- STRONGLY LEWIS ACIDIC METAL-ORGANIC FRAMEWORKS FOR CONTINUOUS FLOW CATALYSIS
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Lewis acidic metal-organic framework (MOF) materials comprising triflate-coordinated metal nodes are described. The materials can be used as heterogenous catalysts in a wide range of organic group transformations, including Diels-Alder reactions, epoxide-ring opening reactions, Friedel-Crafts acylation reactions and alkene hydroalkoxylation reactions. The MOFs can also be prepared with metallated organic bridging ligands to provide heterogenous catalysts for tandem reactions and/or prepared as composites with support particles for use in columns of continuous flow reactor systems. Methods of preparing and using the MOF materials and their composites are also described.
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Paragraph 0230-0232; 0236; 0239; 0259
(2021/02/26)
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- Efficient hydrogenation of levulinic acid catalysed by spherical NHC-Ir assemblies with atmospheric pressure of hydrogen
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A practical, efficient, and mild hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) under 1 atm H2was realized by single-sited 3D porous self-supported N-heterocyclic carbene iridium catalysts. Quantitative yields and selectivities were achieved at 0.02 mol% catalyst loading, and the catalyst could be reused for 9 runs without obvious loss of selectivity or activity.
- Liu, Yaoqi,Lu, Zeye,Shen, Lingyun,Tu, Tao,Wu, Jiajie,Zheng, Qingshu
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supporting information
p. 5037 - 5042
(2021/07/29)
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- Preparation method of delta-caprolactone
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The invention relates to a preparation method of delta-caprolactone. The method comprises the following steps: dissolving a beta-dicarbonyl compound and a basic catalyst in a solvent, and conducting preheating; dropwise adding alkyl acrylate into a reaction system for a Michael addition reaction; cooling the system, adding alkali, and then heating the reaction system for saponification reaction; adding water, cooling the system, and adding a reducing agent for reaction; and cooling the system, adjusting the pH value with acid, and carrying out post-treatment to obtain the delta-caprolactone. The method disclosed by the invention is simple in process operation, high in safety, high in raw material utilization rate, short in total consumed time and free of generation of carbon dioxide.
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Paragraph 0077; 0083; 0085-0086; 0088
(2021/08/25)
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- Synthesis method of delta-caprolactone spice
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The invention discloses a synthesis method of delta-caprolactone spice, which comprises the following steps of by taking ethyl acetoacetate and methyl acrylate as initial raw materials, adding an alkaline substance with the mass fraction of 0.1-1%, controlling the temperature to be 30-100 DEG C, reacting for 1-8 hours, reacting to obtain acetyl succinate, stirring, heating and washing an acidic substance and acetyl succinate to obtainacetobutyric acid, adding the acetylbutyric acid and hydrogen into a hydrogenation kettle, and performing hydrogenation under the conditions that the temperatureis 60-120 DEG C and the pressure intensity is 0.4-1.2 MPa to obtain delta-caprolactone. The method is simple in process step, high in yield, free of side reaction and simple to separate from impurities, and delta-caprolactone is an important organic compound and an intermediate; the method has a wide application and development prospect in the field of synthesis of essences, fragrances and medicines, and natural products exist in coconut oil, hot milk fat and the like and are widely applied to edible essences and tobacco essences.
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Paragraph 0016; 0023; 0027-0028; 0032-0033; 0037-0038; 0042
(2021/02/06)
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- Photo-induced radical borylation of hemiacetals via C–C bond cleavage
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In this study, we reported a photo-induced radical borylation of hemiacetal derivatives via C–C bond cleavage. This transformation can be realized under mild conditions with simple reaction settings and irradiation of visible light. A series of substrates, including both cyclic and linear hemiacetal derivatives, were effectively transformed to the borylation product in moderate to good yields. Finally, the mechanism was studied in detail by DFT calculations, suggesting insight of the radical borylation process.
- Liu, Qianyi,Zhang, Jianning,Zhang, Lei,Mo, Fanyang
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supporting information
(2021/01/05)
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- (Cyclopentadienone)iron-Catalyzed Transfer Dehydrogenation of Symmetrical and Unsymmetrical Diols to Lactones
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Air-stable iron carbonyl compounds bearing cyclopentadienone ligands with varying substitution were explored as catalysts in dehydrogenative diol lactonization reactions using acetone as both the solvent and hydrogen acceptor. Two catalysts with trimethylsilyl groups in the 2- A nd 5-positions, [2,5-(SiMe3)2-3,4-(CH2)4(δ4-C4C= O)]Fe(CO)3 (1) and [2,5-(SiMe3)2-3,4-(CH2)3(δ4-C4C= O)]Fe(CO)3 (2), were found to be the most active, with 2 being the most selective in the lactonization of diols containing both primary and secondary alcohols. Lactones containing five-, six-, and seven-membered rings were successfully synthesized, and no over-oxidations to carboxylic acids were detected. The lactonization of unsymmetrical diols containing two primary alcohols occurred with catalyst 1, but selectivity was low based on alcohol electronics and modest based on alcohol sterics. Evidence for a transfer dehydrogenation mechanism was found, and insight into the origin of selectivity in the lactonization of 1°/2° diols was obtained. Additionally, spectroscopic evidence for a trimethylamine-ligated iron species formed in solution during the reaction was discovered.
- Tang, Yidan,Meador, Rowan I. L.,Malinchak, Casina T.,Harrison, Emily E.,McCaskey, Kimberly A.,Hempel, Melanie C.,Funk, Timothy W.
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p. 1823 - 1834
(2020/02/04)
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- Strongly Lewis Acidic Metal-Organic Frameworks for Continuous Flow Catalysis
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The synthesis of highly acidic metal-organic frameworks (MOFs) has attracted significant research interest in recent years. We report here the design of a strongly Lewis acidic MOF, ZrOTf-BTC, through two-step transformation of MOF-808 (Zr-BTC) secondary building units (SBUs). Zr-BTC was first treated with 1 M hydrochloric acid solution to afford ZrOH-BTC by replacing each bridging formate group with a pair of hydroxide and water groups. The resultant ZrOH-BTC was further treated with trimethylsilyl triflate (Me3SiOTf) to afford ZrOTf-BTC by taking advantage of the oxophilicity of the Me3Si group. Electron paramagnetic resonance spectra of Zr-bound superoxide and fluorescence spectra of Zr-bound N-methylacridone provided a quantitative measurement of Lewis acidity of ZrOTf-BTC with an energy splitting (?E) of 0.99 eV between the ?x? and ?y? orbitals, which is competitive to the homogeneous benchmark Sc(OTf)3. ZrOTf-BTC was shown to be a highly active solid Lewis acid catalyst for a broad range of important organic transformations under mild conditions, including Diels-Alder reaction, epoxide ring-opening reaction, Friedel-Crafts acylation, and alkene hydroalkoxylation reaction. The MOF catalyst outperformed Sc(OTf)3 in terms of both catalytic activity and catalyst lifetime. Moreover, we developed a ZrOTf-BTC?SiO2 composite as an efficient solid Lewis acid catalyst for continuous flow catalysis. The Zr centers in ZrOTf-BTC?SiO2 feature identical coordination environment to ZrOTf-BTC based on spectroscopic evidence. ZrOTf-BTC?SiO2 displayed exceptionally high turnover numbers (TONs) of 1700 for Diels-Alder reaction, 2700 for epoxide ring-opening reaction, and 326 for Friedel-Crafts acylation under flow conditions. We have thus created strongly Lewis acidic sites in MOFs via triflation and constructed the MOF?SiO2 composite for continuous flow catalysis of important organic transformations.
- Ji, Pengfei,Feng, Xuanyu,Oliveres, Pau,Li, Zhe,Murakami, Akiko,Wang, Cheng,Lin, Wenbin
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supporting information
p. 14878 - 14888
(2019/10/02)
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- Calcium(II)- And Triflimide-Catalyzed Intramolecular Hydroacyloxylation of Unactivated Alkenes in Hexafluoroisopropanol
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We report an efficient intramolecular hydroacyloxylation of unactivated alkenes, offering a streamlined access to relevant γ-lactones, which features the utilization of either a calcium(II) salt or triflimide as a catalyst in hexafluoroisopropanol. This method could be applied to the synthesis of natural products and the late-stage functionalization of natural and bioactive molecules. Additionally, DFT computations were used to elucidate the twist of reactivity observed between the hydroamidation and hydroacyloxylation of unactivated alkenes regarding the formation of 5- and 6-membered rings.
- Qi, Chenxiao,Yang, Shengwen,Gandon, Vincent,Leb?uf, David
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supporting information
p. 7405 - 7409
(2019/10/02)
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- W(OTf)6-Catalyzed Synthesis of Γ-Lactones by Ring Contraction of Macrolides or Ring Closing of Terminal Hydroxyfatty Acids in Ionic Liquid
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γ-Lactones are an important class of fine chemical products and are widely used in perfumes, medicines, pesticides, dyes, and other fields. Herein, a new method for γ-lactones preparation based on ring contraction was developed. Starting from macrolides, W(OTf)6 was used to catalyze the ring-opening polymerization then depolymerization. The depolymerization step was not a common ring-closing process, and the carbon number of the ring was reduced one by one by rearrangement to form the most thermodynamically stable five-membered ring compounds. γ-Caprolactone (180 °C for 10 h) was obtained in a yield of 94 % when [EMIM]OTf was used as the solvent, and the yield of isolated product was up to 85 %. The interaction of various components and the reaction mechanism were studied by FTIR spectroscopy and 1H NMR spectroscopy, respectively. Furthermore, γ-lactones could be produced when the substrate was extended to terminal hydroxyfatty acids. Unexpectedly, the catalyst was poisoned by 1 equivalent of H2O added during the process and thus the yield decreased greatly. The reaction is green and simple, and proceeds in one pot with high atom economy (100 % for macrolides and with water as the only byproduct for terminal hydroxyfatty acid), which provides a promising approach to synthesizing γ-lactones.
- Xie, Zhong-Yu,Deng, Jin,Fu, Yao
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p. 2332 - 2339
(2018/07/31)
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- Aldol condensation among acetaldehyde and ethanol reactants on TiO2: Experimental evidence for the kinetically relevant nucleophilic attack of enolates
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Combinations of rate measurements as functions of reactant pressures, in situ infrared spectroscopy, comparisons of kinetic isotope effects, and rate inhibition effects provide experimental evidence that aldol condensation of acetaldehyde proceeds by kinetically relevant nucleophilic attack of a reactive enolate upon an acetaldehyde molecule over anatase TiO2. Steady-state turnover rates of aldol condensation measured as a function of the pressures of C2H4O, C2H5OH, H2O, and H2 between 503 K and 537 K show that rates reflect a second order dependence on C2H4O pressure and an inverse second order dependence on the C2H5OH pressure at the lowest C2H4O-to-C2H5OH ratios. Infrared spectra obtained in situ show that the exposed cationic Ti-atoms that facilitate aldol addition on TiO2 surfaces are saturated with C2H5OH? species and C2H4O? coverages are much smaller. In addition, aldol rates increase when C2D4O replaces C2H4O as a reactant, which likely reflects an inverse, secondary isotope effect caused by rehybridization of C-atoms at the transition state that forms a C–C bond between two reactive intermediates derived from acetaldehyde. These results suggest that the kinetically relevant step is a bimolecular surface reaction, specifically the nucleophilic attack of an enolate onto a vicinal C2H4O? species. This conclusion is consistent also with aldol condensation rates that decrease with an inverse second order dependence on pyridine (C5H5N) pressure, because C5H5N displaces C2H4O from the two Lewis acid sites involved in the kinetically relevant step (confirmed by in situ FTIR). Comparisons to recent reports on the mechanism of this reaction on anatase TiO2 indicate that the presence of high coverages of C2H5OH? causes nucleophilic attack to become the kinetically relevant step by significantly reducing the number of enolate-acetaldehyde reactant pairs upon the surface.
- Zhang, Hongbo,Ibrahim, Malek Y.S.,Flaherty, David W.
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p. 290 - 302
(2018/04/02)
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- Efficient Iridium Catalysts for Base-Free Hydrogenation of Levulinic Acid
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The synthesis and characterization of new dicationic ruthenium and iridium complexes bearing a dipyridylamine ligand (dpa) are reported. These complexes display an unusual zwitterionic molecular structure in the solid state. The iridium complex [Cp?Ir(dpa)(OSO3)] (Ir1) was found to be very efficient in base-free hydrogenation of levulinic acid into γ-valerolactone (GVL). TONs as high as 174000 in hydrogenation have been obtained. We have demonstrated that reduction of LA into GVL by transfer hydrogenation with formic acid is in fact operating by hydrogenation fed by preliminary formic acid dehydrogenation. A mechanism based on the characterization and isolation of Ir-H complexes is proposed.
- Wang,Huang,Dorcet,Roisnel,Bruneau,Fischmeister
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supporting information
p. 3152 - 3162
(2017/09/05)
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- (HMe 2 SiCH 2) 2: A Useful Reagent for B(C 6 F 5) 3 -Catalyzed Reduction-Lactonization of Keto Acids: Concise Syntheses of (-)- cis -Whisky and (-)- cis -Cognac Lactones
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(HMe 2 SiCH 2) 2 has been utilized as a useful reagent for B(C 6 F 5) 3 -catalyzed reduction-lactonization of keto acids to synthesize γ- and δ-lactones. The process led concisely to (-)- cis -whisky and (-)- cis -cognac lactones in respective overall yields of 32% and 36%.
- Xie, Hengmu,Lu, Ji,Gui, Yingying,Gao, Lu,Song, Zhenlei
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supporting information
p. 2453 - 2459
(2017/10/06)
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- Efficient Hydrogenation of Biomass Oxoacids to Lactones by Using NHC–Iridium Coordination Polymers as Solid Molecular Catalysts
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A series of NHC–iridium coordination polymers have proven to be robust, efficient and recyclable solid molecular catalysts toward the hydrogenation of biomass levulinic acid (LA) to γ-valerolactone. Along with quantitative yields attained at 0.01 mol % catalyst loading under 50 atm of H2, the solid molecular catalyst was readily recovered and reused for 12 runs without obvious loss of the selectivity and activity. Remarkably, up to 1.2×105 TON, an unprecedented value could be achieved in this important transformation. In addition, a number of LA homologues, analogues and derivatives were well tolerated to deliver various intriguing and functional lactones in good to excellent yields, which further confirmed the feasibility of the solid molecular catalysts.
- Liu, Yaoqi,Sun, Zheming,Huang, Changyu,Tu, Tao
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p. 355 - 360
(2017/02/05)
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- H-Bonding-promoted radical addition of simple alcohols to unactivated alkenes
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H-Bonding-induced radical addition of simple alcohols to unactivated olefins was achieved. It effectively solved the long-standing problems of reactivity and selectivity in this type of reaction. The hydroxyalkylation occurred via site-specific cleavage of the α-hydroxyl-C-H bond in alcohols. This method allows a highly atom-economical, operationally simple and environmentally benign access to diverse primary, secondary and tertiary alcohols, diols, and even polyfluorinated alcohols. These useful chemicals are traditionally synthesized by using commercially unavailable organometallics via complex operations. In contrast, they can be facilely obtained through this protocol utilizing widely available starting materials.
- Tian, Yunfei,Liu, Zhong-Quan
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supporting information
p. 5230 - 5235
(2017/11/09)
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- Efficient Baeyer-Villiger electro-oxidation of ketones with molecular oxygen using an activated carbon fiber electrode in ionic liquid [bmim][OTf]
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A new and efficient method for the synthesis of lactones and esters involving the application of an molecular oxygen-based electro-catalytic oxidation system and ionic liquid [bmim][OTf] as electrolyte has been developed. The reaction between various ketones with molecular oxygen proceeds in a three-electrode cell under constant current conditions in [bmim][OTf] at room temperature to give the corresponding esters and lactones in good to excellent isolated yield. Additionally, the possible mechanism of Baeyer-Villiger oxidation of ketones in the electro-catalytic system is proposed.
- Hu, Yu Lin,Xie, Yi Bi,Li, De Jiang
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p. 297 - 306
(2016/08/05)
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- A sulfonated Schiff base dimethyltin(iv) coordination polymer: Synthesis, characterization and application as a catalyst for ultrasound- or microwave-assisted Baeyer-Villiger oxidation under solvent-free conditions
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The synthesis and crystal structure of the new dimethyltin(iv) compound [SnMe2(HL)(CH3OH)]n·(0.5nCH3OH) (1) derived from the Schiff base 2-[(2,3-dihydroxyphenyl)methylideneamino]benzenesulfonic acid (H3L) are described. Despite having six potentially donating centres (one imine nitrogen, two phenoxo and three sulfonate oxygen atoms), the monoprotonated dianionic ligand (HL2-) behaves as an O,O,O-tridentate chelator. Single crystal X-ray diffraction revealed that 1 is a 1D coordination polymer with every tin(iv) ion bound to two methyl groups, a methanol molecule, two Ophenoxo and one μ-Osulfonate atom from HL2-. The coordination polymer 1 was applied as a heterogeneous catalyst for the Baeyer-Villiger oxidation of ketones to esters or lactones, using aqueous hydrogen peroxide as oxidant, under ultrasound (US) or microwave (MW) irradiation and solvent- and additive-free conditions. Overall conversions up to 76/82, 98/93, 93/89, 91/94, 83/90, 68/62 and 81/87% under US/MW irradiations were obtained with 3,3-dimethyl-2-butanone, cyclopentanone, 2-methylcyclopentanone, cyclohexanone, 3-methylcyclohexanone, benzophenone and acetophenone, respectively. The catalyst can be recycled up to five cycles without losing appreciable activity.
- Martins, Luísa M.D.R.S.,Hazra, Susanta,Guedes Da Silva, M. Fátima C.,Pombeiro, Armando J. L.
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p. 78225 - 78233
(2018/06/22)
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- LYMPH DIRECTING PRODRUGS
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H:\dar\Interwoven\NRPortbl\DCC\DAR\8230712_1.doc-12/08/2015 Abstract The present invention relates to compounds and their uses, in particular, compounds in the form of prodrugs that promote transport of a pharmaceutical agent to the lymphatic system and subsequently enhance release of the parent drug.
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Page/Page column 75; 76
(2016/02/29)
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- Enantioselective Construction of Quaternary Carbon Stereocenter via Palladium-Catalyzed Asymmetric Allylic Alkylation of Lactones
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An efficient and practical method for the synthesis of α,α-disubstituted six-membered lactones was developed. Enantioselective construction of quaternary carbon centers by utilizing Pd-catalyzed asymmetric allylic alkylation proved its feasibility.
- Li, Xiao-Hui,Wan, Shi-Li,Chen, Di,Liu, Qing Rong,Ding, Chang-Hua,Fang, Ping,Hou, Xue-Long
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supporting information
p. 1568 - 1572
(2016/05/24)
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- Biocatalytic Characterization of Human FMO5: Unearthing Baeyer-Villiger Reactions in Humans
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Flavin-containing mono-oxygenases are known as potent drug-metabolizing enzymes, providing complementary functions to the well-investigated cytochrome P450 mono-oxygenases. While human FMO isoforms are typically involved in the oxidation of soft nucleophiles, the biocatalytic activity of human FMO5 (along its physiological role) has long remained unexplored. In this study, we demonstrate the atypical in vitro activity of human FMO5 as a Baeyer-Villiger mono-oxygenase on a broad range of substrates, revealing the first example to date of a human protein catalyzing such reactions. The isolated and purified protein was active on diverse carbonyl compounds, whereas soft nucleophiles were mostly non- or poorly reactive. The absence of the typical characteristic sequence motifs sets human FMO5 apart from all characterized Baeyer-Villiger mono-oxygenases so far. These findings open new perspectives in human oxidative metabolism.
- Fiorentini, Filippo,Geier, Martina,Binda, Claudia,Winkler, Margit,Faber, Kurt,Hall, Mélanie,Mattevi, Andrea
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p. 1039 - 1048
(2016/05/19)
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- METHOD FOR PRODUCING δ-VALEROLACTONE
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PROBLEM TO BE SOLVED: To provide a method for producing δ-valerolactone from γδ unsaturated-δ-valerolactone at a high yield while suppressing the hydrolysis as the by-product in the hydrogenation reaction of γδ unsaturated-δ-valerolactone. SOLUTION: Provided is a method for producing δ-valerolactone capable of having a substituent group as a methyl group and/or an ethyl group characterized in that γδ unsaturated-δ-valerolactone capable of having a substituent group as a methyl group and/or an ethyl group in the presence of a palladium-alumina catalyst, preferably, in an ester-based solvent. COPYRIGHT: (C)2016,JPO&INPIT
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Paragraph 0019; 0031
(2016/10/31)
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- Efficient and Selective Cu/Nitroxyl-Catalyzed Methods for Aerobic Oxidative Lactonization of Diols
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Cu/nitroxyl catalysts have been identified that promote highly efficient and selective aerobic oxidative lactonization of diols under mild reaction conditions using ambient air as the oxidant. The chemo- and regioselectivity of the reaction may be tuned by changing the identity of the nitroxyl cocatalyst. A Cu/ABNO catalyst system (ABNO = 9-azabicyclo[3.3.1]nonan-N-oxyl) shows excellent reactivity with symmetrical diols and hindered unsymmetrical diols, whereas a Cu/TEMPO catalyst system (TEMPO = 2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl) displays excellent chemo- and regioselectivity for the oxidation of less hindered unsymmetrical diols. These catalyst systems are compatible with all classes of alcohols (benzylic, allylic, aliphatic), mediate efficient lactonization of 1,4-, 1,5-, and some 1,6-diols, and tolerate diverse functional groups, including alkenes, heterocycles, and other heteroatom-containing groups.
- Xie, Xiaomin,Stahl, Shannon S.
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supporting information
p. 3767 - 3770
(2015/04/14)
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- Efficient and convenient oxidation of aldehydes and ketones to carboxylic acids and esters with H2O2 catalyzed by Co4HP2Mo15V3O62 in ionic liquid [TEBSA][BF4]
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A simple, efficient, and eco-friendly procedure for the oxidation of aldehydes and ketones to carboxylic acids and esters with H2O2 catalyzed by Co4HP2Mo15V3O62 in ionic liquid [TEBSA][BF4] has been developed. This atom-economical protocol affords the target products in good to high yields. The products can be separated by a simple extraction with organic solvent, and the catalytic system can be recycled and reused without loss of catalytic activity. Additionally, the possible mechanism of oxidation in the catalytic system is proposed. This journal is
- Hu, Yu-Lin,Li, De-Jiang,Li, Dong-Sheng
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p. 24936 - 24943
(2015/03/30)
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- Aldol Additions of Titanium and Boron Enolates of Achiral and Chiral δ-Lactones to Achiral Model Aldehydes: Simple and Induced Diastereoselectivities
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We studied the steric course of aldol additions of CpTiCl2 (novel) or Bu2B enolates of the unsubstituted δ-lactone and of the four monomethylated δ-lactones to isobutyraldehyde, crotonaldehyde, and para-bromobenzaldehyde. The titanium enolates reacted syn-selectively with >95:5 ds in most cases. The boron enolates reacted anti-selectively without exception (ds = 98:2 to 92:8). These selectivities paired with a preferred trans-orientation of the α-hydroxyalkyl substituents relative to the lactone's β- or γ-methyl group and with a preferred cis-orientation relative to the lactone's δ-methyl group. Our preparation of γ-methyl-δ-lactone (20) features a tandem glycol cleavage/lactol → lactone conversion with cat. TEMPO/stoichiom. PhI(OAc)2, which we believe is novel. Aldol additions of CpTiCl2 and Bu2B enolates of δ-lactone and its monomethyl derivatives to model aldehydes were studied. The CpTiCl2 enolates reacted syn-selectively (ds >95:5), the Bu2B enolates anti-selectively (ds up to 98:2). The α-hydroxyalkyl groups were oriented trans relative to the lactone's β- or γ-methyl group but cis relative to the lactone's δ-methyl group.
- Weber, Fabian,Becker, Fabian,Keller, Manfred,Hillebrecht, Harald,Brückner, Reinhard
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supporting information
p. 7892 - 7918
(2015/12/24)
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- Functional divergence between closely related Baeyer-Villiger monooxygenases from Aspergillus flavus
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Baeyer-Villiger monooxygenases (BVMOs) catalyse the chemo-, regio- and enantioselective oxidation of ketones to esters and lactones. To date, most of the cloned BVMOs available are derived from bacteria, although Baeyer-Villiger oxidations using fungi have frequently been demonstrated. Here we report the cloning and characterization of four BVMOs from the fungus Aspergillus flavus NRRL3357. Phylogenetic analysis shows these four BVMOs to cluster in a distinct group apart from other well-characterized BVMOs including cyclohexanone, phenylacetone and 4-hydroxyacetophenone monooxygenase. Building on the Grogan classification/clustering of BVMOs, we have designated this new group of BVMOs, Group VI. Group VI BVMOs show an early divergence from the cyclopentanone monooxygenase (CPMO) type BVMOs (Group I). Substrate profiling using cyclic, bicyclic, aliphatic and aryl ketones show a clear divergence in function and specificity not only between this new group of BVMOs and the CPMO-type BVMOs, but also between the four A. flavus BVMO paralogues despite their high sequence similarity. This study not only contributes to the growing number of available BVMOs, but also addresses the current classification of Type I BVMOs, and the usefulness of phylogenetic clustering and prediction of function and selectivity when genome-mining is used to search for new biocatalysts.
- Ferroni,Smit,Opperman
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- Efficient Transfer of Chelating Amides into Different Types of Esters and Lactones
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We describe a general and versatile approach for the conversion of carboxylic acid amides into their corresponding esters despite the fact that the former are thermodynamically more stable. The transformations are mediated by the coordination of CuI by a chelating entity. The resulting weakening of the amide bond allows for nucleophilic attack by alcoholic hydroxyl functions. The principle is demonstrated for a wide variety of transformations, leading to different kinds of esters and lactones. Due to their high resonance energy, amides are generally very stable towards solvolysis. However, bispicolylamides can be activated for alcoholysis by an unusual metal coordination involving the electron pair of the amide nitrogen. Herein, we widened the scope of the reaction by transforming the amides into a range of esters and lactones.
- Jakob, Uwe,Mundinger, Stephan,Bannwarth, Willi
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p. 6963 - 6974
(2016/02/18)
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- Oxorhenium complexes bearing the water-soluble tris(pyrazol-1-yl) methanesulfonate, 1,3,5-triaza-7-phosphaadamantane, or related ligands, as catalysts for Baeyer-Villiger oxidation of ketones
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New rhenium(VII or III) complexes [ReO3(PTA)2] [ReO4] (1) (PTA = 1,3,5-triaza-7-phosphaadamantane), [ReO 3(mPTA)][ReO4]I (2) (mPTA = N-methyl-1,3,5-triaza-7- phosphaadamantane cation), [ReO3(HMT)2][ReO4] (3) (HMT = hexamethylenetetramine), [ReO3(η2-Tpm)(PTA) ][ReO4] (4) [Tpm = hydrotris(pyrazol-1-yl)methane, HC(pz) 3, pz = pyrazolyl], [ReO3(Hpz)(HMT)][ReO4] (5) (Hpz = pyrazole), [ReO(Tpms)(HMT)] (6) [Tpms = tris(pyrazol-1-yl) methanesulfonate, O3SC(pz)3-] and [ReCl 2{N2C(O)Ph}(PTA)3] (7) have been prepared from the Re(VII) oxide Re2O7 (1-6) or, in the case of 7, by ligand exchange from the benzoyldiazenido complex [ReCl2{N 2C(O)Ph}(Hpz)(PPh3)2], and characterized by IR and NMR spectroscopies, elemental analysis and electrochemical properties. Theoretical calculations at the density functional theory (DFT) level of theory indicated that the coordination of PTA to both Re(III) and Re(VII) centers by the P atom is preferable compared to the coordination by the N atom. This is interpreted in terms of the Re-PTA bond energy and hard-soft acid-base theory. The oxo-rhenium complexes 1-6 act as selective catalysts for the Baeyer-Villiger oxidation of cyclic and linear ketones (e.g., 2-methylcyclohexanone, 2-methylcyclopentanone, cyclohexanone, cyclopentanone, cyclobutanone, and 3,3-dimethyl-2-butanone or pinacolone) to the corresponding lactones or esters, in the presence of aqueous H2O2. The effects of a variety of factors are studied toward the optimization of the process.
- Martins, Luisa M. D. R. S.,Alegria, Elisabete C. B. A.,Smolenski, Piotr,Kuznetsov, Maxim L.,Pombeiro, Armando J. L.
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p. 4534 - 4546
(2013/06/04)
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- Oxidation of cyclohexane with hydrogen peroxide over β-zeolites with various Si/Al ratios
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Selective oxidation of cyclohexanone to ε-caprolactone by H 2O2 was investigated on β-zeolites with various Si/Al ratio. The yield of ε-caprolactone was increased with decreasing Si/Al ratio. The β-zeolites in which Si/Al ratio was l
- Ohno, Ryohei,Taniya, Keita,Tsuruya, Shigeru,Ichihashi, Yuichi,Nishiyama, Satoru
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- Direct room-temperature lactonisation of alcohols and ethers onto amides: An "amide strategy" for synthesis
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Last-minute deal: A direct lactonisation of ethers and alcohols onto amides that proceeds at room temperature under mild conditions is reported (see scheme). This allows the effective saving of up to two unproductive, sequential deprotection operations in synthetic sequences. Mechanistic studies are described, and a new "amide strategy" that exploits the dual robustness/late-stage selective activation properties of this functional group is outlined. Copyright
- Valerio, Viviana,Petkova, Desislava,Madelaine, Claire,Maulide, Nuno
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supporting information
p. 2606 - 2610
(2013/03/14)
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- From diols to lactones under aerobic conditions using a laccase/TEMPO catalytic system in aqueous medium
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An efficient catalytic system to oxidize quantitatively aliphatic diols using Trametes versicolor laccase and TEMPO has been developed in aqueous medium. Oxidations have occurred in a non-stereoselective fashion but with complete regio- and/or monoselectivity, obtaining lactones with excellent purity after simple extraction. This catalytic system has been demonstrated to be scalable, compatible with the presence of a variety of functionalities, and also allowed the successful enzyme recycling using a laccase-cross-linked enzyme aggregates (CLEA) preparation.
- Gotor-Fernandez, Vicente,Diaz-Rodriguez, Alba,Lavandera, Ivan,Kanbak-Aksu, Seda,Sheldon, Roger A.,Gotor, Vicente
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supporting information
p. 3405 - 3408
(2013/02/22)
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- Baeyer-Villiger oxidation of ketones catalysed by rhenium complexes bearing N- or oxo-ligands
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Rhenium (I, III-V or VII) complexes bearing N-donor or oxo-ligands catalyse the Baeyer-Villiger oxidation of cyclic and linear ketones (e.g. 2-methylcyclohexanone, 2-methylcyclopentanone, cyclohexanone, cyclopentanone, cyclobutanone and 3,3-dimethyl-2-butanone) into the corresponding lactones or esters, in the presence of aqueous H2O2 (30%). The effects of various reaction parameters are studied allowing to achieve yields up to 54%.
- Alegria, Elisabete C.B.A.,Martins, Luísa M.D.R.S.,Kirillova, Marina V.,Pombeiro, Armando J.L.
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- PRODUCTION OF 2,4-HEXADIENOIC ACID AND 1,3-PENTADIENE FROM 6-METHYL-5,6-DIHYDRO-2-PYRONE
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Described is a method of making sorbic acid, pentadiene, or 3-penten-2-one. The method includes partially hydrogenating 4-hydroxy-6-methyl-2-pyrone (HMP) to yield 5,6-dihydro-4-hydroxy-6-methyl-2H-pyran-2-one (4-DHMMP). Then, if 3-penten-2-one is desired, thermally decomposing the 4-DHMMP to yield 3-penten-2-one. If sorbic acid or pentadiene are desired, the 4-DHMMP is hydrogenated to yield 4-hydroxy-6-methyltetrahydro-2-pyrone (4-HMTHP). The 4-HMTHP is then dehydrated by contacting it with a solid acid catalyst to yield parasorbic acid (PSA). The PSA can then be ring-opened by contacting it with a solid acid catalyst. The reaction conditions of the ring-opening reaction can be controlled to yield sorbic acid and/or pentadiene.
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Page/Page column 5
(2012/05/20)
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- Highly practical copper(I)/TEMPO catalyst system for chemoselective aerobic oxidation of primary alcohols
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Aerobic oxidation reactions have been the focus of considerable attention, but their use in mainstream organic chemistry has been constrained by limitations in their synthetic scope and by practical factors, such as the use of pure O2 as the oxidant or complex catalyst synthesis. Here, we report a new (bpy)CuI/TEMPO catalyst system that enables efficient and selective aerobic oxidation of a broad range of primary alcohols, including allylic, benzylic, and aliphatic derivatives, to the corresponding aldehydes using readily available reagents, at room temperature with ambient air as the oxidant. The catalyst system is compatible with a wide range of functional groups and the high selectivity for 1° alcohols enables selective oxidation of diols that lack protecting groups.
- Hoover, Jessica M.,Stahl, Shannon S.
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supporting information; experimental part
p. 16901 - 16910
(2011/12/04)
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- Electron-rich PNP-and PNN-type ruthenium(ii) hydrido borohydride pincer complexes. synthesis, structure, and catalytic dehydrogenation of alcohols and hydrogenation of esters
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Electron-rich PNP-and PNN-type ruthenium(II) hydrido borohydride pincer complexes, [RuH(BH4)(tBu-PNP)] (tBu-PNP = (2,6-bis(di-tert-butylphosphinomethyl)pyridine) (5) and [RuH(BH 4)(tBu-PNN)] (tBu-PNN = 2-di-tert- butylphosphinomethyl-6-diethylaminomethylpyridine) (6), were prepared from their corresponding N2-bridged dinuclear Ru(II) complexes [(tBu-PNP) RuCl2]2(μ-N2) (3) and [(tBu-PNN) RuCl2]2(μ-N2) (4), respectively. The X-ray structure of 5 reveals a BH4 -anion η2 coordinated to ruthenium through two bridging hydrides. A variable-temperature 1H NMR study of 6 exhibits interesting fluxional behavior of the BH4 -ligand. Similarly, the Ru(II) hydrido borohydride complex 9, in which the BH4 -moiety is coordinated in a η1 bonding mode, was obtained by reaction of [RuCl 2(PPh3)(iPr-PNP)] (iPr-PNP = 2,6-bis(diisopropylphosphinomethyl)pyridine) (8) with two equivalents of NaBH4 at room temperature. The hydrido borohydride pincer complexes 5, 6, and 9 catalyze the acceptorless dehydrogenative coupling of primary alcohols to esters and the dehydrogenation of secondary alcohols to the corresponding ketones, accompanied by evolution of hydrogen gas. The reactivity follows the order 6 > 9 > 5. With the hydrido borohydride complex 6 as catalyst, high yields (up to 98%) and high turnover numbers (TON~1000) were obtained in the dehydrogenation of primary alcohols under mild and neutral conditions. In addition, 6 effectively catalyzes the hydrogenation of nonactivated aromatic and aliphatic esters to the corresponding alcohols with TON ~200 under a relatively mild pressure of dihydrogen and neutral and homogeneous conditions. Thus, an efficient homogeneous catalytic system for the dehydrogenation- hydrogenation reactions of alcohols is developed, which is relevant to the current interest in hydrogen storage.
- Zhang, Jing,Balaraman, Ekambaram,Leitus, Gregory,Milstein, David
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experimental part
p. 5716 - 5724
(2012/01/14)
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- Catalytic oxidation of cyclic ethers to lactones over various titanosilicates
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Various crystalline microporous metallosilicates have been used in the liquid phase catalytic oxidation of different cyclic ethers into their corresponding lactones in the presence of dilute aqueous H2O 2 as oxidant. Among the various metallosilicates studied for the oxidation of tetrahydrofuran to γ-butyrolactone, titanosilicates exhibited the best activity than the other metallosilicates such as chromium silicalite-1 (CrS-1), chromium silicalite-2 (CrS-2) and vanadium silicalite-1 (VS-1). The intrinsic activity of TS-1 was found to be marginally higher than the other titanosilicates. Cyclic ethers undergo αC-H oxidation to give the corresponding lactones; whereas open-chain ether produce carboxylic acids by initial αC-H bond oxidation to give ester as an intermediate product, which further undergoes cleavage of -O- linkage to give the final carboxylic acids. The conversion of substituted tetrahydrofuran is decreased with number of -CH3 groups at α- and/or β-position. The lactone formation is hindered when both the α-positions are substituted with methyl substituents. Mechanistically, titanium hydroperoxo complex formed in the titanosilicate/H2O2/H2O system is believed to oxidize the αC-H bond of ethers producing the respective α-hydroxylated product, which undergoes further oxidation to give the lactones (for cyclic ethers) or carboxylic acids (for open-chain ethers).
- Sasidharan, Manickam,Bhaumik, Asim
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experimental part
p. 105 - 110
(2011/05/04)
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- Oxidant-free lactonization of diols using a hydrotalcite-supported copper catalyst
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We newly synthesized well-crystallized hydrotalcite-supported copper nanoparticles, denoted as Cu/HT(c), which acted as a highly efficient heterogeneous catalyst for oxidant-free lactonization of various diols under liquid-phase conditions. The Cu/HT(c) catalyst could be recovered by simple filtration and reused without the significant loss of its activity and selectivity.
- Mikami, Yusuke,Ebata, Kaori,Mitsudome, Takato,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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experimental part
p. 855 - 861
(2010/09/16)
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- Lactones 34 [1]. Application of alcohol dehydrogenase from horse liver (HLADH) in enantioselective synthesis of δ- and ε-lactones
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The ability of horse liver alcohol dehydrogenase (HLADH) to the enantioselective oxidation of primary-primary, primary-secondary and primary-tertiary aliphatic 1,5- and 1,6-diols 1a-i was studied. No enantioselectivity of the transformations of primary-primary 1,6-diols 1a-d to ε-lactones 4a-d was observed. Regioselective oxidation of primary-secondary 1,6-diols 1e,f and 1,5-diols 1h,i afforded enantiomerically enriched ε-lactones 4e,f and δ-lactones 4h,i. ε-Lactones 4e,f were formed with higher enantiomeric excesses (e.e. = 85-99%). Enzymatic oxidation of primary-tertiary 1,6-diol 1g did not give lactone product.
- Boratynski, Filip,Kielbowicz, Grzegorz,Wawrzenczyk, Czeslaw
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experimental part
p. 30 - 36
(2010/12/18)
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- Supported sulfonic acid as green and efficient catalyst for Baeyer-Villiger oxidation with 30% aqueous hydrogen peroxide
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Silica-supported propylsulfonic acid is a very good heterogeneous catalyst for the Baeyer-Villiger oxidation of cyclic ketones to lactones with stoichiometric 30% aqueous hydrogen peroxide in 1,1,1,3,3,3-hexafluoro-2- propanol as solvent.
- Piscopo, Calogero G.,Loebbecke, Stefan,Maggi, Raimondo,Sartori, Giovanni
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experimental part
p. 1625 - 1629
(2010/10/01)
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- Exploration of the interrupted Fischer indolization reaction
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A convergent method to access the fused indoline ring system present in a multitude of bioactive molecules has been developed. The strategy involves the condensation of hydrazines with latent aldehydes to ultimately deliver indoline-containing products by way of an interrupted Fischer indolization sequence. The method is convergent, mild, operationally simple, broad in scope, and can be used to access enantioenriched products. In addition, our approach is amenable to the synthesis of furoindoline and pyrrolidinoindoline natural products as demonstrated by the concise formal total syntheses of physovenine and debromoflustramine B. The strategy will likely enable the synthesis of more complex targets such as the communesin alkaloids.
- Schammel, Alex W.,Boal, Ben W.,Zu, Liansuo,Mesganaw, Tehetena,Garg, Neil K.
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supporting information; experimental part
p. 4687 - 4695
(2010/08/06)
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- Remote control of regio- and diastereoselectivity in the hydroformylation of bishomoallylic alcohols with catalytic amounts of a reversibly bound directing group
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(Figure Presented) Remote and reversible! Phosphinites serve as reversibly bound directing groups for the remote control of the regio- and diastereoselective hydroformylation of bishomoallylic alcohols (see scheme; r.r: regioisomer ratio). The distance between the double bond and the functional hydroxy group to which the directing group is reversibly bound is the longest ever reported.
- Gruenanger, Christian U.,Breit, Bernhard
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supporting information; experimental part
p. 967 - 970
(2010/05/02)
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- Copper-catalysed intramolecular O-H addition to unactivated alkenes
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Intramolecular cyclisation of ω-alkenoic acids and alkenols can be achieved using a catalytic amount of Cu(OTf)2 to afford lactones and cyclic ethers, offering a practical alternative to existing catalysts.
- Adrio, Luis A.,Quek, Louisa Shuyi,Taylor, Jason G.,Kuok (Mimi) Hii, King
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experimental part
p. 10334 - 10338
(2010/02/28)
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- Barium manganate in microwave-assisted oxidation reactions: synthesis of lactones by oxidative cyclization of diols
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Microwave irradiation of a range of diols at 150 °C in acetonitrile in the presence of three equivalents of barium manganate facilitates a novel tandem oxidation/heterocyclocondensation to give the corresponding lactone, including both small and medium ring lactones, in only one hour and in high yield without the need for chromatographic purification.
- Bagley, Mark C.,Lin, Zhifan,Phillips, David J.,Graham, Andrew E.
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experimental part
p. 6823 - 6825
(2010/04/27)
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- An interrupted fischer indolization approach toward fused indoline-containing natural products
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An efficient method to access the fused indoline ring system present in a multitude of bioactive molecules has been developed. The strategy involves the condensation of hydrazines with latent aldehydes to ultimately deliver indoline-containing products by way of an interrupted Fischer indolization sequence. Our studies show that the approach will likely be amenable to the synthesis of complex targets, such as the communesin natural products.
- Boal, Ben W.,Schammel, Alex W.,Garg, Neil K.
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supporting information; experimental part
p. 3458 - 3461
(2009/12/07)
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- Synthesis and stereochemistry of the terminal spiroketal domain of the phosphatase inhibitor dinophysistoxin-2
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An expedient synthesis of both axially and equatorially C35 methyl substituted spiroketals representing the C28-C38 domain of the potent and selective protein serine/threonine phosphatase inhibitor dinophysistoxin-2 (DTX-2) was developed to enable comparative stereochemical analyses and a stereochemically correct total synthesis of DTX-2. Comparison of proton and carbon NMR data of the synthetic diastereomers with those published for DTX-2 indicates that DTX-2 possesses the (30S*,34R*,35S*)-relative configuration with an axial C35 methyl substituent.
- Forsyth, Craig J.,Wang, Ce
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p. 3043 - 3046
(2008/12/23)
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- Further explorations on bridged 1,2,4-trioxanes
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Three new bicyclo[3.2.1]-type 1,2,4-trioxanes have been designed and synthesized. One of them demonstrates better tolerance of the intramolecular hemiketals to steric crowding in hydroperoxidation. The other represents a prototype for possible manipulation of the transient radicals generated in cleavage reactions. A new substitution pattern in the bridged system is explored through synthesis of the third molecule. The configurations of all stereogenic centers in the bridged system can be effectively controlled by the chirality of the allyl alcohol as illustrated by the enantioselective synthesis of the fourth molecule. Finally, similar bicyclo[3.3.1]-type 1,2,4-trioxanes are shown very difficult to be synthesized because of the involvement of a conformer with two substituents at axial positions at the same time.
- Zhang, Qi,Wu, Yikang
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p. 10189 - 10201
(2008/02/13)
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- Oppenauer oxidation of secondary alcohols with 1,1,1-trifluoroacetone as hydride acceptor
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(Chemical Equation Presented) 1,1,1-Trifluoroacetone (2a) reacts as a hydride-acceptor in the Oppenauer oxidation of secondary alcohols (1) in the presence of diethylethoxyaluminum. The oxidant allows for selective oxidation of secondary alcohols in the presence of primary alcohols.
- Mello, Rossella,Martinez-Ferrer, Jaime,Asensio, Gregorio,Gonzalez-Nunez, Maria Elena
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p. 9376 - 9378
(2008/03/13)
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- Nanoflow microreactor for dramatic increase not only in reactivity but also in selectivity: Baeyer-Villiger oxidation by aqueous hydrogen peroxide using lowest concentration of a fluorous lanthanide catalyst
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Not only the reaction rate but also the regioselectivity in the scandium bis(perfluorooctanesulfonyl)amide-catalyzed Baeyer-Villiger reaction is remarkably increased by the development of the fluorous nanoflow microreactor system continuously controlled by the nanofeeder DiNaS (Direct Nanoflow System) even in the lowest concentration of the catalyst (?0.1 mol%). The Baeyer-Villiger reaction completes within few seconds as a contact time in the nanoflow microreactor to give the lactone products with high regioselectivity without hydrolysis.
- Mikami, Koichi,Yamanaka, Masahiro,Islam, Md. Nazrul,Tonoi, Takayuki,Itoh, Yoshimitsu,Shinoda, Masaki,Kudo, Kenichi
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p. 592 - 596
(2008/03/27)
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- Isomerisation of ω-hydroxyalkenes under hydroxycarbonylation conditions in palladium catalysed aqueous phase systems
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The ω-hydroxyolefins 3-buten-1-ol, 3-buten-1-methyl-1-ol and 4-penten-1-ol were subjected to hydroxycarbonylation conditions in water in the presence of PdCl2(PhCN)2 and 4-8 equiv. of water soluble tris(3-sodiumsulfonatophenyl)phosphine (TPPTS), or N-bis(N′,N′-diethyl-2-aminoethyl)-4-aminomethylphenyl-diphenylphosphine (N3P). Under conditions of high conversion, the olefins primarily undergo isomerisation through a chain walking mechanism with selectivities for aldehyde ranging from 65% to 98%, with the lower values for longer chain alcohols. The lactones formed as the minor product are almost exclusively branched, indicating that in the first step 2,1-insertion is strongly favoured over 1,2-insertion. In the N3P system also linear lactone is produced at lower conversion. Running the reaction in D2O produces multiple deuterium incorporation in all positions of the carbon chain. A mechanism is discussed.
- Ionescu, Adriana,Ruppel, Markus,Wendt, Ola F.
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p. 3806 - 3815
(2007/10/03)
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- WO3 Nanoparticles on MCM-48 as a Highly Selective and Versatile Heterogeneous Catalyst for the Oxidation of Olefins, Sulfides, and Cyclic Ketones
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It is shown that nanosized WO3 particles supported on MCM-48 work as a highly efficient and selective heterogeneous catalyst for the oxidation of olefins, sulfides, and cyclic ketones using hydrogen peroxide or peracetic acid. The catalytic activity of the supported tungstate was dependent on the nature of the supporting materials and particle size. The catalyst system employs environmentally benign oxidants in halide-free solvents, and it does not require phase-transfer agents and pH control.
- Koo, Dong Hyun,Kim, Min,Chang, Sukbok
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p. 5015 - 5018
(2007/10/03)
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- Nanoflow system for perfect regiocontrol in the Baeyer-Villiger oxidation by aqueous hydrogen peroxide using lowest concentration of a fluorous lanthanide catalyst
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The scandium bis(perfluorooctanesulfonyl)amide-catalyzed Baeyer-Villiger reaction significantly increased the regioselectivity as well as the reaction rate by nanoflow system continuously controlled by a nanofeeder even in the lowest concentration of the catalyst (0.1mol%). The Baeyer-Villiger reaction completed within few seconds as a contact time in the microcell to afford the lactone products high regioselectively without hydrolysis.
- Mikami, Koichi,Islam, Md. Nazrul,Yamanaka, Masahiro,Itoh, Yoshimitsu,Shinoda, Masaki,Kudo, Kenichi
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p. 3681 - 3683
(2007/10/03)
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- A new 2H-azirin-3-amine as a synthon for α-methyl glutamate
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The synthesis of a novel 2,2-disubstituted 2H-azirin-3-amine 10 as a building block for racemic Glu(2Me) is described. This synthon contains an ester group in the side chain. The reaction of 10 with thiobenzoic S-acid and the amino acid Z-Val-OH yielded the racemic monothiodiamide 17 and the dipeptide 18 as a mixture of diastereoisomers, respectively (Scheme 2). From 18, each of the protecting groups was removed selectively (Scheme 3).
- Hilty, Florentine M.,Brun, Kathrin A.,Heimgartner, Heinz
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p. 2539 - 2548
(2007/10/03)
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