- Electrocarboxylation of chloroacetonitrile mediated by electrogenerated cobalt(I) phenanthroline
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The electrocarboxylation of chloroacetonitrile mediated by [Co(II)(phen)3]2+ has been investigated. Cyclic voltammetry studies of [Co(II)(phen)3]2+ have shown that [Co(I)(phen)3]+, an 18 electron complex, activates chloroacetonitrile by an oxidative addition through the loss of a phenanthroline ligand to give [RCo(III)(phen)2Cl]+. The unstable one-electron-reduced complex underwent Co-C bond cleavage. In carbon dioxide saturated solution, CO2 insertion proceeds after reduction of the alkylcobalt complex. A catalytic current is observed which corresponds to the electrocarboxylation of chloroacetonitrile into cyanoacetic acid. Electrolyses confirmed the process and gave faradic yield of 62% in cyanoacetic acid at potentials that are about 0.3 V less cathodic than the one required for Ni(salen).
- Fabre,Reynes
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Read Online
- Hydrogen peroxide oxidation of 2-cyanoethanol catalyzed by metal complexes
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Oxidation of 2-cyanoethanol, a relatively inert primary alcohol, with several systems (both homogeneous and heterogenized) based on transition metal complexes was studied. The oxidation was performed under homogeneous conditions with 35% hydrogen peroxide upon catalysis by the chlorides FeCl3 or OsCl3. The best result was obtained upon the oxidation catalyzed by OsCl3 at 70°C for 3 h in the absence of solvent: the total yield of the corresponding aldehyde and cyanoacetic acid reached 90%, and the turnover number was 1500. The systems [LMnIV(O)3Mn IVL]n(X)m-oxalic acid (where L = 1,4,7-trimethyl-1,4,7-triazacyclononane) also catalyze oxidation of 2-cyanoethanol with yields of 50-70% either under homogeneous conditions (X = PF- 6, n = 1, and m = 2) or with the use of the catalyst in the heterogenized form (as insoluble heteropoly acid salt), where X = W 12SiO4- 40, n = 2, and m = 1. Nauka/Interperiodica 2006.
- Veghini,Shul'pina,Strelkova,Shul'pin
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Read Online
- 5-Oxyacetic Acid Modification Destabilizes Double Helical Stem Structures and Favors Anionic Watson–Crick like cmo5U-G Base Pairs
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Watson–Crick like G-U mismatches with tautomeric Genol or Uenol bases can evade fidelity checkpoints and thereby contribute to translational errors. The 5-oxyacetic acid uridine (cmo5U) modification is a base modification at the wobble position on tRNAs and is presumed to expand the decoding capability of tRNA at this position by forming Watson–Crick like cmo5Uenol-G mismatches. A detailed investigation on the influence of the cmo5U modification on structural and dynamic features of RNA was carried out by using solution NMR spectroscopy and UV melting curve analysis. The introduction of a stable isotope labeled variant of the cmo5U modifier allowed the application of relaxation dispersion NMR to probe the potentially formed Watson–Crick like cmo5Uenol-G base pair. Surprisingly, we find that at neutral pH, the modification promotes transient formation of anionic Watson–Crick like cmo5U?-G, and not enolic base pairs. Our results suggest that recoding is mediated by an anionic Watson–Crick like species, as well as bring an interesting aspect of naturally occurring RNA modifications into focus—the fine tuning of nucleobase properties leading to modulation of the RNA structural landscape by adoption of alternative base pairing patterns.
- Strebitzer, Elisabeth,Rangadurai, Atul,Plangger, Raphael,Kremser, Johannes,Juen, Michael Andreas,Tollinger, Martin,Al-Hashimi, Hashim M.,Kreutz, Christoph
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Read Online
- Kinetics of the Deamination of Amides by Nitrous Acid
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The kinetic profile of the rate constant for the nitrous acid-amide reaction in sulfuric acid as a function of acidity for a range of aliphatic and aromatic primary amides has been interpreted in terms of the HNO2/NO+ and the amide/ amide · H+ equilibria.
- Al-Mallah, Khawla,Stedman, Geoffrey
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Read Online
- Facile dehydration of primary amides to nitriles catalyzed by lead salts: The anionic ligand matters
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The synthesis of nitrile under mild conditions was achieved via dehydration of primary amide using lead salts as catalyst. The reaction processes were intensified by not only adding surfactant but also continuously removing the only by-product, water from the system. Both aliphatic and aromatic nitriles can be prepared in this manner with moderate to excellent yields. The reaction mechanisms were obtained with high-level quantum chemical calculations, and the crucial role the anionic ligand plays in the transformations were revealed.
- Ruan, Shixiang,Ruan, Jiancheng,Chen, Xinzhi,Zhou, Shaodong
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- Surface active ionic liquid assisted metal-free electrocatalytic-carboxylation in aqueous phase: A sustainable approach for CO2utilization paired with electro-detoxification of halocarbons
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Electrocarboxylation of halocarbons is a promising green synthetic strategy for capture, fixation and utilization of CO2 for the synthesis of high-added-value industrial compounds. However, the unparalleled kinetic/thermodynamic stability and solubility concerns of CO2 and halocarbons warrant the use of appropriate (often precious metal based) electrocatalytic electrodes and environmentally non-green solvent systems to drive this otherwise kinetically slow electrochemical process. Herein we demonstrate that owing to their unique solubility and excellent electrocatalytic properties, the aqueous micellar solutions of imidazolium-based surface active ionic liquids (SAILs) can be used for the efficient and selective electrocatalytic-carboxylation of halocarbons to produce carboxylic acids. Specifically, we present results from our detailed electrochemical investigations regarding the electroreductive cleavage of the C-X bond and electrocarboxylation of 9-bromoanthracene (9-BAN) and chloroacetonitrile (CAN) in buffered (pH 7, phosphate buffer) micellar solutions of 1-dodecyl-3-methyl-imidazolium chloride ([DDMIM][Cl]). We demonstrate that the unique ability of [DDMIM][Cl] micelles to stabilize the electrogenerated reactive intermediates facilitates a novel reaction pathway that ensures selective and efficient electrocatalytic-reductive carboxylation of 9-BAN and CAN. The presented results clearly establish that besides allowing for the electrocarboxylation of halocarbons in aqueous green electrolytes, the use of SAILs ensures electrochemical fixation of CO2 at practically low cost current and potential conditions imposed over metal free, economically viable and electrochemically robust carbon electrodes. The use of SAILs is reported to improve the faradaic efficiency (～95%) and reduce the chances of undesired side product reactions which continue to be a major concern in the state of art electro-carboxylation processes. The presented approach we opine offers a promising avenue toward design of eco-green pathways in the direction of CO2 fixation and electro-organic synthesis of a diverse range of value-added products from water insoluble halocarbons (toxic pollutants) in aqueous media.
- Bhat, Khursheed Ahmad,Bhat, Mohsin Ahmad,Bhat, Sajad Ahmad,Ingole, Pravin P.,Manzoor Bhat, Zahid,Pandit, Sarwar Ahmad,Rather, Mudasir Ahmad,Rehman, Shakeel U.,Sofi, Feroz Ahmad,Thotiyl, Musthafa Ottakam
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p. 9992 - 10005
(2021/12/24)
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- Synthesis of α-aminonitriles using aliphatic nitriles, α-amino acids, and hexacyanoferrate as universally applicable non-toxic cyanide sources
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In cyanation reactions, the cyanide source is often directly added to the reaction mixture, which restricts the choice of conditions. The spatial separation of cyanide release and consumption offers higher flexibility instead. Such a setting was used for the cyanation of iminium ions with a variety of different easy-to-handle HCN sources such as hexacyanoferrate, acetonitrile or α-amino acids. The latter substrates were first converted to their corresponding nitriles through oxidative decarboxylation. While glycine directly furnishes HCN in the oxidation step, the aliphatic nitriles derived from α-substituted amino acids can be further converted into the corresponding cyanohydrins in an oxidative C-H functionalization. Mn(OAc)2 was found to catalyze the efficient release of HCN from these cyanohydrins or from acetone cyanohydrin under acidic conditions and, in combination with the two previous transformations, permits the use of protein biomass as a non-toxic source of HCN.
- Nauth, Alexander M.,Konrad, Tim,Papadopulu, Zaneta,Vierengel, Nina,Lipp, Benjamin,Opatz, Till
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supporting information
p. 4217 - 4223
(2018/09/29)
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- Study on the degradation mechanism and pathway of benzene dye intermediate 4-methoxy-2-nitroaniline: Via multiple methods in Fenton oxidation process
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Benzene dye intermediate (BDI) 4-methoxy-2-nitroaniline (4M2NA) wastewater has caused significant environmental concern due to its strong toxicity and potential carcinogenic effects. Reports concerning the degradation of 4M2NA by advanced oxidation process are limited. In this study, 4M2NA degradation by Fenton oxidation has been studied to obtain more insights into the reaction mechanism involved in the oxidation of 4M2NA. Results showed that when the 4M2NA (100 mg L-1) was completely decomposed, the TOC removal efficiency was only 30.70-31.54%, suggesting that some by-products highly recalcitrant to the Fenton oxidation were produced. UV-Vis spectra analysis based on Gauss peak fitting, HPLC analysis combined with two-dimensional correlation spectroscopy and GC-MS detection were carried out to clarify the degradation mechanism and pathway of 4M2NA. A total of nineteen reaction intermediates were identified and two possible degradation pathways were illustrated. Theoretical TOC calculated based on the concentration of oxalic acid, acetic acid, formic acid, and 4M2NA in the degradation process was nearly 94.41-97.11% of the measured TOC, indicating that the oxalic acid, acetic acid and formic acid were the main products. Finally, the predominant degradation pathway was proposed. These results could provide significant information to better understand the degradation mechanism of 4M2NA.
- Guo, Ying,Xue, Qiang,Cui, Kangping,Zhang, Jia,Wang, Hui,Zhang, Huanzhen,Yuan, Fang,Chen, Honghan
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p. 10764 - 10775
(2018/03/26)
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- Unusual differences in the reactivity of glutamic and aspartic acid in oxidative decarboxylation reactions
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Amino acids are potential substrates to replace fossil feedstocks for the synthesis of nitriles via oxidative decarboxylation using vanadium chloroperoxidase (VCPO), H2O2 and bromide. Here the conversion of glutamic acid (Glu) and aspartic acid (Asp) was investigated. It was observed that these two chemically similar amino acids have strikingly different reactivity. In the presence of catalytic amounts of NaBr (0.1 equiv.), Glu was converted with high selectivity to 3-cyanopropanoic acid. In contrast, under the same reaction conditions Asp showed low conversion and selectivity towards the nitrile, 2-cyanoacetic acid (AspCN). It was shown that only by increasing the amount of NaBr present in the reaction mixture (from 0.1 to 2 equiv.), could the conversion of Asp be increased from 15% to 100% and its selectivity towards AspCN from 45% to 80%. This contradicts the theoretical hypothesis that bromide is recycled during the reaction. NaBr concentration was found to have a major influence on reactivity, independent of ionic strength of the solution. NaBr is involved not only in the formation of the reactive Br+ species by VCPO, but also results in the formation of potential intermediates which influences reactivity. It was concluded that the difference in reactivity between Asp and Glu must be due to subtle differences in inter- and intramolecular interactions between the functionalities of the amino acids.
- But, Andrada,Van Der Wijst, Evie,Le N?tre, Jér?me,Wever, Ron,Sanders, Johan P. M.,Bitter, Johannes H.,Scott, Elinor L.
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supporting information
p. 5178 - 5186
(2017/11/09)
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- Preparation method for cyanoacetic acid and derivatives thereof
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The invention discloses a preparation method for cyanoacetic acid and derivatives thereof. According to the invention, a mixed solution of cyanoacetic acid and sodium chloride is subjected to continuous chromatographic separation so as to obtain a cyanoacetic acid solution and sodium chloride; so the cyanoacetic acid solution with low chloride ion content or high-content solid cyanoacetic acid products and derivatives thereof are obtained, and the disadvantages of considerable decomposition and low yield of cyanoacetic acid in traditional distillation, concentration and separation are overcome. The preparation method is simple to operate, low in production cost, high in product yield and low in the amounts of waste gas, waste water and industrial residues, is an environment-friendly clean production method and can prepare the cyanoacetic acid solution with low chloride ion content or high-content solid cyanoacetic acid products and derivatives thereof.
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Paragraph 0022; 0023; 0024; 0025; 0026; 0027; 0028-0045
(2016/12/01)
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- A cyamoacetic acid method for preparing and its derivatives (by machine translation)
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The invention discloses a cyamoacetic acid and process for preparing derivatives thereof, sodium chloride containing cyamoacetic acid by the evaporation in a mixture of concentrated portion of the water, part of the sodium chloride is filtered to remove precipitated solid, avoid the traditional distillation and condensation in addition to salt the cyanoacetic acid a large amount of decomposition, shortcoming of low yield, in addition to at the same time after salt solution containing cyamoacetic acid and sodium chloride by a continuous chromatographic separation cheng Qing acetic acid solution and the sodium chloride solution, avoiding the cyanoacetic acid concentration being decomposed in the process. The operation of the invention is simple, the production cost is low, the product yield is high, little amount of the three wastes, is an environmentally friendly clean production method, low chlorine content of the solution or cyanoacetate with high content of solid cyanoacetic acid product and its derivatives. (by machine translation)
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Paragraph 0032
(2016/11/21)
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- METHOD FOR PRODUCING CYANOACETIC ACID, METHOD FOR PRODUCING CYANOACETIC ACID DERIVATIVE AND METHOD FOR PRODUCING METAL CONTAINING COMPOUND
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Provided is a method for producing cyanoacetic acid in a hydrolysis reaction of a predetermined cyanoacetate in the presence of an acid catalyst. Further, are provided methods for producing a cyanoacetic acid derivative and a metal containing compound by using the produced cyanoacetic acid as a staring material. Herein, the method for producing cyanoacetic acid enables the content of a malonic acid byproduct generated in the hydrolysis reaction to be greatly lowered, allowing the produced cyanoacetic acid to be used as a starting material without any purification treatments. Those advantageous effects result in the great improvement in the purity and yields of the cyanoacetic acid derivative and the metal containing compound produced by said cyanoacetic acid. Accordingly, the above mentioned methods make it possible to produce cyanoacetic acid, the cyanoacetic acid derivative and the metal containing compound, as excellent in the productivity and economical efficiency.
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Paragraph 0244; 0245; 0247; 0249
(2013/10/07)
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- GABAB-agonistic activity of certain baclofen homologues
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Baclofen (1) is a potent and selective agonist for bicuculline-insensitive GABAB receptors and is used clinically as an antispastic and muscle relaxant agent. In the search for new bioactive chemical entities that bind specifically to GABAB receptors, we report here the synthesis of certain baclofen homologues, namely (R,S)-5-amino-3-arylpentanoic acid hydrochlorides (R,S)-1a-h as well as (R,S)-5-amino-3-methylpentanoic acid [(RS)-1i] to be evaluated as GABABR agonists. Compound 1a is an agonist to GABAB receptors with an EC50 value of 46 μM on tsA201 cells transfected with GABAB1b/GABAB2/Gqz5, being the most active congener among all the synthesized compounds.
- Attia, Mohamed I.,Herdeis, Claus,Braeuner-Osborne, Hans
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p. 10266 - 10284
(2013/10/22)
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- ANTI VIRAL COMPOUNDS
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There is provided small molecule anti-human immunodeficiency virus (anti-HIV) compounds as well as a phenotypic cell-based high throughput screening (HTS) assay for their identification.
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Page/Page column 36
(2010/05/13)
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- Hydrolysis of amides to carboxylic acids using phthalic anhydride under microwave irradiation and solvent-free conditions
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Amides efficiently and rapidly give carboxylic acids in high yields upon reaction with phthalic anhydride under microwave irradiation in the absence of solvent.
- Heravi, Majid M.,Zargarani, Dordaneh,Shoar, Rahim Hekmat,Khaleghi, Shahnaz
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p. 119 - 120
(2007/10/03)
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- An insight of the reactions of amines with trichloroisocyanuric acid
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The reaction between amines or α-aminoacids with trichloroisocyanuric acid is studied under various conditions: N,N-dichloroamines, nitriles and ketones can be obtained from primary amines, while free aminoacids undergo oxidative decarboxylation to the corresponding nitrile of one less carbon atom.
- De Luca, Lidia,Giacomelli, Giampaolo
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p. 2180 - 2184
(2007/10/03)
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- Aggregation in oxidation of aspartic and glutamic acids by chloramine-T in presence of surfactants: A kinetic study
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The kinetics of oxidation of aspartic and glutamic acids by chloramine-T in HClO4 medium have been investigated in the absence and presence of anionic (sodium lauryl sulphate), cationic (cetyltrimethylammonium bromide) and non-ionic (Brij 35) surfactants. In the absence of surfactant the rate of oxidation may be represented as, d[Chloramine-T]/dt=k[Chloramine-T] 2[Amino acid]/(1+K[H+]) where k and K are constants. The presence of a small amount of surfactant (below its critical micelle concentration) strongly enhances the rate of oxidation and the observed rate constant attains constancy at higher surfactant concentration. Using Piszkiewicz's cooperativity model, the cooperative index n has been calculated for these reactions to be between 1-3, indicating the existence of catalytically productive submicellar aggregates. The values of n have been used to calculate the binding constants of reactants with the surfactant using Raghvan and Srinivasan's model proposed for biomolecular micellar catalysed reactions. The evaluated binding constants are in good agreement from those obtained by Piszkiewicz's model. The formation of aggregate is further supported by the enhancement of rate in presence of a common hydrotrope, namely, sodium benzoate.
- Pandey, Ekta,Grover, Neeti,Kambo, Neelu,Upadhyay, Santosh K.
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p. 1186 - 1192
(2007/10/03)
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- Paired Electrosynthesis of Cyanoacetic Acid
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Cyanoacetic acid is formed by cathodic reduction of CO2 and anodic oxidation of the tetraalkylammonium salt anion; the process is conduced in acetonitrile using a divided cell with a medium porosity glass-frit diaphragm. A mechanism for this paired electrochemical reaction is proposed.
- Batanero, Belen,Barba, Fructuoso,Sanchez-Sanchez, Carlos M.,Aldaz, Antonio
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p. 2423 - 2426
(2007/10/03)
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- Chemical uncouplers for the treatment of obesity
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This invention relates to chemical uncouplers with a broader safety window making the use of them in treating obesity and, consequently, in the treatment of obesity related diseases and conditions such as atherosclerosis, hypertension, diabetes, especially type 2 diabetes (NIDDM (non-insulin dependent diabetes mellitus)), impaired glucose tolerance, dyslipidemia, coronary heart disease, gallbladder disease, osteoarthritis and various types of cancer such as endometrial, breast, prostate and colon cancers and the risk for premature death as well as other conditions, such as diseases and disorders, which conditions are improved by an increase in mitochondrial respiration, more attractive.
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- Hydrolysis of nitriles using an immobilized nitrilase: Applications to the synthesis of methionine hydroxy analogue derivatives
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Mild and selective hydrolysis of a large range of nitriles leading to carboxylic acids was achieved under neutral conditions by an immobilized and genetically modified enzyme preparation from Alcaligenes faecalis ATCC8750. This immobilized nitrilase has been shown to be an effective catalyst for the stereoselective hydrolysis of mandelonitrile 1a to R-(-)-mandelic acid 1c. This method is particularly useful for the production of hydroxy analogues of methionine derivatives 2c-4c that could have an interest in cattle feeding and for the transformation of compounds containing other acid- or base-sensitive groups 3a-10a. A series of aliphatic dinitriles 11a-15a was hydrolyzed to the corresponding cyano acids. The suitability of the immobilized catalyst as a robust and versatile biocatalyst is discussed, and models to account for the stereoselectivity of the enzymic hydrolysis have been proposed.
- Rey, Patrick,Rossi, Jean-Christophe,Taillades, Jacques,Gros, Georges,Nore, Olivier
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p. 8155 - 8162
(2007/10/03)
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- Glucocorticoid receptor modulators
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The present invention provides non-steroidal compounds of formula I which are selective modulators (i.e., agonists and antagonists) of a steroid receptor, specifically, the glucocorticoid receptor. The present invention also provides pharmaceutical compositions containing these compounds and methods for using these compounds to treat animals requiring glucocorticoid receptor agonist or antagonist therapy. Glucocorticoid receptor modulators are useful to treat diseases, such as obesity, diabetes, inflammation and others as described below. The present invention also provides intermediates and processes for preparing these compounds. STR1
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- Methods for the synthesis of highly substituted 2,4-dioxopiperidine libraries
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The invention relates to methods of synthesizing libraries of diverse and complex highly substituted 2,4-dioxopiperidine compounds of the general formula: wherein R1, R2 and R3 are as herein described, novel intermediates useful for synthesizing such 2,4-dioxopiperidine compounds and methods for identifying and isolating the compounds.
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- Selective hydrolysis of aliphatic dinitriles to monocarboxylic acids by a nitrilase from Arabidopsis thaliana
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The hydrolysis of a variety of dinitriles including α,ω-dicyanoalkanes 1, β-substituted glutaronitriles 5, and γ-cyanopimelonitrile 7 with a recombinant plant nitrilase from Arabidopsis thaliana, expressed in E. coli, is described. Conversion rate and selectivity of the hydrolysis of dinitriles 1a-f to ω-cyanocarboxylic acids 2a-f depend on the chain length. The enzyme activity markedly increases from malononitrile (1a) to octanedinitrile (1f). The selectivity, however, does not correlate with the rates. Up to a chain length of 6 C-atoms, the cyanocarboxylic acid is the only product, even at complete conversion of the starting material. Pimelonitrile (1e) is hydrolyzed to the cyanocarboxylic acid 2e without formation of diacid (1%) up to 73% conversion. Glutaronitriles 5a-c were also hydrolyzed to the corresponding cyanobutanoic acids 6a-c with perfect selectivity. The nitrilase hydrolyzes exclusively the primary cyano group of 7 to give 3,5-dicyanoheptanoic acid (8a), whereby the selectivity is slightly reduced compared to the unsubstituted pimelonitrile (1e). If the hydrolysis is terminated at conversions ≤90%, pure 8a can be isolated in 72% yield (92% referred to conversion). After esterification of 8a to the methyl ester 8b, only the 5-cyano group but not the ester function was hydrolyzed enzymatically to give cyanoheptanedioic acid monoester (10).
- Effenberger,Osswald
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p. 1866 - 1872
(2007/10/03)
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- Kinetics and mechanism of the hydrolysis of 1-aryloxyethyl alkanoates
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The kinetics and mechanism of the hydrolysis of 1-aryloxyethyl alkanoates are reported.In acidic media, 18O isotope exchange studies, kinetics, activation parameters and substituent effects point clearly to an AAl-1 mechanism with the formation of an alkoxycarbonium ion as the rate-limiting step.In basic media the data indicate a conventional BAc-2 mechanism through attack of hydroxide ion on the carbonyl carbon.In neutral medium (pH 2.5-8.8) there is a certain amount of conflicting evidence which leads, however, to the proposal that hydrolysis occurs via attack of a water molecule on the acyl carbon as the rate-limiting step.
- Hall, C. Dennis,Goulding, Celia W.
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p. 1471 - 1478
(2007/10/02)
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- Stereoselective syntheses of substituted 5,6-dihydro-2(1H)-pyridinones in polyphosphate media
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δ-Lactams have been synthesized with excellent stereocontrol of substituents by condensing 3-alkenamides with aryl aldehydes in polyphosphoric ester. The scope of the condensation of 3-alkenamides with aryl aldehydes in several phosphate media is examined, and a rationale is proposed regarding γ-lactam versus δ-lactam formation.
- Marson,Grabowska,Fallah,Walsgrove,Eggleston,Baures
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p. 291 - 296
(2007/10/02)
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- The catalytic decarboxylation of cyanoacetic acid: Anionic tungsten carboxylates as homogeneous catalysts
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Cyanoacetic acid was observed to catalytically decompose to its component parts, CO2 and CH3CN, in the presence of soluble tungsten(0) carboxylates. In the case in which W(CO)5O2CCH2CN- was used as the catalyst, the reaction was inhibited by the substrate via an equilibrium process in which the free acid displaced the carboxylate ligand and bound to the metal through the nitrogen atom. The equilibrium constant for this process was measured and determined to be 0.413 at 50°C, where kf = 6.11 × 10-3 M-1 s-1 and kr = 1.48 × 10-2 M-1 s-1. Activation parameters for the decarboxylation process were determined and yielded ΔH* = 21.0 ± 0.7 kcal·mol-1 and ΔS* = -3.4 ± 1.9 eu. The rate limiting step is proposed to be loss of cis CO from the metal with concomitant formation of cis-W(CO)4(O2CCH2CN)(NCCH2COOH) -, since the free energy of activation is quite similar to that for cis carbonyl loss, 23.0 ± 0.9 kcal·mol-1. Subsequent proton transfer and CO2 loss are fast relative to cis CO displacement. The carboxylate ligand acts as an intramolecular Lewis base, mediating the proton-transfer steps. This was demonstrated by the use of W(CO)PPh2(CH2)nX- (n = 1 or 2, X = base) as catalysts for the same decarboxylation. Detailed kinetic studies and a proposed mechanism are presented.
- Darensbourg, Donald J.,Chojnacki, Jennifer A.,Atnip, Earl V.
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p. 4675 - 4682
(2007/10/02)
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- Photolysis of the 1-naphthylmethyl ester of substituted phenylacetic acids: intramolecular charge transfer and rates of decarboxylation of arylacyl radicals
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The photolysis of esters 6 and 8 in methanol leads to products resulting from both naphthylmethyl cations and radicals.The product distribution is nearly independent of X for the esters 6 except when X equals methoxy.A mechanism involving initial homolytic cleavage of the carbon-oxygen bond in the excited singlet state of the ester is proposed.Competition between electron transfer in the radical pair to form the ion pair and decarboxylation of the arylacyloxy radical allows calculations of the rates of this decarboxylation process.The ρ values versus ? is close to zero.When X equals methoxy, intramolecular electron transfer occurs with the naphthalene ring serving as the acceptor and the methoxyaromatic as the donor.This exciplex fragments to carbon dioxide and 1-(1-naphthyl)-2-arylethane. Key words: acyloxy radical, decarboxylation, photolysis of benzylic esters.
- Hilborn, James W.,Pincock, James A.
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p. 992 - 999
(2007/10/02)
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- Structural and reactivity studies of a cyanoacetic acid derivative of tungsten pentacarbonyl. X-ray structure of W(CO)5NCCH2COOH
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The new cyanoacetic acid complex W(CO)5NCCH2COOH (1) has been synthesized from the reaction of W(CO)5THF and NCCH2COOH. The molecular structure of 1 has been determined by X-ray diffraction methods. The compound crystallizes in the triclinic space group P1 with two molecules in a cell of dimensions a = 6.7390 (10) ?, b = 9.745 (2) ?, c = 10.241 (2) ?, α = 63.57 (2)°, β = 81.71 (2)°, γ = 76.22 (2)°. Full-matrix least-squares refinement gives final R and Rw on F of 0.026 and 0.037 for 2030 observed [F > 4σ(F)] data. The structure confirms the presence of the nitrile ligand located 2.178 (7) ? from the tungsten center, with the carboxyl groups of two molecules coupled by strong intermolecular hydrogen-bonding (O-H?O = 2.627 (3) ?). This hydrogen-bonding structure was observed as well in solution as indicated by infrared spectroscopy. The displacement of the cyanoacetic acid ligand in 1 by carbon monoxide was shown to proceed via a solvent-assisted Id process in tetrahydrofuran and by a D process in the less-interacting solvent methylene chloride. The activation parameters for these processes are consistent with the proposed mechanism, with ΔH? and ΔS? for the displacement of the NCCH2COOH ligand determined to be 19.4 kcal/mol and -14.7 eu in THF and 29.2 kcal/mol and 11.8 eu in CH2Cl2, respectively. Comparable kinetic data were observed for the tungsten complexes containing the electronically similar ligands NC(CH2)10COOH and CH3CN. The relevance of this study to the catalytic decarboxylation reaction of cyanoacetic acid in the presence of W(CO)5O2CCH2CN- is discussed.
- Darensbourg, Donald J.,Atnip, Earl V.,Reibenspies, Joseph H.
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p. 4475 - 4480
(2008/10/08)
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- The Carboxylation of Active Methylene Compounds with Diphenylcarbodiimide and Potassium Carbonate
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Active methylene compounds were carboxylated by employing the reagent system, diphenylcarbodiimide and potassium carbonate, in dimethyl sulfoxide at room temperature and atmospheric pressure.The reaction proceeded even in the absence of carbon dioxide, but the carboxylation easily proceeded in carbon dioxide atmosphere.
- Chiba, Koji,Tagaya, Hideyuki,Karasu, Masa,Ono, Tsuyoyuki,Kugiya, Masashi
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- Proton transfers among oxygen and nitrogen acids and bases in DMSO solution
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Rate constants for the proton-transfer reactions between conjugate acids and bases of several amines, phenols, carboxylic acids, and the solvated proton in DMSO-d6 at 20 °C have been determined by the use of NMR line-shape analysis. Equilibrium constants for the same reactions are obtained from the pKa's of the acids in dimethyl sulfoxide, some of which have been reported in earlier work and the rest obtained in the present work by use of Bordwell's indicator techniques. All of the reactions have rale constants considerably below expected diffusion-controlled limits for the proton transfers in the thermodynamically favorable direction, and several of the reactions, including the identity reactions of carboxylic acids, have kinetic deuterium isotope effects, kH/kD, between 0.8 and 1.3. For reactions of N,N-dimethylbenzylammonium ion with several phenoxides, carboxylates, and solvent, the rate constants for transfers in the unfavorable directions show a reasonable Bronsted correlation with β ≈ 1 and a reasonably constant reverse rate constant of ≈3 × 106 M-1 s-1. The data clearly indicate that the proton-transfer step is not rate-limiting in these reactions. Most likely, desolvation is involved in the rate-limiting steps, but the rate constants are not simple functions of acidities as might have been expected if hydrogen bonding of acid to solvent were the major factor involved in the solvation Other factors, particularly dispersion interactions of solvent with solutes, are discussed. We suggest that the formation of an acid-base complex with proper orientation to allow contact between the proton and the basic site is rate-determining and involves desolvation along with detailed steric interactions of the acid-base pair.
- Ritchie, Calvin D.,Lu, Shanzheng
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p. 7748 - 7756
(2007/10/02)
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- MONOHYDROLYSIS OF AN ALIPHATIC DINITRILE COMPOUND BY NITRILASE FROM RHODOCOCCUS RHODOCHROUS K22
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Nitrilase from Rhodococcus rhodochrous K22 catalyzes the conversion of various aliphatic nitrile derivatives to the corresponding acids.Using this resting cells, 4-cyanobutyric acid was synthesized from glutaronitrile with 100percent molar conversion.
- Kobayashi, Michihiko,Yanaka, Noriyuki,Nagasawa, Toru,Yamada, Hideaki
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p. 5587 - 5590
(2007/10/02)
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- The E1cb Route for Ester Hydrolysis; Volumes of Activation as an Additional Criterion of Mechanism
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Hydrolyses of esters which possess an acidic proton at the α or vinylogous position can, in principle, hydrolyse by the E1cb route via a ketenoid intermediate.To the kinetic evidence for such a mechanism in the hydrolyses of 4-hydroxybenzoates, malonates, acetoacetates and fluorenecarboxylates is now added the further criterion of volumes of activation.Values of ΔV(excit.) for reactions proceeding by the E1cb route are positive and contrast with the negative values associated with hydrolyses by the more usual BAc2 mechanism.
- Isaacs, Neil S.,Najem, Tariq S.
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p. 557 - 562
(2007/10/02)
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- Kinetics and mechanism of uncatalysed and Chloride-catalysed Oxidative Decarboxylation of Glycine and Aspartic Acid by Chloramine-T in Perchloric Acid medium
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The kinetics of oxidative decarboxylation of glycine and L-aspartic acid by chloramine-T has been investigated both in the absence and presence of chloride ion in perchloric acid medium.In the absence of chloride ion, the rate followed second order kinetics in (CAT)0, first order in (substrate), inverse first order in (H+) with both the amino acids.Chloride was found to enhance the rate of oxidation and affect the kinetics.In the presence of chloride, the rate followed first order kinetics in (CAT)0 in both cases.But the rate was fractional and zero order in (substrate) with glycine and aspartic acid, respectively.The kinetic order in (H+) was also different, i.e. inverse fractional order and fractional order respectively with glycine and aspartic acid.The effect of chloride was more pronounced with aspartic acid.Effects of added reaction product and the variation of ionic strength and dielectric constant of the reaction medium have also been investigated.Reaction schemes in conformity with the observed kinetics have been proposed and the related rate laws derived.The constants of the rate limiting and other steps have been calculated in some cases.
- Gowda, B. Thimme,Rao, R. Vijayalakshmi
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p. 467 - 473
(2007/10/02)
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- Kinetics and Mechanism of Uncatalysed and mercury(II)-catalysed Alkaline Chloramine-T Oxidation of Aspartic Acid
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Kinetics of oxidation of aspartic acid by chloramine-T in aqueous sodium hydroxide media in absence and in presence of Hg(II) has been investigated.A first order dependence each on chloramine-T and aspartic acid, both in absence and in presence of Hg(II) has been observed.An inverse first order dependence on sodium hydroxide concentration has been established for both uncatalysed and catalysed oxidation reactions.Hg(II) ions catalyse the reaction significantly and the catalytic action of Hg(II) is ascribed to the complex formation with aspartic acid anions.A negligible salt-effect points to a mechanism involving a neutral molecule and anion in the rate determining step.The activation parameters for both uncatalysed and Hg(II)-catalysed oxidations have also been computed.Rate laws consistent with the experimental results have been deduced and suitable mechanism has been proposed.
- Sengar, Satish K. S.,Yadav, B. S.
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p. 596 - 599
(2007/10/02)
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- Certain β-oxo-α-carbamoylpyrrolepropionitriles
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1-Unsubstituted β-oxo-α-(phenylcarbamoyl)-β-pyrrolylpropionitriles, e.g. those of the formula STR1 wherein R1 and R2 =H or alkyl, and R3 and R4 =H, alkyl, alkoxy, OH, halogen or CF3, are analgesic, and antiarthritic agents. Their synthesis, pharmaceutical compositions thereof, and methods of treatment utilizing such compounds are included.
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- Anodic Oxidation of 2-Cyanoethanol to Cyanoacetic Acid
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2-Cyanoethanol (3-hydroxypropionitrile, 1) has been oxidized electrochemically in aqueous sulfuric acid at platinum- and lead dioxide anodes with current densities of 30-200 mA cm-2 to give cyanoacetic acid (3).Current efficiencies and material yields were up to 60percent.Side products are HCN via an anodic attack at β-CH2 with 8-15percent and cyanoacetaldehyde with 3-13percent current efficiency on platinum.In principle, HCN can be recycled to new starting material and cyanoacetaldehyde to yield further product.Electrooxidation at Pt takes place at an anode, which is partially covered with platinum oxides.High overvoltages are interpreted in terms of voltage drop in a rigid organic adsorbate layer.
- Wermeckes, Bernd,Beck, Fritz
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p. 3771 - 3780
(2007/10/02)
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- Novel nitriles and use as perfume chemicals
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Novel nitriles based on the carbon skeleton of menthane are disclosed, having the structural formula These compounds are useful in a variety of perfumery applications.
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- Effect of the acyl substituent on the equilibrium constant for hydration of esters
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Heats of hydrolysis have been measured for the trimethyl orthoesters of isobutyric, propionic, benzoic, methoxyacetic, chloroacetic, and cyanoacetic acids using aqueous acid with an organic cosolvent where necessary, and of the corresponding esters in alkaline solution.Solubilities of free energies of transfer from gas to aqueous solution have been measured, permitting calculation of the free energies of formation of the aqueous orthoesters, and by methods which we have published previously, calculations of the free energies of formation of the covalent hydrates of the esters, and the free energy changes for hydration of these esters.Using estimated pKa values equilibrium constants were calculated for the addition of hydroxide to esters.The data are in good agreement with the appropriate Marcus equation relating rate and equilibrium constants with a value for b of 8.99+-0.17.This line was used to estimate the equilibrium constant for addition of hydroxide, and thence of water, to some additional esters where only the rate constant was available.Rate constants for hydrolysis of methyl esters in aqueous solution at 25 deg C were calculated from literature data, correcting for the effect of other conditions as necessary.From the equilibrium constants for addition of water we could estimate the rate constants for uncatalyzed hydrolysis; for the cases where this rate constant has been measured, the agreement was satisfactory.For acid catalyzed hydrolysis the data permit a test of the two alternative mechanisms considered previously, namely specific acid catalysis and general acid catalysis with hydronium ion acting as a general acid.For esters the mechanism is clearly specific acid catalysis, but for aldehydes and ketones it appears very likely that the mechanism is general acid catalysis
- Guthrie, J.Peter,Cullimore, Patricia A.
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p. 1281 - 1294
(2007/10/02)
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- Carane nitriles
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Novel nitriles are disclosed based on the structure of 3,7,7-trimethylbicycloheptane. These compounds are disclosed and shown to be useful as ingredients in perfume compositions.
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- Methods and intermediates for preparing cis-4-oxoazetidine intermediates
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The stereospecific cycloaddition of nitrogen containing acetic acid halides or anhydrides with Schiff bases having a carbalkoxy group substituted on the methine carbon atom offers new intermediates and methods for preparing synthetic cephalosporin congeners having antibacterial activity.
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- 7-Acyl-3-(sulfonic acid and sulfamoyl substituted tetrazolyl thiomethyl) cephalosporins
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The compounds of this invention are cephalosporins having a 3- or 4-aminomethylphenylacetamido substituent at the 7-position and a sulfonic acid substituted tetrazolyl thiomethyl group at the 3-position of the cephem nucleus. The compounds have antibacterial activity.
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- 8-Oxo-4-thia-1-azabicyclo (4.2.0)-oct-2-ene derivatives
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Novel bicyclic β-lactams and intermediates useful in their preparation are disclosed. In particular, 7β-acyl-amino- and 7β-amino-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acids are prepared. The acylated compounds are antibacterial agents.
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- 7-Acyl-3-(sulfaminoalkyl substituted tetrazolylthiomethyl)cephalosporins, antibacterial compositions containing them and methods of treating bacterial infections with them
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The compounds of this invention are cephalosporins having various acyl substituents at the 7-position and a sulfaminoalkyl substituted tetrazolylthiomethyl group at the 3-position of the cephem nucleus and intermediates for the preparation thereof. The 7-acylated cephalosporin compounds have antibacterial activity.
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- 7β-Acylamino-3-(phosphonoalkyl and esterified phosphonoalkyl substituted tetrazolylthiomethyl)cephalosporins
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The compounds of this invention are cephalosporins having various acylamino substituents at the 7-position and a phosphonoalkyl or esterified phosphonoalkyl substituted tetrazolylthiomethyl group at the 3-position of the cephem nucleus and intermediates for the preparation thereof. The 7-acylated compounds have antibacterial activity.
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- 7β-Acylamino-3-(alkanesulfonamidoalkyl substituted tetrazolylthiomethyl) cephalosporins, antibacterial compositions containing them and methods of treating bacterial infections with them
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The compounds of this invention are cephalosporins having various acyl substituents at the 7-position and an alkanesulfonamidoalkyl substituted tetrazolylthiomethyl group at the 3-position of the cephem nucleus and intermediates for the preparation thereof. The 7-acylated compounds have antibacterial activity.
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- Cis-4-oxoazetidine intermediates and methods of preparing them
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The stereospecific cycloaddition of nitrogen containing acetic acid halides or anhydrides with Schiff bases having a carbalkoxy group substituted on the methine carbon atom offers new intermediates and methods for preparing synthetic cephalosporin congeners having antibacterial activity.
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- 7-Acyl-3-(sulfonic acid and sulfamoyl substituted tetrazolyl thiomethyl) cephalosporins
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The compounds of this invention are cephalosporins having various acyl substituents at the 7-position and a sulfonic acid or sulfamoyl substituted tetrazolyl thiomethyl group at the 3-position of the cephem nucleus. The compounds have antibacterial activity.
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