- Synthesis and thermodynamics of lead(II), manganese(II), and cobalt(II) pivalate complexes
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Manganese and cobalt oxopivalates and lead pivalate have been synthesized, mass spectral and thermogravimetric analysis have been performed. Sublimation enthalpies of cobalt and manganese oxopivalates have been determined for the first time, while the sub
- Dement’ev,Rodyakina,Kayumova,Kamkin,Yaryshev,Alikhanyan
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Read Online
- Formation of carboxylic acids from small alkanes in zeolite H-ZSM-5
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The activation of propane and isobutane in acidic zeolite H-ZSM-5 in the presence of both CO and H2O has been studied by in situ solid-state NMR and GC analysis. Evidence was provided for the conversion of propane to isobutyric acid at 373-473
- Luzgin, Mikhail V.,Stepanov, Alexander G.,Sassi, Alain,Sommer, Jean
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Read Online
- Hydrolysis of amides to carboxylic acids catalyzed by Nb2O5
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Hydrolysis of amides to carboxylic acids is an industrially important reaction but is challenging due to the difficulty of cleaving the resonance stabilized amidic C-N bond. Twenty-three heterogeneous and homogenous catalysts were examined in the hydrolysis of acetamide. Results showed that Nb2O5was the most effective heterogeneous catalyst with the greatest yield of acetic acid. A series of Nb2O5catalysts calcined at various temperatures were characterized and tested in the hydrolysis of acetamide to determine the effects of crystal phase and surface properties of Nb2O5on catalytic performance. The high catalytic performance observed was attributed mainly to the facile activation of the carbonyl bond by Lewis acid sites that function even in the presence of basic inhibitors (NH3and H2O). The catalytic studies showed the synthetic advantages of the present method, such as simple operation, catalyst recyclability, additive free, solvent free, and wide substrate scope (>40 examples; up to 95% isolated yield).
- Siddiki,Rashed, Md. Nurnobi,Touchy, Abeda Sultana,Jamil, Md. A. R.,Jing, Yuan,Toyao, Takashi,Maeno, Zen,Shimizu, Ken-Ichi
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p. 1949 - 1960
(2021/03/26)
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- (Hexamethylbenzene)Ru catalysts for the Aldehyde-Water Shift reaction
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The Aldehyde-Water Shift (AWS) reaction uses H2O as a benign oxidant to convert aldehydes to carboxylic acids, producing H2, a valuable reagent and fuel, as its sole byproduct. (Hexamethylbenzene)RuIIcomplexes are demonstrated to have higher activity and selectivity (up to 95%) for AWS over disproportionation than previously reported catalysts.
- Phearman, Alexander S.,Moore, Jewelianna M.,Bhagwandin, Dayanni D.,Goldberg, Jonathan M.,Heinekey, D. Michael,Goldberg, Karen I.
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supporting information
p. 1609 - 1615
(2021/03/09)
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- Nucleophilic reactivity of a mononuclear cobalt(iii)-bis(: Tert -butylperoxo) complex
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A mononuclear cobalt(III)-bis(tert-butylperoxo) adduct (CoIII-(OOtBu)2) bearing a tetraazamacrocyclic ligand was synthesized and characterized using various physicochemical methods, such as X-ray, UV-vis, ESI-MS, EPR, and NMR analyses. The crystal structure of the CoIII-(OOtBu)2 complex clearly showed that two OOtBu ligands bound to the equatorial position of the cobalt(iii) center. Kinetic studies and product analyses indicate that the CoIII-(OOtBu)2 intermediate exhibits nucleophilic oxidative reactivity toward external organic substrates.
- Cho, Jaeheung,Jeong, Donghyun,Park, Younwoo,Shin, Bongki
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supporting information
p. 9449 - 9452
(2020/09/07)
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- Toward Orally Absorbed Prodrugs of the Antibiotic Aztreonam. Design of Novel Prodrugs of Sulfate Containing Drugs. Part 2
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Aztreonam, first discovered in 1980, is an FDA approved, intravenous, monocyclic beta-lactam antibiotic. Aztreonam is active against Gram-negative bacteria and is still used today. The oral bioavailability of aztreonam in humans is less than 1%. Herein we describe the design and synthesis of potential oral prodrugs of aztreonam.
- Ding, Pingyu,Duncton, Matthew A. J.,Fan, Dazhong,Gordon, Eric M.,Grygorash, Ruslan,Li, Xianfeng,Low, Eddy,Ni, Zhi-Jie,Qi, Longwu,Sun, Jiawei,Wang, Brian J.,Yu, Guijun
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p. 162 - 165
(2020/01/31)
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- Organocatalyzed Aerobic Oxidation of Aldehydes to Acids
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The first example organocatalyzed aerobic oxidation of aldehydes to carboxylic acids in both organic solvent and water under mild conditions is developed. As low as 5 mol % N-hydroxyphthalimide was used as the organocatalyst, and molecular O2 was used as the sole oxidant. No transition metals or hazardous oxidants or cocatalysts were involved. A wide range of carboxylic acids bearing diverse functional groups were obtained from aldehydes, even from alcohols, in high yields.
- Dai, Peng-Fei,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 1393 - 1396
(2019/02/26)
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- Palladium-catalyzed 2-pyridylmethyl-directed β-C(sp3)–H activation and cyclization of aliphatic amides with gem-dibromoolefins: A rapid access to γ-lactams
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The direct Pd-catalyzed β-C(sp3)–H activation and cyclization of aliphatic amides bearing a removable 2-pyridylmethyl directing group with gem-dibromoolefins is described for the first time to construct a variety of γ-lactams. The resulting products with Z- and E-configurations can be easily separated and purified after the reaction, demonstrating the effectiveness and applicability of the method herein developed.
- Zhou, Danni,Wang, Chunxia,Li, Mingliang,Long, Zheng,Lan, Jingbo
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supporting information
p. 191 - 193
(2017/11/17)
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- An Efficient Aerobic Oxidation Protocol of Aldehydes to Carboxylic Acids in Water Catalyzed by an Inorganic-Ligand-Supported Copper Catalyst
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A method for the aerobic oxidation of aldehydes to carboxylic acids in water by using an inorganic-ligand-supported copper catalyst was developed. This method was performed with the use of atmospheric oxygen as the sole oxidant under extremely mild aqueous conditions, and furthermore, a wide range of aldehydes with various functional groups were tolerated. The copper catalyst could be recycled and used in successive reactions at least six times without any appreciable degradation in performance. This method is operationally simple and avoids the use of high-costing, toxic, air/moisture-sensitive, and commercially unavailable organic ligands. The generality of this method gives it potential to be used on the industrial scale.
- Yu, Han,Ru, Shi,Zhai, Yongyan,Dai, Guoyong,Han, Sheng,Wei, Yongge
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p. 1253 - 1257
(2018/02/16)
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- A aldehyde or mellow directly converted into the carboxylic acid (by machine translation)
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The invention discloses a aldehyde or mellow oxidation can be directly transformed into carboxylic acid, is characterized in that the pure oxygen environment, in N - hydroxy imide compound under the catalysis of the imide compound or N - hydroxy and nitrous acid ester compound common under the catalysis, the CH2 OH and CHO oxidation directly converted into the carboxylic acid compounds. The invention using oxygen as the oxidizing agent, does not add any metal catalyst, environment-friendly, high catalytic efficiency, simple and convenient operation. With the previous metal catalytic system complex and different catalytic system, has some metal catalytic system in the process, the use of transition metal will cause the transition metal of the residual, the invention adopts the non-metallic catalytic system, environmental protection, preventing the metal residue problem, this to the solution of the drug in the synthesis of transition metal residue problem and provides a new method of thinking. (by machine translation)
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Paragraph 0025; 0026
(2018/08/03)
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- ANTIBODY DRUG CONJUGATES (ADCS) AND ANTIBODY PRODRUG CONJUGATES (APDCS) WITH ENZYMATICALLY CLEAVABLE GROUPS
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The present invention relates to novel binder-prodrug conjugates (APDCs) where binders are conjugated with inactive precursor compounds of kinesin spindle protein inhibitors, and to antibody-drug conjugates ADCs and to processes for producing these APDCs and ADCs.
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- Nickel-catalysed direct alkylation of thiophenes via double C(sp3)-H/C(sp2)-H bond cleavage: The importance of KH2PO4
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A Ni-catalyzed oxidative C-H/C-H cross-dehydrogenative coupling (CDC) reaction was developed for constructing various highly functionalized alkyl (aryl)-substituted thiophenes. This method employs thiophenes and aliphatic (aromatic) amides that contain an 8-aminoquinoline as a removable directing group in the presence of a silver oxidant. The approach enables the facile one-step synthesis of substituted thiophenes with high functional group compatibility via double C-H bond cleavage without affecting C-Br and C-I bonds. DFT calculations verify the importance of KH2PO4 as an additive for promoting C-H bond cleavage and support the involvement of a Ni(iii) species in the reaction.
- Wang, Xie,Xie, Peipei,Qiu, Renhua,Zhu, Longzhi,Liu, Ting,Li, You,Iwasaki, Takanori,Au, Chak-Tong,Xu, Xinhua,Xia, Yuanzhi,Yin, Shuang-Feng,Kambe, Nobuaki
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supporting information
p. 8316 - 8319
(2017/07/26)
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- An Efficient Iron(III)-Catalyzed Aerobic Oxidation of Aldehydes in Water for the Green Preparation of Carboxylic Acids
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The first example of a heterogeneous iron(III)-catalyzed aerobic oxidation of aldehydes in water was developed. This method utilizes 1 atmosphere of oxygen as the sole oxidant, proceeds under extremely mild aqueous conditions, and covers a wide range of various functionalized aldehydes. Chromatography is generally not necessary for product purification. Its operational simplicity, gram-scale oxidation, and the ability to successively reuse the catalyst, make this new methodology environmentally benign and cost effective. The generality of this methodology gives it the potential to be used on an industrial scale.
- Yu, Han,Ru, Shi,Dai, Guoyong,Zhai, Yongyan,Lin, Hualin,Han, Sheng,Wei, Yongge
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p. 3867 - 3871
(2017/03/27)
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- Method for catalytically synthesizing organic carboxylic acid by strong-acidic ion exchange resin
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The invention provides a method for catalytically synthesizing organic carboxylic acid by strong-acidic ion exchange resin. The method comprises the following steps: taking olefin and carbon monoxide as raw materials, taking the organic carboxylic acid as a solvent and taking the strong-acidic ion exchange resin as a catalyst; synthesizing the organic carboxylic acid through a Koch reaction; during the reaction, adding the solvent and the catalyst in one step; keeping system pressure being 2MPa to 8MPa by the carbon monoxide; adding the olefin into liquid in a carbon monoxide pressure keeping process by adopting a constant-pressure dripping or spraying manner and adding gas by adopting a bubbling manner; keeping the temperature being at 10 DEG C to 80 DEG C, wherein the charging time is 0.2h to 2.0h; after charging is finished, keeping the material for 1.0h to 5.0h; after the reaction is finished, obtaining a target product, namely the organic carboxylic acid, through a post-treatment procedure including a hydrolysis process. According to the method provided by the invention, industrial green production is realized.
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Paragraph 0011
(2017/07/18)
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- High Catalytic Efficiency Combined with High Selectivity for the Aldehyde-Water Shift Reaction using (para-cymene)Ruthenium Precatalysts
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A family of (para-cymene)RuII complexes are shown to be competent precatalysts for the oxidation of aldehydes to carboxylic acids using water as the oxidant. This reaction, known as the "aldehyde-water shift" (AWS), has been previously demonstrated to be in competition with aldehyde disproportionation. For the few reported mononuclear catalysts for this reaction, either high selectivity for AWS and low conversion or low AWS selectivity and high conversion is observed. A homogeneous precatalyst which is both highly selective for the desired AWS and is highly efficient for conversion of the aldehyde to products is reported herein. In addition, catalyst activity is found to be general to a variety of sterically unencumbered aliphatic aldehydes producing the corresponding carboxylic acid and hydrogen gas.
- Brewster, Timothy P.,Goldberg, Jonathan M.,Tran, Jeremy C.,Heinekey, D. Michael,Goldberg, Karen I.
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p. 6302 - 6305
(2016/09/09)
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- METHOD FOR PRODUCING a-HALO-TETRAACYL-GLUCOSE
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There is provided an efficient and excellent preparation method of an α-halo-tetraacyl-glucose which is suitable for industrial preparation, which comprises reacting D-glucose or lower alkyl D-glucoside with a reactive derivative of a carboxylic acid and a metal halide to prepare the α-halo-tetraacyl-glucose represented by the formula (III): wherein R represents an optionally substituted lower alkyl group or an optionally substituted aryl group, and X represents a halogen atom, in one step, and the resulting α-halo-tetraacyl-glucose (III) can be converted into a compound of the formula (I) or a salt thereof by subjecting to a conventional method.
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- Treatment of o-tert-Butyl phenol micro-polluted water with electro-oxidation and microporous aeration: Method development, performance evaluation and mechanism study
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This study investigated the treatment of organic micro-pollutants in drinking water using a combination of electro-oxidation and microporous aeration (EOMA) technique. Results indicated that microporous aeration enhanced the turbulence of reaction solution and improved the efficiency of organic contaminant removal two-fold versus electro-oxidation alone. o-tert-Butyl phenol (OTBP) was used as a representative pollutant. 1600 mL OTBP solution contained 160 mg sodium sulfate and 2 mL 30 % hydrogen peroxide. When the current density was 5 mA cm-2, 1 and 2 mg L-1 o-tert-butyl phenol was removed up to 98.0 and 75.1 %, respectively. The major intermediate products included trimethylacetic acid, succinic acid and other acid. These have much less toxicity than o-tert-butyl phenol. After 30 min, the organics were mineralized completely. Electro-oxidation and microporous aeration was applied to actual source water that was contaminated by complicated organics. No toxicity was shown to algae growth after 15 min of treatment and total organic carbon was removed completely after 30 min.
- Chen
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p. 450 - 454
(2016/01/20)
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- An efficient and green method for regio- and chemo-selective Friedel-Crafts acylations using a deep eutectic solvent ([CholineCl][ZnCl2]3)
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[CholineCl][ZnCl2]3, a deep eutectic solvent between choline chloride and ZnCl2, has been used as a dual function catalyst and green solvent for the Friedel-Crafts acylation of aromatic compounds instead of using the moisture-sensitive Lewis acids and volatile organic solvents. The reactions are performed with high yields under microwave irradiation with short reaction times for the synthesis of ketones. Interestingly, indole derivatives are regioselectively acylated in the 3-position under mild conditions with high yields without NH protection. Three new ketone products are synthesized. [CholineCl][ZnCl2]3 is easily synthesized from choline chloride and zinc chloride at a low cost, with easy purification and environmentally benign compounds. [CholineCl][ZnCl2]3 can be reused up to five times without loss of catalytic activity, making it ideal in industrial processes.
- Tran, Phuong Hoang,Nguyen, Hai Truong,Hansen, Poul Erik,Le, Thach Ngoc
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p. 37031 - 37038
(2016/05/24)
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- [Ru(bpy)3]Cl2-catalyzed aerobic oxidative cleavage β-diketones to carboxylic acids under visible light irradiation
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A mild and highly efficient method for the preparation of carboxylic acids is developed through a visible-light-mediated aerobic oxidative cleavage of β-diketones. This process provides a potential general, practical and scalable protocol for both laboratory synthesis and industrial production of carboxylic acids in a green manner.
- Wang, Xiao-Yan,Shang, Zhen-Peng,Zha, Gao-Feng,Chen, Xiao-Qing,Bukhari, Syed Nasir Abbas,Qin, Hua-Li
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supporting information
p. 5628 - 5631
(2016/11/23)
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- Method for synthesizing trimethylacetic acid and 2,2,4,4-tetramethylvaleric acid through diisobutylene carbanyl group
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The invention discloses a method for synthesizing trimethylacetic acid and 2,2,4,4-tetramethylvaleric acid through a diisobutylene carbanyl group, and belongs to the technical field of organic carboxylic acid synthesis. An oxo synthesis method is adopted, and the method for synthesizing trimethylacetic acid and 2,2,4,4-tetramethylvaleric acid through the diisobutylene carbanyl group comprises the following steps that 1, a carbonylation reaction is conducted, wherein diisobutylene, carbonic oxide and water serve as the raw materials, a sulfuric acid aqueous solution with the concentration ranging from 65% to 80% serves as a catalyst, pressurization is conducted under the condition of 20 DEG C to 30 DGE C for a reaction, and a mixture of pivalic acid sulfonate and 2,2,4,4-tetramethylvaleric acid sulfonate is obtained; 2, hydrolysis is conducted, wherein the obtained mixture of pivalic acid sulfonate and 2,2,4,4-tetramethylvaleric acid sulfonate in the first step is subjected to hydrolysis at 5 DEG C to 10 DEG C, standing is conducted for layering, an aqueous phase is subjected to extraction and concentration and then recycled, an organic phase is subjected to rectification, and trimethylacetic acid and 2,2,4,4-tetramethylvaleric acid are obtained. According to the method for synthesizing trimethylacetic acid and 2,2,4,4-tetramethylvaleric acid through the diisobutylene carbanyl group, diisobutylene is adopted to replace pure isobutylene in the prior art to react with sulfuric acid and carbonic oxide to produce trimethylacetic acid, and 2,2,4,4-tetramethylvaleric acid is generated simultaneously; the method is convenient and safe, and potential safety hazards are greatly reduced.
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Paragraph 0024-0026
(2017/06/02)
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- Electrocatalytic Alcohol Oxidation with TEMPO and Bicyclic Nitroxyl Derivatives: Driving Force Trumps Steric Effects
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Bicyclic nitroxyl derivatives, such as 2-azaadamantane N-oxyl (AZADO) and 9-azabicyclo[3.3.1]nonane N-oxyl (ABNO), have emerged as highly effective alternatives to TEMPO-based catalysts for selective oxidation reactions (TEMPO = 2,2,6,6-tetramethyl-1-piperidine N-oxyl). Their efficacy is widely attributed to their smaller steric profile; however, electrocatalysis studies described herein show that the catalytic activity of nitroxyls is more strongly affected by the nitroxyl/oxoammonium redox potential than by steric effects. The inexpensive, high-potential TEMPO derivative, 4-acetamido-TEMPO (ACT), exhibits higher electrocatalytic activity than AZADO and ABNO for the oxidation of primary and secondary alcohols. Mechanistic studies provide insights into the origin of these unexpected reactivity trends. The superior activity of ACT is especially noteworthy at high pH, where bicyclic nitroxyls are inhibited by formation of an oxoammonium hydroxide adduct.
- Rafiee, Mohammad,Miles, Kelsey C.,Stahl, Shannon S.
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supporting information
p. 14751 - 14757
(2015/12/08)
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- Thermodynamically leveraged tandem catalysis for ester RC(O)O-R′ bond hydrogenolysis. scope and mechanism
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Rapid and selective formal hydrogenolysis of aliphatic ester RC(O)O-R′ linkages is achieved by a tandem homogeneous metal triflate + supported palladium catalytic system. The triflate catalyzes the mildly exothermic, turnover-limiting O-R′ cleavage process, whereas the exothermic hydrogenation of the intermediate alkene further drives the overall reaction to completion.
- Lohr, Tracy L.,Li, Zhi,Assary, Rajeev S.,Curtiss, Larry A.,Marks, Tobin J.
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p. 3675 - 3679
(2015/06/16)
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- Alcohol cross-coupling for the kinetic resolution of diols via oxidative esterification
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We present an organocatalytic C-O-bond cross-coupling strategy to kinetically resolve racemic diols with aromatic and aliphatic alcohols, yielding enantioenriched esters. This one-pot protocol utilizes an oligopeptide multicatalyst, m-CPBA as the oxidant, and N,N-diisopropylcarbodiimide as the activating agent. Racemic acyclic diols as well as trans-cycloalkane-1,2-diols were kinetically resolved, achieving high selectivities and good yields for the products and recovered diols.
- Hofmann, Christine,Schümann, Jan M.,Schreiner, Peter R.
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p. 1972 - 1978
(2015/02/19)
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- Comparative Analysis of Acyclovir Esters Stability in Solutions: The Influence of the Substituent Structure, Kinetics, and Steric Effects
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Reversed-phase high-performance liquid chromatography has been applied to the determination of acyclovir (ACV) esters such as acetate, isobutyrate, pivalate, ethoxycarbonate, and nicotinate. All analyses were carried out at laboratory temperature using a column LiChrospher RP-18 (250 × 4 mm, 5 μm) and a proper mobile phase consisting of acetonitrile and phosphate buffer (pH 6 or 6.7) or acetonitrile and potassium dihydrogen phosphate, and acetic acid. The methods were validated by the determination of the following parameters: selectivity, precision, accuracy, and linearity. Kinetic studies on the hydrolysis were investigated in solutions at 310 K over the pH range 0.42-1.38. The pH-profiles indicated specific acid-catalyzed and spontaneous water-catalyzed degradation. The stability of the studied ACV esters were determined not only by steric factors. In the case of ethoxycarbonyl ester of ACV, the hydrolysis was a two-step reaction.
- Lesniewska, Monika A.,Gola, Micha?,Dutkiewicz, Zbigniew,Muszalska, Izabela
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p. 724 - 733
(2015/10/06)
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- New acyloxy nitroso compounds with improved water solubility and nitroxyl (HNO) release kinetics and inhibitors of platelet aggregation
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New acyloxy nitroso compounds, 4-nitrosotetrahydro-2H-pyran-4-yl 2,2,2-trichloroacetate and 4-nitrosotetrahydro-2H-pyran-4-yl 2,2-dichloropropanoate were prepared. These compounds release HNO under neutral conditions with half-lives between 50 and 120 min, identifying these HNO donors as kinetically intermediate to the much slower acetate derivative and the faster trifluoroacetic acid derivative. These compounds or HNO-derived from these compounds react with thiols, including glutathione, thiol-containing enzymes and heme-containing proteins in a similar fashion to other acyloxy nitroso compounds. HNO released from these acyloxy nitroso compounds inhibits activated platelet aggregation. These acyloxy nitroso compounds augment the range of release for this group of HNO donors and should be valuable tools in the further study of HNO biology.
- Mohamed, Heba A.H.,Abdel-Aziz, Mohamed,Abuo-Rahma, Gamal El-Din A.A.,King, S. Bruce
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p. 6069 - 6077
(2015/11/10)
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- Reactions of hydroxyl-containing compounds with tert-butyl hydroperoxide in the presence of chromium tetra-tert-butoxide
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Primary and secondary aliphatic, alkylaromatic, cyclic, and organoelement alcohols are efficiently oxidized by tert-butyl hydroperoxide in the presence of both equimolar and catalytic quantities of chromium tetra-tert-butoxide (C6H6, 20°C). α-Diols containing tertiary hydroxyl groups interact with this system via oxidative splitting of the carbon scaffold. The oxidation includes the stages of formation and decomposition of chromium-containing peroxy compounds. Further transformations of the carbonyl compounds depend on the structure of radicals in the molecules.
- Stepovik,Zaburdaeva,Fukin,Karaghiosoff
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p. 2547 - 2559
(2015/12/30)
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- 2-Iodoxybenzenesulfonic acid-catalysed oxidation of primary and secondary alcohols with oxone in cetyl trimethylammonium bromide micelles at room temperature
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A mild and green protocol for alcohol oxidation using 2-iodoxybenzene sulfonic acid/oxone at room temperature in CTAB micelles has been developed. Typically, secondary benzyl alcohols were oxidised to ketones and primary benzyl alcohols to aldehydes in good yields in 2 h. Under harsher conditions (100 °C/24 h), aliphatic alcohols were oxidised to ketones or organic acids in moderate to high yields.
- Liu, Yangyang,Wang, Boliang
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p. 427 - 431
(2014/08/05)
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- Iridium, rhodium, and ruthenium catalysts for the "aldehyde-water shift" reaction
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A series of half-sandwich complexes of iridium, rhodium, and ruthenium are shown to be active catalysts for the conversion of aldehydes and water to carboxylic acids. Depending on the catalyst, H2 is either released (the "aldehyde-water shift") or transferred to a second equivalent of aldehyde (aldehyde disproportionation). Mechanistic studies suggest hydride transfer to be the selectivity-determining step along the reaction pathway. Using [(p-cymene)Ru(bpy)OH2][OTf]2as precatalyst, we demonstrate a novel example of a highly selective aldehyde-water shift in the absence of a hydrogen acceptor or base. (Chemical Equation Presented).
- Brewster, Timothy P.,Ou, William C.,Tran, Jeremy C.,Goldberg, Karen I.,Hanson, Susan K.,Cundari, Thomas R.,Heinekey, D. Michael
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p. 3034 - 3038
(2015/02/19)
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- Nucleofugality of aliphatic carboxylates in mixtures of aprotic solvents and water
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The leaving group ability (nucleofugality) of fluoroacetate, chloroacetate, bromoacetate, dichloroacetate, trifluoroacetate, trichloroacetate, heptafluorobutyrate, formate, isobutyrate, and pivalate have been derived from the solvolysis rate constants of the corresponding X,Y-substituted benzhydryl carboxylates in 60 % and 80 % aqueous acetonitrile and 60 % aqueous acetone, applying the LFER equation: log k = sf(Ef + Nf). The experimental barriers (ΔG?,exp) for solvolyses of 11 reference dianisylmethyl carboxylates in these solvents correlate very well (r = 0.994 in all solvents) with ΔG?,model of the model σ-assisted heterolytic displacement reaction of cis-2,3-dihydroxycyclopropyl trans-carboxylates calculated earlier. Linear correlation observed between the log k for the reference dianisylmethyl carboxylates and the sf values enables estimation of the reaction constant (sfestim). Using the ΔG?,exp vs. ΔG?,model correlation, and taking the estimated sfestim, the nucleofugality parameters for other 34 aliphatic carboxylates have been determined in 60 % and 80 % aqueous acetonitrile and 60 % aqueous acetone. The most important variable that determines the reactivity of aliphatic carboxylates in aprotic solvent/water mixtures is the inductive effect of the group(s) attached onto the carboxylate moiety.
- Mati, Mirela,Denegri, Bernard,Kronja, Olga
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p. 375 - 384
(2015/10/12)
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- Polyethylene glycol effect on the transient and steady state phases of p-nitrophenyltrimethyl acetate hydrolysis catalyzed by α-chymotrypsin
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The effect of polyethylene glycol (PEG) on the hydrolytic activity of ?-chymotrypsin has been studied using p-nitrophenyltrimethyl acetate (PNTMA) as substrate. This substrate requires long times to reach the steady state condition, allowing the measureme
- Calderon, Cristian,Lissi, Eduardo
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p. 2053 - 2056
(2014/03/21)
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- Metal-free, hydroacylation of CC and NN bonds via aerobic C-H activation of aldehydes, and reaction of the products thereof
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In this report, a thorough evaluation of the use of aerobically initiated, metal-free hydroacylation of various CC and NN acceptor molecules with a wide range of aldehydes is presented. The aerobic-activation conditions that have been developed are in sharp contrast to previous conditions for hydroacylation, which tend to use transition metals, peroxides that require thermal or photochemical degradation, or N-heterocyclic carbenes. The mildness of the conditions enables a number of reactions involving sensitive reaction partners and, perhaps most significantly, allows for α-functionalised chiral aldehydes to undergo radical-based hydroacylation with complete retention of optical purity. We also demonstrate how the resulting hydroacylation products can be transformed into other useful intermediates, such as γ-keto- sulfonamides, sultams, sultones, cyclic N-sulfonyl imines and amides.
- Chudasama, Vijay,Akhbar, Ahmed R.,Bahou, Karim A.,Fitzmaurice, Richard J.,Caddick, Stephen
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p. 7301 - 7317
(2013/10/22)
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- Metal-free reductive cleavage of benzylic esters and ethers: Fragmentations result from single and double electron transfers
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The mechanisms for the reductive cleavage of benzylic esters and ethers by neutral organic electron donor 1 are different (see scheme). Products isolated from the cleavage of benzylic ethers result from the transfer of two electrons, without the intermediacy of benzyl radicals, which are believed to be intermediates in the reductive cleavage of benzylic esters. Copyright
- Doni, Eswararao,O'Sullivan, Steven,Murphy, John A.
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p. 2239 - 2242
(2013/03/28)
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- Selective oxoammonium salt oxidations of alcohols to aldehydes and aldehydes to carboxylic acids
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The oxidation of alcohols to aldehydes using stoichiometric 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (1) in CH2Cl2 at room temperature is a highly selective process favoring reaction at the carbinol center best able to accommodate a positive charge. The oxidation of aldehydes to carboxylic acids by 1 in wet acetonitrile is also selective; the rate of the process correlates with the concentration of aldehyde hydrate. A convenient and high yield method for oxidation of alcohols directly to carboxylic acids has been developed.
- Qiu, Joseph C.,Pradhan, Priya P.,Blanck, Nyle B.,Bobbitt, James M.,Bailey, William F.
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supporting information; experimental part
p. 350 - 353
(2012/03/09)
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- The structural basis for the narrow substrate specificity of an acetyl esterase from Thermotoga maritima
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Acetyl esterases from carbohydrate esterase family 7 exhibit unusual substrate specificity. These proteins catalyze the cleavage of disparate acetate esters with high efficiency, but are unreactive to larger acyl groups. The structural basis for this distinct selectivity profile is unknown. Here, we investigate a thermostable acetyl esterase (TM0077) from Thermotoga maritima using evolutionary relationships, structural information, fluorescent kinetic measurements, and site directed mutagenesis. We measured the kinetic and structural determinants for this specificity using a diverse series of small molecule enzyme substrates, including novel fluorogenic esters. These experiments identified two hydrophobic plasticity residues (Pro228, and Ile276) surrounding the nucleophilic serine that impart this specificity of TM0077 for small, straight-chain esters. Substitution of these residues with alanine imparts broader specificity to TM0077 for the hydrolysis of longer and bulkier esters. Our results suggest the specificity of acetyl esterases have been finely tuned by evolution to catalyze the removal of acetate groups from diverse substrates, but can be modified by focused amino acid substitutions to yield enzymes capable of cleaving larger ester functionalities.
- Hedge, Matthew K.,Gehring, Alexandra M.,Adkins, Chinessa T.,Weston, Leigh A.,Lavis, Luke D.,Johnson, R. Jeremy
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experimental part
p. 1024 - 1030
(2012/09/05)
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- Optimization of HNO production from N, O - Bis -acylated hydroxylamine derivatives
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A wide range of N,O-bis-acylated hydroxylamine derivatives with chloro or arenesulfonyl leaving groups, and a related set of N-hydroxy-N-acylsulfonamides, have been synthesized and evaluated for nitroxyl (HNO) production. Mechanistic studies have revealed that the observed aqueous chemistry is more complicated than originally anticipated, and have been used to develop a new series of efficient HNO precursors (4u-4x, 7c-7d) with tunable half-lives.
- Sutton, Art D.,Williamson, Morgan,Weismiller, Hilary,Toscano, John P.
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supporting information; experimental part
p. 472 - 475
(2012/03/26)
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- Biomimetic flavin-catalyzed aldehyde oxidation
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The oxidation of alkyl and aryl aldehydes to their corresponding carboxylic acids has been achieved through the action of a biomimetic bridged flavin catalyst. The reaction uses readily available 35% aqueous hydrogen peroxide and is operationally simple. The oxidation is a green and sustainable reaction, obviating chlorinated solvents with minimal byproducts.
- Murray, Alexander T.,Matton, Pascal,Fairhurst, Nathan W. G.,John, Matthew P.,Carbery, David R.
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supporting information; experimental part
p. 3656 - 3659
(2012/08/28)
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- Biochemical and molecular analysis of carboxylesterase-mediated hydrolysis of cocaine and heroin
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Background and purpose: Carboxylesterases (CEs) metabolize a wide range of xenobiotic substrates including heroin, cocaine, meperidine and the anticancer agent CPT-11. In this study, we have purified to homogeneity human liver and intestinal CEs and compared their ability with hydrolyse heroin, cocaine and CPT-11. Experimental approach: The hydrolysis of heroin and cocaine by recombinant human CEs was evaluated and the kinetic parameters determined. In addition, microsomal samples prepared from these tissues were subjected to chromatographic separation, and substrate hydrolysis and amounts of different CEs were determined. Key results: In contrast to previous reports, cocaine was not hydrolysed by the human liver CE, hCE1 (CES1), either as highly active recombinant protein or as CEs isolated from human liver or intestinal extracts. These results correlated well with computer-assisted molecular modelling studies that suggested that hydrolysis of cocaine by hCE1 (CES1), would be unlikely to occur. However, cocaine, heroin and CPT-11 were all substrates for the intestinal CE, hiCE (CES2), as determined using both the recombinant protein and the tissue fractions. Again, these data were in agreement with the modelling results. Conclusions and implications: These results indicate that the human liver CE is unlikely to play a role in the metabolism of cocaine and that hydrolysis of this substrate by this class of enzymes is via the human intestinal protein hiCE (CES2). In addition, because no enzyme inhibition is observed at high cocaine concentrations, potentially this route of hydrolysis is important in individuals who overdose on this agent.
- Hatfield,Tsurkan,Hyatt,Yu,Edwards,Hicks,Wadkins,Potter
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scheme or table
p. 1916 - 1928
(2011/04/25)
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- The Ever-surprising chemistry of boron: Enhanced acidity of phosphine·boranes
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The gas-phase acidity of a series of phosphines and their corresponding phosphine·borane derivatives was measured by FT-ICR techniques. BH 3 attachment leads to a substantial increase of the intrinsic acidity of the system (from 80 to 110 kJ mol-1). This acidity-enhancing effect of BH3 is enormous, between 13 and 18 orders of magnitude in terms of ionization constants. This indicates that the enhancement of the acidity of protic acids by Lewis acids usually observed in solution also occurs in the gas phase. High- level DFT calculations reveal that this acidity enhancement is essentially due to stronger stabilization of the anion with respect to the neutral species on BH3 association, due to a stronger electron donor ability of P in the anion and better dispersion of the negative charge in the system when the BH3 group is present. Our study also shows that deprotonation of ClCH2PH2 and ClCH 2PH2·BH3 is followed by chloride departure. For the latter compound deprotonation at the BH3 group is found to be more favorable than PH2 deprotonation, and the subsequent loss of Cl- is kinetically favored with respect to loss of Cl - in a typical SN2 process. Hence, ClCH2PH 2·BH3 is the only phosphine·borane adduct included in this study which behaves as a boron acid rather than as a phosphorus acid.
- Hurtado, Marcela,Yanez, Manuel,Herrero, Rebeca,Guerrero, Andres,Juan Z. Davalos,Jose-Luis, M. Abboud,Khater, Brahim,Guillemin, Jean-Claude
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supporting information; experimental part
p. 4622 - 4629
(2009/12/29)
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- Highly reactive and chemoselective cleavage of allyl esters using an air- and moisture-stable [CpRu(IV)(π-C3H5)(2-quinolinecarboxylato)]PF6 catalyst
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A new catalytic process for allyl ester cleavage has been developed by using a robust cationic CpRu(IV) π-allyl complex of 2-quinolinecarboxylic acid that can be stored for over six months in air without any loss of catalytic activity. The deprotection of various alcohols and acids can be attained simply with high reactivity and chemoselectivity under mild conditions. Furthermore, with continuous removal of the low-boiling point coproduct, a turnover number of 1 000 000 can be achieved.
- Tanaka, Shinji,Saburi, Hajime,Murase, Takanori,Ishibashi, Yoshitaka,Kitamura, Masato
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p. 295 - 298
(2008/02/03)
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- A simple method for the alkaline hydrolysis of esters
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A very mild and rapid procedure for the efficient alkaline hydrolysis of esters in non-aqueous conditions has been developed, by the use of dichloromethane/methanol (9:1) as solvent. This method conveniently provides both carboxylic acids and alcohols from the corresponding esters and sodium hydroxide in a few minutes at room temperature. A plausible reaction mechanism is proposed.
- Theodorou, Vassiliki,Skobridis, Konstantinos,Tzakos, Andreas G.,Ragoussis, Valentine
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p. 8230 - 8233
(2008/03/14)
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- Structure activity studies with xenobiotic substrates using carboxylesterases isolated from Arabidopsis thaliana
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Carboxylesterases (CXEs) catalyse the hydrolysis of xenobiotics and natural products radically altering their biological activities. Whereas the substrate selectivity of animal CXEs, such as porcine liver esterase (PLE) have been well studied, the respective enzymes in plants have yet to be defined and their activities determined. Using Arabidopsis thaliana (At) as a source, five representative members of the α/β hydrolase AtCXE family of proteins have been cloned, expressed and the purified recombinant proteins assayed for esterase activity with xenobiotic substrates. Two members, AtCXE5 and AtCXE18 were found to be active carboxylesterases, though AtCXE5 proved to be highly unstable as a soluble protein. AtCXE18 and the previously characterised S-formylglutathione hydrolase from Arabidopsis (AtSFGH) were assayed against a series of esters based on methylumbelliferone in which the acyl moiety was varied with respect to size and conformation. The same series was used to assay crude esterase preparation from Arabidopsis plants and the results compared with those obtained with the commonly used PLE. With straight chain esters, AtCXE18 behaved like PLE, but the Arabidopsis hydrolases proved less tolerant of branched chain acyl components than the mammalian enzyme. While none of the enzyme preparations accurately reflected all the activities determined with crude Arabidopsis protein extracts, the plant enzymes proved more useful than PLE in predicting the hydrolysis of the more sterically constrained esters.
- Cummins, Ian,Landrum, Marie,Steel, Patrick G.,Edwards, Robert
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p. 811 - 818
(2008/03/13)
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- An efficient and practical system for the catalytic oxidation of alcohols, aldehydes, and α,β-unsaturated carboxylic acids
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(Chemical Equation Presented) Upon exposure to commercial bleach (~5% aqueous sodium hypochlorite), nickel(II) chloride or nickel(II) acetate is transformed quantitatively into an insoluble nickel species, nickel oxide hydroxide. This material consists of high surface area nanoparticles (ca. 4 nm) and is a useful heterogeneous catalyst for the oxidation of many organic compounds. The oxidation of primary alcohols to carboxylic acids, secondary alcohols to ketones, aldehydes to carboxylic acids, and α,β- unsaturated carboxylic acids to epoxy acids is demonstrated using 2.5 mol % of nickel catalyst and commercial bleach as the terminal oxidant. We demonstrate the controlled and selective oxidation of several organic substrates using this system affording 70-95% isolated yields and 90-100% purity. In most cases, the oxidations can be performed without an organic solvent, making this approach attractive as a "greener" alternative to conventional oxidations.
- Grill, Joseph M.,Ogle, James W.,Miller, Stephen A.
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p. 9291 - 9296
(2007/10/03)
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- Method for producing carboxylic acid
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An aldehyde-containing oily solution and an aqueous hydrogen peroxide solution are reacted in the presence of a catalyst comprising a polymer compound having a sulfonic acid group in a side chain thereof in a heterogeneous solution system. According to such a reaction process, carboxylic acid can be efficiently produced under mild conditions having very little influence and toxicity on the environment and a human body, with simple operations, without requiring the operation for removing a solvent after the completion of the reaction.
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Page/Page column 4
(2008/06/13)
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- Kinetics and quantitative structure-activity relationships for pseudomonas sp. Lipase-catalyzed hydrolysis of both monoesters and diesters of ethylene glycol
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The goal of this work is to study kinetics and quantitative structure-activity relationships for steady states of Pseudomonas sp. lipase-catalyzed hydrolysis of both diesters and monoesters of ethylene glycol. Based on the steady-state kinetics of the enzyme-catalyzed hydrolysis of the diesters of ethylene glycol, the diesters and the monoesters react simultaneously as soon as monoester has started to build up in the reaction medium. In other words, the apparent Km values of the diesters are the Km values of the diesters (KmA) plus the Km values of the monoesters (KmB), and all Vmax values are about the same. Moreover, the pH-stat titration curve of the enzyme-catalyzed hydrolysis of the diesters of ethylene glycol is initially hyperbolic, then there is a sharp falloff in the hydrolysis rate. The abrupt stoppage of the reaction (relaxation stage) may be due to the existence of two phases in the reaction medium, that is, the product (ethylene glycol) and the substrates (the diesters of ethylene glycol) are not miscible. Furthermore, quantitative structure-activity relationships for varied acyl groups of mono- and diesters of ethylene glycol are studied. The fact that both pKmA and pK mB values are linearly correlated with the hydrophobicity constant (π) but not with the electronic substituent constants (σ*) indicates that the affinity of these substrates for the enzyme depends only on the hydrophobicitv of substrates. Copyright
- Chiou, Shyh-Ying,Cheng, Yu-Ru,Lu, Chun-Ping,Lin, Yan-Fu,Lin, Long-Yau,Lin, Gialih
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p. 201 - 207
(2007/10/03)
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- Mild conversion of β-diketones and β-ketoesters to carboxylic acids
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A mild protocol for the conversion of β-ketoesters and β-diketones to carboxylic acids with use of CAN in CH3CN is described. The method is compatible with a number of functional groups, and can generate carboxylic acids under neutral conditions at room temperature. The reaction is fast and general, providing an alternative method to the commonly used malonic ester acid preparation. Initial mechanistic studies show that initial oxidation of the enol form of the β-dicarbonyl initiates the reaction. The presence of nitrate as an oxidant ligand or as an additive is critical for success of the reaction.
- Zhang, Yang,Jiao, Jingliang,Flowers II, Robert A.
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p. 4516 - 4520
(2007/10/03)
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- Steric effects in the uncatalyzed and DMAP-catalyzed acylation of alcohols - Quantifying the window of opportunity in kinetic resolution experiments
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The kinetics of the reaction of several alcohols (benzyl alcohol, ethanol, 1-phenylethanol, cyclohexanol, and 1-methyl-1-phenylethanol) with a selection of anhydrides (acetic anyhydride, propionic anhydride, isobutyric anhydride, isovaleric anhydride, and pivalic anhydride) as catalyzed by 4-(N,N-dimethylamino)pyridine (DMAP)/triethyl amine have been studied in CH 2Cl2 at 20°C. In all cases the reaction kinetics can be described by rate laws containing a DMAP-catalyzed term and an uncatalyzed (back-ground) term. The rate constants for the background reaction respond sensi tively to changes in the steric demand of the alcohol and the anhydride substrates, making the reaction of cyclohexanol with acetic anhydride 526 times faster than the reaction with pivalic anhydride. Steric effects are even larger for the catalyzed reaction and the reactivity difference between acetic and pivalic anhydride exceeds a factor of 8000 for the reaction of cyclohexa nol. There is, however, no linear correlation between the steric effects on the catalyzed and the uncatalyzed part. As a consequence there are substrate combinations with dominating catalytic terms (such as the reaction of benzyl alcohol with isobutyric anhydride), while other substrate combinations (such as the reaction of cyclohexanol with pivalic anhydride) are characterized through a dominating background process. The implications of these findings for the kinetic resolution of alcohols are discussed.
- Fischer, Christian B.,Xu, Shangjie,Zipse, Hendrik
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p. 5779 - 5784
(2008/03/14)
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- A versatile method for the hydrogen peroxide oxidation of alcohols using PTC condition in tert-butanol
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An efficient protocol for the oxidation of secondary and primary alcohols to the corresponding ketones and aldehydes and/or carboxylic acids using hydrogen peroxide as oxidant is described. A quasi-homogenous reaction system was obtained by t-butanol as solvent to achieve high yield of the product in short time.
- Chhikara, Bhupender S.,Chandra, Ramesh,Tandon, Vibha
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p. 872 - 874
(2007/10/03)
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- An efficient method for the synthesis of aliphatic acids using microwaves
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Aliphatic acids are prepared by reaction of nitriles with phtalic acid by irradiation under microwaves in a domestic oven.
- Brǎtulescu, George
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p. 161 - 163
(2007/10/03)
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- Enzymatic removal of carboxyl protecting groups. 2. Cleavage of the benzyl and methyl moieties
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Enzymes are versatile reagents for the efficient removal of methyl and benzyl protecting groups. An esterase from Bacillus subtilis (BS2) and a lipase from Candida antarctica (CAL-A) allow a mild and selective removal of these moieties in high yields without affecting other functional groups.
- Barbayianni, Efrosini,Fotakopoulou, Irene,Schmidt, Marlen,Constantinou-Kokotou, Violetta,Bornscheuer, Uwe T.,Kokotos, George
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p. 8730 - 8733
(2007/10/03)
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- A series of crystal structures of a meta-cleavage product hydrolase from Pseudomonas fluorescens IP01 (CumD) complexed with various cleavage products
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Meta-cleavage product hydrolase (MCP-hydrolase) is one of the key enzymes in the microbial degradation of aromatic compounds. MCP-hydrolase produces 2-hydroxypenta-2,4-dienoate and various organic acids, according to the C6 substituent of the substrate. Comprehensive analysis of the substrate specificity of the MCP-hydrolase from Pseudomonas fluorescens IP01 (CumD) was carried out by determining the kinetic parameters for nine substrates and crystal structures complexed with eight cleavage products. CumD preferred substrates with long non-branched C6 substituents, but did not effectively hydrolyze a substrate with a phenyl group. Superimposition of the complex structures indicated that benzoate was bound in a significantly different direction than other aliphatic cleavage products. The directions of the bound organic acids appeared to be related with the kcat values of the corresponding substrates. The Ile139 and Trp143 residues on helix α4 appeared to cause steric hindrance with the aromatic ring of the substrate, which hampers base-catalyzed attack by water.
- Fushinobu, Shinya,Jun, So-Young,Hidaka, Masafumi,Nojiri, Hideaki,Yamane, Hisakazu,Shoun, Hirofumi,Omori, Toshio,Wakagi, Takayoshi
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p. 491 - 498
(2008/02/01)
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- SYNTHESIS OF 3,5-DIHYDROXY-7-PYRROL-1-YL HEPTANOIC ACIDS
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Atorvastatin and related 3,5-dihydroxy-7-pyrrol-1-yl heptanoic acids can be made by oxidation of a 3,5-dihydroxy-7-pyrrol-1-yl heptanol precursor from novel but readily accessible starting materials. Silylether-protected 7-amino-3,5-dihydroxy heptanoic acid esters undergo Paal Knorr reaction with 1,4-diketones to give valuable silylether-diprotected 3,5-dihydroxy-7-pyrrol-1-yl heptanoic acid ester intermediates for preparing atorvastatin. The Paal Knorr reaction of ketal-proctected 7-amino-3R, 5R-dihydroxy heptanoic acid esters with 4-fluoro-α-(2-methyl-1-oxopropyl-γ-oxo-N,β-diphenylbenzenebutanamide occurs in high yield with few side products when it is conducted in a low boiling point ether.
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