derived from cis-cyclopentanediols and the bicyclo[2.2.1]heptane-exo,exo-2,3- diols are relatively more stable. This study not only presents the qualitative picture of relative stability of various boronic esters, but also provides helpful hints regarding the possible recovery of chiral auxiliaries. Many C 2-symmetric chiral auxiliaries, such as 2,3-butanediol, 2,4-pentanediol, DIPT, and cis-cyclohexane-1,2-diol, can be retrieved by simple transesterification of the corresponding boronic esters with commercial inexpensive diols, such as pinacol, 1,3-propanediol, and neopentyl glycol.
- Roy, Chandra D.,Brown, Herbert C.
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p. 879 - 887
(2008/02/11)
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- (Triisopropylsilyl)acetaldehyde acetal as a novel protective group for 1,2-diols
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(Triisopropylsilyl)acetaldehyde dimethyl acetal (TIPS-ADMA) was synthesized from chlorotriisopropylsilane in three steps. Cyclic and acyclic 1,2-diols can be transformed to (triisopropylsilyl)ethylidene acetals (TIPS-AA). Removal of the acetal by LiBF4 regenerates the starting diol in excellent yield even in the presence of an acetonide of 1,2-diol. The TIPS-AA group can survive under the deprotection conditions of the acetonide in acetic acid at 80 °C. Selective protection of 2,3- and 4,6-diols for O-methyl d-mannoside with TIPS-ADMA and selective deprotection of the acetals have been achieved.
- Uenishi, Jun'ichi,Tanaka, Yusuke,Kawai, Nobuyuki
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p. 5553 - 5555
(2007/10/03)
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- Alkene cis-dihydroxylation by [(Me3tacn)(CF3CO 2)RuVIO2]CIO4 (Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane): Structural characterization of [3 + 2] cycloadducts and kinetic studies
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cis-Dioxoruthenium(VI) complex [(Me3tacn)(CF3CO 2)RuVIO2]CIO4 (1, Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane) reacted with alkenes in aqueous tert-butyl alcohol to afford cis-1,2-diols in excellent yields under ambient conditions. When the reactions of 1 with alkenes were conducted in acetonitrile, oxidative C=C cleavage reaction prevailed giving carbonyl products in >90% yields without any cis-diol formation. The alkene cis-dihydroxylation and C=C cleavage reactions proceed via the formation of a [3 + 2] cycloadduct between 1 and alkenes, analogous to the related reactions with alkynes [Che et al. J. Am. Chem. Soc. 2000, 122, 11380], With cyclooctene and trans-β-methylstyrene as substrates, the Ru(III) cycloadducts [(Me3tacn)(CF 3CO2)RuIIIO(H)CH(CH2) 6HCO]CIO4 (4a) and [(Me3tacn)(CF 3CO2)RuIIIO(H)-PhCHCH(CH3)O]CIO 4 (4b) were isolated and structurally characterized by X-ray crystal analyses. The kinetics of the reactions of 1 with a series of p-substituted styrenes has been studied in acetonitrile by stopped-flow spectrophotometry. The second-order rate constants varied by 14-fold despite an overall span of 1.3 V for the one-electron oxidation potentials of alkenes. Secondary kinetic isotope effect (KIE) was observed for the oxidation of β-d2-styrene (kH/kD = 0.83 ± 0.04) and α-deuteriostyrene (kH/kD = 0.96 ± 0.03), which, together with the stereoselectivity of cis-alkene oxidation by 1, is in favor of a concerted mechanism.
- Yip, Wing-Ping,Yu, Wing-Yiu,Zhu, Nianyong,Che, Chi-Ming
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p. 14239 - 14249
(2007/10/03)
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- Homogeneous cis-dihydroxylation and epoxidation of olefins with high H2O2 efficiency by mixed manganese/activated carbonyl catalyst system
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The use of [Mn2O3(tmtacn)2](PF6)2 (tmtacn=1,4,7-trimethyl-1,4,7-triazacyclononane) in combination with glyoxylic acid methylester methyl hemiacetal (GMHA) results in a highly active and hydrogen peroxide efficient catalyst for the epoxidation of olefins as well as the first homogeneous catalytic cis-dihydroxylation system with H2O2 and with turnover numbers up to 420.
- Brinksma, Jelle,Schmieder, Lizette,Van Vliet, Gerbert,Boaron, Rob,Hage, Ronald,De Vos, Dirk E,Alsters, Paul L,Feringa, Ben L
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p. 2619 - 2622
(2007/10/03)
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- A heterogeneous cis-dihydroxylation catalyst with stable, site-isolated osmium-diolate reaction centers
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Involatile OsO4! A tetrasubstituted olefin is immobilized on SiO2 and reacts with OsO4 to form a stable osmate (IV) ester (see scheme), which is a leak-proof heterogeneous catalyst for the cis-dihydroxylation of olefins.
- Severeyns, An,De Vos, Dirk E.,Fiermans, Lucien,Verpoort, Francis,Grobet, Piet J.,Jacobs, Pierre A.
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p. 586 - 589
(2007/10/03)
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- Highly trans-selective intramolecular pinacol coupling of dials catalyzed by bulky Cp2TiPh
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Cp2Ti(Ph)Cl in the presence of Me3SiCl and Zn provides an effective pinacol coupling catalyst for aromatic and aliphatic aldehydes.
- Yamamoto, Yoshihiko,Hattori, Reiko,Itoh, Kenji
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p. 825 - 826
(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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- Reductions, reductive alkylations, and intramolecular cyclizations of acyl silanes with samarium diiodide or tributyltin hydride
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A series of acyl silanes including aliphatic-, aromatic-, and bis-acyl silanes, as well as the acyl silanes bearing other substituents such as a bromine atom and alkenyl, succinimide, and carbonyl groups, were prepared, and their reactions with samarium diiodide or tributylstannane were studied. The reactions of acyl silanes occurred in various manners such as reductions, reductive alkylations, intramolecular radical cyclizations, pinacol couplings, aldol reactions, and Tishchenko reactions, depending on the nature of substrates and reaction conditions. Acyl silanes were generally reduced to give the corresponding α-silyl alcohols without transfer of silyl groups. Intramolecular radical cyclizations of 5-hexenoyl silanes and 1-silyl-1,5-pentanedione were realized to give α-silyl cyclopentanols and 1,2-cyclopentanediol derivatives, respectively. On treatment with samarium diiodide in tetrahydrofuran, 1-(trimethylsilyl)-1,6-hexanedione underwent a pinacol coupling reaction in the presence of t-BuOH, whereas it underwent a Tishchenko reaction in the presence of MeOH. The Tishchenko reaction of 1-silyl-1,5-pentanedione gave a δ-silyl-δ-lactone. On treating with samarium diiodide, 1-(trimethylsilyl)-1,5-hexanedione and 1,5-bis(trimethylsilyl)-1,6-hexanedione, underwent, respectively, intramolecular aldol reactions.
- Chuang, Tsung-Hsun,Fang, Jim-Min,Jiaang, Weir-Torn,Tsai, Yeun-Min
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p. 1794 - 1805
(2007/10/03)
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- Asymmetric Catalysis, Part 91: Enantioselective Monophenylation of cis-1,2-Cyclopentanediol with Triphenylbismuth Diacetate and Chiral Copper(II) Complexes as Catalysts
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The monophenylation of cis-1,2-cyclopentanediol with triphenylbismuth diacetate in the presence of chiral Cu(II) complexes as catalysts gave cis-2-hydroxy-1-phenoxy-cyclopentane with enantiomeric excesses up to 38percent.The optically active ligands used were triamine derivatives of 2,6-bis(aminomethyl)pyridine and diamine derivatives of 2-(aminomethyl)pyridine.Selectivity in the monophenylation occurred only in the presence of the latter as auxiliary ligands. - Keywords.Enantioselective catalysis; Chiral Cu(II) complexes; Monophenylation; Triphenylbismuth diacetate; cis-1,2-Cyclopentanediol.
- Brunner, H.,Chuard, T.
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p. 1293 - 1300
(2007/10/02)
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- Oxidation of homochiral ketals by rhenium(VII) oxide. V
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2-Hydroxyethyl enol ethers react with Re2O7 to produce 2-hydroxyketals. Where homochiral starting enol ethers are employed, greater than 99:1 diastereoselectivities are obtained. The stereocontrol is rationalized by invoking a transition state that approximates the geometry of a metallaoxetane. Finally, homochiral ketals are themselves oxidized to provide 2-hydroxyketals with high diastereoselectivity.
- Tang,Kennedy
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p. 7823 - 7826
(2007/10/02)
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- An Insight into Enantioselective Hydrolyses of Cyclic Acetates Catalysed by Pseudomonas Fluorescens Lipase
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Hydrolysis of racemic acetates with Pseudomonas fluorescens lipase (PFL) afforded optically active alcohols with the R-configuration, independent of ring size; a three-site model for PFL-catalysed hydrolysis is proposed.
- Xie, Zhuo-Feng,Nakamura, Izumi,Suemune, Hiroshi,Sakai, Kiyoshi
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p. 966 - 967
(2007/10/02)
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- Preparation of Optically Active 1,2-Diols and α-Hydroxy Ketones Using Glycerol Dehydrogenase as Catalyst: Limits to Enzyme-Catalyzed Synthesis due to Noncompetitive and Mixed Inhibition by Product
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Glycerol dehydrogenase (GDH, EC 1.1.1.6, from Enterobacter aerogenes or Cellulomonas sp.) catalyzes the interconversion of analogues of glycerol and dihydroxyacetone.Its substrate specificity is quite different from than of horse liver alcohol dehydrogenase (HLADH), yeast alcohol dehydrogenase, and other alcohol dehydrogenases used in enzyme-catalyzed organic synthesis and is thus a useful new enzymic catalyst for the synthesis of enantiomerically enriched and isotopically labeled organic molecules.This paper illustrates synthetic applications of GDH as a reduction catalyst by the enantioselective reduction of 1-hydroxy-2-propanone and 1-hydroxy-2-butanone to the corresponding R 1,2-diols (ee = 95-98percent). (R)-1,2-Butanediol-2-d1 was prepared by using formate-d1 as the ultimate reducing agent.Comparison of (R)-1,2-butanediol prepared by reduction of 1-hydroxy-2-butanone enzymatically and with actively fermenting bakers' yeast indicated than yield and enantiomeric purity were similar by the two procedures.Reactions proceeding in the direction of substrate oxidation usually suffer from slow rates and incomplete conversions due to product inhibition.The kinetic consequences of product inhibition (competitive, noncompetitive, and mixed) for practical synthetic applications of GDH, HLADH, and other oxidoreductases are analyzed.In general, product inhibition seems the most serious limitation to the use of these enzymes as oxidation catalysts in organic synthesis.
- Lee, Linda G.,Whitesides, George M.
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- PARTICIPATION D'UN GROUPE AMIDE A LA FORMATION DE SELS DE DIOXOLANNE-1,3 YLIUM-2; MODELE BIOMIMETIQUE DE REACTION DE PEPTIDATION
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An amide group is shown to be capable of intramolecular participation in the formation of an 1,3-dioxolan 2-ylium cation giving a tricyclic organic cation of a new type 5a,b.This cation may be considered as a model of an electrophilic intermediate which m
- Mestdagh, Helene,Pancrazi, Ange
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p. 3399 - 3414
(2007/10/02)
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- METHODS FOR THE INTERCONVERSION OF PROTECTIVE GROUOPS. TRANSFORMATION OF MEM ETHERS INTO ISOPROPYLTHIOMETHYL ETHERS OR CYANOMETHYL ETHERS
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This letter describes methods for the synthesis of isopropylthiomethyl and cyanomethyl ethers from the corresponding MEM ethers and also a process for the cleavage of MEM or MOM ethers of 1,2- and 1,3-diols which avoids cyclization to formals.
- Corey, E. J.,Hua, Duy H.,Seitz, Steven P.
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- Vinyl Epoxide Hydrolysis Reactions
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The rates of hydrolysis of cyclopentadiene oxide (3), cyclohexadiene oxide (4), cycloheptadiene oxide (5), cyclooctadiene oxide (6), butadiene oxide (7), and styrene oxide (8) have been determined as a function of pH.Each epoxide exhibited acid-catalyzed hydrolysis at low pH, and 3-5 showed significant rates for "spontaneous" reaction with solvent at intermediate pH values.The hydrolyses of several of the vinyl epoxides (4 and 5) showed kinetic terms in HO- at pH > ca. 13.Specific chloride effects attributed to nucleophilic addition of Cl- to neutral epoxide were observed for those compounds (3, 4, and 8) hydrolyzed in KCl solutions.From kinetic and product studies, mechanisms for hydrolyses of the vinyl epoxides are postulated.Acid-catalyzed hydrolyses of 3, 4, 5, and 6 were found to be A-1 in nature, proceeding via intermediate allyl cations.Product distributions depended on the structure of the cation.Mechanisms and product distributions for the spontaneous hydrolyses of vinyl epoxides were found to be variable, and dependent on the structure of the epoxide.
- Ross, Angela M.,Pohl, Terese M.,Piazza, Kathryn,Thomas, Michael,Fox, Bonnie,Whalen, Dale L.
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p. 1658 - 1665
(2007/10/02)
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- Oxidation by Cobalt(III) Acetate. Part 4. Kinetics and Mechanism of the Oxidation of Glycols in Acetic Acid
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The oxidative cleavage of 1,2-glycols by cobalt(III) acetate in acetic acid was studied kinetically in order to clarify the reaction mechanism.The rates were first-order in both cobalt(III) acetate and substrate for the oxidation of all the diols used. cis-Cyclopentane-1,2-diol and decalin-9,10-diol were more rapidly oxidized than the corresponding trans-isomers, respectively, whereas cis-cyclohexane-1,2-diol was more slowly oxidized than the trans-isomer.The oxidation of trans-2-methoxycyclohexanol was much slower than that of the corresponding diol.The mechanism involving the formation of a bidentate complex between cobalt(III) acetate dimer and glycol is discussed.
- Morimoto, Takashi,Hirano, Masao
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p. 1087 - 1090
(2007/10/02)
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- INTRINSIC MIGRATION APTITUDES OF ALKYL GROUPS IN A PINACOL REARRANGEMENT
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From rates of solvolysis of substituted cis-2-tosyloxy-cyclopentanols 3 in sodium acetate buffered acetic acid the following relative migration aptitudes were deduced: H(171); CH3(6.7); C2H5(9.7); 2-C3H7(5.2); t-C4H9(2.5); C6H5(62).
- Wistuba, Eckehardt,Ruechardt, Christoph
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p. 4069 - 4072
(2007/10/02)
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- Cyclic 1,2-diol benzyl ether compounds
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Novel benzyl ethers of cyclic 1,1-diols, of the formula STR1 wherein R1 is phenyl or substituted phenyl, R2 is hydrogen, alkyl, alkenyl, alkynyl, haloalkyl or --CHX--R1, X is hydrogen, alkyl, alkenyl, alkynyl, haloalkyl, phenyl or substituted phenyl, Y and Y' are individually selected from hydrogen, alkyl, phenyl and substituted phenyl and A is saturated or unsaturated alkylene or substituted alkylene; have been found outstandingly effective as herbicides, particularly as selective herbicides.
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