bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zur Kenntnis des Kohlenstoffringes. 80. Mitteilung [1]. 1,1,6,6‐Tetramethyl‐cyclodecan und seine Derivate
Authors: Cordes C. , Prelog V. , Troxler E. , Westen H. H. 
Published: December 2004

Abstract1,1,6,6‐Tetramethyl‐cyclodecane and various of its derivatives have been synthesized. The influence of geminal methyl groups on the properties of cyclodecane derivatives, especially on their n.m.r. spectra, has been investigated.
Propriétés thermodynamiques des mélanges binaires Énergie libre et entropie de formation des solutions de l'hexadécane dans les isomères de l'hexane
Authors: Fernández‐Garcia J. G. , Guillemin M. , Boissonnas Ch. G. 
Published: December 2004

AbstractVapour pressures were measured at 20°C for the systems composed of hexadecane and the isomers of hexane. Activities and free energies were deduced. From previous measures of the heat of mixing values of the entropy of mixing were obtained. The excess free energies are negative. The excess entropies are positive.
Massenspektrometrie und ihre Anwendung auf strukturelle und stereochemische Probleme CLXVII Langkettige Wasserstoffverschiebung in der Massenspektrometrie
Authors: Brandt R. , Djerassi Carl 
Published: December 2004

AbstractThe mass spectral fragmentation behavior of various α‐substituted tetrahydrofuran derivatives and their deuterium labeled analogs has been examined. It was established that the ester and hydroxy derivatives undergo ring fragmentation associated with long range hydrogen transfer. The mass spectra of the deuterium labeled samples provided evidence that direct hydrogen transfer takes place from positions as far as thirteen or more carbon atoms away from the oxygen function in preference to the McLafferty rearrangement. Examination of the spectra of the deuterium labeled derivatives shed further light on the mechanism of the loss of water from the molecular ion and various fragment ions.
Synthesen in der Isochinolinreihe Synthesen von 7‐Hydroxy ‐6‐methoxy‐2‐methyl‐ 1‐(4‐hydroxy‐3, 5‐dimethoxy‐phenäthyl)‐1, 2, 3, 4‐tetrahydro‐isochinolin, einem wichtigen Zwischenprodukt zur Synthese von Homoapomorphin‐Alkaloiden
Authors: Brossi A. , Van Burik J. , Teitel S. 
Published: December 2004

AbstractPolymethoxylated 1‐phenethyl‐3, 4‐dihydro‐ and ‐1, 2, 3, 4‐tetrahydro‐isoquinolines were selectively demethylated by varying the mineral acid treatment. Under these conditions, the 6‐methoxyl was the most stable, while the 4′‐methoxyl was the most labile. Based on this study and by employing an unprotected phenolic intermediate in the Bischler‐Napieralski cyclization, an efficient, simple and technically feasible synthesis of the diphenol 1, an important intermediate in the synthesis of homoapomorphine alkaloids, was achieved.
Lösungsmittel‐sensibilisierte strahlungschemische Reaktionen II FRIES‐Umlagerungen von Arylestern und Arylamiden [1]
Authors: Belluš D. , Schaffner K. , Hoigné J. 
Published: December 2004

AbstractIn a series of screening experiments p‐tolyl acetate (1a), phenyl benzoate (1b), p‐tolyl benzoate (1c), acetanilide (1d), and 2‐naphthyl acetate (5) have been subjected to γ‐radiolysis in aromatic and saturated hydrocarbon solutions. Qualitatively, the products formed correspond to those observed also with the respective photo‐FRIES reactions, i.e., hydroxy‐ and amino‐aryl ketones due to rearrangements, and products due to homolytic fission into aryloxy and aniline radicals, respectively, were produced.The relatively high G values of conversion in dilute solutions indicate that energy transfer from the solvent is operative. E.g., 0,1 M p‐tolyl acetate (1a) in benzene has a G value of over 0.3 for ortho‐rearrangement to 2a, and of 0.55 for cresol (4a) formation. Kinetic evidence points to different energy requirements of the ortho‐rearrangement and the phenol formation, and to more than one excited state of benzene acting as energy donor. The ratio of the observed rate constants of the energy transfer to self‐quenching in benzene is about 80 1 · mole−1 for the ortho‐rearrangement to 2a. The over‐all reaction is strongly quenched upon addition of p‐terphenyl.A comparison of the quantitative data obtained in this work with available published data reveals differences between benzene‐sensitized runs with γ radiation and photochemical experiments. Thus, the ratios of ortho vs. para and amphi rearrangement, and of homolytic fission vs. rearrangements are higher in the solvent‐sensitized radiolyses.
Synthese und Eigenschaften von [n] (2,5) Pyridinophanen und ihren Derivaten
Authors: Gerlach H. , Huber E. 
Published: December 2004

Abstract[n] (2,5) Pyridinophanes (I) have been synthesized by acid catalyzed cyclization of bis‐(β‐aminovinyl)‐diketones to [n] (2,5) pyridinophan‐n‐ones (V), followed by WOLFF‐KISHNER reduction. The conformational stability of the lower members (n < 12) of the series is shown by reduction of V to diastereomeric [n] (2,5) pyridinophan‐n‐ols (XI). In addition [9] (2,5) pyridinophane (I, n = 9) has been resolved into enantiomers.
(4‐phenyl‐2‐thiazolyl)‐acetone and its enamines: Synthesis and NMR. Spectra
Authors: Govindachari T. R. , Rajappa S. , Nagarajan K. 
Published: December 2004

AbstractThe synthesis of (4‐phenyl‐2‐thiazolyl)‐acetone and its enamines is reported. Their NMR. spectra are discussed.
Zerfall von Diazoniumsalzen in homogener Lösung I: Arylierung von Aromaten mit Benzoldiazonium‐ und p‐Nitrobenzoldiazonium‐fluoroborat in Dimethylsulfoxid Vorläufige Mitteilung
Authors: Kaul B. L. , Zollinger H. 
Published: December 2004

AbstractThe decomposition of two aryldiazonium tetrafluoroborates in homogeneous solution in a mixture of dimethylsulphoxide and benzene or nitrobenzene has been studied quantitatively. The isomer ratios for the arylation of benzene and of nitrobenzene respectively are consistent with a heterolytic substitution mechanism for benzenediazonium tetrafluoroborate, and a homolytic mechanism for p‐nitrobenzenediazonium tetrafluoroborate. The latter compound gives astonishingly high arylation yields under the conditions mentioned.
Abschätzung von Reaktivitäts‐Parametern von Nucleophilen auf Graund der Kern‐Spin‐Spin‐Kopplungskonstanten J1H‐199Hg ihrer Methylquecksilberkomplexe
Authors: Scheffold R. 
Published: December 2004

AbstractThe value of the nuclcear‐spin‐coupling‐constant J1H‐199Hg of methylmecury compounds CH3HgL is related to:
(a) the electrode potential for oxidative dimerisation of L,
(b) the interatomic distances C‐Hg in CH3HgL,
(c) the interatomic distances Hg‐Hg in L‐Hg‐Hg‐L,
(d) the energy of dissociation of CH3HgL into CH3 and HgL,
(e) the logarithms of the stability constants of CH3HgL,
(f) the logarithms of the relative nucleophilic reactivites of L in SN2 reactions at a saturated carbon atom
(g) the proton‐bascicity of L (in series of structurally similar ligands, possessing the same ligating atom, as for example carboxylate anions).
Approximately linear correlations were found between J1H‐199Hg and the values of (a), (e), (f), and (g). It is suggested that the value of the nuclear‐spin‐spin‐coupling‐constant J1H‐199Hg of CH3HgL provides a measure of the relative energy of the occupied frontier orbital of the nucleophile L.
Ein neuer Abbau des Indolalkaloids Kopsin; chemische Korrelierung der Alkaloide vom Kopsin‐ und Pleiocarpin‐Typ mit Minovincin
Authors: Guggisberg A. , Gorman A. A. , Bycroft B. W. , Schmid H. 
Published: December 2004

AbstractA new chemical degradation of (–)‐kopsine is described which completely confirms the structure of this alkaloid. Correlation of (–)‐aspidofractinine, (–)‐pleiocarpine and (–)‐kopsine with (–)‐minovincine establishes the absolute stereochemistry of these bases. It appears that, in contrast to the aspidospermine group, all alkaloids containing the aspidofractinine skeleton possess the same absolute stereochemistry.
Umwandlung von Krötengiften (Bufadienoldien) durch Mikroorganismen IV. 7β‐Hydroxybufalin, 7β‐Hydroxyresibufogenin und 12α‐Hydroxyresibufogenin. 16. Mitteilung über Reaktionen mit Mikroorganismen [1]
Authors: Gsell L. , Tamm Ch. 
Published: December 2004

AbstractBufalin (1) was transformed to 7β‐hydroxybufalin (2) by an aqueous suspension of the mycelium of Absidia orchidis VUILL. (HAGEM.). Incubation of resibuforgenin (9) under the same conditions yielded 12α‐hydroxyresibufogenin (7) and, under changed conditions, another monohydroxylated derivative which possesses most likely the structure of 7β‐hydroxyresibufogenin (10). The corresponding cardenolide 3‐O‐acetyl‐14β, 15β‐epoxy‐14‐anhydro‐digitoxigenin (17) gave both the 7β‐ and the 12α‐monohydroxylated derivatives 18 and 22 and another monohydroxylated product 21 of unknown structure. All microbial transformation products are new.
Notiz über Radikal‐Ionen des 3,6‐Dimethyl‐1,2,4,5‐tetrazins und seines 1,4‐Dihydroderivats
Authors: Gerson F. , Skorianetz W. 
Published: December 2004

AbstractParamagnetic solutions of 3,6‐dimethyl‐1,2,4,5‐tetrazine and its 1,4‐dihydroderivative in aqueous bases and acids have been investigated by ESR. spectroscopy.
Niederdruck‐Oligomerisation von Mono‐Olefinen mit löslichen Nickel/Aluminium‐Bimetallkatalysatoren Teil III. Reaktionskinetische Untersuchungen über die Dimerisation und Trimerisation des Áthylens
Authors: Onsager Olav‐Torgeir , Wang Hagbarth , Blindheim Ulf 
Published: December 2004

AbstractThe kinetics of the di‐ and trimerization of ethylen in organic solvents under the influence of a homogeneous catalyst containing π‐tetramethylcyclobutadiene‐nickeldichloride and a prereacted mixture of ethylaluminiumdichloride and tri‐n‐butylphosphine are reported. The primary reaction product is 1‐butene, which is isomerized to 2‐butene (cis/trans) during the reaction. The C6‐Olefins are formed by the reaction of ethylene with 1‐butene and with the 2‐butenes. The following primary reaction products are obtained: 3‐hexene (cis/trans), 1‐hexene, 2‐ethyl‐1‐butene, 3‐methyl‐1‐pentene and 3‐methyl‐2‐pentene (cis/trans).The effect of other phosphines on the reaction was also studied. The relative composition of the reaction product is strongly dependent upon the amount and the LEWIS base strength of the phosphine present. The results are in accordance with a coordinative mechanism on nickel.
Über die Wirkungsweise löslicher Nickel‐/Aluminium‐Bimetallkatalysatoren auf der Basis von π‐Cyclobutadien‐Nickel‐(II)‐Verbindungen beider Niederdruck‐Oligomerisation von Mono‐Olefinen
Authors: Onsager Olav T. , Wang Hagbarth , Blindheim Ulf 
Published: December 2004

AbstractMixtures of π‐cyclobutadiene‐nickeldihalides and LEWIS acids such as Al(R)nCl3‐n,, n = 1–2, represent very active homogeneous catalysts for dimerization of mono‐olefins. As active cocatalyst may be used LEWIS bases, in particular compounds containing three‐coordinated phosselectivity of the catalytic system has been investigated. The kinetics of the dimerization‐reaction is outlined.The mechanisms of the olefin‐dimerization is best characterized as a «double‐cis‐insertionreaction». The main catalytic activity is thought to be connected either to free positively charged nickel cations or to bimetallic nickel‐aluminium‐complexes, depending on theconditions of reaction, in particular the amount and chemical nature of the cocatalyst.
Untersuchungen über das Verhalten organischer Mischphasen 7. Mitteilung. Dampfdrücke, Dichten und thermodynamische Mischungsfunktionen des binären Systems Cyclohexan‐ Tetrahydrofuran bei 25°
Authors: Arm H. , Bánkay D. 
Published: December 2004

AbstractThe total vapor pressures and the heats of mixing of the system cyclohexane‐tetrahydrofuran were measured at 25°C. The density was used to determine concentrations for the total pressure measurements. The partial pressures, activity coefficients, excess free energies, entropy functions, and excess volumes were calculated.
Zur Synthese von 3‐Desoxy‐aldulosonsäuren
Authors: Baschang Gerhard , Fritz Hans 
Published: December 2004

AbstractThe condensation of 2.4‐ethylidene‐erythrose with the sodium salt of diethyl‐phosphono‐piperidino‐ethylacetate yields an enamino‐lacton V which is converted under mild conditions into an α‐keto ester, 2‐oxo‐3‐desoxy‐gluconic acid, and its quinoxaline derivative.
Synthèse et purification de l'acide (trifluorométhyl‐3‐phénylamino)‐2‐nicotinique (acide niflumique) à Carboxyle [14C], d'activité spécifique élevée
Authors: Colombini C. , Deganello G. , Benakis A. , Strolin‐Benedetti M. 
Published: December 2004

AbstractOn décrit la synthèse de l'acide (trifluoroéthyl‐3‐phénylamino)‐2‐nicotinique (acide niflumique) à carboxyle‐[14C], d'activité spécifique élevée (11 mCi/mmole), et sa purification par chromatographie qui permet d'obtenir une pureté de 99,9%.
Über 1,4‐Di‐äthoxycarbonyl‐cyclohexandion‐(2,3) und daraus erhaltene Phenazinderivate
Authors: Schweizer H. R. 
Published: December 2004

AbstractDas bisher unbekannte 1,4‐Di‐äthoxycarbonyl‐cyclohexandion‐(2,3) wurde durch Kondensation von Diäthyladipat mit Diäthyloxalat in 10% Ausbeute erhalten. Von den beiden Ketogruppen des Dions reagiert im allgemeinen nur die eine. Mit o‐Phenylendiamin bildet sich 1,4‐Di‐äthoxycarbonyl‐2,3,5,10‐tetrahydrophenazin, das sich über die 5, 10‐Dihydroverbindung zum 1,4‐Di‐äthoxycarbonyl‐phenazin dehydrieren lässt. Die Verseifung des letzteren führt zur bisher unbekannten Phenazin‐1,4‐dicarbonsäure. Die Umsetzungen lassen sich auf substituierte o‐Phenylendiamine ausdehnen.
Bemerkung zur vorstehenden Notiz [1] von H. REMBOLD
Authors: Viscontini M. 
Published: December 2004

AbstractDer von Herrn Dr. REMBOLD beanstandete Satz aus meiner Veröffentlichung mit PROVENZALE [2] ist tatsächlich nicht glücklich formuliert. Ich wollte keinesfalls eine polemische Mitteilung schreiben, sondern nur eine génstige Synthese von analysenreinen und stereospezifisch einheitlichen 6‐Polyhydroxyalkyl‐pterinen bekanntgeben. Da ich bis dahin auf viele Schwierigkeiten bei der chromatographischen Reinigung dieser synthetisch hergestellten Substanzen stiess, fasste ich meine Erfahrungen in diesem zu allgemein formulierten Satz zusammen, ohne auf irgendeinen bestimmten Kollegen bezugnehmen zu wollen. Ich habe keinerlei Grund zu bezweifeln, dass Herr Dr. REMBOLD seine biologischen Experimente immer mit ganz reinen Pterinen durchgeführt hat.
Zur Stereochemie der aromatischen CLAISEN‐Umlagerung
Authors: Fráter Gy. , Habich A. , Hansen H.‐J. , Schmid H. 
Published: December 2004

AbstractThe possible transition state conformations (chair (S), boat (W), and twist (T), respectively cross (K) forms) and methods for their determination in the thermal ortho‐CLAISEN rearrangement of allyl aryl ethers are discussed.Crotyl 3,5‐dimethylphenyl ether (11) gives a mixture of 2‐(α‐methylallyl)‐3,5‐dimethyl‐phenol (12) and 4‐crotyl‐3,5‐dimethyl‐phenol (13) on heating in N, N‐diethylaniline. Values of 3 and 31 were obtained for the ratio of 12/13 for trans‐11 and cis‐11, respectively. It therefore follows that both ethers rearrange steroselectively ( > 90%) by the S or W forms of the activated complex.αMethylallyl 6‐alkylphenyl ethers rearrange on heating in various solvents to a mixture of trans‐and cis‐2‐crotyl‐6‐alkyl‐phenols. The amount of the cis‐phenols in the rearrangement products decreases with the increasing bulk of the 6‐alkyl substituent. This result is only obvious if the chair form of the transition state during the rearrangement of these ethers is highly favoured.trans‐Crotyl 2,6‐dimethylphenyl ether (trans‐33) rearranges highly steroselectively (94%) on heating to trans‐4‐crotyl‐2,6‐dimethyl‐phenol (trans‐34). In the case of the corresponding cis ether 33, the rapid cis → trans isomerisation of this ether and the cis/trans ratio of the phenol 34 indicate that the reverse rearrangement of the intermediate ortho‐dienone to the ether 33 and the further rearrangement to 4‐crotyl‐2,6‐dimethyl‐phenol (34) has little stereoselective character.
Assoziation in Lösung. Eine graphische Methode zur Bestimmung von Gleichgewichtskonstanten aus kolligativen Eigenschaften
Authors: Wachter A. H. , Simon W. 
Published: December 2004

AbstractA graphical procedure for the evaluation of association equilibria in solution is given. It consists of families of master plots that are superimposed on a diagram of experimental values (namely practical osmotic coefficient vs. concentration). Different models (dimerisation, multimerisation, chain association) can be tested, and the values of up to two association constants can be read off. Tables of the normalized variables and various examples are presented.
Reaktionen mit Blei(IV)‐acetat, XVI. Eine neuartige Umwandlung von 2‐Acetoxy‐3‐oxo‐4,5‐epoxy‐steroiden
Authors: Mihailović M. Lj. , Foršek J. , Lorenc Lj. , Maksimovic Z. , Fuhrer H. , Kalvoda J. 
Published: December 2004

AbstractTreatment of 3‐oxo‐4, 5‐oxido steroids with lead tetraacetate results in acetoxylation in the 2α‐position as could be shown by independent synthesis of the acetoxylated compounds. The products of this reaction rearrange even under very mild conditions (chromatography on silicagel or alumina) to the corresponding 2,3‐dioxo‐Δ4 compounds. The influence of structure and conformation of the various intermediates on their NMR.‐spectra is discussed. A mechanism for this new transformation is proposed.
Theviridosid, ein Iridoid‐glucosid aus Thevetia peruviana (PERS.) K. SCHUM. (Thevetia neriifolia JUSS.). Vorläufige Mitteilung
Authors: Sticher O. , Schmid H. 
Published: December 2004

AbstractFrom stem bark of Thevetia peruviana a new iridoid glucoside, theviridoside was isolated. Its structure II was established by chemical degradations and spectroscopic methods.
Sur la composition de l'arôme de thé. III. Identification de deux cétones apparentées aux ionones
Authors: Müggler‐Chavan F. , Viani R. , Bricout J. , Marion J. P. , Mechtler H. , Reymond D. , Egli R. H. 
Published: December 2004

AbstractLa triméthyl‐2, 6, 6‐hydroxy‐2‐cyclohexanone et l'époxy‐5, 6‐ionone ont été identifiées dans l'arǒme de thé noir.
Expression and transport function of the glutamate transporter EAAC1 in Xenopus oocytes is regulated by syntaxin 1A
Authors: Zhu Yani , Fei Jian , Schwarz Wolfgang 
Published: December 2004

AbstractThe function of several membrane proteins is regulated by interaction with the SNARE protein syntaxin 1A; this includes regulation of GAT1, the transporter for the dominating inhibitory neurotransmitter γ‐aminobutyric acid (GABA). Here we demonstrate that also EAAC1, the transporter for the dominating excitatory neurotransmitter, is down‐regulated by interaction with syntaxin 1A. This is shown by coexpression of EAAC1 and syntaxin 1A in Xenopus oocytes. Total EAAC1 expression is not significantly affected by the coexpression of syntaxin 1A, but more proteins become targeted to the membrane as demonstrated by biotinylation. Colocalization by coimmunoprecipitation suggests direct interaction between the two proteins. In contrast to the number of transporters, the glutamate transport activity becomes reduced, and even stronger inhibition is observed for the EAAC1‐mediated conductance uncoupled from glutamate translocation. We conclude that the interaction of syntaxin 1A with EAAC1 particularly disrupts the structure of the conductance pathway of EAAC1. © 2004 Wiley‐Liss, Inc.
A data programme for population analysis of crystal‐band structures
Authors: Flodmark Stig 
Published: December 2004

AbstractAn electronic‐computer programme has been written by the author for calculations of energy bands in the tight‐binding approximation. This programme has been applied to crystals of α zirconium with and without dissolved oxygen. The resulting energy bands and orbital distributions represent an enormous amount of numerical data. Another programme has now also been written by the author for population analysis of the occupied bands. This programme will reduce the resulting output considerably, and only occupied bands are represented in a number of directions in k space. The occupation numbers are summed up for orbitals with equal quantum numbers l and |m|, and are found for each band as a function of k.
Zur eindeutigkeit der darstellungen von energiehyperflachen
Authors: Preuss H. 
Published: December 2004

AbstractThe first part of this paper gives an introduction of different kinds of atomic associations. Furthermore it will be shown that partial systems of united atoms are not only described by their nuclear‐charge number, but additionally by their number of electrons. Both characteristics of a partial system of atomic associations may lead to an apparent multiple‐valuedness in the transitions between atomic associations. It is shown that the multiple‐valuedness of the atomic associations can be understood and eliminated within the Born–Oppenheimer‐approximation, which leads to the concept “energyhypersurface”. An example is given by the system {He, H, H, H}+.
Electrostatic corrections to extended Hückel theory
Authors: Carbó R. , Fornos J. M. , Hernández J. A. , Sanz F. 
Published: December 2004

AbstractAn electrostatic correction to the energy of the EH method is deduced from the Hartree energy. A recent correction, due to Anderson and Hoffmann, is easily deduced as a particular case. Some calculations show how the correction can improve the description of stretching problems by EH calculations but poor results are obtained in bending and torsion problems.
Diagrammatic perturbation theory: Potential curves for the ground state of the carbon monoxide molecule
Authors: Wilson Stephen 
Published: December 2004

AbstractDiagrammatic many‐body perturbation theory is used to calculate the potential energy function for the X1 σ+ state of the CO molecule near the equilibrium nuclear configuration. Spectroscopic constants are derived from a number of curves which are obtained from calculations taken through third order in the energy. By forming [2/1] Padé approximants to the constants we obtain: re = 1.125 Å (1.128 Å), Be = 1.943 cm−1 (1.9312 cm−1), aBe = 0.0156 cm−1 (0.0175 cm−1), We = 2247 cm−1 (2170 cm−1), WeXe = 12.16 cm−1 (13.29 cm−1), where the experimental values are given in parenthesis.
PCILO calculations on hydrogen bonded complexes
Authors: Lochmann R. 
Published: December 2004

AbstractThe PCILO method was used to study systematically systems with the following types of intermolecular hydrogen bonds: . In all cases the PCILO method gives a correct description of the stabilization energies in a good agreement with reliable ab initio results. The PCILO calculated equilibrium distances are only somewhat smaller than the corresponding experimental or ab initio values. Qualitatively, also, the changes in the charge distributions are in accordance with the results of ab initio calculations.