bluuebunny/crossref_metadata_2025_split huggingface dataset:
α‐Melanotropin Labelled at its Tyrosine2 Residue: Synthesis and Biological Activities of 3′‐Iodotyrosine2‐,3′‐125Iodotyrosine2‐,3′,5′‐Diiodotyrosine2‐, and (3′,5′‐3H2)tyrosine2‐α‐Melanotropin, and of Related Peptides
Authors: Eberle Alex , Hübscher Willy 
Published: December 2004

Abstractα‐MSH was labelled at its tyrosine2 residue with tritium and iodine. Several synthetic routes were investigated by preparing 13 precursor or mode compounds and 4 different labelled products (via about 40 intermediates). Their melanotropic activity was determined with an in vitro frog skin assay and, for some of the compounds, with a tyrosinase assay. The tritiation was performed on [Tyr(I2)2]α‐MSH by catalytic halogen/tritium exchange, yielding α‐MSH of high specific radioactivity (34 Ci/mmol) and full biological activity. Iodination was studied in detail using five different techniques. An equimolar chloramine T procedure proved to be the most convenient and reproducible method, resulting in monoiodinated α‐MSH containing 99% of the label in position 2. The biological activity was 50% that of α‐MSH; the specific radioactivity, determined in a competitive binding assay with a highly specific α‐MSH antiserum and [Tyr(I)2]α‐MSH as competitor, was 1530 Ci/mmol. The labelling techniques and the bioligical results are discussed.
The Radical Anion of 1,2‐Diphenylcyclopentene
Authors: Gerson Fabian , Martin William B. , Wydler Christoph 
Published: December 2004

AbstractESR. and ENDOR. studies are reported for the radical anions of 1,2‐diphenylcyclopentene (3) and its di(pe+deuteriophenyl)‐derivative (3‐D10). Comparison of the coupling constants of the phenyl protons in 3\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}. with the analogous values for the radical anions of 1,2‐diphenyl substituted cyclopropene (1) and cyclobutene (2) reveals regular changes in the sequence 1\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, 2\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, 3\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, which are caused by an increasing twist of the phenyl groups about the C(1), C(1′)‐ and C(2), C(1″)‐bonds linking them to the ethylene fragment. Such a twist is shown to be also responsible for the large difference in the coupling constants of the methylene β‐protons in 3\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}. (0.659 and 0.293 mT). It is suggested that ‐ in order to minimize the losses caused by this twist in the π‐delocalization energy ‐ the 2 pz‐axes at the centres 1 and 2 deviate from a perpendicular orientation to the mean plane of the cyclopentene ring. A deviation by 19° from such an orientation is required to account for the observed β‐proton coupling constants in terms of their conventional cos2‐dependence on the dihedral angles θ.
Synthese und Chiralität von (5R, 6R)‐5,6‐Dihydro‐β, ψ‐carotin‐5,6‐diol, (5R, 6R, 6′R)‐5,6‐Dihydro‐β, ε‐carotin‐5,6‐diol, (5S, 6R)‐5,6‐Epoxy‐5,6‐dihydro‐β, ψ‐carotin und (5S, 6R, 6′R)‐5,6‐Epoxy‐5,6‐dihydro‐β,ε‐carotin
Authors: Eschenmoser Walter , Uebelhart Peter , Eugster Conrad Hans 
Published: December 2004

Synthesis and Chirality of (5R, 6R)‐5,6‐Dihydro‐β, ψ‐carotene‐5,6‐diol, (5R, 6R, 6′R)‐5,6‐Dihydro‐β, ε‐carotene‐5,6‐diol, (5S, 6R)‐5,6‐Epoxy‐5,6‐dihydro‐β,ψ‐carotene and (5S, 6R, 6′R)‐5,6‐Epoxy‐5,6‐dihydro‐β,ε‐caroteneWittig‐condensation of optically active azafrinal (1) with the phosphoranes 3 and 6 derived from all‐(E)‐ψ‐ionol (2) and (+)‐(R)‐α‐ionol (5) leads to the crystalline and optically active carotenoid diols 4 and 7, respectively. The latter behave much more like carotene hydrocarbons despite the presence of two hydroxylfunctions. Conversion to the optically active epoxides 8 and 9, respectively, is smoothly achieved by reaction with the sulfurane reagent of Martin [3]. These syntheses establish the absolute configurations of the title compounds since that of azafrin is known [2].
Carotenoids of Rhizobia. IV. Isolation and structure elucidation of the carotenoids of a mutant of Rhizobium lupini
Authors: Beyer Peter , Kleinig Hans , Englert Gerhard , Meister Walter , Noack Klaus 
Published: December 2004

AbstractThe structures of the main carotenoid pigments from the mutant 1‐207 of Rhizobium lupini were elucidated by spectroscopic techniques (UV./VIS., CD., 270 MHz 1H‐NMR., and MS.). Ten carotenoids were identified, namely β,β‐carotene (1), β,β‐caroten‐4‐one (echinenone, 2), β,β‐carotene‐4,4′‐dione (canthaxanthin, 3), (3S)‐3‐hydroxy‐β,β‐caroten‐4‐one ((3S)‐3‐hydroxyechinenone, 4), (2R, 3R)‐β,β‐carotene‐2,3‐diol (5), (3S)‐3‐hydroxy‐β,β‐carotene‐4,4′‐dione ((3S)‐adonirubin, 6), (2R, 3S)‐2,3‐dihydroxy‐β,β‐caroten‐4‐one (7), (2R, 3S)‐2,3‐dihydroxy‐β,β‐caroten‐4,4′‐dione (8), (2R, 3S, 2′R, 3′R)‐2,3,2′,3′‐tetrahydroxy‐β,β‐caroten‐4‐one (9) and the corresponding (2R, 3S, 2′R, 3′S)‐4,4′‐dione (10). Structures 5, 7, 8 and 10 have not been reported before. From the observed carotenoid pattern it is concluded that in this mutant the oxidation to 4‐oxo compounds is favoured compared to the hydroxylation at C(3) and C(2).
Über Pterinchemie. 71. Mitteilung. Trennung der Diastereomeren (6R)‐ und (6S)‐5,6,7,8‐Tetrahydro‐L‐neopterin
Authors: Furrer Hans‐Jürg , Bieri Jost H. , Viscontini Max 
Published: December 2004

Separation of the Diastereomers (6R) and (6S)‐5,6,7,8‐Tetrahydro‐L‐neopterinThe mixture of the diastereomers of the pentaacetylderivative IV of (6RS)‐5,6,7,8‐tetrahydro‐L‐neopterins could be separated by fractional crystallisation in methanol into the diastereomers IV A and IV B. Hydrolysis with hydrochloric acid gives the pure, diastereomeric, (6R)‐ and (6S)‐5,6,7,8‐tetrahydro‐L‐neopterins.
The Radical Anions of Some Substituted [2.2]Paracyclophanes
Authors: Fürderer Peter , Gerson Fabian , Ohya‐Nishiguchi Hiroaki , Böhm Ingrid , Hopf Henning 
Published: December 2004

AbstractThe radical anions of the following substituted [2.2]paracyclophanes have been characterized by ESR. and ENDOR. spectroscopy: 4, 16‐dicyano‐ (o‐2), 4, 12‐dicyano‐ (p‐2), 4,5,12,13‐tetracyano‐ (3) and 4,5,12,13‐tetrakis (alkoxycarbonyl)‐ [2.2]paracyclophanes (4‐R, where R = Me, Et, iPr or tBu is the ester alkyl group); 4,5‐bis(methoxycarbonyl)[2.2]paracyclophane‐12, 13‐dicarboxylic anhydride (5); [2.2]paracyclophane‐4,5:12, 13‐tetracarboxylic bisanhydride (6) and bisimides (7‐R, where R = H, D, Me or Ph is the substituent at the imide N‐atom). Comparison of the hyperfine data for these radical anions with those for analogously substituted derivatives of benzene indicates that the most prominent coupling constants are approximately halved on passing from the latter to the former. Lowering of the symmetry, as a consequence of ion pairing, has been observed for the radical anions 4‐iPr\documentclass{article}\pagestyle{empty}\begin{document}$^{\ominus \atop \dot{}}$\end{document} and 4‐tBu\documentclass{article}\pagestyle{empty}\begin{document}$^{\ominus \atop \dot{}}$\end{document} associated with the counterion K⊕ in 1,2‐dimethoxyethane at 183 K, but not for 4‐Me\documentclass{article}\pagestyle{empty}\begin{document}$^{\ominus \atop \dot{}}$\end{document} and 4‐Et\documentclass{article}\pagestyle{empty}\begin{document}$^{\ominus \atop \dot{}}$\end{document} under the same conditions. This result suggests that the migration of K⊕ between the preferred sited in two equivalent ion pairs is slowed down by the steric hindrance arising from the bulky iPr and tBu ester groups.
Die Cope‐Umlagerung als Prinzip einer repetierbaren Ringerweiterung
Authors: Bruhn Jens , Heimgartner Heinz , Schmid Hans 
Published: December 2004

The Cope Rearrangement, a Reaction for Repeatable Ring ExpansionsStarting with the unsaturated β‐ketoesters of type I, a vinyl group is introduced into the β‐position by 1,4‐addition of vinyl magnesium chloride to give II (Scheme 3). Treatment of the β‐ketoester II with phenyl vinyl sulfoxide in the presence of sodium hydride yields the sulfoxides III, which on thermolysis lead to the α, β‐divinyl ketoesters of type IV via elimination of sulfinic acid (Scheme 3). The Cope‐System IV undergoes rearrangement to V, which is again an unsaturated β‐ketoester. The latter is suitable for a further ring expansion sequence. These reaction steps were carried out with the nine‐, twelve‐ and fifteen‐membered ketoesters 32, 33 and 34, as well as with the open‐chain compound 35 (Table 1). With the cyclohexane derivative 31, ring expansion could not be achieved with the described sequence.
Beitrag zur absoluten Konfiguration der Spermin‐Alkaloide O‐Methylorantin und Aphelandrin. 175. Mitteilung über organische Naturstoffe
Authors: Dätwyler Peter , Bosshardt Herbert , Hesse Manfred , Johne Siegfried 
Published: December 2004

Contribution to the Absolute Configuration of the Spermine Alkaloids O‐Methylorantine and AphelandrineThe absolute configuration of the spermine alkaloid O‐methylorantine (1) isolated from Chaenorhinum minus (L.) WILLK. ET LGE. and Ch. villosum (L.) WILLK. ET LGE. was determined. Besides the difference in the substitution at C(31) (OCH3 versus OH) the constitution of 1 and aphelandrine (2) [6] is the same. This was established by spectroscopic evidence, by isomerization reactions of 2, orantine (4) and their derivatives (Scheme 2), and by degradation reactions of 1 and 4, respectively. The methyl ether 1 of orantine (4), the latter prepared by base catalyzed isomerization from aphelandrine (2), is in all respects identical with the natural O‐methylorantine (1). Orantine (4) is identical (UV., CD., 1H‐NMR. and TLC. evidence) with ephedradine A, recently isolated by Hikino et al. [8], who determined the absolute configuration of ephedradine A by X‐ray analysis. The absolute configuration of aphelandrine (2) was related to the one of 4 by chemical degradation.
Anion Coordination Chemistry: Polyguanidinium Salts as Anion Complexones
Authors: Dietrich Bernard , Fyles Deborah L. , Fyles Thomas M. , Lehn Jean‐Marie 
Published: December 2004

AbstractThe synthesis of a series of polyguanidinium salts of potential interest as anion complexones is described. Among the various synthetic methods investigated, the polyguanidinium salts were found to be most conveniently prepared from polyamines via polynitroguanidine intermediates. The complexation of phosphate and carboxylate anions by these complexones and by related polyammonium salts were studied by analysis of pH‐metric titration data. The ligands studied from relatively stable complexes (log Ks = 2.0–4.0 for PO in water) which also present good selectivities in some cases. Both the stability and the selectivity of complexation are primarily governed by electrostatic forces and thus depend on charge accumulation in the interacting species; structural effects are also observed. Since the binding is primarily electrostatic, polyammonium salts from more stable complexes (at a given charge) than do polyguanidinium salts. However, whereas the complexation properties of the latter are independent of pH, the complexes of the former are observed only in the limited ranges of pH where both the protonated polyamine and the anion of interest can coexist. The polycationic ligands may, in principle, form chelate type anion complexes. Comparison with the corresponding single binding sites reveals an increase in complexation constant of about two or three orders of magnitude; this may be considered as a thermodynamic indication of a chelate effect for the polydentate ligands (by analogy with the well known effects displayed by cation complexones); however, structural data on the formation of chelate ‘rings’ are not yet available. The nature of the complexes and the prospects of anion complexones in various fields are discussed.
Die Synthese von 4‐substituierten Bicyclo[2.2.2]oct‐1‐yl‐p‐nitrobenzolsulfonaten
Authors: Grob Cyril A. , Rich Roland 
Published: December 2004

Synthesis of 4‐Substituted Bicyclo[2.2.2]oct‐1‐yl‐p‐NitrobenzenesulfonatesThe syntheses of the 4‐substituted bicyclo[2.2.2]oct‐1‐yl‐p‐nitrobenzenesulfonates 1a–2s are described.
Mehrkernige Kobaltkomplexe. V. Präparative Herstellung von Tetrakis (äthylendiamin)‐μ‐peroxo‐μ‐amido‐ und μ‐peroxo‐μ‐thiocyanatodikobalt (III)‐Komplexen ausgehend von Tetrakis (äthylendiamin)bis‐(ammin)‐μ‐peroxo‐dikobalt (III)‐tetraperchlorat
Authors: Zehnder Margareta 
Published: December 2004

Polynuclear Cobalt Complexes. V. Preparation of tetrakis (ethylenediamine)‐μ‐peroxo‐μ‐amido and μ‐peroxo‐μ‐thiocyanato‐dicobalt (III) complexes starting from tetrakis (ethylenediamine)bis‐(ammine)‐μ‐peroxo‐dicobalt (III)‐tetraperchlorateRacemic tetrakis (ethylenediamine)‐μ‐peroxo‐μ‐amido‐dicobalt (III) thiocyanate and its corresponding hydroperoxo‐ and superoxo‐complexes have been isolated from [(en)2(NH3)Co(O2)(NH3)(en)2](ClO4)4. A new binuclear peroxo complex containing thiocyanate as bridging ligand was prepared by the same method. The stretching frequencies of the CN‐ and CS‐group as well as the NCS‐bending frequence in the IR. spectrum of [(en)2Co(O2, SCN)Co(en)2](NO3)3 suggest that the μ‐thiocyanato group is N‐bonded (2050, 750, 475 cm−1). A comparison of IR. spectra of known singly and doubly bridged μ‐peroxo complexes is made. Characteristic absorption bands, assignable to ν(OO) and ν(CoO) are given.
Chemie des 2‐Aminospiro[indan‐1,3′‐pyrrolidin]‐Systems
Authors: Strasser Michael , Loosli Hans‐Rudolf , Zardin‐Tartaglia Therese 
Published: December 2004

The chemistry of the 2‐aminospiro[indan‐1,3′‐pyrrolidine]system2‐Aminospir[indan‐1,3′‐pyrrolidines] 1 are easily synthesized from the α‐hydroxyiminoketones 6 and 19 (Schemes 2 and 3, and 6 respectively). Removal of the N‐acetyl group in the intermediate 8 of the trans series induces transposition to the 3a‐aminomethyl‐indano[2,1‐b]pyrrolidine system. The configurations of all compounds have been determined by 1H‐NMR. spectroscopy.
Synthese von [1,2,4]Triazolo [1,5‐a]chinazolinen. Ableitung der Konformation von Substituenten mit Hilfe der 13C‐NMR.‐Spektroskopie
Authors: Heckendorn Roland , Winkler Tammo 
Published: December 2004

Synthesis of [1,2,4]Triazolo[1,5‐a]quinazolines. Assignment of the Conformation of Substituents with the Aid of 13C‐NMR. SpectroscopyThe synthesis of [1,2,4]triazolo[1,5‐a]quinazolines by condensation of 2‐hydrazinobenzoic acid with N‐cyano‐imidates is reported. The preferred conformation of substituents at C (5), e.g. N (CH3)2, N (CH3)NH2, N (CH3)OH, relative to the aromatic system is deduced with the aid of 13C‐NMR. chemical shifts and proton nuclear Overhauser effect experiments.
13C‐ and 1H‐NMR. Assignments for colchicine derivatives
Authors: Hufford Charles D. , Capraro Hans‐Georg , Brossi Arnold 
Published: December 2004

AbstractThe 13C‐NMR. spectra of a number of colchicine derivatives are given comprising examples of the normal series (4→10), iso series (11→16) and colchicine series (17), which were either reported in the literature or obtained by partial synthesis or degradation reactions. The 13C‐NMR. assignments were made by comparisons with known compounds and selective single‐frequency offresonance decoupling experiments. Selective proton decoupling experiments have also allowed assignments of the H—C(11) and H—C(12) protons of the iso and colchicine series.
Struktur von sechs Coleonen (Diterpenen) aus Solenostemon monostachys (P. BEAUV.) BRIQ. (Labiatae)
Authors: Miyase Toshio , Rüedi Peter , Eugster Conrad Hans 
Published: December 2004

AbstractStructures of Six Coleons (Diterpenoids) from Solenostemon monostachys (P. BEAUV.) BRIQ. (Labiatae)The above mentioned African labiate has been investigated for its leaf‐gland pigments. Besides the already known coleons C (1) and H (2), 2a‐formoxy‐coleon C (3), 12β‐O‐acetyl‐coleon Z (7), 12β‐O‐acetyl‐7‐O‐formyl‐7‐O‐desacetyl‐coleon Z (8) and a not separated mixture of 17‐acetoxy‐12β‐O‐acetyl‐coleon Z (9a) and 12β‐O‐acetyl‐17‐formoxy‐coleon Z (9b) have been isolated.
Nucleophile Aminoalkylierung mit Thiopivalamiden
Authors: Lubosch Winfried , Seebach Dieter 
Published: December 2004

Nucleophilic Aminoalkylation with ThiopivalamidesVorläufige Mitt. [1].
Of the twelve thioamides 7a‐e and 8a‐g, only N,N‐dimethylthiopivalamide (7a) could be metallated at the CH‐group in a‐position to the N‐Atom. The reagent 9 thus obtained (Table 1) reacts in high yields with primary haloalkanes, with aldehydes, and with non‐enolizable ketones (Table 2). As shown in Scheme 1, the products can be hydrolyzed to pivalamides, cleaved to secondary amines, or reduced to neopentylamines (see 18/19, 15/equation (4) and (5), and 16/20, respectively).
Globularifolin, A New Acyl Iridoid Glucoside from Globularia cordifolia
Authors: Chaudhuri Ratan K. , Sticher Otto 
Published: December 2004

AbstractSix iridoid glucosides have been isolated from Globularia cordifolia by the combination of open column ‐ and high performance liquid chromatography. The structure of the new compound, named globularifolin, and the identity of the others have been established by chemical transformations and spectral evidence of the compounds and their derivatives.
N,N,N′,N′‐Tetrabutyl‐3,6‐dioxaoctan‐dithioamid, Ionophor mit Selektivität für Cd2+
Authors: Schneider Jürg K. , Hofstetter Peter , Pretsch Ernö , Ammann Daniel , Simon Wilhelm 
Published: December 2004

N,N,N′,N′‐Tetrabutyl‐3,6‐dioxaoctane‐dithioamide, an Ionophore with Selectivity for Cd2+The dioxa‐dithioamide 3 behaves as a highly selective ionophore for Cd2+ in solvent polymeric membranes. It induces cation‐permselectivity in these membranes with a transference number of 1 for Cd(NO3)2‐ and of 2 for CdCl2‐solutions. In the presence of a proton carrier, 3 may be used to selectively pump Cd2+ through membranes by coupling with a pH gradient.
Synthesis of (±)‐4‐Demethoxydaunomycinone by Double Diels‐Alder Additions to 2, 3, 5, 6‐Tetramethylidene‐7‐oxanorbornane
Authors: Bessière Yvonne , Vogel Pierre 
Published: December 2004

AbstractSequential Diels‐Alder additions of methylvinyl ketone and dehydrobenzene to 2, 3, 5, 6‐tetramethylidene‐7‐oxanorbornane (4) yielded the (5, 12‐epoxy‐1, 2, 3, 4, 5, 6, 11, 12‐octahydro‐2‐naphtacenyl) methyl ketone (10) which, in few steps was oxidized to a precursos of (±)‐4‐demethoxydaunomycinone. The preparations of two precursors of anthracyclinones, the (5‐acetoxy‐) and (12‐acetoxy‐1, 2, 3, 4‐tetrahydro‐2‐naphtacenyl) methyl ketones (14, 15) are presented. The synthesis of 6, 13‐epoxy‐6, 13‐dihydropentacene (8) is also reported.
Volumes of Activation for Dimethylsulfoxide and N,N‐Dimethylformamide Exchange with Hexasolvates of Aluminium (III) and Gallium (III) Ions in Deuterionitromethane Solution
Authors: Ammann Claude , Moore Peter , Merbach André E. , McAteer Colin H. 
Published: December 2004

AbstractHigh‐pressure 1H‐NMR. has been used to determine volumes of activation (ΔV#) for solvent exchange with [M(S)6]3+ ion (M = Al(III), Ga(III); S = dimethylsulfoxide (DMSO) and N,N‐dimethylformamide (DMF)) in [2H]3‐nitromethane solution. For Al(III),Δ V# = + 15.6 ± 1.4 (S = DMSO, 358.5 K) and ΔV# = + 13.7 ± 1.2 cm3mol−1 (S = DMF, 354.5 K), whilst for Ga(III), ΔV# = + 13.1 ± 1.0 (S = DMSO, 334.6 K) and ΔV# = +7.9 ± 1.6 cm3mol−1 (S= DMF, 313.8 K). Variable temperature studies over a temperature range of 107.2 K (Al(III)) and 101.1 K (Ga(III)) were carried out for solvent exchange with [M(DMF)6]3+ ions in [2H]3‐nitromethane solution, using stopped‐flow NMR, and conventional linebroadening, and gave ΔH# = 88.3 ± 0.9 and 85.1 ± 0.6 kJ+ mol−1, and ΔS# = 28.4 ± 2.7 and 45.1 ± 1.9 JK−1 mol−1 for Al(III) and Ga(III) ions respectively. All of these results are consistent with dissociative modes of activation.
Carotinoid‐Glycosylester 4. Mitteilung. Synthese von 8′‐Apo‐β‐carotin‐8′‐säure‐(β‐D‐glucosyl)ester und Vitamin‐A‐säure‐(β‐D‐glucosyl)ester
Authors: Pfander Hanspeter , Läderach Manfred , Wittwer Fritz 
Published: December 2004

Carotenoid Glycosyl Esters Synthesis of β‐D‐Glucosyl 8′‐Apo‐β‐carotene‐8′‐oate and β‐D‐Glucosyl Vitamin‐A‐oate (β‐D‐Glucosyl Retionate)β‐D‐glucosyl 8′‐apo‐β‐carotene‐8′‐oate (III) and β‐D‐glucosyl vitamin‐A‐oate (VI) were regio‐ and stereoselectively synthesized in high yields from the N‐acylimidazoles I and IV, respectively, or from the N‐acyltriazoles II and V, respectively, and unprotected β‐D‐glucose, according to the method described for the synthesis of di(β‐D‐glucosyl) 8,8′‐diapo‐carotene‐8,8′‐dioate [1]. It seems that this method can generally be applied for the synthesis of β‐D‐glucosyl esters of polyene carboxylic acids.
Eine einfache Methode zur Herstellung von Benzoxazolen
Authors: Seha Zdenek , Weis Claus D. 
Published: December 2004

A Facile Method for the Synthesis of BenzoxazolesThe preparation of benzoxazoles by a facile one‐pot reaction is reported. The reaction of carboxylic acids with 2‐chloro‐N‐methyl‐Δ1‐pyrrolinium chloride in an excess of N‐methyl‐2‐pyrrolidone afforded carboxylic acid chlorides which were converted subsequently to their 2‐hydroxyanilides by addition of 2‐aminophenols. Cyclization of the 2‐hydroxy‐anilides at elevated temperatures furnished the benzoxazoles in high yield and purity.
Réactions chimiques oscillantes III. Effets de la température et de la composition chimique sur la «période d'induction» des systèmes BrO/Ce4+/Cyclohexanone et BrO/Ce4+/Cyclopentanone
Authors: Farage par Vincent J. , Janjic Désimir 
Published: December 2004

Oscillating Chemical Reactions. III. Effects of the Temperature and Chemical Composition on the ‘Induction Period’ of the BrO/Ce4+/Cyclohexanon and BrO/Ce4+/Cyclopentanon SystemsA study of the influence of the temperature and composition of the BrO/Ce4+/cyclohexanon (S1) and BrO/Ce4+/cyclopentanon (S2) systems has shown a very particular behaviour for τind. for a given ratio α of concentrations:

Moreover, for 0.27 ⩽ α ⩽ 0.32, log1/τind. is no longer a linear function of the inverse of the temperature: a break in the line log1/τind. = f(1/T) occurs.
Eine einfache Allencarbonsäureester‐Synthese mittels der Wittig‐Reaktion
Authors: Lang Robert W. , Hansen Hans‐Jürgen 
Published: December 2004

A Simple Synthesis of Alkyl Allenecarboxylates (Allenic Esters) by the Wittig‐ReactionA simple one‐pot synthesis of variously substituted α‐allenic esters (7–23, cf. Scheme 4) is described. Either of the phosphonium salts 1 and 2 or the phosphoranes 3–6 in methylene chloride (or acetonitrile) when treated with acid chlorides at room temperature in the presence of triethylamine give the corresponding allenic compounds in fairly good yields (cf. Tables 3a and 3b). This procedure shows for the first time, that the Wittig‐reaction with acid chlorides as starting material can also be used for the synthesis of 2‐H‐substituted allenic esters (7–13; for numbering see Scheme 7). The deuterium labeled compounds 26–31 (cf. Scheme 7) are prepared in the same manner. The course of the reaction involves an in situ generation of ketenes which are trapped by the resonance stabilized phosphonium ylides. The thus formed betains readily decompose, already at room temperature, to the anticipated allenes by the well known Wittig‐reaction.
Etude du Comportement Photochimique de quelques Diaryl‐1,3‐triazènes
Authors: Julliard Par Michel , Vernin Gaston , Metzger Jacques 
Published: December 2004

Study of the Photochemical Behaviour of Some Diaryl‐1,3‐triazenesThe photolysis of Diaryl‐1,3‐triazenes gives products whose structures are consistent with a cage recombination process of homolytically formed radicals and subsequent abstraction of hydrogen from the solvent molecules by arylamino radicals. In aromatic solvents, a free‐radical chain process leads to the formation of products resulting from the homolytic substitution on the solvent. Quenching experiments show that singlet and triplet excited states are reactive but that intersystem crossing efficiency is low.
Photochemical Rearrangement of a Steroidal α, β‐Epoxylactam. Photochemical reactions, XII [1]
Authors: Cánovas Antonio , Bonet Juan‐Julio 
Published: December 2004

AbstractThe UV. irradiation of 17β‐hydroxy‐4α, 5α‐epoxy‐2‐azaandrostan‐3‐one (1) yields 17β‐hydroxy‐2‐aza‐10 (5 → 4‐abeo)‐4ζ (H)‐androsta‐3,5‐dione (3).