bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Diels‐Alder Reactivity of 2,3,5,6,7,8‐Hexamethylidenebicyclo [2.2.2]octane (‘[2.2.2]Hericene’). Force‐field calculations of exocyclic dienes as a moiety of bicyclic skeletons
Authors: Pilet Olivier , Birbaum Jean‐Luc , Vogel Pierre 
Published: December 2004

The [2.2.2]hericene (6), a bicyclo[2.2.2]octane bearing three exocyclic s‐cis‐butadiene units has been prepared in eight steps from coumalic acid and maleic anhydride. The hexaene 6 adds successively three mol‐equiv. of strong dienophiles such as ethylenetetracarbonitrile (TCE) and dimethyl acetylenedicarboxylate (DMAD) giving the corresponding monoadducts 17 and 20 (k1), bis‐adducts 18 and 21 (k2) and tris‐adducts 19 and 22 (k3), respectively. The rate constant ratio k1/k2 is small as in the case of the cycloadditions of 2,3,5,6‐tetramethylidene‐bicyclo [2.2.2]octane (3) giving the corresponding monoadducts 23 and 27 (k1) and bis‐adducts 25 and 29 (k2) with TCE and DMAD, respectively. Constrastingly, the rate constant ratio k2/k3 is relatively large as the rate constant ratio k1/k2 of the Diels‐Alder additions for 5,6,7,8‐tetramethylidenebicyclo [2.2.2]oct‐2‐ene (4) giving the corresponding monoadducts 24 and 28 (k1) and bis‐adducts 26 and 30 (k2). The following second‐order rate constants (toluene, 25°) and activation parameters were obtained for the TCE additions: 3+TCE→23: k1 = 0.591±0.012 mol−1·l·s−1, ΔH≠=10.6±0.4 kcal/mol, and ΔS≠ = −24.0±1.4 cal/mol·K (e.u.); 23+TCE→25: k2=0.034±0.0010 mol−1·l·s−1, ΔH≠ = 10.6±0.6 kcal/mol, and ΔS≠ = −29.7±2.0 e.u.; 4+TCE→26: k1 = 0.172±0.035 mol−1·l·s−1, ΔH≠ 11.3±0.8 kcal/mol, and ΔS≠ = −24.0±2.8 e.u.; 24+TCE→26: k2 = (6.1±0.2)·10−4 mol−1·l·s−1, ΔH≠ = 13.0±0.3 kcal/mol, and ΔS≠ = −29.5±0.8 e.u.; 6+TCE→17: k1 = 0.136±0.002 mol−1·l·s−1, ΔH≠ = 11.3±0.2 kcal/mol, and ΔS≠ = −24.5±0.8 e.u.; 17+TCE→18: k2 = 0.0156±0.0003 mol−1·l·s−1, ΔH≠ = 10.9±0.5 kcal/mol, and ΔS≠ = −30.1 ± 1.5 e.u.; 18+TCE→19: k3=(5±0.2) · 10−5 mol−1 mol−1 ·l·s−1, ΔH≠ = 15±3 kcal/mol, and ΔS≠ = −28 ± 8 e.u. The following rate constants were evaluated for the DMAD additions (CD2Cl2, 30°): 6+DMAD→20: k1 = (10±1)·10−4 mol−1 · l·s−1; 20+DMAD→21: k2 = (6.5±0.1) · 10−4 mol−1 ·l·−1; 21+DMAD→22: k3 = (1.0±0.1) · 10−4 mol−1 ·l·s−1.The reactions giving the barrelene derivatives 19, 22, 26 and 30 are slower than those leading to adducts that are not barrelenes. The former are estimated less exothermic than the latter. It is proposed that the Diels‐Alder reactivity of exocyclic s‐cis‐butadienes grafted onto bicycle [2.2.1]heptanes and bicyclo [2.2.2]octanes that are modified by remote substitution of the bicyclic skeletons can be affected by changes inthe exothermicity of the cycloadditions, in agreement with the Dimroth and Bell‐Evans‐Polanyi principle.Force‐field calculations (MMPI 1) of 3, 4, 6 and related exocyclic s‐cis‐butadienes as a moiety of bicyclo [2.2.2]octane suggested single minimum energy hypersurfaces for these systems (eclipsed conformations, planar dienes). Their flexibility decreases with the degree of unsaturation of the bicyclic skeleton. The effect of an endocyclic double bond is larger than that of an exocyclic diene moiety.
Photochemisch induzierte Reaktionen von 3‐Amino‐2H‐azirinen
Authors: Dietliker Kurt , Heimgartner Heinz 
Published: December 2004

Photochemically Induced Reactions of 3‐Amino‐2H‐azirinesIrradiation of 3‐(N‐methylanilino)‐2H‐azirines with a mercury low pressure lamp induces the cleavage of the C(2), C(3)‐ring bond thus affording nitrilio‐methanide dipols, substituted by an amino group at C(1). Depending on the substitution pattern at C(3), these intermediates can be trapped by dipolarophiles to yield five‐membered heterocycles with high regioselectivity, or they undergo a 1,4‐H‐shift forming 2‐azabutadiene derivatives. Further, the dipol is protonated at C(1) even by weak CH–acids.
Kreuzkonjugierte Cyanine und Merocyanine aus Salzen 1‐substituierter 2,3‐Dimethylchinoxaline. 3. Mitteilung. Über die Indikatoreigenschaften der Farbbasen und die Tautomerie der konjugaten Farbsäuren
Authors: Schelz Dieter 
Published: December 2004

Crossconjugated Cyanines and Merocyanines, Obtained from Salts of 1‐Substituted 2,3‐Dimethylquinoxalines: On the Properties of the Dye Bases in Acidic MediaUV./VIS. and 1H‐NMR. spectra of the indicator bases 1 in acidic solutions are presented. The solutions of the dye acids N and NN′ (Scheme 2) are in general not stable due to tautomerism. The relative pKa‐values are set in relation to data of equilibria and half‐life periods. The latter ones depend on the substituents and on the acidity of the solutions. An inverse substituent effect observed in protic solvents is ascribed to solvolytic reactions.The dye base 1S (X = SO3Na, R = C6H5) was synthesized starting with chlorobenzene. The cyanines 2 were obtained on treatment of 1 with HClO4 in CH3CN; solutions of 1 in H2SO4, however, yielded on dilution tautomeric salts that were isolated as the perchlorates 3.
The Structure of C‐Alkaloid‐O, a Constituent of Calabash Curare. Part 187. Papers on organic natural products
Authors: Borris Robert P. , Guggisberg Armin , Hesse Manfred 
Published: December 2004

AbstractThe structure of C‐alkaloid‐O (1=his HCL‐salt) was established on the basis of spectral data and comparison with the analogous compound 2, synthesized from a natural product of known absolute configuration. Internally consistent 13C‐NMR. assignments are given for 1, 2, huntrabrine methochloride (4) and its diacetate derivative 5.
Reinigung der D‐Oxynitrilase aus Mandeln mit Hilfe der Affinitäts‐Chromatographie
Authors: Hochuli Erich 
Published: December 2004

A Rapid Purification of D‐Oxynitrilase from Almond Meal by Affinity ChromatographyOxynitrilase from almond meal is capable of catalyzing the stereospecific addition of cyanide to a variety of aldehydes. Thus, the enzyme is potentially useful in the synthesis of optically active cyanohydrins on a preparative scale [1]. As the currently available purification procedures for this enzyme [2] are rather tedious, we have elaborated a simple and rapid procedure based on affinity chromatography. An inhibitor for the enzyme, methyl p‐(3‐aminopropoxy)benzoate (4), has been synthesized and attached covalently to Sepharose 4B as a solid matrix (5). With this affinity gel it was possible to prepare the D‐oxynitrilase in a simple procedure with high yields.
Tetraazamacrocycles lipophiles: Application à l'extraction liquide‐liquide des ions métalliques
Authors: Handel Henri , Muller Frédéric R. , Guglielmetti Robert 
Published: December 2004

Lipophilic Tetraazamacrocycles: Application to Liquid‐liquid Extraction of Metal IonsLiquid‐liquid extraction of Co2+, N2+, Cu2+, Zn2+, Cd2+, Pb2+, and Ag+ by lipophilic tetraazamacrocycles is reported in different solvents. Extraction efficiency is sensitive to the metal ion identity, the cavity size of the macrocycle and the pH of the aqueous phase. The influence of the organic receiving phase and the anion identity is discussed and expressed in terms of donnor‐acceptor concepts. Further‐more, the lipophilic tetraazamacrocycles exhibit high extraction efficiency towards these transition‐ and heavy‐metal ions.
Die Acylierung von 5‐Amino‐1 H‐1, 2, 4‐triazolen. Eine 13C‐NMR.‐Studie
Authors: Winkler Tammo , Kristinsson Haukur 
Published: December 2004

The Acylation of 5‐Amino‐1 H‐1,2,4‐triazoles. A 13C‐NMR. StudyThe acylation of 3‐substituted‐5‐amino‐1 H‐1,2,4‐triazoles (1) with methyl chloroformate or dimethylcarbamoyl chloride yielded mainly 1‐acyl‐5‐amino‐1,2,4‐triazoles (2 and 3). Acylation of 3‐methyl‐, 3‐methoxy‐ and 3‐methylthio‐5‐amino‐1 H‐1,2,4‐triazole (1b, 1c and 1d) with methyl chloroformate gave up to 10% of the 1‐acyl‐3‐amino‐1,2,4‐triazoles. For the unsubstituted 5‐amino‐1,2,4‐triazole (1a), a (1:1)‐mixture of the 3‐ and 5‐isomers 2a and 4 was obtained in dioxane in the presence of triethylamine. No 4‐acylated product was detected in contrast to earlier reports. The structures of the reaction products were determined with the aid of proton coupled 13C‐NMR. spectra using the corresponding N‐methyl‐1,2,4‐triazoles as reference compounds.
The Crystal Structure of Methyl β‐orcinol‐carboxylate (= Methyl 2,4‐dihydroxy‐3,6‐dimethylbenzoate)
Authors: Brehm Lotte , Stoeckli‐Evans Helen , Tabacchi Raphael , Bürgi Hans‐Beat 
Published: December 2004

AbstractThe mono‐arylic compound, methyl β‐orcinol‐carboxylate (I) is one of the principal components of lichens which grow on the oak tree. In the crystal structure of I the molecules are H‐bonded to form sheets separated by 3.56 (5) Å. The carbonyl O‐atom of the ester group and the ortho‐hydroxyl group form a strong intramolecular H‐bond. The IR. spectrum of the solid contains two (O‐‐H)‐stretching frequencies which, by comparison with the spectra of the 4‐methoxy and the 2‐methoxy analogues, can be assigned to one intra‐ and one intermolecular H‐bond.
Synthesis of 2‐Norzizaene and 9,10‐Dehydro‐2‐norzizaene (7,7‐Dimethyl‐6‐methylidenetricyclo[6.2.1.01,5]undec‐9‐ene) via Intramolecular Allyl Cation Induced Cycloaddition
Authors: Hoffmann H. M. R. , Henning Rolf 
Published: December 2004

Abstract7,7‐Dimethyl‐6‐methylidenetricyclo[6.2.1.01,5]undec‐9‐ene (10) has been prepared from allylic alcohol 8 in one step in 16% yield. Selective hydrogenation of 10 with diazene gives the 2‐norzizaenes 1a and 11.
The Calf Intestinal Alkaline Phosphatase. II. Reaction between the metal content and the enzyme activity
Authors: Portmann Plato , Schaller Hubert , Leva Geneviève , Venetz Werner , Müller Thomas 
Published: December 2004

AbstractPure alkaline phosphatase (EC 3.1.3.1; 1500 U/mg) was dialyzed at 4° during 168 h against water, 10−4M EDTA or 10−4M o‐phenanthroline. During the dialysis, samples were periodically removed and analyzed for metal content and activity. The results indicate that 1 mol of native calf intestinal alkaline phosphatase contains 4 g‐atom of zinc and 4 g‐atom of magnesium tightly bound, and that both metal ions are necessary for full enzyme activity. The dialyzed, partially demetallized enzyme could be reactivated by the addition of zinc and/or magnesium salts.
Etudes sur les composés organométalliques. XIX. Synthèse et caractérisation de composés alkoxy (alkyl)titane (IV)
Authors: Meyer Edouard Marc , Jacot‐Guillarmod André 
Published: December 2004

Studies of Organometallic Compounds. Synthesis and Characterization of Some Alkoxy (alkyl)‐titanium(IV) CompoundsAlkoxy(benzyl)titanium and alkoxy(cyclohexyl)titanium compounds are prepared by alcoholysis of tetrabenzyl‐ and tetracyclohexyltitanium. Structural features are investigated by means of 1H‐NMR.
Synthese stereoisomerer Pinanthromboxane und Evaluation der Verbindungen als Plättchenaggregationsinhibitoren
Authors: Bounameaux Yves , Coffey John W. , O'Donnell Margaret , Kling Klaus , Quinn Ronald J. , Schönholzer Peter , Szente André , Tobias Lawrence D. , Tschopp Thomas , Welton Ann F. , Fischli Albert 
Published: December 2004

Synthesis of Stereisomeric Pinanthromboxane Derivatives and Evaluation of the Compounds as Platelet Aggregation InhibitorsStarting from the two enantiomeric myrtenols ((−)‐1 and (+)‐1; cf. Scheme 1), the synthesis of twelve stereoisomeric pinanthromboxane derivatives ((+)‐ and (−)‐10, ‐11, ‐14, ‐15, ‐21 and ‐22) is described (cf. Schemes 1–4). Biological data from the evaluation as platelet aggregation inhibitors (cf. Table 6 and 7), thromboxane synthetase inhibitors (cf. Table 8) and from the assessment as antagonists of leukotriene E4 induced bronchoconstriction (cf. Table 9) are presented.
Untersuchungen der Reaktionsprodukte von Isocyanaten mit Hydroxylamin
Authors: Becker Alfred , Heizler Werner 
Published: December 2004

Investigations of the Products of Isocyanates with HydroxylamineThe reactions of isocyanates with hydroxylamine give rise to several compounds according to the different conditions involved when starting with the primary reaction products, the hydroxy‐ureas. The pure compounds have been isolated. An interesting reaction of N‐phenyl‐N′‐phenylcarbamoyloxyurea with sodium hydroxide has been observed. This compound is converted to 3‐hydroxy‐1, 5‐diphenylbiuret under conditions described.
Preparation of α‐Bromo‐ and α‐Chlorocarboxylic Acids from α‐Amino Acids
Authors: Olah George A. , Shih Joseph , Prakash G. K. Surya 
Published: December 2004

AbstractDiazotization of α‐amino acids in 48:52 (w/w) hydrogen fluoride/pyridine along with excess of potassium halide results in the corresponding α‐halocarboxylic acids in good to excellent yields (Table 1 and 2).
Fragmentation of Homoallylic Alkoxides. Preparation of 1‐(3′‐cyclopentenyl)‐2‐alkanones from 2‐substituted bicyclo[2.2.1]hept‐5‐en‐2‐ols
Authors: Snowden Roger L. 
Published: December 2004

AbstractThe potassium 2‐substituted bicyclo[2.2.1]hept‐5‐en‐2‐alkoxides derived from alcohols 2–9 at 30° in hexamethylphosphoric triamide (HMPA) afford 1‐(3′‐cyclopentenyl)‐2‐alkanones 10–19 via heterolytic C(1), C(2)‐allylic bond cleavage in the substrate alkoxide followed by intramolecular protonation of the resultant transient allylic anion.
Hydroxyphenyl‐1‐methylpyridinium‐jodide als potentielle Reaktivatoren von mit Organophosphor‐Verbindungen vergifteten Acetylcholinesterasen
Authors: Riggio Gaetano , Hopff Wolfgang Herbert , Hofmann Alfred André , Waser Peter Gaudenz 
Published: December 2004

Hydroxyphenyl‐1‐methylpyridinium‐iodide as Potential Reactivators of Acetylcholinesterase Poisoned with Organophosphorus Compounds.It was our aim to reactivate acetylcholinesterase poisoned with sarin.We synthesized 2‐(o‐hydroxyphenyl)‐1‐methylpyridinium‐iodide (9), 2‐(p‐hydroxyphenyl)‐1‐methylpyridinium‐iodide (19) and 4‐(o‐hydroxyphenyl)‐1‐methylpyridinium‐iodide (14) as potential reactivators. All substances showed moderate toxicity against mice; their reactivity potency in vitro and in vivo was negligible.
Notiz zur Synthese von Alkyl‐, Cycloalkyl‐ und Aryl‐(4‐aminophenyl)‐sulfonen
Authors: Courtin Alfred 
Published: December 2004

Syntheses of Some Alkyl‐, Cycloalkyl‐ and Aryl‐(4‐aminophenyl)‐sulfonesSyntheses of (4‐aminophenyl)‐alkyl, ‐cycloalkyl and ‐aryl sulfones 2 were achieved both by alkylation of 4‐(acetylamino)‐benzenesulfinic acid (7) to the corresponding acetanilides 9 followed by hydrolysis and by oxidation of the appropriate (4‐nitrophenyl)‐sulfides 11 to (4‐nitrophenyl)‐sulfones 1 with subsequent Béchamp reduction.
The Intramolecular Ramberg‐Bäcklund Reaction: A Convenient Method for the Synthesis of Strained Bridgehead Olefins
Authors: Becker Konrad B. , Labhart Marco P. 
Published: December 2004

AbstractThe stereochemical aspects of the intramolecular Ramberg‐Bäcklund reaction, i.e. the 1,3‐elimination of hydrogen halide followed by sulfur dioxide extrusion, have been studied on the α‐bromosulfones of the 1‐thiadecalinThroughout this paper ‘1‐thiadecalin’ will be used in place of ‘decahydro‐1‐thianaphthalene’.
series. Whereas the cis,exo‐bromosulfone 23a containing the ideal W‐type arrangement of the reacting atoms undergoes a clean Ramberg‐Bäcklund reaction, the trans,exo‐ and trans,endo‐bromosulfones, 24a and 24b, respectively, lead to an α,β‐unsaturated sulfone by simple 1,2‐elimination of HBr. Application of the Ramberg‐Bäcklund reaction to 9‐bromo‐8‐thiabicyclo[5.2.1]decane‐8,8‐dioxide (17) permits a short synthesis of the Bredt olefin bicyclo[5.1.1]non‐1(8)‐ene (5), which can be isolated but shows the typical high reactivity of other methylene‐bridged (E)‐cyclooctenes.
Cross Conjugated Polyenes Derived from 2‐Vinyl‐butadiene: Electronic States of their Radical Cations, and Triplet Energy
Authors: Bally Thomas , Neuhaus Louis , Nitsche Stephan , Haselbach Edwin , Janssen Johann , Lüttke Wolfgang 
Published: December 2004

AbstractThe doublet states of the radical cations of the cross conjugated polyenes 4,4‐dimethyl‐1‐methylidene‐2,5‐cyclohexadiene 2 and its bis‐derivative 1 have been investigated by photoelectron spectroscopy and by electronic spectroscopy of \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{+\kern-4pt {.} } $\end{document}+, prepared at 77 K in an electron scavenging matrix by γ‐irradiation. Simultaneous consideration of the spectral results shows \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{+\kern-4pt {.} } $\end{document} to be the second hydrocarbon molecular cation (after 2,2‐dimethyl isoindene) which possesses a first excited doublet state (D1) of non‐Koopmans nature (2B3g). The first Koopmans‐type excited state (2B2g) expected from PE. spectroscopy lies, however, very close in energy. In addition T1 of 1 was observed by electron energy loss spectroscopy at 2.0±0.1 eV. Application of the ‘SDT‐equation’ predicts for this state only 1.05 eV; there is at present no reasonable explanation for this failure.
The Crystal Structure of 1,2‐Didehydrocrotalanine Picrate: A Macrocyclic Pyrrolizidine Alkaloid Analogue
Authors: Stoeckli‐Evans Helen , Robins David J. 
Published: December 2004

Abstract1,2‐Didehydrocrotalanine (2) is the first synthetic macrocyclic pyrrolizidine alkaloid analogue to be studied by X‐ray crystallography. The crystal structure was solved by multisolution direct methods and refined by full‐matrix least‐squares to R = 0.036 for 693 reflections. The alkaloid analogue has an 11‐membered macrocycle containing two ester groups with their carbonyl groups nearly antiparallel.
3,3‐Dialkyltriazencarbonsäure‐Derivate durch oxydative Hydro‐Acyl‐Elimination von 3,3‐Dialkyltriazan‐1,2‐dicarbonsäure‐Derivaten
Authors: Egger Notker , Hoesch Lienhard , Dreiding André S. 
Published: December 2004

3,3‐Dialkyltriazenecarboxylic Derivatives by Oxidative Hydro‐Acyl‐Elimination from 3,3‐Dialkyltriazane‐1,2‐dicarboxylic DerivativesThe preparation and some properties of esters and amides of 3,3‐dialkyltriazenecarboxylic acids (6) are described. These novel triazenes 6 were obtained by treatment of diesters, diamides and ester‐amides of 3,3‐dialkyltriazane‐1,2‐dicarboxylic acids (3) with lead tetraacetate, when an elimination of the COOR‐ or the CONHR‐group at N(2) together with the H‐atom at N(1) took place. The precursor triazanes 3 were readily available from the addition of secondary amines 2 to diesters, diamides or ester‐amides of diazenedicarboxylic acid (1). The spectral properties of the triazanes 6, including the 15N‐NMR signals of one example, are compared with those of the triazanes 3. They express the structural features due to conjugation in 3,3‐dialkyltriazenecarboxylic derivatives, including the resistance to rotation around the N(2), N(3)‐bond.
1H‐NMR Spectroscopy of Gold Drugs. High‐Resolution Studies of β‐D‐Thioglucosetetraacetate Phosphine Complexes of Au(I)
Authors: Pregosin Paul S. , Becker Edwin D. 
Published: December 2004

Abstract1H‐NMR data (11.74 Tesla) for the gold(I) complexes [R3P‐Au‐(2,3,4, 6‐tetra‐O‐acetyl‐1‐thio‐β‐D‐glucopyranosido‐S)] (R = Et, Cyclohexyl, C6H5, p‐CH3OC6H4) with sulfur coordination to gold, are reported. The resonances associated with the sugar protons have been assigned although these have similar chemical environments. The coordination chemical shifts, Δδ, for the AuSCH proton are ≈︁ 0.6 ppm, and support S‐coordination to gold.
Conjugative, Exciton and Charge‐Resonance Interactions in D2d‐9,9′‐Spirobifluorene and D2d‐Tetrabenzotricyclo [5.5.0.02,8]dodeca‐3,5,9,11‐tetraene. Photoelectron and Polarized Absorption Spectra
Authors: Spanget‐Larsen Jens , Gleiter Rolf , Haider Rudolf 
Published: December 2004

AbstractPhotoelectron spectroscopy, polarized electronic absorption spectroscopy in stretched polymer sheets, and semiempirical theoretical methods have been applied to investigate the valence electronic structures of the two title compounds 1 and 2, considering fluorene (3) as a reference compound. The results are analyzed in terms of ‘through space’ and ‘through bond’ conjugative effects and exciton and charge‐resonance interactions. Spiro‐conjugation in 1 is found to play a similar role as ‘through bond’ interaction via the cyclobutane ring in 2. In contrast to the results of a recent investigation, exciton coupling is found to be relatively insignificant, while charge‐resonance effects are important. The transition close to 41 000 cm−1 in the absorption spectra of 1 and 2 has no obvious counterpart in the spectrum of 3; it is assigned to a 1E− state with large charge‐resonance character, involving promotion of an electron from the HOMO of one half‐chromophore to the LUMO of the other.
Synthesis of β‐pyrazinyl‐L‐alanine (Paa) and of peptide derivatives
Authors: Petermann Claudia , Fauchère Jean‐Luc 
Published: December 2004

AbstractThe title compound was prepared via a malonic ester synthesis starting with α‐chloromethylpyrazine [2], and ending, after an asymmetric enzymatic hydrolysis of the racemic N‐acetyl‐β‐2‐pyrazinylalanine to the L‐form of the new amino acid. The optical purity was ascertained by 1H‐NMR analysis at 360 MHz of the diastereoisomeric dipeptides L‐pyrazinylalanine‐L‐leucine and D‐pyrazinylalanine‐L‐leucine. Hydrophobic, steric and electronic parameters for its side chain were also estimated, which can be useful for the quantitative study of structure‐activity relationships of biologically active peptide derivatives. The new amino acid could be introduced in the place of phenylalanine in the enkephalin‐like pentapeptide [D‐alanyl2, leucine5]enkephalin, thus showing good stability towards the classical methods of peptide synthesis.
Tétraazamacrocycles lipophiles: Extraction d'ions métalliques par une résine imprégnée
Authors: Muller Frédéric R. , Handel Henri , Guglielmetti Robert 
Published: December 2004

Lipophilic Tetraazamacrocyles: Extraction of Metal Ions by Impregnated ResinExtraction of Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+ and Ag+ by lipophilic tetraazamacrocycles dispersed on a solid matrix (Amberlite XAD7) is reported. Extraction efficiency is sensitive to the metal ion identity and the cavity size of the macrocycle. The influence of kinetic factors upon extraction efficiency is discussed.
Mesomorphic properties of some 6‐n‐alkyl‐2‐(4′‐cyanophenyl)naphthalenes. Preliminary Communication
Authors: Lauk Urs , Skrabal Peter , Zollinger Heinrich 
Published: December 2004

AbstractThe synthesis of the title compounds 4 is described and their transition temperatures are compared with the nematic phases of the respective 6‐n‐alkoxynaphthalene derivatives.
Azimine. VII. Herstellung durch Oxydation von Triazanen
Authors: Egger Notker , Hoesch Lienhard , Dreiding André S. 
Published: December 2004

Azimines. VIITeil VI, s. [1].

.
Preparation by Oxidation of Triazanes
A novel method for the preparation of certain azimines 4 by oxidation of 1,2,3‐trisubstituted triazanes 3 is described. Treatment of 3‐aryl‐triazane‐1,2‐diesters 3a‐3c with lead tetraacetate afforded the 3‐aryl‐azimine‐1,2‐diesters 4a‐4c. The precursor triazanes 3a‐3c were prepared by addition of p‐substituted anilines to diisopropyl diazene‐1,2‐dicarboxylate 1b. A comparison of the spectral properties of the azimines 4 with those of the correspondingly substituted triazanes 3 reveals the unsaturated and dipolar nature of the azimines 4.
On the stereochemistry of allylmetal‐aldehyde condensations. Preliminary communication
Authors: Denmark Scott E. , Weber Eric J. 
Published: December 2004

AbstractThe stereochemical course of the intramolecular allylsilane‐aldehyde condensation of 1a has been investigated. A modest preference for the product arising from a synclinal orientation of double bonds was observed with Lewis‐acid catalysts. Cyclization induced by fluoride ion resulted in stereochemical reversal.