- Effect of particle restructuring during reduction processes over polydopamine-supported Pd nanoparticles
-
The effect of catalyst restructuring on the polydopamine-supported Pd catalyzed transfer hydrogenation of ethyl 4-nitrobenzoate and the catalytic hydrogenation of (E)-2-methyl-2-butenoic acid is reported. Transmission electron microscopy investigation of different catalyst pre-treatment and reaction conditions revealed high catalytic activity in both reactions unless drastic aggregation of the active metal occurred. In the transfer hydrogenation reaction aggregation was primarily dependent on the H-source used, while in the catalytic hydrogenation additives in combination with the reductive environment led to extensive Pd aggregation and thus decreased catalytic activity. The enantioselective hydrogenation of (E)-2-methyl-2-butenoic acid showed increased enantioselectivity and decreased conversion with increased particle size.
- Gazdag, Tamás,Baróthi, ádám,Juhász, Koppány Levente,Kunfi, Attila,Németh, Péter,Sápi, András,Kukovecz, ákos,Kónya, Zoltán,Szori, Kornél,London, Gábor
-
-
Read Online
- Kinetics and mechanism of oxidation of isoleucine by n-bromophthalimide in aqueous perchloric acid medium
-
The kinetics of oxidation of isoleucine with N-bromophthalimide has been studied in perchloric acid medium potentiometrically. The reaction is of first order each in [NBP] and [amino acid] and negative fractional order in [H +]. The rate is decreased by the addition of phthalimide. A decrease in the dielectric constant of the medium increases the rate. Addition of halide ions or acrylonitrile has no effect on the kinetics. Similarly, variation of ionic strength of the medium does not affect the reaction rate. The reaction rate has been determined at different temperatures and activation parameters have been calculated. A suitable mechanism involving hypobromous acid as reactive species has been proposed. Copyright E-Journal of Chemistry 2004-2011.
- Alhaji,Mary, S. Sofiya Lawrence
-
-
Read Online
- Synthesis and reactions of allenic amides. Allenes-XXXI
-
Allenic amides are prepared from allenic nitriles using alkaline hydrogen peroxide and by a Ritter reaction with t-butyl alcohol, when N-t-butylamides are obtained. Strong nucleophiles attack the central carbon of the allene system to give α,β-unsaturated addition products.
- Greaves,Landor,Landor,Odyek
-
-
Read Online
- Synthesis and characterization of chiral phosphirane derivatives of [(μ-H)4Ru4(CO)12] and their application in the hydrogenation of an α,β-unsaturated carboxylic acid
-
Ruthenium clusters containing the chiral binaphthyl-derived mono-phosphiranes [(S)-([1,1′-binaphthalen]-2-yl)phosphirane] (S)-1a, [(R)-(2′-methoxy-1,1′-binaphthyl-2-yl)phosphirane] (R)-1b, and the diphosphirane [2,2′-di(phosphiran-1-yl)-1,1′-binaphthalene] (S)-1c have been synthesized and characterized. The clusters are [(μ-H)4Ru4(CO)11((S)-1a)] (S)-2, [(μ-H)4Ru4(CO)11((R)-1b)] (R)-3, 1,1-[(μ-H)4Ru4(CO)10((S)-1c)] (S)-4, [(μ-H)4Ru4(CO)11((S)-binaphthyl-P(s)(H)Et)] (S,Sp)-5, [(μ-H)4Ru4(CO)11((S)-binaphthyl-P(R)(H)Et)] (S,Rp)-6, [(μ-H)4Ru4(CO)11((R)-binaphthyl-P(s)(H)Et)] (R,Sp)-7, [(μ-H)4Ru4(CO)11((R)-binaphthyl-P(R)(H)Et)] (R,Rp)-8 and the phosphinidene-capped triruthenium cluster [(μ-H)2Ru3(CO)9(PEt)] 9. Clusters 5–8 are formed via hydrogenation and opening of the phosphirane ring in clusters (S)-2 and (R)-3. The phosphirane-substituted clusters were found to be able to catalyze the hydrogenation of trans-2-methyl-2-butenoic acid (tiglic acid), but no enantioselectivity could be detected. The molecular structures of (S)-4, (R,Sp)-7 and 9 have been determined and are presented.
- Abdel-Magied, Ahmed F.,Majeed, Maitham H.,Abelairas-Edesa, Manuel F.,Ficks, Arne,Ashour, Radwa M.,Rahaman, Ahibur,Clegg, William,Haukka, Matti,Higham, Lee J.,Nordlander, Ebbe
-
-
Read Online
- Expedient method for oxidation of alcohol by hydrogen peroxide in the presence of amberlite IRA 400 resin (basic) as phase-transfer catalyst
-
Amberlite IRA 400 (strongly basic), a classical polymer imparts phase-transfer catalysis in the oxidation of primary and secondary alcohols by hydrogen peroxide to give excellent yields of the corresponding carbonyl compounds or carboxylic acids in acetonitrile solvent at reflux temperature in 4-6 h. The catalytic system is inert to other susceptible oxidation sites such as carbon-carbon double bonds. Copyright Taylor & Francis Group, LLC.
- Bhati, Nishi,Sarma, Kuladip,Goswami, Amrit
-
-
Read Online
- Diterpenoid alkaloids from the lateral root of Aconitum carmichaelii
-
Twenty-six new diterpenoid alkaloids, 1-26 (1-4: hetisan-type C 20-diterpenoid alkaloids; 5-26: aconitane C19-diterpenoid alkaloids), and two known analogues, hypaconitine 27 and benzoylmesaconine 28, have been isolated from a water extract of the lateral root of Aconitum carmichaelii. Compounds 7 and 8 are rare examples of conformational isomers obtained from the same material. The conformation and conformational transformation of ring A in the C19- diterpenoid alkaloids are discussed on the basis of NMR data analysis in combination with single-crystal X-ray crystallography of 6 and 27 by anomalous scattering of Cu K7α radiation. In preliminary analgesic and toxicity assays, the isomer with ring A in the chair conformation (8 or 27) was found to be more active than that with ring A in the boat conformation (7 or 27a). In addition, 15, 16, and 19 showed neuroprotective activity.
- Jiang, Bingya,Lin, Sheng,Zhu, Chenggen,Wang, Sujuan,Wang, Yanan,Chen, Minghua,Zhang, Jianjun,Hu, Jinfeng,Chen, Naihong,Yang, Yongchun,Shi, Jiangong
-
-
Read Online
- Reaction of Carbocations Derived from Alkanes with Carbon Monoxide in HF-SbF5 Superacid
-
Alkanes readily react with CO and H2O in HF-SbF5 at 30 deg C under atmospheric pressure and give considerably different product distributions from those in the usual Koch-Haaf reaction.When using C5- or C6-alkanes with tertiary C-H bonds, a considerable amount of secondary carboxylic acids are produced by the reaction of CO with secondary alkyl cations.Such cations may appear as transient intermediates in the course of the carbon skeletal isomerization of initially formed tertiary cations.For the straightchain alkanes, the protonolysis at C-C bonds initiated the reaction to give fragment alkyl cations.This resulted in the formation of carboxylic acids with a lower number of carbon atoms than the starting alkanes.Intermolecular hydride shift between the fragment cations and the starting alkanes occured at the same time to form a large amount of carboxylic acids with the alkyl group of the same number of carbon atoms as the starting alkane.On the other hand, for alkanes with more than seven carbon atoms, β-scission occurs exclusively to produce C4-, C5-, and C6-carboxylic acids.
- Yoneda, Norihiko,Takahashi, Yukio,Fukuhara, Tsuyoshi,Suzuki, Akira
-
-
Read Online
- Synthesis and pyrolysis of two novel pyrrole ester flavor precursors
-
In order to develop the high-temperature-released pyrrole aroma, two novel flavors precursors of methyl 2-methyl-5-(((2-methylbutanoyl)oxy)methyl)-1-propyl-1H-pyrrole-3-carboxylate and methyl 2-methyl-5-(((2-methylbutanoyl)oxy)methyl)-1-propyl-1H-pyrrole-3-carboxylate were synthesized using glucosamine hydrochloride and methyl acetoacetate as raw materials through cyclization, oxidation, alkylation, reduction, and esterification. The target compounds were characterized by nuclear magnetic resonance (1H NMR, 13C NMR), infrared spectroscopy (IR) and high-resolution mass spectrometry (HRMS). Thermogravimetry (TG), differential scanning calorimeter (DSC) and the pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) methods were used to analyze the heating-stability of the target compounds, and the pyrolysis mechanism was inferred. Py-GC/MS results indicated that some fragrance compounds were formed during?thermal degradation such as 2-methylbutyric acid, 2-methylbutyrate, alkylpyrroles, and benzoic acid, which were important aroma components or flavor additives. This provided a theoretical reference for the application of pyrrole ester in cigarette and heat-processed food flavoring.
- Cheng, Biao,Chu, Wenjuan,Fan, Wenpeng,Feng, Yingjie,Gao, Ziting,Ji, Xiaoming,Lai, Miao,Tian, Haiying,Zhang, Zhan
-
-
- Nucleophilic reactivity of a mononuclear cobalt(iii)-bis(: Tert -butylperoxo) complex
-
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
-
supporting information
p. 9449 - 9452
(2020/09/07)
-
- Oxidation of aromatic and aliphatic aldehydes to carboxylic acids by Geotrichum candidum aldehyde dehydrogenase
-
Oxidation reaction is one of the most important and indispensable organic reactions, so that green and sustainable catalysts for oxidation are necessary to be developed. Herein, biocatalytic oxidation of aldehydes was investigated, resulted in the synthesis of both aromatic and aliphatic carboxylic acids using a Geotrichum candidum aldehyde dehydrogenase (GcALDH). Moreover, selective oxidation of dialdehydes to aldehydic acids by GcALDH was also successful.
- Hoshino, Tomoyasu,Yamabe, Emi,Hawari, Muhammad Arisyi,Tamura, Mayumi,Kanamaru, Shuji,Yoshida, Keisuke,Koesoema, Afifa Ayu,Matsuda, Tomoko
-
-
- 1,3,2-Diazaphospholenes Catalyze the Conjugate Reduction of Substituted Acrylic Acids
-
The potent nucleophilicity and remarkably low basicity of 1,3,2-diazaphospholenes (DAPs) is exploited in a catalytic, metal-free 1,4-reduction of free α,β-unsaturated carboxylic acids. Notably, the reduction occurs without a prior deprotonation of the carboxylic acid moiety and hence does not consume an additional hydride equivalent. This highlights the excellent nucleophilic character and low basicity of DAP-hydrides. Functional groups such as Cbz group or alkyl halides which can be problematic with classical transition-metal catalysts are well tolerated in the DAP-catalyzed process. Moreover, the transformation is characterized by a low catalyst loading, mild reaction conditions at ambient temperature as well as fast reaction times and high yields. The proof-of-principle for a catalytic enantioselective version is described.
- Reed, John H.,Cramer, Nicolai
-
p. 4262 - 4266
(2020/07/13)
-
- Visible-Light Promoted Selective Imination of Unactivated C-H Bonds via Copper-nitrene Intermediates for the Synthesis of 2 H-Azirines
-
A novel strategy to trap iminyl radicals with copper ions has been developed at room temperature, the resulted high-valent Cu(III) imine intermediate resets quickly to form nitrene and then to furnish a 2H-azirine. This protocol with dual copper/photoredox catalyst enables the selective imination of unactivated C-H bonds under mild conditions with a broader scope. Moreover, this method also uncovers a novel ring-expansion rearrangement from cyclobutyl oxime derivatives to give the α-acylamino cyclopentanones.
- Feng, Liyan,Yang, Chao,Xia, Wujiong
-
supporting information
p. 8323 - 8327
(2019/10/16)
-
- Organocatalyzed Aerobic Oxidation of Aldehydes to Acids
-
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
-
supporting information
p. 1393 - 1396
(2019/02/26)
-
- Hydrogen/deuterium isotopic labeling study of enantioselective hydrogenation of (E)-2-Methyl-2-butenoic acid over a cinchonidine-modified Pd/C catalyst
-
In the enantioselecitve hydrogenation of (E)-2-methyl-2butenoic acid (1) over a cinchonidine-modified Pd/C catalyst, the addition of hydrogen preferentially proceeds from the Re-Si enantioface of the C=C double bond of 1 to yield (S)-2methylbutanoic acid ((S)-3). Double bond migration of 1 takes place under the reaction conditions and is followed by immediate hydrogenation to yield 3 in a poor enantiomeric purity. Deuterium labeling experiments at 0.1 MPa and 1.9 MPa of D2verified the previous assumption of competitive double bond migration. The combination of isotopic labeling experiments and chiral analysis revealed that the double bond migration of 1 proceeds with the same enantiofacial differentiation as the hydrogenation of 1. Thus, interaction of 1 with cinchonidine adsorbed on the Pd surface may control the configuration of the double bond migration and the hydrogenation.
- Sugimura, Takashi,Tomatsuri, Satoshi,Fujita, Morifumi,Okamoto, Yasuaki
-
p. 1737 - 1742
(2019/10/01)
-
- A aldehyde or mellow directly converted into the carboxylic acid (by machine translation)
-
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)
- -
-
Paragraph 0029; 0030
(2018/08/03)
-
- Preparation method of low carbon fatty acid
-
The invention discloses a preparation method of low carbon fatty acid and belongs to the field of organic synthesis technology. The preparation method comprises the following technological steps: weighing low carbon fatty alcohol, water and urea, stirring and mixing, dropwise adding hydrogen peroxide and carrying out an oxidation reaction, wherein concentration of hydrogen peroxide is 5-30%; reaction temperature is 0-50 DEG C; reaction time is 5-20 h; and molar ratio of urea to hydrogen peroxide to low carbon fatty alcohol is 0.1-1: 2-5: 1. The method for preparing low carbon fatty acid has advantages of simple operation, less environmental pollution, no corrosion to reaction equipment, high efficiency and low processing cost, and can be widely applied in the field of low carbon fatty acid preparation.
- -
-
Paragraph 0021; 0022
(2017/04/20)
-
- Substrate selectivity of an isolated enoyl reductase catalytic domain from an iterative highly reducing fungal polyketide synthase reveals key components of programming
-
A cis-acting enoyl reductase (ER) catalytic domain was isolated from a fungal highly reducing iterative polyketide synthase (HR-iPKS) for the first time and studied in vitro. The ER from the squalestatin tetraketide synthase forms a discrete dimeric protein in solution. The ER shows broad substrate selectivity, reducing enoyl species including both natural and unnatural substrates. Pantetheine-bound substrate thiolesters reacted much faster than the corresponding SNAC thiolesters. The unnatural substrates included Z-olefins, 2-ethyl olefins and pentaketides. Methylation of the substrate modifies the activity of the ER such that the 2,4-dimethyl oct-2-enoyl substrate fits into the active site but cannot be reduced. A new NMR-based assay was developed for the direct observation of the stereochemical preferences at the 4′ position of the NADPH cofactor and the C-2 and C-3 positions of the substrates. The assay reveals that the fungal iPKS ER-catalysed reaction is stereochemically identical to that of the vertebrate FAS (vFAS) at the cofactor 4′ position and the substrate 3-position, but the high stereoselectivity displayed by intact SQTKS is lost such that reprotonation at the 2-position is unselective by the isolated ER. A 3D model of ER was consistent with these observations and showed that the ER may sequester its final substrate to prevent further chain extension. The results support a developing model for programming by HR-iPKS in which competition for substrates between restrictive and permissive catalytic domains chaperones the growing polyketide to completion, while allowing for errors and evolution.
- Roberts, Douglas M.,Bartel, Christoph,Scott, Alan,Ivison, David,Simpson, Thomas J.,Cox, Russell J.
-
p. 1116 - 1126
(2017/02/10)
-
- A 2 - methyl butyric acid preparation method
-
A preparation method of 2-methylbutyric acid. The invention belongs to the field of industry of fine chemicals. The present invention provides a preparation method of 2-methylbutyric acid. Ethyl acrylic aldehyde as the raw material is subjected to catalytic hydrogenation reduction at atmospheric pressure, and then oxidized to obtain 2-methylbutyric acid with the content of no less than 99.5%.
- -
-
Paragraph 0015-0018
(2017/09/01)
-
- 2-methyl butyric acid catalytic preparation method
-
The invention discloses a 2-methyl butyric acid catalytic preparation method. The method includes steps: step S1, well stirring 2-ethyl acrylaldehyde and acetone solvent, adding into a reaction kettle, adding a solid catalyst being 10-20% of the weight of 2-ethyl acrylaldehyde, feeding hydrogen to 0.1-0.2MPa after nitrogen displacement, and allowing reaction for 4-8h at 40-60 DEG C; step S2, dropwise adding hydrogen peroxide solution being 24-28% in mass fraction to the solution obtained at the step S1 at the temperature of 30-50 DEG C, and performing thermal reaction for 3-5h at the temperature of 30-50 DEG C; step S3, filtering reaction liquid obtained at the step S2 to remove the solid catalyst, and rectifying filtrate to obtain a target product 2-methyl butyric acid. The 2-methyl butyric acid catalytic preparation method is simple in step and high in raw material conversion rate; the adopted solid catalyst is recyclable, and evident reduction of catalytic efficiency of the solid catalyst is avoided after repeated recycling of the solid catalyst.
- -
-
Paragraph 0021-0024; 0029-0032; 0037-0040; 0045-0048
(2017/08/27)
-
- Preparation method of carboxylic acid compound
-
The invention provides a preparation method of a carboxylic acid compound. The preparation method comprises the following step of taking a lactone component to react with hydrogen in the presence of a compound catalyst to obtain the carboxylic acid compound. The compound catalyst comprises a hydrogenation catalyst and Lewis acid. In the presence of the compound catalyst comprising the hydrogenation catalyst and the Lewis acid, the lactone component is subjected to hydrogenation ring-opening reaction to obtain the carboxylic acid compound. The preparation method has the advantages of moderate reaction conditions and high yield; compared with a traditional method, less byproducts are generated, green and chemical requirements are met and the industrial value is better.
- -
-
Paragraph 0113; 0186-0188
(2017/08/29)
-
- A Comprehensive Study on Metal Triflate-Promoted Hydrogenolysis of Lactones to Carboxylic Acids: From Synthetic and Mechanistic Perspectives
-
Direct hydrogenolysis of lactone to carboxylic acid (i.e., hydrogenolysis of the Calkoxy-O bond with the carbonyl group untouched) is generally difficult, as the current strategies employing Br?nsted acids as the catalyst usually require harsh conditions such as a high temperature and a high H2 pressure. Herein, we report a developed solvent-free catalytic transformation, in which W(OTf)6 is believed to promote the hydrogenolysis process. This strategy could efficiently hydrogenate lactones to carboxylic acids under extra mild conditions (e.g., a reaction temperature of 2) and showed a broad substrate scope. In addition, the catalytic protocol can be further applied to the hydrogenolysis of polyhydroxyalkanoate, as a renewable polymer, to the corresponding straight-chain carboxylic acids. An extensive mechanistic study was subsequently performed, and the density functional theory calculations revealed a reaction pattern, including the complete cleavage of the C=O bond with the assistance of the W(OTf)6 catalyst. Moreover, the key intermediate created in the mechanism, as an oxonium with an OTf moiety, was successfully detected by electrospray ionization mass spectra. Through a comparison with the Br?nsted acid-catalyzed system, the study confirmed that the existence of the OTf moiety can significantly lower the barriers associated with the rearrangement and elimination processes. Meanwhile, emphasis was placed on the critical role that the anion plays, as well as the fact that the anion effect is directly related to the chemoselectivity.
- Zhu, Rui,Jiang, Ju-Long,Li, Xing-Long,Deng, Jin,Fu, Yao
-
p. 7520 - 7528
(2017/11/10)
-
- Synthesis of Enantiomerically Enriched 2-Hydroxymethylalkanoic Acids by Oxidative Desymmetrisation of Achiral 1,3-Diols Mediated by Acetobacter aceti
-
The stereoselective desymmetrisation of achiral 2-alkyl-1,3-diols is performed by oxidation of one of the two enantiotopic primary alcohol moieties by means of Acetobacter aceti MIM 2000/28 to afford the corresponding chiral 2-hydroxymethyl alkanoic acids (up to 94 % ee). The procedure, carried out in aqueous medium under mild conditions of pH, temperature and pressure, contributes to enlarge the portfolio of enzymatic oxidations available to organic chemists for the development of sustainable manufacturing processes.
- Brenna, Elisabetta,Cannavale, Flavia,Crotti, Michele,De Vitis, Valerio,Gatti, Francesco G.,Migliazza, Gaia,Molinari, Francesco,Parmeggiani, Fabio,Romano, Diego,Santangelo, Sara
-
p. 3796 - 3803
(2016/12/24)
-
- Dehydrogenative Synthesis of Carboxylic Acids from Primary Alcohols and Hydroxide Catalyzed by a Ruthenium N-Heterocyclic Carbene Complex
-
Primary alcohols have been reacted with hydroxide and the ruthenium complex [RuCl2(IiPr)(p-cymene)] to afford carboxylic acids and dihydrogen. The dehydrogenative reaction is performed in toluene, which allows for a simple isolation of the products by precipitation and extraction. The transformation can be applied to a range of benzylic and saturated aliphatic alcohols containing halide and (thio)ether substituents, while olefins and ester groups are not compatible with the reaction conditions. Benzylic alcohols undergo faster conversion than other substrates, and a competing Cannizzaro reaction is most likely involved in this case. The kinetic isotope effect was determined to be 0.67 using 1-butanol as the substrate. A plausible catalytic cycle was characterized by DFT/B3LYP-D3 and involved coordination of the alcohol to the metal, β-hydride elimination, hydroxide attack on the coordinated aldehyde, and a second β-hydride elimination to furnish the carboxylate.
- Santilli, Carola,Makarov, Ilya S.,Fristrup, Peter,Madsen, Robert
-
p. 9931 - 9938
(2016/11/02)
-
- Marinopyrones A-D, α-pyrones from marine-derived actinomycetes of the family Nocardiopsaceae
-
Two actinomycetes, a member of the rare halophilic genus Streptomonospora and a Nocardiopsis sp. (Nocardiopsaceae), strains CNQ-082 and CNQ-675, respectively, were isolated from marine sediments collected off shore near La Jolla, California. HPLC-UV guided fractionations of the extracts of these strains yielded marinopyrones A-D (1-4), the structures of which were elucidated by interpretation of 1D and 2D NMR and HRMS spectroscopic data. Oxidative ozonation, followed by conversion of the acid product to an α-naphthyl amide, provided the absolute configuration at the chiral center on the side-chain. Marinopyrones A-D were examined for the inhibitory activity on nitric oxide production in LPS-activated mouse macrophage cells (RAW 264.7); marinopyrone D (4) was inhibitory with an IC50 value of 13 μM. To our knowledge, marinopyrones A-C are only the second reported natural products from the rare halophilic genus Streptomonospora.
- Lee, Jihye,Han, Chulkyeong,Lee, Tae Gu,Chin, Jungwook,Choi, Hyukjae,Lee, Wonjae,Paik, Man Jeong,Won, Dong Hwan,Jeong, Gyusang,Ko, Jaeyoung,Yoon, Yeo Joon,Nam, Sang-Jip,Fenical, William,Kang, Heonjoong
-
p. 1997 - 2000
(2016/04/20)
-
- Structurally well-characterized new multinuclear Cu(II) and Zn(II) clusters: X-ray crystallography, theoretical studies, and applications in catalysis
-
Two new trinuclear Cu(ii) and dinuclear Zn(ii) clusters are crystallized out by reacting the metal salts with the triethanolamine (H3tea) ligand in the presence of benzoic acid (Hba). The complexes are characterized by elemental, thermal, magnetic, spectral (FTIR, UV-Visible, EPR, and photoluminescence) and single crystal X-ray studies. Single crystal X-ray crystallography reveals the composition of the complexes to be [Cu3(H2tea)2(ba)2(NO3)2] (1) and [Zn2(H2tea)(ba)3]H2O (2). FTIR ascertains the binding modes of H2tea-, ba- and NO3-. Triethanolamine binds in both the complexes in the monoanionic (H2tea-) mode. ba- is present as an anchoring auxiliary to generate di- and trinuclear clusters. The Cu(ii) ion is present as a distorted octahedral center in the Cu3 cluster (1), while the two Zn(ii) ions in 2 have been reported for the first time to possess distorted octahedral as well as tetrahedral geometry in the same molecule. The intriguing features of the non-covalent supramolecular interactions have been investigated and supported theoretically by using Hirshfeld surface analysis and ab initio methods. The solid state photoluminescence (PL) spectra of 1 and 2 disclose the luminescence property of the complexes. Due to the closed or nearly closed shell configuration (d9 or d10), the present complexes are screened for catalytic properties in the hydrocarboxylation of alkanes and cycloalkanes. The catalytic activity data are indicative of the potential catalytic properties of 1 and 2.
- Ansari, Istikhar A.,Sama, Farasha,Raizada, Mukul,Shahid,Ahmad, Musheer,Siddiqi, Zafar A.
-
supporting information
p. 9840 - 9852
(2016/11/11)
-
- Unactivated C(sp3)-H hydroxylation through palladium catalysis with H2O as the oxygen source
-
A novel palladium catalyzed hydroxylation of unactivated aliphatic C(sp3)-H bonds was successfully developed. Different from conventional methods, water serves as the hydroxyl group source in the reaction. This new reaction demonstrates good reactivity and broad functional group tolerance. The C-H hydroxylated products can be readily transformed into various highly valuable chemicals via known transformations. Based on experimental and theoretical studies, a mechanism involving the Pd(ii)/(iv) pathway is proposed for this hydroxylation reaction.
- Hu, Jiantao,Lan, Tianlong,Sun, Yihua,Chen, Hui,Yao, Jiannian,Rao, Yu
-
supporting information
p. 14929 - 14932
(2015/10/06)
-
- A study of the reaction of n-BuLi with Ti(Oi-Pr)4 as a method to generate titanacyclopropane and titanacyclopropene species
-
The use of the combination of reagents Ti(Oi-Pr)4/n-BuLi, introduced by the group of J.J. Eisch in 2001, has only found a few applications so far, with sometimes conflicting observations. This article describes a study aimed at clarifying the nature, the stability and the reactivity of the active organometallic species involved. Reactions with CO2 and other trapping reagents reveal that it is generated within a few minutes at 0 C in THF, where it can be considered to be stable for 30 min. Most of our results are consistent with the expected titanacyclopropane nature of this reagent but some observations suggest that the chemistry at play may be more complicated.
- Rassadin, Valentin A.,Six, Yvan
-
supporting information
p. 787 - 794
(2014/01/23)
-
- Asymmetric hydrogenation using rhodium complexes generated from mixtures of monodentate neutral and anionic phosphorus ligands
-
A series of monodentate neutral and anionic phosphorus ligands was synthesized and evaluated in the asymmetric rhodium-catalyzed hydrogenation of functionalized olefins by using either catalysts containing identical ligands or catalysts generated from mixtures of two different ligands. We expected that the combination of an anionic ligand with a neutral ligand would favor the formation of hetero over homo bis-ligand complexes due to charge repulsion. NMR spectroscopic studies confirmed that charge effects can indeed shift the equilibrium toward the hetero bis-ligand complexes. In several cases, the combination of a neutral phosphane with an anionic phosphane, one chiral and the other achiral, furnished significantly higher enantioselectivities than analogous mixtures of two neutral ligands. The best results were obtained with a mixture of an anionic phosphoramidite and a neutral phosphoric acid diester. It is supposed that in this case a hydrogen bond between the two ligands additionally stabilizes the hetero ligand combination. Charge effects and hydrogen bonding favor the formation of rhodium hetero bis-ligand complexes from mixtures of neutral and anionic monodentate phosphorus ligands. The combination of a neutral phosphoric acid diester as a hydrogen donor and an anionic phosphoramidite as a hydrogen acceptor gives very high enantioselectivities in Rh-catalyzed hydrogenation reactions, thus exceeding the ee values of the corresponding homo bis-ligand complexes (see scheme). Copyright
- Frank, Dominik J.,Franzke, Axel,Pfaltz, Andreas
-
supporting information
p. 2405 - 2415
(2013/03/28)
-
- Mild oxidative alkane functionalization with peroxides in the presence of ferrocene
-
Ferrocene in an unexpected emploi: alkanes can be efficiently oxygenated by H2O2 in the presence of catalytic amounts of this well-known organometallic compound in combination with pyrazine-2-carboxylic acid or 2,2′-bipyridine. Saturated hydrocarbons, RH, are also transformed into carboxylic acids, RCOOH, when reacted with the ferrocene/CO/S 2O82 -/H2O system in acetonitrile solution.
- Shul'pin, Georgiy B.,Kirillova, Marina V.,Shul'pina, Lidia S.,Pombeiro, Armando J.L.,Karslyan, Eduard E.,Kozlov, Yuriy N.
-
-
- Production of C5 carboxylic acids in engineered Escherichia coli
-
Valeric acid and 2-methylbutyric acid serve as chemical intermediates for a variety of applications such as plasticizers, lubricants and pharmaceuticals. The commercial process for their production uses toxic intermediates like synthesis gas and relies on non-renewable petroleum-based feedstock. In this work, synthetic metabolic pathways were constructed in Escherichia coli for the renewable production of these chemicals directly from glucose. The native leucine and isoleucine biosynthetic pathways in E. coli were expanded for the synthesis of valeric acid and 2-methylbutyric acid (2MB) respectively by the introduction of aldehyde dehydrogenases and 2-ketoacid decarboxylases. Various aldehyde dehydrogenases and 2-ketoacid decarboxylases were investigated for their activities in the constructed pathways. Highest titers of 2.59 g/L for 2-mthylbutyric acid and 2.58 g/L for valeric acid were achieved in shake flask experiments through optimal combinations of these enzymes. This work demonstrates the feasibility of renewable production of these high volume aliphatic carboxylic acids.
- Dhande, Yogesh K.,Xiong, Mingyong,Zhang, Kechun
-
p. 1965 - 1971
(2013/02/25)
-
- Efficient cluster-based catalysts for asymmetric hydrogenation of α-unsaturated carboxylic acids
-
The new clusters [H4Ru4(CO)10(μ-1,2-P- P)], [H4Ru4(CO)10(1,1-P-P)] and [H 4Ru4(CO)11(P-P)] (P-P=chiral diphosphine of the ferrocene-based Josiphos or Walphos ligand families) have been synthesised and characterised. The crystal and molecular structures of eleven clusters reveal that the coordination modes of the diphosphine in the [H4Ru 4(CO)10(μ-1,2-P-P)] clusters are different for the Josiphos and the Walphos ligands. The Josiphos ligands bridge a metal-metal bond of the ruthenium tetrahedron in the "conventional" manner, that is, with both phosphine moieties coordinated in equatorial positions relative to a triangular face of the tetrahedron, whereas the phosphine moieties of the Walphos ligands coordinate in one axial and one equatorial position. The differences in the ligand size and the coordination mode between the two types of ligands appear to be reflected in a relative propensity for isomerisation; in solution, the [H4Ru4(CO)10(1,1-Walphos)] clusters isomerise to the corresponding [H4Ru4(CO) 10(μ-1,2-Walphos)] clusters, whereas the Josiphos-containing clusters show no tendency to isomerisation in solution. The clusters have been tested as catalysts for asymmetric hydrogenation of four prochiral α-unsaturated carboxylic acids and the prochiral methyl ester (E)-methyl 2-methylbut-2-enoate. High conversion rates (>94 %) and selectivities of product formation were observed for almost all catalysts/catalyst precursors. The observed enantioselectivities were low or nonexistent for the Josiphos-containing clusters and catalyst (cluster) recovery was low, suggesting that cluster fragmentation takes place. On the other hand, excellent conversion rates (99-100 %), product selectivities (99-100 % in most cases) and good enantioselectivities, reaching 90 % enantiomeric excess (ee) in certain cases, were observed for the Walphos-containing clusters, and the clusters could be recovered in good yield after completed catalysis. Results from high-pressure NMR and IR studies, catalyst poisoning tests and comparison of catalytic properties of two [H4Ru4(CO)10(μ-1,2-P-P)] clusters (P-P=Walphos ligands) with the analogous mononuclear catalysts [Ru(P-P)(carboxylato)2] suggest that these clusters may be the active catalytic species, or direct precursors of an active catalytic cluster species. Copyright
- Moberg, Viktor,Duquesne, Robin,Roehrs, Oliver,Nachtigall, Jonny,Nordlander, Ebbe,Contaldi, Simone,Monari, Magda,Damoense, Llewellyn,Green, Michael,Hutton, Alan T.,Santelia, Daniela,Haukka, Matti
-
p. 12458 - 12478,21
(2020/08/24)
-
- Diterpenoid alkaloids from the lateral root of Aconitum carmichaelii
-
Twenty-six new diterpenoid alkaloids, 1-26 (1-4: hetisan-type C 20-diterpenoid alkaloids; 5-26: aconitane C19-diterpenoid alkaloids), and two known analogues, hypaconitine 27 and benzoylmesaconine 28, have been isolated from a water extract of the lateral root of Aconitum carmichaelii. Compounds 7 and 8 are rare examples of conformational isomers obtained from the same material. The conformation and conformational transformation of ring A in the C19- diterpenoid alkaloids are discussed on the basis of NMR data analysis in combination with single-crystal X-ray crystallography of 6 and 27 by anomalous scattering of Cu K7α radiation. In preliminary analgesic and toxicity assays, the isomer with ring A in the chair conformation (8 or 27) was found to be more active than that with ring A in the boat conformation (7 or 27a). In addition, 15, 16, and 19 showed neuroprotective activity.
- Jiang, Bingya,Lin, Sheng,Zhu, Chenggen,Wang, Sujuan,Wang, Yanan,Chen, Minghua,Zhang, Jianjun,Hu, Jinfeng,Chen, Naihong,Yang, Yongchun,Shi, Jiangong
-
p. 1145 - 1159
(2013/01/14)
-
- Resin glycosides from the aerial parts of Operculina turpethum
-
Three glycosidic acids, turpethic acids A-C, and two intact resin glycosides, turpethosides A and B, all having a common pentasaccharide moiety and 12-hydroxy fatty acid aglycones of different chain lengths, were obtained from the aerial parts of Operculina turpethum. Their structures were elucidated by spectroscopic analyses and chemical correlations. The aglycones were characterized as 12-hydroxypentadecanoic acid in two compounds, 12-hydroxyhexadecanoic acid in two other components, and 12-hydroxyheptadecanoic acid in the fifth compound, which were all confirmed by synthesis. The absolute configurations of these aglycones were all established as S by Mosher's method. These compounds represent the first examples of resin glycosides with a monohydroxylated 12-hydroxy fatty acid as an aglycone, and one compound is the first described resin glycoside having a hydroxylated C17 fatty acid as its aglycone.
- Ding, Wenbing,Jiang, Zi-Hua,Wu, Ping,Xu, Liangxiong,Wei, Xiaoyi
-
experimental part
p. 165 - 174
(2012/10/08)
-
- TPAP-catalyzed direct oxidation of primary alcohols to carboxylic acids through stabilized aldehyde hydrates
-
We present a simple, mild, and highly effective method for the direct conversion of primary alcohols to carboxylic acids. TPAP serves as the catalyst, and NMO?H2O plays a dual role, acting as the co-oxidant and as a reagent for aldehyde hydrate stabilization. This previously unknown stabilizing effect of geminal diols by N-oxides is the key for the efficiency of the overall transformation.
- Schmidt, Andrea-Katharina C.,Stark, Christian B. W.
-
supporting information; experimental part
p. 4164 - 4167
(2011/10/08)
-
- SULFANYLAMIDE DERIVATIVES, USES THEREOF AND COMPOSITIONS COMPRISING THEM
-
The present invention concerns a family of sulfanilamide derivatives of formula (I) as anticonvulsant agents, where R1 is selected from optionally substituted C4-C9 alkyl, optionally substituted C6-C10 aryl, optionally substituted C6-C10 alkylenearyl and optionally substituted C5-C10 heteroaryl; R2 is selected from -H and optionally substituted C1-C6 alkyl; each of R3 and R4, independently of each other, is selected from -H, optionally substituted C1-C6 alkyl, optionally substituted C6-C10 aryl and optionally substituted C5-C10 heteroaryl; n is 0, 1, 2, 3 or 4. The derivatives have been prepared and their anticonvulsant profile was evaluated for the control of epileptic seizures.
- -
-
Page/Page column 26-27
(2011/04/19)
-
- New diamondoid-like [Cu3B(μ-O)6] core self-assembled from Bis-Tris biobuffer for mild hydrocarboxylation of alkanes to carboxylic acids
-
The new tricopper(ii) complex [Cu3(μ3-BO)(H 3L)3][BF4]·2H2O (1) with an unprecedented diamondoid-like [Cu3B(μ-O)6] core has been easily generated by self-assembly in an aqueous medium from Cu(NO 3)2, NaBF4, NaOH and Bis-Tris (H5L) biobuffer, (HOCH2)3CN(CH2CH2OH) 2. Compound 1 efficiently promotes the mild single-pot hydrocarboxylation, by CO and H2O, of various linear and cyclic Cn (n = 2-8) alkanes into the corresponding Cn+1 carboxylic acids.
- Kirillov, Alexander M.,Karabach, Yauhen Y.,Kirillova, Marina V.,Haukka, Matti,Pombeiro, Armando J. L.
-
supporting information; experimental part
p. 6378 - 6381
(2011/08/06)
-
- CONVERSION OF NITRILE COMPOUNDS INTO CORRESPONDING CARBOXYLIC ACIDS AND ESTERS
-
Hydrocarbon compounds having at least one nitrile function are converted into compounds having at least one carboxylic function by hydrating the nitrile functions into amide functions by reaction with water in the presence of a strong inorganic acid, and then hydrolyzing the amide functions into carboxylic functions by reaction with water and a strong inorganic acid; the carboxylic compounds thus obtained can be esterified into diesters, advantageously diester solvents.
- -
-
Page/Page column 3
(2010/06/19)
-
- IONIC LIQUID SOLVENTS
-
A chiral ionic compound comprising an alkyl substituted imidazolium or pyridinium cationic core having an alkyl ester side chain (-alkyl-C(O)O-) directly linked to the core and an associated counter anion, characterized in that the -O- atom of the ester side chain is linked to an alpha, a beta or a gamma hydroxycarboxylic acid functionality via the alpha, beta or gamma hydroxy of the acid functionality and the hydroxycarboxylic acid functionality has at least one asymmetric carbon, or characterized in that an -N= atom of the alkyl substituted imidazolium or pyridinium cationic core is substituted with an alpha, a beta or a gamma hydroxy group of a alpha, a beta or a gamma hydroxycarboxylic acid functionality and the hydroxycarboxylic acid functionality has at least one asymmetric carbon. The chiral ionic liquids (CILs) may be used as novel solvents, in particular for organic synthesis. The CILs have the potential to induce asymmetry into substrates or catalysts in a variety of organic transformations. A number of the compounds have low antimicrobial and low antifungal toxicities and are also biodegradable CILs.
- -
-
Page/Page column 58-59
(2010/09/17)
-
- Syntheses and evaluation of anticonvulsant profile and teratogenicity of novel amide derivatives of branched aliphatic carboxylic acids with 4-aminobenzensulfonamide
-
Despite the availability of 14 new antiepileptic drugs (AEDs), about 30% of epileptic patients are not seizure-free. Consequently there is substantial need to develop new effective AEDs. A novel class of aromatic amides composed of phenylacetic acid or branched aliphatic carboxylic acids, with five to nine carbons in their carboxylic moiety, and aminobenzenesulfonamide were synthesized and evaluated in the anticonvulsant rat-maximal electroshock (MES) and subcutaneous metrazol seizure (scMet) tests. Fourteen of the synthesized amides had an anticonvulsant ED50 of 50 values of 7.6, 9.9, and 9.4 mg/kg and remarkable protective index (PI = TD 50/ED50) values of 65.7, 50.5, and 53.2, respectively. These potent sulfanylamides caused neural tube defects only at doses markedly exceeding their effective dose. The anticonvulsant properties of these compounds make them potential candidates for further development as new, potent, and safe AEDs.
- Hen, Naama,Bialer, Meir,Wlodarczyk, Bogdan,Finnell, Richard H.,Yagen, Boris
-
experimental part
p. 4177 - 4186
(2010/09/04)
-
- Mild, single-pot hydrocarboxylation of gaseous alkanes to carboxylic acids in metal-free and copper-promoted aqueous systems
-
A direct, selective and highly efficient method has been developed for the hydrocarboxylation of Cn gaseous alkanes into Cn+1 carboxylic acids, in aqueous acid-solvent-free medium at low temperatures. The approach is based on a metal-free or copper-promoted reaction of ethane, propane or n-butane with carbon monoxide and water, in a H2O/MeCN medium at 50-60 °C, in the presence of potassium peroxodisulfate. The effects of various reaction parameters, such as the absence or presence of a copper promoter, solvent composition, temperature, time, CO and alkane pressure, were studied. A free radical mechanism was confirmed by radical trap experiments involving acyl radical formation, oxidation and subsequent hydroxylation by water. Remarkable yields (based on alkane) of carboxylic acids in the 34- 41% range were achieved even in the metal-free systems, although in the presence of a tetracopper(II) triethanolaminate derived promoter they reach superior values of 58 and 87% for the hydrocarboxylations of propane and nbutane, respectively; in these cases, branched isobutyric and 2-methylbutyric acids were the predominant products. From a green perspective, important features of the present alkane hydrocarboxylations include the exceptional metal-free, mild and acid-solvent- free reaction conditions, the operation in aqueous medium with a rare hydroxylating role of water, with high selectivities, and yields of carboxylic acids. Taken together, these conditions correspond to the mildest and the most efficient method so far reported for the oxidative functionalisation of gaseous alkanes.
- Kirillova, Marina V.,Kirillov, Alexander M.,Pombeiro, Armando J.L.
-
experimental part
p. 9485 - 9493
(2010/11/04)
-
- Glycolipid ester-type heterodimers from Ipomoea tyrianthina and their pharmacological activity
-
Tyrianthins A (1) and B (2), two new partially acylated glycolipid ester-type heterodimers were isolated from Ipomoea tyrianthina. Scammonic acid A was determined as the glycosidic acid in both monomeric units. Tyrianthin A (1) (IC50 0.24 ± 0.0
- Leon-Rivera, Ismael,Miron-Lopez, Gumersindo,Estrada-Soto, Samuel,Aguirre-Crespo, Francisco,Gutierrez, Maria del Carmen,Molina-Salinas, Gloria Maria,Hurtado, Gerardo,Navarrete-Vazquez, Gabriel,Montiel, Elizur
-
experimental part
p. 4652 - 4656
(2010/04/28)
-
- PROCESS FOR ALKALINE HYDROLYSIS OF CARBOXYLIC ACID DERIVATIVES TO CARBOXYLIC ACIDS
-
The invention relates to a process for alkaline hydrolysis of carboxylic acid derivatives, especially carboxylic esters, to carboxylic acids, wherein, for the alkaline hydrolysis of the carboxylic acid derivatives, red mud which is produced by the Bayer process used for aluminum production is used as a reaction-promoting component, especially as a hydroxide ion source.
- -
-
Page/Page column 4; 5
(2009/10/31)
-
- Alkanes to carboxylic acids in aqueous medium: Metal-free and metal-promoted highly efficient and mild conversions
-
A convenient and clean route to transform, in aqueous medium, various alkanes to carboxylic acids via single-pot carboxylation with CO and water, under mild conditions, has been achieved, proceeding efficiently and selectively even without any metal catalyst and any acid additive, at low temperatures; the relevant hydroxylating role of H2O and radical mechanisms are disclosed by radical-trap, H218O and DFT studies. The Royal Society of Chemistry 2009.
- Kirillova, Marina V.,Kirillov, Alexander M.,Kuznetsov, Maxim L.,Silva, Jose A. L.,Frausto Da Silva, Joao J. R.,Pombeiro, Armando J. L.
-
supporting information; experimental part
p. 2353 - 2355
(2009/09/06)
-
- METHOD FOR THE CONVERSION, UNDER MILD CONDITIONS AND IN AQUEOUS MEDIUM, OF GASEOUS AND LIQUID ALKANES INTO CARBOXYLIC ACIDS
-
The present invention concerns a new efficient method for the selective transformation, under mild conditions and in aqueous medium, of gaseous (ethane, propane and n-butane) and liquid (n-pentane, n-hexane, cyclopentane and cyclohexane) alkanes into carboxylic acids bearing one more carbon atom, characterized by a single-pot low- temperature (25-60 °C) reaction of the alkane with carbon monoxide in water/acetonitrile liquid medium, either in the absence or in the presence of a metal catalyst, in systems containing also an oxidant (a peroxodisulphate salt).
- -
-
Page/Page column 7-10
(2008/12/07)
-
- Vanadium(I) chloride and lithium vanadium(I) dihydride as selective epimetallating reagents for π- and σ-bonded organic substrates
-
Subvalent vanadium(I) salts, of empirical formulas, VCl, vanadium(I) chloride and LiVH2, lithium vanadium(I) dihydride, whose efficient preparation, structural constitution and mode of reaction toward certain organic substrates have been described in a preceding article, are here evaluated in their reactions toward a wide variety of π- and σ-bonded organic substrates, namely carbonyl, imine, azo, alkene, 1,3-diene, nitrile π-bonds and C-X, C-O, C-N and N-N σ-bonds. Compared with the high reactivity of CrCl and LiCrH2 reagents in attacking both types of bonds, the VCl and LiVH2 reagents were much milder and selective in epimetallating π-bonds, often forming the 1:1 adduct of LiVH2 and π-bonded substrate as the major product. Finally, the vanadium reagents showed little tendency to cleave C-O, C-S and C-N bonds and a smaller scope in cleaving C-X bonds than their chromium counterparts. Because of their selectivity these vanadium reagents offer the following preparative promise: 1) smooth McMurry carbonyl coupling to their reductive dimers; 2) deoxygenation of epoxides; 3) selective aromatic C-X reduction; 4) high yields of epimetallated carbonyls or imines as intermediates to α-hydroxy and α-amino acids; 5) 1,4-reductions of 1,3-alkadienes; 6) reductive dimerization of nitriles to ketones; 7) 1,4 or 1,n-epimetallations leading to acyloins or indoles; and 8) reductive dimerizations of azines to produce unusual imidazole derivatives. In explaining the greater kinetic stability of the 1:1 LiVH2 adduct with carbonyl or imine substrates it is pointed out that such epimetallated adducts from LiVH2 would likely be diamagnetic, whereas such adducts from LiCrH2 have an unpaired electron on the Cr center and hence would rupture, so that the electron would be on the C center. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Eisch, John J.,Fregene, Paul O.
-
scheme or table
p. 4482 - 4492
(2009/05/07)
-
- Perhydrolase
-
The present invention provides methods and compositions comprising at least one perhydrolase enzyme for cleaning and other applications. In some particularly preferred embodiments, the present invention provides methods and compositions for generation of peracids. The present invention finds particular use in applications involving cleaning, bleaching and disinfecting.
- -
-
Page/Page column 51-53
(2008/12/06)
-
- Inverted supercritical carbon dioxide/aqueous biphasic media for rhodium-catalyzed hydrogenation reactions
-
An inverted supercritical carbon dioxide (scCO2)/aqueous biphasic system has been used as reaction media for Rh-catalysed hydrogenation of polar substrates. Chiral and achiral CO2-philic catalysts were efficiently immobilised in scCO2 as the stationary phase, while the polar substrates and products were contained in water as the mobile phase. Notably, product separation and catalyst recycling were conducted without depressurisation of the autoclave, The catalyst phase was reused several times with high conversion and product recovery of more than 85%. Loss of rhodium and phosphorus by leaching were found to be below the detection limit after the first two cycles in the majority of repetitive experiments. The reaction conditions were optimised with a minimum of experiments by using a simplex algorithm in a sequential optimisation. Total turnover numbers (TTNs) of up to 1600, turnover frequencies (TOFs) of up to 340 h-1 and ee's up to 99% were obtained in repetitive batch operations. The scope of the devised catalytic system has been investigated and a semicontinuous reaction setup has been implemented. The chiral ligand (R,S)-3-H2F6-BINAPHOS allowed highly enantioselective hydrogenation of itaconic acid and methyl-2-acetamidoacrylate combined with a considerable catalyst stability in these reaction media.
- Burgemeister, Katja,Francio, Giancarlo,Gego, Volker H.,Greiner, Lasse,Hugl, Herbert,Leitner, Walter
-
p. 2798 - 2804
(2008/02/04)
-
- Enantiomeric products formed via different mechanisms: asymmetric hydrogenation of an α,β-unsaturated carboxylic acid involving a Ru(CH3COO)2[(R)-binap] catalyst
-
Hydrogenation of (Z)-3-phenyl-2-butenoic acid with a Ru(CH3COO)2[(R)-binap] (BINAP=2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) catalyst in methanol gives (S)-3-phenyl-2-butanoic acid and its R enantiomer in a 97:3 (4 atm) to 94:6 (100 atm) ratio in quantitative yield. Both hydrogen gas and protic methanol participate in the saturation of the olefinic bond. Analysis of the products obtained using (Z)-3-phenyl-2-butenoic acid-3-13C and either H2, a 1:1 H2-D2 mixture, or D2 in CH3OD indicates that several catalytic cycles are operative, showing different reactivity and stereoselectivity. The major S enantiomer was formed primarily by the standard Ru monohydride mechanism, whereas the minor R isomer is produced via more complicated routes.
- Yoshimura, Masahiro,Ishibashi, Yoshitaka,Miyata, Kengo,Bessho, Yuhki,Tsukamoto, Masaki,Kitamura, Masato
-
p. 11399 - 11409
(2008/03/13)
-
- Process for the preparation of aliphatic linear and ?-alkyl-branched carboxylic acids
-
Preparation of aliphatic straight chain or beta -alkyl branched 5-13C alkyl carboxylic acid (I) comprises oxidizing an aldehyde with oxygen or oxygen-containing gas mixtures at 20-100[deg]C in the presence of an alkali and/or alkaline earth metal carboxylate, where the quantity of alkali or alkaline earth metal is calculated as 1-10 mmol/mol of used aldehyde, and group 5-11 metal (compound). Preparation of aliphatic straight chain or beta -alkyl branched 5-13C alkyl carboxylic acid (I) comprises oxidation of an aldehyde with oxygen or oxygen-containing gas mixtures at 20-100[deg]C in the presence of an alkali and/or alkaline earth metal carboxylate, where the quantity of alkali or alkaline earth metal is 1-10 mmol/mol of aldehyde and in the present of 0.1-5 ppm of a metal of the groups 5-11 of the periodic table of the elements or the corresponding quantity of a compound such as metal or its mixtures and/or metallic components, based on used aldehyde.
- -
-
Page/Page column 8-9; 11
(2008/06/13)
-
- On the behaviour of Ru(I) and Ru(II) carbonyl acetates in the presence of H2 and/or acetic acid and their role in the catalytic hydrogenation of acetic acid
-
The reactivity of phosphine substituted ruthenium carbonyl carboxylates Ru(CO)2(MeCOO)2(PBu3)2, Ru 2(CO)4(μ-MeCOO)2(PBu3) 2, Ru4(CO)8(μ-MeCOO)4(PBu 3)2 with H2 and/or acetic acid was investigated by IR and NMR spectroscopy to clarify their role in the catalytic hydrogenation of acetic acid. Evidences were collected to suggest hydride ruthenium complexes as the catalytically active species. Equilibria among ruthenium hydrides and carboxylato complexes take place in the presence of hydrogen and acetic acid, that is in the conditions of the catalytic reaction. Nevertheless the presence of acetic acid reduces the rate of the formation of hydrides. Working at a very high temperature (180°C) polynuclear phosphido hydrides such as [Ru 6(μ-H)6(CO)10(μ-PHBu)(μ-PBu 2)2(PBu3)2(μ6-P)] were formed. These phosphido clusters are suggested as the resting state of the catalytic system. Furthermore the bi- or tetranuclear Ru(I) carboxylato complexes react with acetic acid giving a mononuclear ruthenium complex Ru(CO)2(MeCOO)(μ-MeCOO)(PBu3), containing a monodentate and a chelato acetato ligands. This complex was spectroscopically characterised. Its identity and structure were confirmed by its reactivity with stoichiometric amount of PPh3 to give Ru(CO)2(MeCOO) 2(PBu3)(PPh3), a new mononuclear ruthenium carbonyl carboxylate containing two different phosphines, that was fully characterised.
- Salvini, Antonella,Frediani, Piero,Giannelli, Carlo,Rosi, Luca
-
p. 371 - 382
(2007/10/03)
-
- A series of crystal structures of a meta-cleavage product hydrolase from Pseudomonas fluorescens IP01 (CumD) complexed with various cleavage products
-
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
-
p. 491 - 498
(2008/02/01)
-
- Direct carbonylation of paraffins using solid strong acid catalyst
-
A process for the direct carbonylation of saturated hydrocarbons has been developed. The process involves contacting the saturated hydrocarbons, which contain at least one primary, secondary or tertiary carbon atom, with carbon monoxide in the presence of a solid strong acid catalyst to produce an oxygenated saturated hydrocarbon. In a specific embodiment isobutane is reacted with carbon monoxide using sulfated zirconia as the catalyst to produce methylisopropyl ketone. The oxygenated hydrocarbon can subsequently be hydrogenated to give a reduced oxygenated saturated hydrocarbon. The hydrogenation can also be done simultaneously with the carbonylation, i.e., reductive carbonylation.
- -
-
Page column 9
(2010/01/31)
-
