- Ba(OH)2 as Catalyst in Organic Reactions. 20. Structure-Catalytic Activity Relationship in the Wittig Reaction
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Three barium hydroxide catalysts with different surface-area values and amounts of basic and reducing sites are used as catalysts in the Wittig reactions.These catalysts have different microcrystalline structures and therefore different geometrical properties in the active sites, that govern the adsorption of the reagents on the solid surface.Several phosphonium salts (Ph3P+CH2R; R = H, CH2CH2CH3, CO2Et, and COPh) with different pKa, geometrical, and electronic characteristic have been used.The structure-catalytic activity relationship is analyzed.The most active catalyst, C-200, is less active in the Wittig reaction than in the Wittig-Horner reaction.This fact is explained by geometrical reasons.The process takes place in the homogeneous phase with phosphonium salts of a strong acid character (R = CO2Et, COPh) that lead to stable yields.The weak acids (R = H, CH3CH2CH2) lead to reaction products in the heterogeneous solid-liquid conditions.The cell lattice of the solid governs the process that is carried out in the heterogeneous phase.The process with the strongest acid (R = COPh, pKa = 6.0) is not governed by the cell lattice because this acid can react to any kind of basis site in the solid.The reaction with R = CO2Et (pKa = 8.8) is carried out in the homogeneous phase because the ylide is stable.However, the formation of the ylide is controlled by the cell lattice because basic sites with pKa > 8.8 and adequate geometry are necessary to produce the ylide on the solid surface.
- Climent, M. S.,Marinas, J. M.,Mouloungui, Z.,Bigot, Y. Le,Delmas, M.,et al.
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Read Online
- SYNTHESIS OF (2-FURYL)-β-ALKYLACETALDEHYDES BY THE HYDROFORMYLATION OF 2-ALKENYLFURANS
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A study was carried out on the hydroformylation of 2-vinyl-, and 2-propenylfurans in the presence of HRh(CO)(PPh3)3 as a homogeneous catalyst.The substrate/catalyst mole ratio was 600.Gas-liquid chromatography, PMR, and 13C NMR spectroscopy were used to establish that the reaction proceeds regioselectively in the case of 2-vinylfuran and regiospecifically in the case of 2-propenylfuran.
- Lapidus, A. L.,Rodin, A. P.,Pruidze, I. G.,Ugrak, B. I.
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Read Online
- On the valence shell electronic spectroscopy of 2-vinyl furan
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The vacuum ultraviolet (VUV) absorption spectra of 2-vinyl furan was investigated. The spectroscopic properties of the 2-vinyl furan was analyzed using electron energy loss spectroscopy and synchrotron radiation source with absolute cross section determinations. The semiempirical molecular orbital calculations was used for the interpretation of the HeI photoelectron spectrum. A photoabsorption spectrum was observed in the first band in the UV absorption spectra in solution of furans in position 2 of polyenyl groups of increasing size.
- Giuliani,Walker,Delwiche,Hoffmann,Kech,Limao-Vieira,Mason,Hubin-Franskin
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Read Online
- Br?nsted Acid Catalyzed Peterson Olefinations
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A mild and facile Peterson olefination has been developed employing low catalyst loading of the Br?nsted acid HNTf2. The reactions are typically performed at room temperature, with the reaction tolerant to a range of useful functionalities. Furthermore, we have extended this methodology to the synthesis of enynes.
- Britten, Thomas K.,McLaughlin, Mark G.
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Read Online
- Method for synthesizing biomass-based functional monomer based on furfuryl alcohol/methanol catalytic conversion and catalyst application
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The invention provides an application of a solid catalyst in synthesis of a furylethylene functional monomer and a method for synthesizing a biomass-based functional monomer based on furfuryl alcohol/methanol catalytic conversion. The invention provides the application of the solid catalyst in the synthesis of the furylethylene functional monomer for the first time. Cheap and easily available bulk chemical furfuryl alcohol and derivatives thereof and methanol are used as raw materials, and the biomass-based functional monomer is synthesized on solid catalysts such as a molecular sieve and a modified molecular sieve catalyst by a gas-phase one-step method. The functional monomer has the characteristics that a furan group and a carbon-carbon double bond are contained in the structure, the synthesis method has the characteristics of a methanol-to-olefin industrial technology, the operation is simple, the flow is short, harsh experimental conditions are not needed, the cost of raw materials and a catalyst is low, the preparation is easy, and the defects of a conventional synthesis strategy based on a Witting reaction are broken through. The invention provides a green and sustainable new strategy for synthesizing the furylethylene functional monomer, and the method has a good industrial prospect.
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Paragraph 0121-0144
(2021/04/17)
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- A Systems Approach to a One-Pot Electrochemical Wittig Olefination Avoiding the Use of Chemical Reductant or Sacrificial Electrode
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An unprecedented one-pot fully electrochemically driven Wittig olefination reaction system without employing a chemical reductant or sacrificial electrode material to regenerate triphenylphosphine (TPP) from triphenylphosphine oxide (TPPO) and base-free in situ formation of Wittig ylides, is reported. Starting from TPPO, the initial step of the phosphoryl P=O bond activation proceeds through alkylation with RX (R=Me, Et; X=OSO2CF3 (OTf)), affording the corresponding [Ph3POR]+X? salts which undergo efficient electroreduction to TPP in the presence of a substoichiometric amount of the Sc(OTf)3 Lewis acid on a Ag-electrode. Subsequent alkylation of TPP affords Ph3PR+ which enables a facile and efficient electrochemical in situ formation of the corresponding Wittig ylide under base-free condition and their direct use for the olefination of various carbonyl compounds. The mechanism and, in particular, the intriguing role of Sc3+ as mediator in the TPPO electroreduction been uncovered by density functional theory calculations.
- Chakraborty, Biswarup,Kostenko, Arseni,Menezes, Prashanth W.,Driess, Matthias
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supporting information
p. 11829 - 11834
(2020/08/19)
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- N,N,O-Coordinated tricarbonylrhenium precatalysts for the aerobic deoxydehydration of diols and polyols
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Rhenium complexes are well known catalysts for the deoxydehydration (DODH) of vicinal diols (glycols). In this work, we report on the DODH of diols and biomass-derived polyols using L4Re(CO)3as precatalyst (L4Re(CO)3= tricarbonylrhenium 2,4-di-tert-butyl-6-(((2-(dimethylamino)ethyl)(methyl)amino)methyl)phenolate). The DODH reaction was optimized using 2 mol% of L4Re(CO)3as precatalyst and 3-octanol as both reductant and solvent under aerobic conditions, generating the active high-valent rhenium speciesin situ. Both diol and biomass-based polyol substrates could be applied in this system to form the corresponding olefins with moderate to high yield. Typical features of this aerobic DODH system include a low tendency for the isomerization of aliphatic external olefin products to internal olefins, a high butadiene selectivity in the DODH of erythritol, the preferential formation of 2-vinylfuran from sugar substrates, and an overall low precatalyst loading. Several of these features indicate the formation of an active species that is different from the species formed in DODH by rhenium-trioxo catalysts. Overall, the bench-top stable and synthetically easily accessible, low-valent NNO-rhenium complex L4Re(CO)3represents an interesting alternative to high-valent rhenium catalysts in DODH chemistry.
- Klein Gebbink, Robertus J. M.,Li, Jing,Lutz, Martin
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p. 3782 - 3788
(2020/06/22)
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- Synthetic Entry to Polyfunctionalized Molecules through the [3+2]-Cycloaddition of Thiocarbonyl Ylides
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Here we present a comprehensive study on the [3+2]-cycloaddition of thiocarbonyl ylides with a wide variety of alkenes and alkynes. The obtained dihydro- and tetrahydrothiophene products serve as exceptionally versatile intermediates providing access to thiophenes, dienes, dendralenes, and vic-quarternary carbon centers. The use of high-pressure conditions enables thermally unstable, sterically encumbered or moderately reactive substrates to undergo the cycloaddition under mild conditions, thereby increasing the yield by up to 58percent. In addition, we showcase its utility by the formal syntheses of the pharmaceuticals NGB 4420 and tenilapine.
- Habiger, Christoph,Haut, Franz-Lucas,Korber, Johannes Nepomuk,Müller, Thomas,Magauer, Thomas,Mayer, Peter,Speck, Klaus,Wurst, Klaus
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supporting information
(2019/09/06)
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- Efficient and Practical Transfer Hydrogenation of Ketones Catalyzed by a Simple Bidentate Mn?NHC Complex
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Catalytic reductions of carbonyl-containing compounds are highly important for the safe, sustainable, and economical production of alcohols. Herein, we report on the efficient transfer hydrogenation of ketones catalyzed by a highly potent Mn(I)?NHC complex. Mn?NHC 1 is practical at metal concentrations as low as 75 ppm, thus approaching loadings more conventionally reserved for noble metal based systems. With these low Mn concentrations, catalyst deactivation is found to be highly temperature dependent and becomes especially prominent at increased reaction temperature. Ultimately, understanding of deactivation pathways could help close the activity/stability-gap with Ru and Ir catalysts towards the practical implementation of sustainable earth-abundant Mn-complexes.
- van Putten, Robbert,Benschop, Joeri,de Munck, Vincent J.,Weber, Manuela,Müller, Christian,Filonenko, Georgy A.,Pidko, Evgeny A.
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p. 5232 - 5235
(2019/07/18)
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- A Cptt-Based Trioxo-Rhenium Catalyst for the Deoxydehydration of Diols and Polyols
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Trioxo-rhenium complexes are well known catalysts for the deoxydehydration (DODH) of vicinal diols (glycols). In this work, we report on the DODH of diols and biomass-derived polyols using CpttReO3 as a new catalyst (Cptt=1,3-di-tert-butylcyclopentadienyl). The DODH reaction was optimized using 2 mol % of CpttReO3 and 3-octanol as both reductant and solvent. The CpttReO3 catalyst exhibits an excellent activity for biomass-derived polyols. Specifically, glycerol is almost quantitatively converted to allyl alcohol and mucic acid gives 75 % of muconates at 91 % conversion. In addition, the loading of CpttReO3 can be reduced to 0.1 mol % to achieve a turn-over number as high as 900 per Re when using glycerol as substrate. Examination of DODH reaction profiles by NMR spectroscopy indicates that catalysis is related to Cp-ligand release, which raises questions on the nature of the actual catalyst.
- Li, Jing,Lutz, Martin,Otte, Matthias,Klein Gebbink, Robertus J. M.
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p. 4755 - 4760
(2018/10/02)
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- Terminal Alkenes from Acrylic Acid Derivatives via Non-Oxidative Enzymatic Decarboxylation by Ferulic Acid Decarboxylases
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Fungal ferulic acid decarboxylases (FDCs) belong to the UbiD-family of enzymes and catalyse the reversible (de)carboxylation of cinnamic acid derivatives through the use of a prenylated flavin cofactor. The latter is synthesised by the flavin prenyltransferase UbiX. Herein, we demonstrate the applicability of FDC/UbiX expressing cells for both isolated enzyme and whole-cell biocatalysis. FDCs exhibit high activity with total turnover numbers (TTN) of up to 55000 and turnover frequency (TOF) of up to 370 min?1. Co-solvent compatibility studies revealed FDC's tolerance to some organic solvents up 20 % v/v. Using the in-vitro (de)carboxylase activity of holo-FDC as well as whole-cell biocatalysts, we performed a substrate profiling study of three FDCs, providing insights into structural determinants of activity. FDCs display broad substrate tolerance towards a wide range of acrylic acid derivatives bearing (hetero)cyclic or olefinic substituents at C3 affording conversions of up to >99 %. The synthetic utility of FDCs was demonstrated by a preparative-scale decarboxylation.
- Aleku, Godwin A.,Prause, Christoph,Bradshaw-Allen, Ruth T.,Plasch, Katharina,Glueck, Silvia M.,Bailey, Samuel S.,Payne, Karl A. P.,Parker, David A.,Faber, Kurt,Leys, David
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p. 3736 - 3745
(2018/08/03)
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- α-Alkylidene-γ-butyrolactone Formation via Bi(OTf)3-Catalyzed, Dehydrative, Ring-Opening Cyclizations of Cyclopropyl Carbinols: Understanding Substituent Effects and Predicting E/Z Selectivity
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A Bi(OTf)3-catalyzed ring-opening cyclization of (hetero)aryl cyclopropyl carbinols to form α-alkylidene-γ-butyrolactones (ABLs) is reported. This transformation represents different chemoselectivity from previous reports that demonstrated formation of (hetero)aryl-fused cyclohexa-1,3-dienes upon acid-promoted cyclopropyl carbinol ring opening. ABLs are obtained in up to 89% yield with a general preference for the E-isomers. Mechanistically, Bi(OTf)3 serves as a stable and easy to handle precursor to TfOH. TfOH then catalyzes the formation of cyclopropyl carbinyl cations, which undergo ring opening, intramolecular trapping by the neighboring ester group, subsequent hydrolysis, and loss of methanol resulting in the formation of the ABLs. The nature and relative positioning of the substituents on both the carbinol and the cyclopropane determine both chemo- and stereoselective outcomes. Carbinol substituents determine the extent of cyclopropyl carbinyl cation formation. The cyclopropane donor substituents determine the overall reaction chemoselectivity. Weakly stabilizing or electron-poor donor groups provide better yields of the ABL products. In contrast, copious amounts of competing products are observed with highly stabilizing cyclopropane donor substituents. Finally, a predictive model for E/Z selectivity was developed using DFT calculations.
- Sandridge, Matthew J.,McLarney, Brett D.,Williams, Corey W.,France, Stefan
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p. 10883 - 10897
(2017/10/27)
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- C2-Alkenylation of N-heteroaromatic compounds: Via Br?nsted acid catalysis
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Substituted heteroaromatic compounds, especially those based on pyridine, hold a privileged position within drug discovery and medicinal chemistry. However, functionalisation of the C2 position of 6-membered heteroarenes is challenging because of (a) the difficulties of installing a halogen at this site and (b) the instability of C2 heteroaryl-metal reagents. Here we show that C2-alkenylated heteroaromatics can be accessed by simple Br?nsted acid catalysed union of diverse heteroarene N-oxides with alkenes. The approach is notable because (a) it is operationally simple, (b) the Br?nsted acid catalyst is cheap, non-toxic and sustainable, (c) the N-oxide activator disappears during the reaction, and (d) water is the sole stoichiometric byproduct of the process. The new protocol offers orthogonal functional group tolerance to metal-catalysed methods and can be integrated easily into synthetic sequences to provide polyfunctionalised targets. In broader terms, this study demonstrates how classical organic reactivity can still be used to provide solutions to contemporary synthetic challenges that might otherwise be approached using transition metal catalysis.
- Crisenza, Giacomo E. M.,Dauncey, Elizabeth M.,Bower, John F.
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p. 5820 - 5825
(2016/07/06)
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- Direct Olefination of Alcohols with Sulfones by Using Heterogeneous Platinum Catalysts
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Carbon-supported Pt nanoparticles (Pt/C) were found to be effective heterogeneous catalysts for the direct Julia olefination of alcohols in the presence of sulfones and KOtBu under oxidant-free conditions. Primary alcohols, including aryl, aliphatic, allyl, and heterocyclic alcohols, underwent olefination with dimethyl sulfone and aryl alkyl sulfones to give terminal and internal olefins, respectively. Secondary alcohols underwent methylenation with dimethyl sulfone. Under 2.5 bar H2, the same reaction system was effective for the transformation of alcohol OH groups to alkyl groups. Structural and mechanistic studies of the terminal olefination system suggested that Pt0 sites on the Pt metal particles are responsible for the rate-limiting dehydrogenation of alcohols and that KOtBu may deprotonate the sulfone reagent. The Pt/C catalyst was reusable after the olefination, and this method showed a higher turnover number (TON) and a wider substrate scope than previously reported methods, which demonstrates the high catalytic efficiency of the present method. Olefination of alcohols: The first heterogeneous catalytic terminal and internal olefination of primary alcohols and methylenation of secondary alcohols with sulfones, a reusable carbon-supported Pt catalyst, and KOtBu is reported (see scheme).
- Hakim Siddiki,Touchy, Abeda Sultana,Kon, Kenichi,Shimizu, Ken-Ichi
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p. 6111 - 6119
(2016/04/26)
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- Ex situ catalytic upgrading of lignocellulosic biomass components over vanadium contained H-MCM-41 catalysts
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H-V-MCM-41 catalysts containing 5, 10, and 30 wt% of vanadium were synthesized and applied to the ex situ catalytic pyrolysis (CP) of three polymeric components of lignocellulosic biomass for the first time. Characterization of the catalysts was performed using N2 adsorption-desorption, XRD, FT-IR, and NH3-TPD. The results of XRD analysis showed that 5 wt% and 10 wt% H-V-MCM-41 catalysts maintained the mesoporous structure, whereas the mesoporous structure was destroyed in 30 wt% H-V-MCM-41 with considerable amount of small V2O5 crystalline outside the framework. NH3-TPD showed that H-V-MCM-41 has mostly weak acid sites and that 10 wt% H-V-MCM-41 had the largest quantity of acid sites due to framework vanadium. In the case of CP of cellulose using Py-GC/MS, 10 wt% H-V-MCM-41 showed the highest catalytic activity for the production of valuable furanic compounds such as furfural because of the enhanced deoxygenation over the acid sites formed on framework vanadium. In the case of CP of xylan as well, 10 wt% H-V-MCM-41 led to the largest yield of mono-aromatics. The production of acetic acid was also promoted by H-V-MCM-41 catalysts. The CP of lignin over H-V-MCM-41 catalysts promoted substantially the production of important feedstock chemicals for the petrochemical industry: phenolics and mono-aromatics.
- Kim, Beom-Sik,Jeong, Chang Seok,Kim, Ji Man,Park, Su Bin,Park, Sung Hoon,Jeon, Jong-Ki,Jung, Sang-Chul,Kim, Sang Chai,Park, Young-Kwon
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p. 184 - 191
(2016/03/08)
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- Synthesis of tris[2-(2-furyl)ethyl]phosphine its chalcogenides and PdII complex
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Nucleophilic addition of PH3 to 2-vinylfuran in the KOH/DMSO(H2O) suspension affords 65% of tris[2-(2-furyl)ethyl]-phosphine, whose treatment with H2O2, Se or PdCl gives the corresponding phosphine oxide, selenide and complex of trans-[Pd(L)2Cl2] type in good to excellent yields.
- Artem'ev, Alexander V.,Gusarova, Nina K.,Sutyrina, Anastasiya O.,Gatilov, Yurii V.,Trofimov, Boris A.
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p. 314 - 316
(2016/08/09)
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- Methyltriphenylphosphonium Methylcarbonate, an All-In-One Wittig Vinylation Reagent
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The methyltriphenylphosphonium methylcarbonate salt [Ph3PCH3][CH3OCO2], obtained directly by quaternarization of triphenylphosphine with dimethylcarbonate, is a latent ylide that promotes Wittig vinylation of aldehydes and ketones. Alkenes are obtained simply by mixing [Ph3PCH3][CH3OCO2] and the carbonyl and heating in a solvent (no base, no halides, and no inorganic byproducts). Deuterium exchange experiments and the particularly short anion-cation distance measured by XRD in [Ph3PCH3][CH3OCO2] allowed to explain the nature and reactivity of this species. Green chemistry metrics (atom economy, mass index, environmental factor) indicate that this vinylation procedure is more efficient than comparable ones. Deuterated [Ph3PCD3][CH3OCO2] promoted the synthesis of deuterated olefins. Add carbonyl and go! The Wittig reaction is widely applied, despite having shortcomings such as low atom economy (AE), the necessity to use solvents, and stoichiometric amounts of waste from generating the ylide. [Ph3PCH3][CH3OCO2] is a latent phosphorous ylide that promotes Wittig vinylation of aldehydes and ketones by simply heating with the carbonyl. No external base and no halides involved, and the protocol offers good AE, environmental factor, and mass index.
- Cattelan, Lisa,Noè, Marco,Selva, Maurizio,Demitri, Nicola,Perosa, Alvise
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p. 3963 - 3966
(2015/12/17)
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- Deoxygenation of biomass-derived feedstocks: Oxorhenium-catalyzed deoxydehydration of sugars and sugar alcohols
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Turn sugar into oil: The deoxygenation reaction of sugar moieties is important for the conversion of biomass into chemicals and fuels. The methyltrioxorhenium-catalyzed deoxydehydration reaction was successfully applied to this purpose using another alcohol as solvent/reductant. The reaction was highly stereospecific, affording linear polyene products from C 4-C6 sugar alcohols and aromatic compounds from C 4-C6 sugars. Copyright
- Shiramizu, Mika,Toste, F. Dean
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supporting information; experimental part
p. 8082 - 8086
(2012/09/08)
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- Thermal reaction of [3,4]-benzo-8-substituted-3Z,5Z,7E-octatetraenes and quantum-chemical study of the (8π,6π)-electrocyclisation
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The first example of thermal (8π,6π)-electrocyclisation of 1,3,5,7-octatetraene with one double bond embedded in an aromatic moiety is described. By this process, [3,4]-benzo-8-substituted octatetraene derivatives, the cis,trans-1-(o-vinylphenyl)-4-(R = Me, Ph, 2-furyl)buta-1,3-dienes were transformed to a new endo-7-(R = Me, Ph, 2-furyl) and exo-7-(R = Me)-2,3-benzobicyclo[4.2.0]octa-2,4-dienes. Mechanism of reaction was also studied by DFT quantum-chemical calculations. The M06/6-311+G(d,p)//M06/6- 31+G(d,p) calculations indicate that formation of the single endo-isomer in the case of phenyl and 2-furyl substituents is determined by higher activation barriers for exo-6π-electrocyclisation than for 8π-cycloreversion.
- Skoric, Irena,Pavosevic, Fabijan,Vazdar, Mario,Marinic, Zeljko,Sindler-Kulyk, Marija,Eckert-Maksic, Mirjana,Margetic, Davor
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p. 6771 - 6778
(2011/11/12)
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- Synthesis of chiral unsaturated aminolactones using Pd-catalyzed allylic amination
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Stereoselective synthesis of (5R,6R)- and (5S,6S)-5-benzylamino-6-(tert- butyldimethylsilanyloxymethyl)-5,6-dihydropyran-2-ones starting from d-glucal and furanaldehyde, respectively, is described. The synthesis relies on a Sharpless asymmetric dihydroxylation, an Achmatowicz reaction, and a stereoselective Pd-catalyzed allylic amination as the key steps.
- Kallinen, Annukka,Tois, Jan,Sjoeholm, Rainer,Franzen, Robert
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scheme or table
p. 2367 - 2371
(2010/12/25)
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- De novo asymmetric approaches to 2-amino-n-(Benzyloxycarbonyl)-1-(2'fury)ethanol and 2-amino-n-(tert-butoxycarbonyl)-1-(2'furyl)ethanol
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Several methods were investigated for the de novo asymmetric synthesis of 2-amino-N-(benzyloxycarbonyl)-1-(2'-furyl)ethanol and 2-amino-N-(tert-butoxycarbonyl)-1-(2'-furyl)ethanol. A five step procedure was developed for the practical preparation of optically pure 2-amino-N-benzyloxycarbonyl)-1-(2'-furyl)ethanol and a shorter 2-step procedure was developed for 2-amino-N-(tert-butoxycarbonyl)-1-(2'-furyl)ethanol. Both routes used a Noyori reduction to install the asymmetry.
- Haukaas, Michael H.,Li, Miaosheng,Starosotnikov, Alexey M.,O'Doherty, George A.
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experimental part
p. 1549 - 1559
(2009/09/06)
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- Hydrazines and azides via the metal-catalyzed hydrohydrazination and hydroazidation of olefins
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The discovery, study, and implementation of the Co- and Mn-catalyzed hydrohydrazination and hydroazidation reactions of olefins are reported. These reactions are equivalent to direct hydroaminations of C-C double bonds with protected hydrazines or hydrazoic acid but are based on a different concept in which the H and the N atoms come from two different reagents, a silane and an oxidizing nitrogen source (azodicarboxylate or sulfonyl azide). The hydrohydrazination reaction using di-tert-butyl azodicarboxylate is characterized by its ease of use, large functional group tolerance, and broad scope, including mono-, di-, tri-, and tetrasubstituted olefins. Key to the development of the hydroazidation reaction was the use of sulfonyl azides as nitrogen sources and the activating effect of tert-butyl hydroperoxide. The reaction was found to be efficient for the functionalization of mono-, di-, and trisubstituted olefins, and only a few functional groups are not tolerated. The alkyl azides obtained are versatile intermediates and can be transformed to the free amines or triazoles without isolation of the azides. Preliminary mechanistic investigations suggest a rate-limiting hydrocobaltation of the alkene, followed by an amination reaction. Radical intermediates cannot be ruled out and may be involved.
- Waser, Jerome,Gaspar, Boris,Nambu, Hisanori,Carreira, Erick M.
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p. 11693 - 11712
(2007/10/03)
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- A general one-pot synthesis of vinyl-thiiranes and conjugated dienes
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The first general synthesis of vinyl-thiiranes 7 and an effiecient preparation of conjugated dienes 8 and 9 is presented. Methodology described for the preparation of these compounds is based on the corresponding readily available thiophosphates 1 and selenophosphates 2.
- Maciagiewicz,Dybowski,Skowronska
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p. 515 - 523
(2007/10/03)
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- Urokinase inhibitors
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Compounds having the formula are inhibitors of urokinase and are useful in the treatment of diseases in which urokinase plays a role. Also disclosed are urokinase-inhibiting compositions and a method of inhibiting urokinase in a mammal.
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- Ukokinase inhibitors
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Compounds having the formula are inhibitors of urokinase and are useful in the treatment of diseases in which urokinase plays a role. Also disclosed are urokinase-inhibiting compositions and a method of inhibiting urokinase in a mammal.
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- Enantioselective synthesis of N-Cbz-protected 6-amino-6-deoxymannose, -talose, and -gulose
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equation presented The enantioselective synthesis of three 6-amino-6-deoxy sugars has been achieved in six to eight steps from furfural. A sequence of diastereoselective oxidation and reduction reactions produced Cbz-protected 6-aminomannose from furfuryl alcohol 3. The incorporation of a Mitsunobu reaction into the reaction sequence allows for the selective synthesis of both N-Cbz-protected 6-aminotalose and 6-aminogulose. The overall procedure allows for the synthesis of either enantiomer of these three aminosugars.
- Haukaas, Michael H.,O'Doherty, George A.
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p. 3899 - 3902
(2007/10/03)
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- Synthesis of D- and L-Deoxymannojirimycin via an Asymmetric Aminohydroxylation of Vinylfuran
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(Equation Presented) The Sharpless catalytic asymmetric aminohydroxylation has been applied to 2-vinylfuran, producing β-hydroxyfurfurylamine 5a with enantioexcess of >86% and 21% yield from furfural. The Cbz and TBS protected amino alcohol 5a was converted into both the D- and L-isomers of deoxymannojirimycin (DMJ) and deoxygulonojirimycin in five to seven steps and 48% and 66% overall yields. The key steps include the use of an aza-Achmatowicz reaction, a diastereoselective Luche reduction, diastereoselective dihydroxylation, and a tandem Cbz deprotection/reductive amination.
- Haukaas, Michael H.,O'Doherty, George A.
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p. 401 - 404
(2007/10/03)
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- Syntheses of four D- and L-hoxoses via diastereoselective and enantioselective dihydroxylation reactions
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An expeditious approach to various protected hexoses has been developed by the use of the Sharpless catalytic asymmetric dihydroxylation reaction. Applying the Sharpless catalytic asymmetric dihydroxylation reaction on vinylfuran, diols with high enentioexcess are produced. The resulting diols can be stereoselectively transformed into either protected D- or L-mannose in five steps and approximately 39% yield from furfural. Similarly, both D- and L-talose and gulose have been synthesized in 19% overall yields, respectively. Using a modified strategy, both protected D- and L-gulo- and allo-sugar-δ-lactones were synthesized in eight steps and ~-20% overall yield from furfural. (C) 2000 Elsevier Science Ltd.
- Harris, Joel M.,Keraenen, Mark D.,Nguyen, Hang,Young, Victor G.,O'Doherty, George A.
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- Enantioselective synthesis of 5-substituted α,β-unsaturated δ- lactones: Application to the synthesis of styryllactones
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A flexible enantioselective synthesis of highly funcfionalized 5- substituted α,β-unsaturated δ-lactones has been achieved by applying the sharpless catalytic asymmetric dihydroxylation to vinylfuran as the key step. The resulting diols are produced in high enantio excess and can be stereoselectively transformed into differentially protected δ-lactones through a short reaction sequence.
- Harris, Joel M.,O'Doherty, George A.
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p. 183 - 187
(2007/10/03)
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- Synthesis of styrenes through the decarboxylation of trans-cinnamic acids by plant cell cultures
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A new method has been developed for the synthesis of styrenes through the decarboxylation of trans-cinnamic acids by plant cell cultures at room temperature. 4-Hydroxy-3-methoxystyrene (2a), 3-nitrostyrene (2d) and furan (2e) were synthesized quantitatively.
- Takemoto, Masumi,Achiwa, Kazuo
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p. 6595 - 6598
(2007/10/03)
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- SYNTHESIS OF FURAN COMPOUNDS WITH AMINO AND IMINO GROUPS AT THE β-POSITION OF THE SIDE CHAIN BY THE CATALYTIC HYDROFORMAMINATION OF 2-VINYLFURAN
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The hydroformamination of 2-vinylfuran in the presence of HRh(CO)(PPh3)3 was used for the first time to give N--N,N-dilakylamines and N--N-alkylimines.
- Lapidus, A. L.,Rodin, A. P.,Brezhnev, L. Yu.,Pruidze, I. G.,Ugrak, B. I.
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p. 1310 - 1312
(2007/10/02)
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- SYNTHESIS OF THIIRANES FROM EPOXIDES IN THE PRESENCE OF THIOUREA IN A WEAKLY HYDRATED ORGANIC MEDIUM
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Reactivity of thiourea in the absence or in the presence of ethanol, towards several furanic, aromatic, aliphatic, and cyclic epoxides is studied.These results are compared to other ones obtained in the same conditions with another sulfured agent: KSCN.
- Bouda, H.,Borredon, M. E.,Delmas, M.,Gaset, A.
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p. 491 - 500
(2007/10/02)
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- Process for preparation of substituted olefins
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The present invention relates to a process for the preparation of aromatic or furyl substituted olefins, which comprises reacting an olefinic compound with an aromatic compound or furan compound in the presence of carbon monoxide by using a rhodium carbonyl complex as a catalyst to form a corresponding aromatic or furyl substituted olefin.
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