bluuebunny/crossref_metadata_2025_split huggingface dataset:
CO2 hydrogenation on nickel based catalysts supported on alumina
Authors: Ghazi M. , Menezo J. C. , Barrault J. 
Published: September 2010

AbstractOn nickel‐alumina catalysts, the hydrogenation of carbon dioxide into methane is more rapid than that of carbon monoxide due to much slower de‐activation of the catalysts in the presence of the mixture (CO2 + H2). Under the same conditions, competitive hydrogenation of CO and CO2 leads to intermediate results which are, nevertheless, close to those obtained with the mixture (CO + H2) due to significant CO adsorption.
Synthesis and NMR‐spectral characterization of N,N‐dialkyl‐3‐nitroanilines, N,N‐dialkyl‐1,3‐benzenediamines and their acyl derivatives
Authors: Katritzky Alan R. , Rachwal Bogumila , Rachwal Stanislaw 
Published: September 2010

AbstractA recently discovered method for the synthesis of N,N‐dialkyl‐1,3‐benzenediamines with two different alkyl groups is shown to be general. This is demonstrated by the synthesis of N‐butyl‐N‐phenethyl‐1,3‐benzenediamine by the condensation of 3‐nitroaniline with phenyl‐acetaldehyde and benzotriazole, reduction of the adduct with sodium borohydride, acylation of the resulting N‐phenethyl‐3‐nitroaniline with butyryl chloride, catalytic reduction of the nitro group by formic acid in the presence of triethylamine and palladium and finally reduction of the butyramide carbonyl group to the butyl substituent by lithium aluminum hydride. Several other routes were less efficient or failed completely.Classical methods for the synthesis of N,N‐diethyl‐1,3‐benzenediamine were reexamined and improved. The recommended procedure involves alkylation of 3‐nitroaniline with diethyl sulfate, trapping of N‐ethyl‐3‐nitroaniline (by‐product) by benzoylation, distillation of N,N‐diethyl‐3‐nitro‐aniline under reduced pressure and reduction of the nitro group by formic acid catalyzed by palladium.
A Static‐Secondary‐Ion‐Mass‐Spectrometry study of the surfaces of poly(hydroxyalkyl methacrylates) before and after chemical modification
Authors: Lub J. , van der Wei H. , van Vroonhoven F. C. B. M. , Benninghoven A. 
Published: September 2010

AbstractPositive and negative secondary‐ion‐mass spectra of poly(2‐hydroxyethyl methacrylate), poly(2‐hydroxypropyl methacrylate) and both polymers after modification with D2O and propionyl chloride are presented. The spectra were obtained with a Time‐of‐Flight Secondary‐Ion‐Mass Spectrometer. The structures of typical ions in the mass range 10‐150 amu are given and the intensities of these ions were used to obtain quantitative information about the ion formation processes. Furthermore, the spectra of poly(2‐hydroxyethyl methacrylate), poly[2‐(propionyloxy)ethyl methacrylate] and four copolymers of 2‐hydroxyethyl methacrylate and 2‐(propionyloxy)ethyl methacrylate are compared to provide quantitative results on ion‐formation efficiency and/or stability. The results of this study can be used to study the kinetics of the reaction of propionyl chloride with poly(2‐hydroxyethyl methacrylate) at a surface.
Synthesis and spectroscopy of (14′‐13C)‐ and (15′‐13C)spheroidene
Authors: Gebhard R. , van der Hoef K. , Lefeber A. W. M. , Erkelens C. , Lugtenburg J. 
Published: September 2010

AbstractThe preparation of two13C‐labelled isotopomers of spheroidene, the carotenoid bound in the photosynthetic reaction center ofRhodobacter sphaeroides, is described.All‐E(14′‐13C)‐spheroidene has been synthesized in high yield and purity and with more than 98%13C incorporation starting from (2‐13C)acetonitrile; similarly, all‐E(15′‐13C)spheroidene has been obtained starting from (I‐13C)acetonitrile. The spectroscopic properties of all‐Espheroidene and its (14′‐13C)‐ and (15′‐13C)isotopomers are discussed. The mass spectra of the labelled compounds reveal that toluene is eliminated mainly from the central part of the molecule. Analysis of the ′H‐NMR spectrum of all‐E(15′‐13C)spheroidene gives a value of 14.0 Hz for the1H ‐1H coupling constant of the 15‐15′ double bond.
Synthesis, molecular structure, and complexation of 1,4‐dihydropyridines containing ligands for intramolecular complexation of metal electrophiles
Authors: Kaptein Bernard , Kellogg Richard M. , van Bolhuis F. 
Published: September 2010

AbstractA series of 4‐substituted Hantzsch 1,4‐dihydropyridines has been synthesized. Substituents at the 4‐position include 2‐pyridyl, 2‐imidazolyl, and 1‐methyl‐2‐imidazolyl. By use of various acetoacetic ester derivatives methoxy and methylthio groups have been introduced in the ester side chains at the 3,5‐positions. A representative example is bis(2‐methoxyethyl) 1,4‐dihydro‐2,6‐dimethyl‐4‐(1H‐imidazol‐2‐yl)‐3,5‐pyridinedicarboxylate (5h). The crystal structure of bis‐[(2‐methylthio)ethyl] 1,4‐dihydro‐2,6‐dimethyl‐4‐(1H‐imidazol‐2‐yl)‐3,5‐pyridinedicarboxylate (5i) has been determined. The imidazole group at the 4‐position is located in a pseudo‐axial position. In the13C‐ and1H‐NMR spectra line doubling is seen in the 4‐imidazole‐substituted derivatives. This is apparently the result of slow tautomerization. Various complexes with Zn(NO3)2· 4H2O have been prepared but no crystal structures could be obtained. These 1,4‐dihydropyridines have little capacity, either in the presence or absence of metal ions, to carry out reductions. This may be the result of a stereoelectronic effect caused by the (presumably) equatorial orientation of the hydrogen (hydride) to be donated.
Alkaline decarboalkoxylative cyclization in the preparation of antirihine analogues
Authors: Lounasmaa Mauri , Jokela Reija 
Published: September 2010

AbstractAlkaline decarboalkoxylative cyclization of 1.4.5.6‐tetrahydropyridine 3b does not lead to dl‐18‐nor‐18,19‐dihydroantirhine 1b [C(3)H‐C(15)H trans relationship] but to the corresponding 3‐epi analogue 2b [C(3)H‐C(15)H cis relationship].
Synthesis and photoreactions of some spiro[cycloalkanephenalenes]
Authors: Hempenius M. A. , Lugtenburg J. , Cornelisse J. 
Published: September 2010

AbstractReaction of the phenalenyl anion (1−) with 1,2‐dibromoethane, 1,4‐dibromobutane and 1,5‐dibromopentane results in the formation of (bromoalkyl)phenalene derivatives. These derivatives undergo ring closure when treated with base to spiro[cyclopropane‐1,1′‐[1H]phenalene] (2), spiro[cyclopentane‐1,1′‐[1H]phenalene] (4) and spiro[cyclohexane‐1,1′‐[1H]phenalene] (5). Reaction of 1− with 1,3‐dibromopropane gives a 1:1 mixture of 1,2,3,5‐tetrahydropyrene (3a) and 1,2,3,6‐tetrahydropyrene (3b), both of which can easily be dehydrogenated to pyrene.Photochemical reactions of spiro[cycloalkanephenalenes] 2, 4 and 5 are discussed. The introduction and photochemical opening of a spirocyclopropane ring in phenalene results in the formation of 1,2‐dihydro‐4H‐cyclopenta[cd]phenalene (6), a compound with a fused five‐membered ring. The construction of pyrene and cyclopenta[cd]phenalene skeletons starting from phenalene represents a new approach in the synthesis of polycyclic aromatic hydrocarbons and their derivatives.
Unprecedented ring cleavage in the reaction of 1‐methyl‐3‐phenacyl benzimidazolium ylide with diethyl azodicarboxylate
Authors: Sepúlveda‐Arques José , Arbiol Eva Romero , González Rosende M. Eugenia , Lápez‐Rodriguez Matias , Afonso Ricardo Pérez 
Published: September 2010

AbstractThe reaction with diethyl azodicarboxylate (DEAZD) of different cycloimmonium ylides derived from pyridinium, quinolinium, isoquinolinium and 1‐methylbenzimidazolium bromides (3, 4, 5 and 6) yielded 3‐substituted tetraazapentenes (2). In the special case of 1‐methyl‐3‐phenacyl‐benzimidazolium bromide (6a), the ring cleavage compound N‐[1‐[(ethoxycarbonyl)amino]‐2‐oxo‐2‐phenylethylidene]‐N‐formyl‐N‐methyl‐1,2‐benzenediamine (7a) was obtained. Its structure was established by X‐ray crystallography.
A convenient iodonium‐ion‐assisted synthesis of an immunologically active tetrameric β (1→5)‐linked D‐galactofuranoside from the extracellular polysaccharide of Aspergillus and Penicillium species
Authors: Zuurmond H. M. , van der Klein P. A. M. , Veeneman G. H. , van Boom J. H. 
Published: September 2010

AbstractThe non‐terminal glycosyl donor, ethyl 2,3‐di‐O‐benzoyl‐5‐O‐(chloroacetyl)‐6‐O‐pivaloyl‐1‐thio‐α‐D‐galactofuranoside, could be used, with the promoter N‐iodosuccinimide and catalytic trifluoromethanesulfonic acid, for the preparation of β‐D‐Galf‐(1→5)‐β‐D‐Galf‐(1→5)‐β‐D‐Galf‐(1→5)‐β‐D‐Galf‐OMe.
Tuning of tantalum alkylidene reactivity with a terdentate aryl amine ligand: Synthesis, structure and reactivity of [TaCl2{C6H3(CH2NMe2)2‐2,6}(CHBut)]
Authors: Abbenhuis Hendrikus C. L. , Grove David M. , van Koten Gerard , van der Sluis Paul , Spek Anthony L. 
Published: September 2010

AbstractThe terdentate aryldiamine ligand in the aryltantalum(V) alkylidene complex [TaCl2{C6H3(CH2NMe2)2‐2,6}(CHBut)] (1) controls alkylidene reactivity in a range of metal‐mediated Wittig reactions. An X‐ray diffraction study of (1) shows that the hexacoordinate tantalum centre has a very irregular ligand array in which the aryldiamine ligand adopts a new facial N,C,N coordination mode.
Substituent effects. 13. Anomalous dissociation constants in water‐organic solvent mixtures: Alicyclic and aliphatic carboxylic acids
Authors: Hoefnagel A. J. , Wepster B. M. 
Published: September 2010

AbstractThe effects on pK of 3‐, 4‐, and 3,5‐(di)alkyl groups in all‐equatorial cyclohexane‐carboxylic acids are examined in detail. They show quantitatively the same anomalies as in the benzoic acids. Similar characteristics have been found for cyclohexanecarboxylic acids with carboxyl axial, for cyclohexaneacetic acids, β‐tert‐butylpropionic acid, γ‐tert‐butylbutyric acid, and trans‐2‐(trimethylsilyl)cyclohexanecarboxylic acid. Substituent effects from the 2 and α positions usually show the presence of additional factors.
Photochemistry of α‐oxo oximes. Part 10: Photochemistry of three cyclic α‐oxo oxime methyl ethers and their acyclic analogue at λ 254 nm
Authors: Buys Theo S. V. , Cerfontain Hans , Geenevasen Jan A. J. , Stunnenberg Frank 
Published: September 2010

AbstractThe (E)‐ and (Z)‐isomers of the 3,3,n,n‐tetramethyl‐2‐(methoxyimino)‐1‐cycloalkanones (n = 5 to 7) (3a‐c) and their acyclic analogue (Z)‐4‐(methoxyimino)‐2,2,5,5‐tetramethyl‐3‐hexanone [(Z)‐4] have been irradiated at λ 254 nm in acetonitrile as solvent in order to study the influence of ring size on product formation. The dependence of product composition on irradiation time revealed that the (E)‐isomers of 3a‐c undergo both E‐Z isomerization and photodecomposition, whereas the (Z)‐isomers undergo only Z‐E isomerization. The primary step in photodecomposition is homolysis of the NO bond. The observed products result from the various possible reactions of initially formed methoxy and cyclic iminyl radicals 17, cyanoacyl radicals 18 formed by ring opening of 17, cyanoalkyl radicals 19 formed from 18 by decarbonylation and cyclopentaniminyl radical 20b, formed by cyclization of the 5‐cyano‐2‐hexyl radical 19b. Mechanisms for the formation of the various products are proposed and the relative importance of the various steps is discussed, also in relation to the results obtained using carbon tetrachloride as radical scavenger.Irradiation of (Z)‐4 at λ 254 nm leads to decomposition with formation of 2,2‐dimethylpropanenitrile, methanol, isobutane and isobutene.
Electrochemical reduction of benzyl chloride catalyzed by a hetero‐dinuclear complex
Authors: van Veggel Frank C. J. M. , Verboom Willem , Reinhoudt David N. , Bos Martinus 
Published: September 2010

AbstractThe co‐complexed Ba2+ cation in the hetero‐dinuclear complex 1 stabilizes the carbon‐nickel bond that is formed in the reductive coupling of benzyl chloride and 1; the “PhCH2NiII/Ba2+” intermediate reacts with CO2 or acetic anhydride.
1‐Aryl‐2,2‐dimethyl‐1,3‐propanediols as chiral auxiliaries. Acetal formation with α,β‐unsaturated aldehydes and analysis of the stereochemistry of cyclopropanation
Authors: Ebens Rijko , Kellogg Richard M. 
Published: September 2010

AbstractOptically pure 1‐aryl‐ (phenyl and 2‐chlorophenyl) 1,3‐propanediols, 1a and 1b, condense smoothly with aldehydes to provide the corresponding cyclic acetals 3. Except in cases that the aldehyde is substituted at the α‐carbon atom, a single product is obtained. With the aid of 2D‐NMR the stereochemistry was established to be that with the aldehyde substituent as well as the aryl group equatorial in the favored chair form.The condensation products with some α,β‐unsaturated aldehydes were subjected to cyclopropanation with diiodomethane/diethylzinc. Reactions proceeded in good yields. Deprotection was achieved by ozonolysis. The cyclopropanecarboxylic acids 6 were obtained in 34‐67% yields and in enantiomeric excesses ranging from 21‐78%.A stereochemical rationalization of the results is given.
Nucleophilic substitution in diphenylmethyl derivatives. I. Formolysis of diarylmethyl derivatives: An α‐substituent effect
Authors: Strazzolini Paolo , Giumanini Angelo G. , Verardo Giancarlo 
Published: September 2010

AbstractThe reactions of formic acid with and without addition of sodium formate with diphenylmethanol (4) and chlorodiphenylmethane (3) were compared to those with hydroxydiphenylacetic (benzilic) acid (12a) and chlorodiphenylacetic acid (14a). Formic acid did not favour any SNl‐type reaction on 4, but a strong catalysis by iodide ion was observed. Sodium formate rapidly performed the substitution of the chlorine in 3. A similar outcome was obtained with chloro acid 14a, but the rationalization of the results is different. Chloro acid 14a and its methyl ester 14b were prompt to react, but the equilibria were shifted to α‐formyloxy products 13 only by the addition of HCOONa. HCOOH was unable to perform any reduction on either 3 and 4 or 12a and 14a, a fact which was taken as evidence for concerted substitution mechanisms on ion pairs or betaine 15. Mechanistic implications are drawn.
Comparison of flexibly and rigidly bridged donor‐acceptor systems; solvent induced switching between folded and extended emissive charge‐transfer states
Authors: Scherer T. , Willemse R. J. , Verhoeven J. W. 
Published: September 2010

AbstractAniline and naphthalene chromophores were linked by either a flexible trimethylene chain (in 1) or a semirigidly extended piperidine ring (in 2). While 1 undergoes photoinduced intramolecular electron transfer in all solvents 2 does so only in more polar solvents, indicating that solvent stabilization is required to make this process feasible at the donor‐acceptor distance imposed in 2. In both 1 and 2 charge recombination is accompanied by exciplex‐type emission which, in polar solvents, appears to stem from a conformationally extended conformation devoid of extensive direct overlap between the chromophores.
Improved synthesis and application of lanthanide 1,4,7,10‐tetrakis(phosphonomethyl)‐1,4,7,10‐tetraazacyclododecane complexes Ln(DOTP)
Authors: Swinkels Dorine W. , Tesser Godefridus I. , van Duynhoven John P. M. , Hilbers Cornelis W. 
Published: September 2010

AbstractComplexes of lanthanides with 1,4,7,10‐tetrakis(phosphonomethyl)‐1,4,7,10‐tetraazacyclododecane (DOTP) were synthesized for use as shift reagents in a study on the three‐dimensional structure of the gene‐5 protein encoded by Coli‐phage M13. The detailed synthesis is an improvement of methods scattered throughout the literature on three main aspects, and involves a series of three steps. The first step consists of condensation of diethylenetriamine and diethanolamine, yielding the twelve‐membered ring 1,4,7,10‐tetraazacyclododecane (“cyclen”). Ring closure was performed by reaction of N‐(4‐toluenesulfonyl)diethanolamine bis‐4‐toluenesulfonic ester (the synthesis of which was improved), and the disodium salt of tris(4‐toluenesulfonyl)diethylenetriamine. Following hydrolysis, a simplified work‐up procedure was devised. Subsequently, in the second step, phosphonomethyl groups were introduced in the amino functions by condensation with formaldehyde and phosphorous acid to give DOTP. Since DOTP failed to crystallize spontaneously, the previously described work‐up procedure was modified. In the third step, a lanthanide ion (Ln3 +) was added to a small excess of DOTP at 80 °C and pH 8‐9. The identity of each desired Ln(DOTP) complex was determined by: (1)1H NMR and 31PNMR spectroscopy and (2) lanthanide ion fluorescence experiments. Preliminary 1H NMR studies were performed to determine the activity of the Ln(DOTP) complexes as shift reagents for the gene‐5 protein.
Enzymatic hydrolysis and esterification. Routes to optically pure cyclopentanols
Authors: Seemayer R. , Schneider M. P. 
Published: September 2010

AbstractUsing an esterhydrolase from Pseudomonas sp. (SAM II), a series of optically pure cyclopentanols 1‐4 was prepared by enzymatic hydrolysis of their corresponding acetates. Using the same enzyme, these cyclopentanols were esterified by enol esters as acyl donors. Due to identical stereochemical recognition in both reaction modes, opposite pairs of enantiomeres were obtained.
(Bio)dimerisation of unsaturated fatty acids
Authors: Colja N. , Laane M. , Cross Graham A. , Beindorff Chriiaan , Klooerman Jan , Haase K. Dieter 
Published: September 2010

AbstractA comparison has been made between an enzymatic and a chemical route to dimeric fatty acids, using (poly)unsaturated fatty acids as starting material, with respect to mechanism, types of structures generated, yield, and costs. For bioconversion, the enzyme lipoxygenase extracted from soya‐bean pellets was used, whereas for the chemical process the clay‐catalysed route was followed. The enzymatic dimerisation proceeds via a radical mechanism and is more selective, but less co effective and productive than the clay‐catalysed reaction in which carbenium ions are involved.
Chemo‐enzymatic synthesis of rosmarinic acid
Authors: Pabsch K. , Rao N. N. , Wandrey C. , Petersen M. , Alfermann A. W. 
Published: September 2010

Abstract(R)‐(+)‐3‐(3,4‐Dihydroxyphenyl)lactic acid was produced in an enzyme membrane reactor with an optical purity higher than 99%. Complete reactor modelling of the process was done and the theoretically evaluated data was verified by a continuous experiment with space‐time yields more than 1000g/(l·d).For the synthesis of CoA‐activated caffeic acid, a new method was found to prepare the ester via the caffeic acid imidazolide.In a batch experiment, it was shown that enzymatically prepared (R)‐(+)‐3‐(3,4‐dihydroxyphenyl)‐lactic acid and chemically synthesized CoA caffeic ester were converted to rosmarinic acid by an enzyme isolated from Coleus blumei cell cultures.
Plasmid‐based, D‐aminopeptidase‐catalysed synthesis of (R)‐amino acids
Authors: Asano Yasuhisa , Kishino Katsuhiko , Yamada Akiko , Hanamoto Sawako , Kondo Kiyosi 
Published: September 2010

AbstractThe gene for D‐aminopeptidase from Ochrobactrum anthropi SCRC Cl‐38 was cloned in Escherichia coli JM109. An expression plasmid pCl38DP (4.5 kb) was constructed. The amount of the enzyme in a cell‐free extract of E. coli JM109/pCl38DP was elevated up to 288000 units/liter culture, which is about 3600‐fold over that of O. anthropi SCRC Cl‐38. It was calculated that the enzyme comprised about 30% of the total extractable cellular protein. The intact cells of the E. coli transformant were used as a catalyst for (R)‐stereospecific hydrolysis of several racemic amino amides HCl. Complete hydrolysis of (R)‐alanine amide was achieved in a short time (4½h) from 5.0M racemic alanine amide HCl using cells of the E. coli transformant. The concentration of (R)‐alanine reached 220 g/l. The cells or the cell‐free extract catalyzed the synthesis of (R)‐2‐aminobutyric acid, (R)‐methionine, (R)‐norvaline and (R)‐norleucine from their amides in a similar manner.
Enzymes in reversed micelles: 4. Theoretical analysis of a one‐substrate/one‐product conversion and suggestions for efficient application
Authors: Verhaert Raymond M. D. , Hilhor Riet 
Published: September 2010

AbstractA detailed analysis of the conversion of polar and apolar substrates in an heterogeneous medium is given. The enzyme is assumed to follow the mechanism: E + S⇌ES⇌E + P. The effects of various parameters, both enzymic and those of the microemulsion, are presented. In an extension to the model presented earlier, analysis of this simplified case reveals why a large difference is observed between the Km in aqueous solution and its value in microemulsions, suggesting increased affinity of the enzyme for a hydrophilic substrate and decreased affinity for an apolar substrate. It also demonstrates why, in contrast to studies in aqueous solutions, the rate constant of the reverse reaction (k‐2) affects the initial rate of the reaction in microemulsions. Furthermore, it is explained that the bell‐shaped relationship between the initial reaction rate and the water content of the microemulsion can depend on the value of the rate constant of the reverse reaction and on the relationship between the radius of the micelle and the molar ratio of detergent to water (w0) in the system. The model presented here predicts that bell‐shaped curves will only be observed in the conversion of substrates which are, at lea partially, confined to the water pool of the microemulsion. In order to illustrate the dependence of the rate of the reaction on the composition of the microemulsion, the example of δ‐chymotrypsin was chosen. Using this example, the effects of micellar parameters not accessible to systematic experimental variation can be calculated. The results of this analysis show that detailed knowledge of both microemulsion and enzymic parameters is necessary for an adequate description of the reaction rate. Based on the results of this analysis, advice to optimize the enzymatic conversion of both hydrophilic and hydrophobic substrates in heterogenic media is presented.
Enantioselective enzymatic catalysis.:1. A novel method to determine the enantiomeric ratio
Authors: Jongejan Jaap A. , Tol J. Bert , van Tol A , Geerlof Arie , Duine Johannis A. 
Published: September 2010

AbstractThe enantioselective properties of a large number of enzymes are conveniently characterized by the enantiomeric ratio, E = (kcat/KM)s/(kcat/KM)R. Chen and coworkers [Chen et al., J. Am. Chem. Soc. 104, 7294‐9 (1982)] have shown that the value of E can be obtained by measuring the enantiomeric excess, ee, as a function of the degree of conversion, ξ, in kinetic resolutions of a racemic substrate.We noticed that determination of E from ee = f(E, ξ) is not practical when: (a) low amounts of enzyme or substrate are available; (b) analytical procedures for the determination of ee values of substrates or products are cumbersome or inaccurate; (c) complications arise from maturation of reaction mixtures. Direct evaluation of E from the kinetic parameters, on the other hand, requires both enantiomers to be available in enantiomerically pure form.We show that the initial reaction rates for mixtures of enantiomers at fixed substrate concentration under otherwise identical conditions, are related by:

(vs, vR and vx represent the initial reaction rate of homochiral S‐enantiomer, homochiral R‐enantiomer and mixtures with (molar) fraction x of S‐enantiomer, respectively). Analytical procedures for the determination of E, vs and vR by this approach are presented. The merits are demonstrated for the lipase‐catalysed kinetic resolution of racemic glycidol ester and for the resolution of racemic alcohols by a quinoprotein dehydrogenase and an NAD‐dependent dehydrogenase.