bluuebunny/crossref_metadata_2025_split huggingface dataset:
Russula‐Farbstoffe: Zur Struktur von Russupteridin‐sIII
Authors: Iten Peter Xaver , Arihara Shigenobu , Eugster Conrad Hans 
Published: December 2004

AbstractDer rote Hauptfarbstoff aus den zu den Basidiomyceten gehörenden Pilzen Russula emetica Fr., R. sardonia Fr. em. Rom. und anderen Spezies, das sog. Russupteridin‐sIII, ist ein «dimeres» Lumazinderivat. Nach Säurehydrolyse konnte Ribose, bzw. Furfurol nachgewiesen werden, neben dem tricyclischen 2,10‐Dihydro‐4,6,8‐trihydroxy‐10‐ribityl‐2‐oxo‐pyrimido[5,4‐g]pteridin (2). Spaltung mit 2proz. Essigsäure unter Sauerstoffausschluss im geschlossenen Rohr lieferte die N‐Ribityllumazine 3a, 3b und 4, nebst weiteren, bisher nicht identifizierten Verbindungen.Verschiedene Russula‐Arten können, da sie verhältnismässig viel Riboflavin enthalten, als flavinogene Organismen angesprochen werden. Wir postulieren einen Zusammenhang zwischen der Entstehung der roten Russupteridine und der Biosynthese von Riboflavin.
Relationships Between Acidity Functions, Rates of Reactions of Formaldehyde with Cellulose and of Cellulose Hydrolysis. 28th communication on investigations in textile chemistry
Authors: Mohn‐Wehner Angelika , Rouette H. K. , Zollinger H. 
Published: December 2004

AbstractThe rates of hydrolysis of cellulose and the rates of formation of cellulose formal were measured in heterogeneous systems consisting of cotton cellulose and solutions of formaldehyde in aqueous hydrochloric acid and in solutions of hydrochloric acid in various water/acetic acid mixtures. The rates were related to the acidity functions (Ho) of the solutions. Although fairly good linear relationships between the logarithms of the rates and Ho were obtained in most cases, no conclusions concerning the reaction mechanism could be drawn.
Die Elektronenstruktur des Dicyclohepta[c d, g h]pentalens
Authors: Müllen Klaus , Reel Henning 
Published: December 2004

AbstractDicyclohepta[cd, gh]pentalene is shown by ESR.‐ and NMR.‐spectroscopic evidence to be best represented as a perturbed [14] annulene. The orbital interaction between the π‐perimeter and the ethylene‐“bridge” is discussed.
Elektrophile und nucleophile Substitution partiell hydrierter Nicotinsäure‐Derivate. 11. Mitt. über synthetische Indol‐Verbindungen
Authors: Troxler F. 
Published: December 2004

Abstract1‐Methyl‐1,4‐dihydronicotinamide (1)2 reacts with gramines to the corresponding 1‐methyl‐5‐skatyl‐1,4‐dihydronicotinamides (3), the structures of which have been proved by conversion of 6, a homologue of 3, into dimethyl pyridine‐3,5‐dicarboxylate (11). Palladium/H1 reduces 3 to the 1,4,5,6‐tetrahydronicotinamides 12, which are hydrogenated with platinum/H1 to a mixture of the diastereomeric 1‐methyl‐5‐skatyl‐nipecotinamides 14 and 15. Alkaline hydrolysis converts the trans‐amide 15 to the cis‐carboxylic acid 16. Enamine alkylation of 1 with benzylbromide and subsequent catalytic reduction leads in low yield to 5‐benzyl‐1‐methyl 1,4,5,6‐tetrahydronicotinamide (18). 1‐Substituted 1,4,5,6‐tetrahydronicotinic acid derivative 19 are alkylated by strong electrophilic halides to iminium salts 20, which, after catalytic reduction form 3,3‐disubstituted piperidines 21 generally in high yield. The factors influencing the enamine alkylation are discussed. The addition of nucleophiles to iminium salts 20 has been studied. Thus the 1‐methyl‐hexahydro‐2H‐pyrrolo[3.4‐b]pyridines 32 und 33 were prepared by treatment of 20 with cyanide, followed by reduction with LiAlH4 in the case of 33. Intramolecular addition of nucleophiles onto 20 formed the pyrido[2 3‐a]carbazole 35, the indolo[2.3‐a]quinolizines 37 and the benzopyrano[2.3‐b]pyridines 43, 44 and 46. It has been shown that in the iminium salts 20 the group X can eliminate either, if X  CONH2, by a fragmentation mechanism or, if X  CX by nucleophilic attack.
Synthese der Sequenz 1‐34 von menschlichem Parathormon. Vorläufige Mitteilung
Authors: Andreatta R. H. , Hartmann A. , Jöhl A. , Kamber B. , Maier R. , Riniker B. , Rittel W. , Sieber P. 
Published: December 2004

AbstractBrewer et al. [1] have established sequence I for the first 34 amino acid residues of human parathyroid hormone. It differs in 6 and 5 positions respectively from the corresponding bovine [2] [3] and porcine [4] hormone sequences. The synthesis of the protected tetratriacontapeptide II by the fragment‐coupling approach and its purification by counter‐current distribution are described. Removal of the protecting groups by acidolysis then gave I in high purity.I displays hypercalcemic activity in the thyroparathyroidectomized rat indicating that the amino terminal part also constitutes the hormonally active region of human parathyroid hormone.
Über thermische, eine Amino‐Claisen‐Umlagerung einschliessende. Reaktionen von N‐Propargyl‐naphthylaminen
Authors: Scheurer H. , Zsindely J. , Schmid H. 
Published: December 2004

AbstractN‐Propargyl‐1‐naphthylamine (1), the corresponding N‐butinylcompound 5 and N‐propargyl‐2‐naphthylamine (2) ‐ unlike N‐propargyl‐anilines ‐ on heating to 250° are converted to a mixture of py‐tetrahydro‐benzoquinolines and benzoquinolines (scheme 1). The mechanism of these reactions which are induced by a [3s, 3 s] rearrangement of the propargyl group and include a [1,5s] H‐shift is depicted in scheme 4. N‐Methylation of 1 and 2 reduces for steric reasons the rate of the [1,5s] H‐shifts; therefore ring closure of the allenylnaphthylamine intermediates to indols 13 and 14 is favoured (schemes 2 and 5).
Organic Phosphorus Compounds 59. A new method for the synthesis of phosphonic dichlorides
Authors: Maier Ludwig 
Published: December 2004

AbstractHeating of thiophosphonic dichlorides, RP(S)Cl2, R  CH3, C2H3, C2H5, with a molar equivalent of SOCl2 under pressure at 150° for 5 to 8 h yields phosphonic dichlorides in quantitative yield. In addition sulfur and sulfur dichloride is formed according to the equation:

This method is particularly useful for the preparation of CH3P(O)Cl2 since it was observed that chlorination of CH3P(O)(OCH3)2 with PCl5 yields CH3OP(O)Cl2 as a by‐product which is difficult to separate from CH3P(O)Cl2. On the other hand chlorination of methylphosphonic acid with PCl5 also gives pure CH3P(O)Cl2

.
The Conversion of Isoindolobenzazepines into Dibenzazecines: A new Synthesis of α‐Allocryptopine from Schöpf's Base VI
Authors: Teitel S. , Borgese J. , Brossi A. 
Published: December 2004

AbstractDer Hofmann'sche Abbau des Brommethylates 1 der « Schöpf‐Base VI » gibt zwei ungesättigte Basen, für welche die Strukturen 2 und 3 abgeleitet wurden. Das 10gliedrige ces‐Dibenzazecin 3 konnte in schlechter Ausbeute in das Protopinalkaloid α‐Allocryptopin 6 übergeführt werden.
Identifizierung von sechs Komponenten des Spurpheromons der Ameisenart Lasius fuliginosus. Vorläufige Mitteilung
Authors: Huwyler Siegfried , Grob Kurt , Viscontini Max 
Published: December 2004

AbstractHexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, and dodecanoic acid are components of the trail pheromone of the ant species Lasius fuliginosus. The acids were extracted from the contents of the rectal ampullae and identified by the mass spectra and gas chromatographic retention times of the corresponding methyl esters.
Metal Complexes of Free Radicals. Part III: Triplet state ESR. of magnesium(glyoxal‐bis‐N‐t‐butylimine)2
Authors: Clopath Peter , Zelewsky Alexander V. 
Published: December 2004

AbstractThe preparation and the ESR. spectra of a 1 : 2 complex of Mg2+ with the radical anion of glyoxal‐bis‐N‐t‐butylimine (GLI) are reported. The ESR. spectrum of Mg(GLIR)2 in 2‐methyl‐tetrahydrofuran at −165° is interpreted as due to a randomly oriented molecular triplet. The magnetic dipole‐dipole interaction of the two unpaired electrons in Mg(GLIR)2 can be interpreted by an axially symmetric fine structure term with D = 0.021 cm−1.
Über die Wirkung von Auxochromen in Flavyliumsalzen, III. 7‐Dimethylamino‐flavyliumsalze
Authors: Kokkinos Konstantinos , Wizinger Robert 
Published: December 2004

AbstractThe absorption maximum at longest wave lengths of the 7‐dimethylaminoflavylium perchlorate being shifted by 121 nm to longer wave lengths than the maximum of the flavylium perchlorate and yet the auxochromes in 4′‐position having a less strong effect in the 7‐dimethylamino‐flavylium salts than in the flavylium salts, the absorption maxima of both series converge strongly. In the case of the 4′‐dimethylamino derivatives the convergence reaches the high value of 61 nm.
Die Geometrie des aktivierten Komplexes der thermischen und ladungsinduzierten aromatischen para → ortho ‐ Claisen‐Umlagerung
Authors: Wunderli Alfred , Zsindely Janos , Hansen Hans‐Jürgen , Schmid Hans 
Published: December 2004

AbstractPure 10β‐(trans‐2′‐butenyl)‐17β‐hydroxy‐estra‐1,4‐dien‐3‐one (6), 10‐(trans‐2′‐butenyl)‐2‐oxo‐Δ1(9),3(4)‐hexahydronaphthalene (13), trans‐2′‐butenyl 17β‐hydroxy‐3‐estra‐1,3,5‐(10)‐trienyl ether (12) and trans‐2′‐butenyl 5,6,7,8‐tetrahydro‐2‐naphthyl ether (14) were prepared by direct C‐ and O‐alkylation, respectively, of the corresponding phenols (cf. [3] [10]), namely estra‐3, 17β‐diol and 5,6,7,8‐tetrahydro‐2‐naphthol.The Claisen rearrangement of the ether 14 (200°, 12 h) yielded 53% 1‐(1′‐methylallyl)‐ and 34% 3‐(1′‐methylallyl)‐5,6,7,8‐tetrahydro‐2‐naphthol (15 and 16, respectively), whereas in the thermal (120°, 14 h) and in the acid‐catalysed (boron trifluoride in ether, 20°, 20 min) reaction of the corresponding dienone 13 nearly equal amounts of 15 (53–54%) and 16 (46%) were formed by thermal and charge‐induced aromatic [3s, 3s]‐sigmatropic rearrangements [2].The steroid dienone 6, on heating at 120°, was rearranged by [3s, 3s]‐sigmatropic processes to form 52% of 2‐(1′‐methylallyl)‐ and 48% of 4′‐(1′‐methylallyl)‐3, 17β‐dihydroxy‐estra‐1,3,5,(10)‐triene (7 and 8, respectively). The steroid phenols 7 and 8 were carefully separated; subsequent hydrogenation (Raney‐Ni in alcohol) and ozonolysis yielded 2‐methylbutyric acid (9): from 7, S‐(+)‐9, and from 8, R‐(−)‐9, obtained in 88,5 and 88,0% optical purity (cf. [4a]). This means (cf. scheme 2 and Table 2) that both phenols are formed to the extent of at least 94% via a chair‐like activated complex, and of at most 6% via a both‐like activated complex (ΔΔG = 2.15 kcal/mol). Similarly, the boron trifluoride‐induced rearrangement of 6 (born trifluoride in ether, 0°, 45 min) yielded 7 and 8, from which S‐(+)‐9 and R‐(−)‐9 were respectively obtained in 89% and 98% optical purity. For these induced rearrangements this corresponds to at least 94,5 and 99%, respectively, of the chair‐like, and to only 5.5 and 1% of the boat‐like activated complex (ΔΔG = 1.5–2.5 kcal/mol). These results demonstrate that the activated complexes of both [3s,3s]‐sigmatropic processes, i.e. the pure thermal reaction at 120° and the charge‐induced reaction occurring at 0°, must be very similar. Thus, the boron trifluoride accelerates the Cope‐like reactions 6 → 7 + 8, but does not influence the geometries of their transition states.The Claisen rearrangement of the steroid ether 12 (200°, 15 h), yielding 7 and 8, was not influenced by the chiral steroid skeleton, because no optical induction was observed (both phenols, 7 and 8, yielded on degradation racemic 2‐methylbutyric acid (9)).
Hormone: Receptor Interactions. Biological activities of [phenylalanine2, norvaline4]‐adrenocorticotropin‐(1‐24)‐tetrakosipeptide and its 4,5‐dehydro‐4,5‐ditritio‐norvaline4 analogue in isolated rat lipocytes and adrenal cortex cells: Lipolysis, corticosterone and cyclic adenosine‐3′,5′‐monophosphate production
Authors: Lang Ursula , Karlaganis Georg , Seelig Steven , Sayers George , Schwyzer Robert 
Published: December 2004

Abstract[Phenylalanin2, norvalin4]‐adrenocorticotropin‐(1‐24)‐tetrakosipeptid und sein 4,5‐dehydro‐4,5‐ditritio‐Derivat sind in isolierten Ratten‐Lipocyten und ‐Nebennierenrindenzellen biologisch gleich aktiv. In Bezug auf Lipolyse, Corticosteron‐ und cyclo‐AMP‐Produktion zeigen sie gleiche intrinsische Aktivität wie das Adrenocorticotropin‐(1‐24)‐tetrakosipeptid mit der natürlichen Aminosäurensequenz, müssen aber zur Erzielung desselben Effektes in ca. 8–12mal höheren Dosen angewandt werden.
Die Deprotonierung von Metallaquoionen II: Aquochrom(III)‐ion. Zur Struktur aktiver Chromhydroxide
Authors: von Meyenburg Urs , Široký Otokar , Schwarzenbach Gerold 
Published: December 2004

AbstractOn alkalinization of solutions of the chromiun(III)‐aquo ion simple deprotonation takes place first. The degree of hydroxylation nOH however can be brought up to only about 1 (the exact value depending on the total concentration [Cr]t), before the uncharged complex Cr(OH)3(OH2)3 is precipitated. The structure of the very sparingly soluble complex (solubility ∼10−7M) is held together by hydrogen bonds of type I between the molecules, so that its formula may be written as Cr(OH)2H6/2‐lattice. The formation of the well ordered structure is extremely fast. On aging, the metallic centers become connected by μ‐hydroxo‐bridges (type II) and the substances become amorphous and very insoluble. magnified image The dinuclear (H2O)4Cr(OH)2Cr(OH2)44+ behaves similar on deprotonation. Concerning the various equilibria constants see Table 1.
Etude du comportement électrochimique du manganèse dans le tampon borate
Authors: Painot J. , Monnier R. , Augustynski J. 
Published: December 2004

AbstractThe anodic behavior of the manganese electrode in borate buffer solutions have been studied by potentiostatic and galvanostatic electrochemical techniques. Three distinct steps determined on the charging curves are attributed to the formation of Mn (OH)2, MnOOH and MnO2. The manganese dioxide formed anodically in pH 11 borate solution may be reduced cathodically with high faradaic efficiency.
The Dehydrogenation of 1,4‐Cyclohexadienes with 2,3‐Dichloro‐5,6‐dicyanobenzoquinone and Triphenylmethylfluoroborate
Authors: Müller Paul 
Published: December 2004

AbstractThe dehydrogenation of 1,4‐cyclohexadiene (1) cis‐3,6‐dimethyl‐1,4‐cyclohexadiene (2) and trans‐3,6‐dimethyl‐1,4‐cyclohexadiene (3) with triphenylmethylfluoroborate in acetonitrile or 2,3‐dichloro‐5,6‐dicyanobenzoquinone (DDQ) proceeds in the same reactivity sequences 2 > 1 > 3. The mechanism of the dehydrogenation of 1,4‐cyclohexadienes with triphenylmethylfluoroborate and DDQ is discussed in the light of these results and in view of the kinetic isotope effects.
A. New Synthesis of Triasteranedione
Authors: McDonald Ian A. , Dreiding André S. , Hutmacher Hans‐Martin , Musso Hans 
Published: December 2004

AbstractBromierungen von Bicyclo[3.3.1]nonan‐3, 7‐dion (6) mit vier Äquivalenten Brom oder Phyenyltrimethylammonium‐tribromid lieferten zwei Tetrabromide, deren Zusammensetzung (Hydrat) und IR.‐Spektren (keine CO, dafür OH‐Banden) zeigten, dass neben der Bromierung noch eine Cyclisierung unter Anlagerung von Wasser an die beiden Carbonylgruppen zu einem Oxa‐adamantan‐System stattgefunden hatte. Die Ausbildung der eher seltenen α,α′‐Dihydroxyäther‐Funktion wird der kooperativen Wirkung des induktiven Effekts der vier Bromatome, der räumlichen Nähe der beiden Carbonylgruppen und der Stabilität des Adamantangerüstes zugeschrieben. Die NMR.‐spektren mit den zahlreichen Fernkopplungen bestätigen, dass es sich um zwei stereomere 4,8,9,10‐Tetrabrom‐1,3‐dihydroxy‐2‐oxa‐adamantane handelt. Die Zahl der HC(Br)‐Signale sowie deren Fernkopplungsmuster erlauben die Ableitung der 4β, 8β, 9β, 10α‐Konfiguration für das eine Isomere (8), Smp. 177°, und der 4β, 8β, 9β, 10β‐Konfiguration für das andere (9), Smp. 180°E.Dehydrobromierung der rohen Tetrabromierungsprodukte von 6 mit Triäthylamin ergab in 80% Ausbeute ein 1:1‐Gemisch von 2,6‐ und 2,4‐Dibrom‐triasteran‐3, 7‐dion (10 und 11), aus dem sich nur das erstere (10) in reiner Form, Smp. 212°, isolieren liess. Die Lagen der Bromatome wurden aus den NMR.‐Spektren abgeleitet. Als Nebenprodukt entstand auch ein wenig 2‐Brom‐triasteran‐3, 7‐dion (12), Smp. 172°.Die drei Brom‐triasteran‐3, 7‐dione (10, 11 und 12) liessen sich mit Tri‐n‐butyl‐zinnhydrid in 50% Ausbeute zu Triasterandion (7), Smp. 154°, reduktive debromieren. Triasterandion (7) wurde auch direkt aus dem rohen Tetrabromierungsgemisch von Bicyclo[3.3.1]nonan‐3, 7‐dion (6) durch Erhitzen mit Kupferpulver in 31% Ausbeute hergestellt.
Homopolar‐ and Heteropolar Bond Dissociation Energies and Heats of Formation of Radicals and Ions in the Gas Phase. I. Data on organic molecules
Authors: Egger Kurt W. , Cocks Alan T. 
Published: December 2004

AbstractThe literature data on heteropolar and homopolar 2‐center bond dissociation energies in organic molecules in the gas phase and the corresponding heats of formation of radicals and ions have been critically evaluated. Data for more than 500 bonds are represented in tabular form together with the pertinent literature references.Selected electron affinities and π‐bond dissociation energies have also been incorporated. The follow‐up paper will discuss some empirical general aspects of these data particularly regarding the effect of structure on the bond dissociation energies.
Spectre de Resonance Paramagnétique Electronique de la Diphénylthiophosphine cristalline irradiée aux rayons X
Authors: Geoffroy Michel 
Published: December 2004

AbstractThe electron spin resonance spectra of X‐irradiated diphenylphosphine sulfide monocrystal and powder are reported. The results show that the radical Φ2\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm P}\limits^{.} $\end{document}S is mainly produced. The values and directions of the principal components of ḡ and 31P‐hyperfine tensors are determined.
‘Lone pair’ Electronic Structure, Conformation and Oxidation Behaviour of Diaziridines
Authors: Haselbach Edwin , Mannschreck Albrecht , Seitz Werner 
Published: December 2004

AbstractPhotoelectron spectroscopic investigations indicate that (i) monocyclic diaziridines prefer a trans‐conformation of the nitrogen‐lone pairs, and (ii) the interaction between these is comparable to that exhibited by open‐chain analogues, i.e. alkyl‐substituted hydrazines. The chemical experience concerning the particular case of NHNH→NN oxidation of diaziridines can therefore not be accounted for by a prevailing unfavorable ‘lone pair’ interaction. Thermochemical as well as entropy arguments may serve as an explanation. A rather unsatisfactory agreement between predictions from various theoretical procedures and experimental results for the ionization potentials of ‘lone pair’ MO electrons is noted.
Metallbindungsphänomene: Alkoholat‐Aggregate als unmittelbare Teilnehmer an Eliminierungsreaktionen
Authors: Schlosser Manfred , Jan Gérald , Byrne Edeline , Sicher Jiři 
Published: December 2004

AbstractIn solvents of low polarity it is neither a monomolecular nor a dissociated alcoholal species which effects dehydrohalogenation of vic‐dihaloalkanes and vic‐dihalocycloalkanes but rather a dimeric, trimeric or tetrameric alcoholate aggregate. This behavior has important implications for the stereochemical outcome of such elimination reactions.
Intermediaires organiques du germanium divalent: III obtention de germylenes γ‐hydroxyles à partir de 3‐chlorohydrogermyl‐1‐propanols et de 3‐methoxyhydrogermyl‐1‐propanols
Authors: Barrau Jacques , Satgé Jacques , Massol Michel 
Published: December 2004

Abstract3‐chlorohydrogermyl‐1‐propanols ClH2Ge(CH2)3OH and Cl2HGe (CH2)3OH are synthesized by action of mercury (II) chloride, in tetrahydrofuran, on 3‐germyl‐1‐propanol H3Ge(CH2)3OH. By thermal effect these halohydrides released hydrochloric acid, with formation of oxagermacyclopentanes
equation image
(R = H or Cl); these derivatives decomposed by α‐elimination with formation of γ‐hydroxy divalent species of germanium RGe(CH2CH2)3 OH (R = H or Cl).‘Chlorine‐methoxy’ exchange using tributylmethoxygermane on Cl2HGe(CH2)3OH leads to the 3‐methoxyhydrogermyl‐1‐propanols (MeO)ClHGe(CH2)3OH and (MeO)2HGe(CH2)3OH; α‐decomposition on the germanium atom in these latter compounds leads to the formation of the same γ‐hydroxypropylgermylenes. These functional divalent germanium species were characterized by insertion into some σ‐bonds.
Synthese von 1α‐Hydroxycholecalciferol. Vorläufige Mitteilung
Authors: Fürst Andor , Labler Ludvik , Meier Werner , Pfoertner Karl‐Heinz 
Published: December 2004

Abstract1α‐hydroxycholesterol (4a) was synthesized from cholesterol and transformed via its diacetyl derivative 4b into 1α, 3β‐diacetoxycholesta‐5, 7‐diene (6b). Irradiation of the ring‐B‐diene 6b followed by thermal isomerization and saponification gave 1α‐hydroxycholecalciferol (7).
Intramolecular Diels‐Alder reactions: Construction of aza‐ and diaza‐steroid type skeletons
Authors: Gschwend Heinz W. 
Published: December 2004

AbstractThe preparation of 2‐(4‐phenyl)butadienyl‐piperidine 5 is described. An intramolecular Diels‐Alder reaction of the intermediately formed fumaramide thereof produces stereoselectively the tricyclic lactam 6. Its structure, as well as the configurational relationship of its 5 asymmetric centers, is corroborated on the basis of the NMR.‐data. Cycloacylation of the thermodynamically stable precursors 13 and 20 leads to pentacyclic aza‐ or diaza‐steroid type skeletons. Their structures (14, 16, and 21) and in particular their relative configurations are elaborated. A few qualitative kinetic aspects of this intramolecular (4+2)‐cycloaddition are presented.
Über Pterinchemie. 43. Mitteilung [1]. Synthese von D‐Neopterin‐3′‐phosphat und D‐Neopterin‐2′, 3′‐cyclophosphat. Betrachtungen über die Biopterin‐Biogenese
Authors: Viscontini Max , Furuta Yoshiteru 
Published: December 2004

AbstractDie Synthese des D‐Neopterin‐3′‐phosphates (II) und des entsprechenden Cyclophosphates III wird beschrieben. Bei der Behandlung von D‐Neopterin mit Polyphosphorsäure in der Wärme tritt Cyclisierung der Trihydroxypropyl‐Kette mit dem N(5)‐Atom unter Verlust von zwei Molekeln Wasser ein. Ein möglicher Zusammenhang zwischen dieser leichten Wasserabspaltung und der Biogenese des Sepiapterins bzw. Biopterins wird diskutiert.
Säurekatalysierte Dienon‐Phenol‐Umlagerungen von 6‐Propargyl‐6‐methyl‐cyclohexa‐2,4‐dien‐1‐onen; ladungskontrollierte, aromatische [1s, 2s]‐ und [3s, 4s]‐sigmatropische Reaktionen
Authors: Widmer Ulrich , Hansen Hans‐Jürgen , Schmid Hans 
Published: December 2004

AbstractThe acid catalysed dienone‐phenol rearrangement of methyl substituted o‐propargyl‐cyclohexadienones (scheme 3) was investigated. The rearrangements were carried out in acetic anhydride containing about 10/00 sulfuric acid. Under these conditions acetoxy benzenium ions are formed as intermediates. These then undergo charge‐controlled [3s, 4s]‐ and [1s, 2s]‐sigmatropic rearrangements. Thus, the [3s, 4s]‐process leads to the formation of the corresponding allenyl‐phenol acetates (19, 21, 23, 25, 28, 30) whereas the [1s, 2s]‐process yields propargyl‐phenol acetates (20, 22, 24, 26, 29), respectively (cf. scheme 4).
Etude calorimétrique de complexes à transfert de chargeinterhalogène‐quinoléine en solution. (Communication préliminaire)
Authors: Biselx Charles , Schaer Jean‐Jacques , Janjic Désimir 
Published: December 2004

AbstractA calorimetric study has been made for the determination of K and ΔH for quinolineinterhalogen complexes in carbon tetrachloride. The order of stabilities of the complexes with respect to halogens does not agree very well with their acid strength.
Nucleophilic Reactions at Tertiary Carbon. Part 2. σ‐ and π‐routes to the 8‐hydrindanyl cation
Authors: Becker Konrad B. , Boschung André F. , Grob Cyril A. 
Published: December 2004

AbstractStereoisomeric ion pairs are implicated as intermediates in the solvolysis of cis and trans‐8‐hydrindanyl chloride 3, whereas 4‐(cyclopenten‐1‐yl)butyl tosylate 5 appears to cyclize by way of an unsymmetrically solvated 8‐hydrindanyl cation. This follows from the solvolysis products and rates of these compounds in aqueous solvents.The rate and equilibrium constants of the chlorides 3 show that the transition state for the trans‐isomer is more stable by 0.5 kcal than the one for the cis‐isomer. By inference the intermediates differ by a similar amount of energy.Experimental results are not explained satisfactorily by conformationally isomeric 8‐hydrindanyl cations, as suggested in the literature.