bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermische Reaktionen mit 3‐Phenyl‐2H‐azirinen; 1, 3‐dipolare Cycloadditionen und En‐Reaktionen
Authors: Narasimhan Nurani S. , Heimgartner Heinz , Hansen Hans‐Jürgen , Schmid Hans
Published: December 2004

Benzonitrile p‐nitrobenzylide (5) undergoes 1,3‐dipolar cyclo‐additions in the presence of 3‐phenyl‐2H‐azirines (1), yielding in benzene at 0° 2‐(p‐nitrophenyl)‐4,5‐diphenyl‐1,3‐diazabicyclo[3.1.0]hex‐3‐enes (7, scheme 2). Under the basic conditions of the reaction mixture, 7 a and 7 b are partially converted to 2‐(p‐nitrophenyl)‐4,5‐diphenyl‐1,6‐dihydropyrimidines (8a, b) which are dehydrogenated by oxygen to the corresponding pyrimidines 9a and 9b, respectively.

3‐Phenyl‐2H‐azirines (1) form, on heating at 145° in xylene in the presence of the azalactone 32 (2,4‐diphenyl‐Δ2‐oxazolin‐5‐one), 4‐(aziridin‐2′‐yl)‐2,4‐diphenyl‐Δ2‐oxazolin‐5‐ones (33, scheme 11). 33 arises from an ene reaction of the enol form of 32 with 1. Similar ene reactions are observed with the azirines 1 and dimedone (37, scheme 12). Under the ene reaction conditions (xylene, 145°), the non‐isolated intermediate primary adducts (38a and 38b) undergo rearrangements of the vinylcyclopane‐cyclopentene type to give 6,6‐dimethyl‐4‐oxo‐1,3‐diphenyl‐4, 5, 6, 7‐tetrahydroisoindole (40) and 6, 6‐dimethyl‐4‐oxo‐3‐phenyl‐4, 5, 6, 7‐tetrahedroindole (42), respectively.
Nitrierung von 1‐ und 2‐Methoxymethyl‐naphthalin
Authors: Markees Diether G.
Published: December 2004

2‐Methoxymethyl naphthalene (1) was synthesized and its properties were found to be different from those reported in the literature. The reaction of this compound with cold conc. nitric acid gave 8‐nitro‐2‐naphthaldehyde (2). When 1‐methoxymethyl naphthalene (4) was treated similarly 4‐nitro‐1‐methoxymethyl naphthalene (5) and 8‐nitro‐1‐naphthaldehyde (6) were obtained.
Synthesis of Potential Ambra Odorants: 5,5,9‐trimethyldecalyl derivatives
Authors: Ohloff Günther , Näf Ferdinand , Decorzant René , Thommen Walter , Sundt Erling
Published: December 2004

The synthesis of racemic stereoisomeric compounds with the 5,5,9‐trimethyldecalin skeleton and an oxygen function at C(1), C(2), or C(3) is described

Although racemic decalins are described, only the enantiomer related to steroids is drawn. The projection of the decalins was chosen so as to place the angular methyl group above the plane of the molecule and the oxygen function at C(1), C(2) or C(3) on the left side, as represented by formula 1–6. The relative configuration of the substituents in decalins is designated by using the convention of the steroid series: β, meaning on the same side as the angular methyl group at C(9) and α, meaning on the side opposite from the angular methyl group. The prefix cis or trans refers to the fusion of the decalin ring system, not to the position of the substituents.

. A novel general one‐step synthesis of 2‐decalones by means of acid catalyzed cyclization of acyclic or monocyclic precursors has been developed.
Thermische Umlagerungen von halogensubstituierten Aryl‐propargyläthern
Authors: Šarčevic̀ Nada , Zsindely Janos , Schmid Hans
Published: December 2004

7‐Chloro‐2‐chloromethyl‐benzofuran (13) and 3, 8‐dichloro‐2 H‐1‐benzopyran (12) are the main products from the thermal rearrangement (230–260°) of 2, 6‐dichlorophenyl propargyl ether (7). Compounds 17, 18 and 19 are also formed, but in much smaller amounts (scheme 2 and table 1). However, in the case of the bromo‐compounds 8 and 9 the rearrangement products are the benzofuran derivatives 21 and 22, containing one bromine atom less per molecule (scheme 4).

The corresponding naphthyl propargyl ethers 10 and 11 can be rearranged much more easily (180°) to the halogeno‐naphthofurans 24 and 26 respectively. In the case of the bromo‐ether 11, 2‐methyl‐naphtho[2, 1‐b]furan (25) is also formed (scheme 5).

If the propargylic hydrogen atoms in 7 and 11 are replaced by deuterium atoms, then after rearrangement the deuterium atoms in the products d‐13 and d‐26 are found in the β‐positions to the oxygen atom of the furan ring (schemes 3 and 5).

It is suggested that initially a [3s, 3s]‐sigmatropic rearrangement of the aryl propargyl ethers to the 6‐allenyl‐6‐halogeno‐cyclohexa‐2, 4‐dien‐1‐ones (e.g. a) occurs and that from these the isolated products are formed via radical pathways (scheme 6).

Under neutral conditions aryl propargyl ethers containing a free ortho‐position give on heating benzopyran derivatives [2]. When this thermal reaction is carried out in sulfolane in the presence of powdered potassium carbonate, 2‐methyl‐benzofuran derivatives are formed (table 2). This leads to the possibility of preparing, depending on the conditions, either benzopyran or benzofuran derivatives by the Claisen rearrangement of aryl propargyl ethers. The mechanism for the formation of the benzofurans is given in scheme 9.
The Synthesis of Damascenone and β‐Damascone and the possible mechanism of their formation from carotenoids
Authors: Isoe Sachihiko , Katsumura Shigeo , Sakan Takeo
Published: December 2004

A brief synthesis of damascenone (5) from the acetylenic diol 2 and also that of β‐damascone (8) from β‐ionol, resembling the biogenetic synthesis, are described. A possible mechanism for the formation of damascenone from neoxanthin is proposed.
The Interaction of Walsh‐Orbitols in Diademane and Related Hydrocarbons
Authors: Heilbronner Edgar , Gleiter Rolf , Hoshi Toshihiko , de Meijere Armin
Published: December 2004

To obtain further information concerning the interaction between Walsh‐orbitols of ‘conjugated’ cyclopropane rings, the photoelectron spectra of the following compounds have been recorded: bicyclo[4.1.0]heptane 1, cis‐ and trans‐tricyclo[5.1.03, 5]octane 2, 3, diademane 4, trans‐pentacyclo[3.3.2.02, 9.04, 10, 06, 8]decan 5 and bicyclo[4.1.0]heptene‐2 6. The first bands in the PE.‐spectra of these compounds have been assigned on the basis of a ZDO HMO‐approximation. For 2 and 4 the value for resonance integral between linked 2p atomic orbitals of two adjacent eclipsed cyclopropane rings is found to be −1.73 eV.
A Novel Synthesis of 1‐Aryl‐9‐alkyl‐2, 3, 3a, 4, 9, 9a‐hexahydro‐1H‐pyrrolo[2, 3‐b] quinoxalines by lithium aluminium hydride reduction of N‐phenyl‐1‐benzimidazolyl‐succinimides
Authors: Ahmed Quazi , Wagner‐Jauregg Theodor , Pretsch Ernst , Seibl Josef
Published: December 2004

The N‐substituted 1‐benzimidazolyl‐succinimides 6a–v (Scheme 1, Table 1 and 2) have been prepared by the reaction of benzimidazole and its derivatives with maleimides. Reduction of the N‐cyclohexyl and N‐cyclo‐octyl substituted 1‐benzimidazolyl‐succinimides 6i–k with lithium aluminium hydride gives the normally expected substituted (N‐alkyl‐3‐pyrrolidinyl)benzimidazoles 14i–k. However by LiAlH4‐reduction of the N‐phenyl substituted 1‐benzimidazolylsuccinimides 6a–h mainly the 1‐aryl‐9‐alkyl‐2, 3, 3a, 4, 9, 9a‐hexahydro‐1H‐pyrrolo[2, 3‐b]quinoxalines 7a–h are obtained. The mechanism of this unusual reduction has been elucidated.
N‐Carbobenzoxy‐L‐pyroglutamyl‐L‐histidyl Peptides
Authors: Kurath P. , Thomas A. M.
Published: December 2004

N‐Benzyloxycarbonyl‐L‐pyroglutamyl‐L‐histidyl‐peptide reagieren mit Methanol unter Bildung von N‐Benzyloxycarbonyl‐L‐(05‐methyl)glutamyl‐L‐histidyl‐peptiden (Hauptprodukte) und L‐Pyroglutamyl‐L‐histidyl‐peptiden (Nebenprodukte), wenn die basische Histidin‐Seitenkette nicht protoniert ist. Solche basenkatalysierte Methanolysen. wurden an einem Di‐ und an einem Tripeptid‐Amid beobachtet. Die entsprechende Äthanolyse verlauft wesentlich langsamer.
Komplexone XLVI. EDTA‐Komplexe des Pt(II)‐Ions mit und ohne einzähnige Fremdliganden
Authors: Stünzi Hans , Anderegg Giorgio
Published: December 2004

The formation of complexes between Pt(II)EDTA2− and H+, OH−, Cl−, Br−, SCN−, CN− and NH3 was investigated using pH and UV.‐spectrophotometric measurements at ionic strength 1.0 and 25°. The existence of the following species could be proved (charges are omitted): HpPt(EDTA) (0 ≤ p ≤ 3), Pt(EDTA)X (X = OH, NH3, Cl, Br, I, SCN), HpPt(EDTA)X (1 ≤ p ≤ 3; X = Cl, Br) and H4Pt(EDTA)Cl2. They have been characterised by spectral data as well as with equilibrium constants. The different modes of attachment of EDTA are discussed.
Nuclear Quadrupole Resonance and Stereochemistry III. Trichloromethyl derivatives
Authors: Ardalan Ziba , Lucken Edwin A. C.
Published: December 2004

35Cl nuclear quadrupole resonance frequencies are reported of the chlorine atoms in the trichloromethyl group of benzotrichlorides and trichloromethyl derivatives of heterocyclic molecules. They are compared with previously reported results for the same group attached to other planar conjugated radicals. In such compounds the three chlorine atoms cannot be equivalent and all the results are discussed from the point of view of possible orientation‐dependant hyperconjugation between the CCl bonds and the conjugated moiety, particularly with reference to the marked effects observed in trichloromethyl ethers reported in part I of this series. In the benzo‐trichloride and indeed most of the compounds discussed such effects are small.
Photochemical α‐Cleavage of β, γ‐Unsaturated Aryl Ketones: Competition between recombination/disproportionation and dissociation in geminate singlet and triplet radical pairs
Authors: Gonzenbach Hans‐Ulrich , Schaffner Kurt , Blank Bernd , Fischer Hanns
Published: December 2004

The photolysis of (R)‐(+)‐phenyl and (R)‐(+)‐p‐anisyl 1, 2, 3‐trimethylcyclopent‐2‐enyl ketone (1, 2) and the corresponding rac‐1‐ and 3‐desmethyl analogs (3, 4) led to isomerization due to formal 1, 3 aroyl migration and to formation of aryl aldehydes (7, 8), dienes (9, 10) and dimers (5, 6) of the cyclopentenyl radical. Evidence obtained from a chiroptical and mass spectrometric analysis of a crossing experiment and from photolytic CIDNP measurements including the use of CCl4 as a free radical scavenger, supports the conclusion (1): that the ketones undergo photochemical α‐cleavage predominantly in the triplet state; (2): that recombination and disproportionation reactions within the geminate singlet and triplet aroyl/allyl radical pairs (11) compete with the dissociation into free radicals (12): (3): that ketone isomerization by paths not involving polarizable radical intermediates is unimportant; (4): that no triplet oxa‐di‐π‐methane type rearrangement products are formed.
Darstellung von neutralen, lipophilen Liganden für Membranelektroden mit Selektivität für Erdalkali‐Ionen
Authors: Ammann Daniel , Pretsch Ernö , Simon Wilhelm
Published: December 2004

The preparation of a series of non‐cyclic, electrically neutral ligands, able to selectively complex alkaline earth metal cations, is described. Some of the compounds show high Ca2+ selectivity in membrane electrodes.
Über das 2‐Nitrothiophen
Authors: Maag Hubert , Manukian Badrig K.
Published: December 2004

Isomerenreines 2‐Nitro‐thiophen (I) schmilzt bei ca. 41°. Im IR.‐Spektrum lässt sich die Gegenwart von 3‐Nitrothiophen (II) durch die für diese Verbindung charakteristische Absorption bei 834 cm−1nachweisen. Im UV. weist I ein einziges Maximum bei 298 nm auf.
A New Stereoselective Approach to Substituted Pyrrolidines by Intramolecular Ene‐Reactions. Preliminary communication
Authors: Oppolzer Wolfgang , Pfenninger Emil , Keller Kathrin
Published: December 2004

In der vorliegenden Mitteilung wird erstmals die Stereochemie intramolekularer En‐Reaktionen in Beziehung zur Geometrie der En‐Komponente systematisch beschrieben sowie ein neuer, präparativ ergiebiger Weg zu substituierten Pyrrolidinen aufgezeigt. Die N‐(cis‐Crotyl)‐N‐allylamide 1 werden beim Erhitzen ausschliesslich zu den Pyrrolidinen 2 isomerisiert. Unter identischen Bedingungen entstehen aus den N‐(trans‐Crotyl)‐N‐allylamiden 3 die gleichen Stereoisomeren 2 neben geringeren Mengen der epimeren Nebenprodukte 4. Durch die Umsetzungen 5 → 6, 7 8 + 9, 10 → 11 und 12 → 13 wird die thermische Überführung cyclischer Olefine in polycyclische Pyrrolidine unter sterischer Kontrolle mehrerer Chiralitätszentren illustriert. Während die Reaktion 14 → 15 schärfere Bedingungen erfordert, zeigen die Isomerisierungen 16 → 17 und 18 → 19 die glatte Beteiligung von C, C‐Dreifachbindungen an intramolekularen En‐Reaktionen bei weniger hohen Temperaturen.
Photosynthese von Dihydroazepinonen aus 2‐Alkyl‐indazolen
Authors: Heinzelmann W. , Märky M.
Published: December 2004

N(2)‐alkylated indazoles are known to undergo two different photoreactions, namely (i) rearrangement into benzimidazoles in organic solvents and neutral aqueous solution, and (ii) solvolysis yielding o‐amino‐benzaldehydes or acetophenones, in strongly acidic solution.

In diluted acidic solution (pH 3–4) both of these reactions are suppressed and a new photoreaction takes place, leading to two isomeric dihydroazepinones.

Irradiation of 2,3‐dimethyl‐indazole in diluted sulfuric acid (pH = 3.8) yields 7‐acetyl‐1,3 dihydro‐2 H‐azepin‐2‐one and 3‐acetyl‐1,3‐dihydro‐2H‐azepin‐2‐one.
Ein einfacher Zugang zu 4‐hydroxy‐2,5‐dimethyl‐3(2H)‐furanon (furaneol), einem Aromabestandteil von Ananas und Erdbeere
Authors: Re Luciano , Maurer Bruno , Ohloff Günther
Published: December 2004

Furaneol®

Registered trade mark of Firmenich SA.

[4‐hydroxy‐2,5‐dimethyl‐3(2H)‐furanone (1)], a flavour component of pineapple and strawberry, has been prepared by a two‐step synthesis starting with readily available 3‐hexyne‐2,5‐diol.

By the same method 4‐hydroxy‐5‐methyl‐3(2H)‐furanone (2) and 2‐ethyl‐4‐hydroxy‐5‐methyl‐3(2H)‐furanone (3a) have been prepared from 2‐pentyne‐1,4‐diol and 3‐heptyne‐2,5‐diol, respectively.
Photochemische Reaktionen. 73. Mitteilung. Neuartige Photoreaktionen des (±)‐trans‐β‐Jonon‐epoxids
Authors: von Wartburg Beat R. , Wolf Hans R. , Jeger Oskar
Published: December 2004

The racemic trans‐β‐ionone‐epoxide (7) upon irradiation with light of wavelength 254 nm (in pentane solution) gives rise to novel photochemical processes and formation of compounds 12, 13, 14, and 15.
Säurekatalysierte Umlagerung von trans‐5,6‐Dihydroxy‐5,6‐dihydro‐β‐jonon
Authors: Skorianetz Werner , Ohloff Günther
Published: December 2004

On treatment with acid, trans‐5,6‐dihydroxy‐5,6‐dihydro‐β‐ionone 2 undergoes a clean rearrangement to give a mixture of the furylketone 5 and the aliphatic triketone 6 in good yield.
Mechanistische Untersuchung zur Acyl‐Übertragung von Thioestern auf Amino‐ und Imidazolgruppen
Authors: Wenck Helmut , Polster Jürgen
Published: December 2004

Die Reaktion von 4′‐Mercapto‐acetanilid‐acetat mit n‐Butylamin sowie mit Imidazol wurde bei pH 7,5 und 25,0° mit Hilfe von Reaktionsspektren, Extinktionsdifferenzen‐Diagrammen und Extinktionsdifferenzen‐Quotienten‐Diagrammen untersucht. Die Aminolyse des Thioesters ist «spektroskopisch einheitlich», die Imidazolyse verläuft in zwei linear unabhängigen Reaktionen: Bildung und Hydrolyse von N‐Acetyl‐imidazol.

Durch formale Integration wurden die Geschwindigkeitskonstanten pseudo‐erster Ordnung ermittelt. Unter physiologischen Bedingungen verläuft die Imidazolyse schneller, bei Berücksichtigung der pK‐Werte muss jedoch das Amin als reaktiver betrachtet werden.
Fragmentierung von α,β‐Epoxyketoximen zu Alkinonen. Über Steroide, 228. Mitteilung
Authors: Wieland Peter , Kaufmann Heinz
Published: December 2004

The experimental details of the oxidoketone‐alkynone fragmentation brought about by the treatment of steroidal α,β‐oxido‐oximes with hydroxylamine‐O‐sulfonic acid in alcaline solution at room temperature are presented together with a discussion of the mechanism of this reaction. Studies of a ring closure reaction transforming the fragmentation products back into the starting α,β‐unsaturated ketones are discussed.
Über die Wanderung der Carboxylatgruppe bei der Benzilsäureumlagerung. 26. Mitteilung über Reduktone und Tricarbonylverbindungen
Authors: Rodé‐Gowal Heike , Dahn Hans
Published: December 2004

The benzilic acid rearrangement of ethyl α,β‐dioxo‐butyrate was studied by NMR.‐and UV.‐techniques. In weak alkaline media (pH < 10) the ester group is hydrolyzed first, then the carboxylate group migrates to form methyltartronate. The migration of the carboxylate group was proved by radioactive labeling. At higher pH‐values (pH > 11,5) the intakt ester group migrates, with ester hydrolysis occuring as a second step.
4‐Desoxy‐1‐thio‐β‐D‐glucose und deren Auro‐(1:1)‐Komplex
Authors: Vegh L. , Hardegger E.
Published: December 2004

Die aus dem Formelschema ersichtlichen Umsetzungen führten von der 1,6;3,4‐Dianhydro‐D‐galaktose (Ia) über die 1,6‐Anhydro‐4‐desoxy‐D‐glucose (II) zur 1,2,3,6‐Tetra‐O‐acetyl‐4‐desoxy‐β‐D‐glucopyranose (III). Aus III wurden die instabile Acetohalogenose Vb und daraus das krist. Acetylderivat IIIa des (4‐Desoxy‐β‐D‐glucosyl)‐äthylxanthogenats hergestellt. Alkalische Umesterung mit Methanol führte von IIIa zum Natriummercaptid IIIb, aus dem die krist. 4‐Desoxy‐1‐thio‐β‐D‐glucopyranose (IIIc) gewonnen wurde. Der daraus hergestellte Auro‐(1:1)‐Komplex IIIe war instabil.
Zur Struktur der Scilliglaucosids. 56. Mitt. über Herzglykosided
Authors: Lichti Heinz , Niklaus Peter , von Wartburg Albert
Published: December 2004

The structure of scilliglaucoside, a cardiac active squill glycoside, is revised. The assignment of the new structural formula 1 is made on the basis of NMR. spectral data.
Etude des composés d'addition du monochlorure d'iode avec divers hydrocarbures aromatiques par les méthodes réfractométrique, diélectrique et calorimétrique
Authors: Schaer Jean‐Jaques , Torre Bona , Janjic Désimir
Published: December 2004

The composition of complexes resulting from the interaction of ICl with some aromatic hydrocarbons has been investigated by the method of continous variations applied to measurements of the refractive index, of the dielectric constant, and of the heat of reaction.

Further, the equilibrium constant and the enthalpy of reaction for the formation of ICl. mesitylene complex were determined by dielectric and calorimetric methods. The latter yielded satisfactory results consistent with those obtained by UV. spectroscopy.
Nucleophilic Reactions at Tertiary Carbon. Part 3. σ‐ and π‐routes to the 9‐decalyl cation
Authors: Becker Konrad B. , Boschung André F. , Geisel Manfred , Grob Cyril A.
Published: December 2004

The generation of the 9‐decalyl cation by solvolysis of cis‐ and trans‐9‐decalyl chloride (1) has been reinvestigated. The results of product, rate and isomerization studies implicate stereoisomeric ion pairs as intermediates, as in the case of the solvolysis of other stereoisomeric tertiary chlorides (Parts 1 and 2).

On the other hand, both symmetrically and unsymmetrically solvated 9‐decalyl cations are indicated in the cyclization of 4‐(cyclohexen‐1‐yl)butyl tosylate. No evidence was obtained that conformational isomers of the 9‐decalyl cation play a role as product determining intermediates.
Chemistry of Succinylsuccinic Acid Derivatives. Part I. On the photodimerization of diethyl succinylsuccinate
Authors: Sinnreich Joel , Batzer Hans
Published: December 2004

Topochemically controlled photochemical dimerization of diethyl succinylsuccinate in the solid is reported. The structure evaluation by elemental and spectroscopic analysis of the product is given. The participation of chelated enols in photochemical cycloadditions in the crystalline solid state is here demonstrated for the first time.
Umwandlung von 6‐Methylen‐tricyclo[3.2.1.02,7]oct‐3‐en‐8‐onen in Polymethyltropyliumsalze
Authors: Peter‐Katalinić Jasna , Zsindely Janos , Schmid Hans
Published: December 2004

When dissolved in trifluoroacetic or fluorosulfonic acid, 6‐methylene‐tricyclo[3.2.1.02,7]oct‐3‐ene‐8‐one derivatives of type 2 (;scheme 1); give polymethyltropylium salts in moderate to good yields by CO‐extrusion. These tropylium salts can be isolated pure as hexachloroplatinates. Thus the tricyclic compound 6 gives 1,2,4‐trimethyltropylium trifluoroacetate 19 in trifluoroacetic acid (;scheme 3);. This salt in CDCl3 is in equilibrium with its covalent cycloheptatriene (;tropilidene); form 20, the ratio of the two forms being 1.5–2.1/1. The tropylium salt 19 is reduced by lithium aluminium hydride to a mixture of 1,2,4‐trimethylcycloheptatrienes, isomeric with respect to the double bonds, which on hydride abstraction with trityl‐tetrafluoroborate gives again the 1,2,4‐trimethyltropylium salt 19 (;scheme 3);. From the trimethyl‐substituted tricyclic compounds 7 and 8, in trifluoroacetic acid, are obtained respectively the 1,2,4,6‐ and 1,2,3,4‐tetramethyltropylium ions (;22 and 24); (;schemes 4 and 5);. In this way the 1,2,3,5,6‐pentamethyl‐tropylium ion (;26); was obtained from 9 (;scheme 6);. With the higher substituted tropylium trifluoroacetates in CDCl3 the equilibrium tropylium trifluoroacetate ⇄ trifluoroacetoxycycloheptatrienes lies well to the left. The hexamethylated tricyclic compound 10 gives a small quantity of heptamethyltropylium trifluoroacetate (;27); and as the main product the C(;3);‐protonated species 28 (;scheme 7);, which when treated with aqueous sodium hydrogencarbonate yielded unchanged educt 10. ‐ The heptamethyltropylium ion (;27); was, apart from polymeric species, the only product from the treatment of starting material 10 with fluorosulfonic acid (;50%);; its salts have as yet not been isolated in their pure form, however.

The mechanism for the rearrangement of the tricyclic compounds of type 2 into tropylium salts is presented for compound 6 in scheme 8: The first step is the protonation at C(;9);. Ring opening of the cyclopropane of the tertiary carbenium ion 29 gives the allylic ion 30, which then yields the aromatic tropylium salt 19 by carbon monoxide extrusion in a linear cheletropic reaction.

The smooth conversion with strong acids of the easily accessible tricyclic compounds of type 2 to the corresponding polymethylated tropylium salts, presents a new and useful method for the synthesis of the latter compounds.
Über die Hydrolyse von Eisen(III)Salzlösungen. I. Die Hydrolyse der Lösungen von Eisen(III)chlorid
Authors: Feitknecht Walter , Giovanoli Rudolf , Michaelis Werner , Müller Max
Published: December 2004

When a very diluted iron(III)chloride solution is slowly alkalified by a weak base, the deprotonation of [Fe(H2O)6]3+ proceeds in a first stage to form mono‐ and dinuclear hydroxoaquo‐complexes. In a second stage 4 dimers condense around a chloride ion to form an eight membered ring, an embryon, which grows fast to very small crystals of the composition Fe4O3(OH)5Cl and the structure of the β‐FeOOH. These crystalline micells remain colloidally dissolved. If the pH is raised above approximately 3.4 the Cl−‐ are exchanged against OH−‐ions and flocculation occurs. This shows that Pauli, assuming the micells of such sols to be polynuclear complex ions, is basically correct, and it follows that micells can also be micro‐crystals.

When an iron(III)chloride solution is neutralized fast with a strong base, an ‘amorphous’ precipitation is obtained which gives with MoKα‐X‐rays only two broad reflections, showing that the iron oxide hydroxide octahedra are condensed in a highly disordered way. The coherently scattering areas of this precipitate are probably tetramers. Small amounts of primarily formed amorphous iron(III)hydroxide are transformed into β‐FeOOH.
Synthèse de sucres ramifiés et de sucres aminés ramifiés. Communication préliminaire
Authors: Bourgeois Jean‐Marc
Published: December 2004

When treated with cyanide ion, 1,2:5,6‐di‐O‐isopropylidene‐α‐D‐ribo‐hexofuranos‐3‐ulose yields one or the other of the two corresponding epimeric cyanhydrines, depending on the experimental conditions. One of these epimers, reacted with ammonium cyanide, yields the corresponding amino‐nitrile, the other being unreactive. Several derivatives of these compounds are briefly described.
Über Pterinchemie. 45. Mitteilung. Eine neue und eindeutige Synthese isomerenfreier Pteroyl‐λ‐L‐glutamyl‐L‐glutaminsäure
Authors: Khalifa Esam , Bieri Jost H. , Viscontini Max
Published: December 2004

A new and unequivocal synthesis of pteroyl‐λ‐L‐glutamyl‐L‐glutamic acid free of isomers is described. A melt of N(2′)‐acetyl‐6‐formylpterine and trimethyl‐N‐(p‐amino‐benzoyl)‐λ‐L‐glutamyl‐L‐glutamate was quantitatively converted to 6‐azomethin‐pterine‐trimethylester XI. NaBH4‐reduction followed by basic hydrolysis of acetyl and methyl ester groups gives pure pteroyl‐λ‐glutamyl‐glutamic acid in good yield.
α‐Chlor‐nitrone V: Substitutionsreaktionen an Olefin‐ und Benzolderivaten. Eine Methode zur Darstellung von β,γ‐un‐gesättigten und β‐ arylsubstituierten Aldehyden. Stereospezifische Bildung von tetra‐alkylsubstituierten Olefindoppelbindungen. Über synthetische Methoden, 9. (vorläufige) Mitteilung
Authors: Shatzmiller Shimon , Gygax Peter , Hall David , Eschenmoser Albert
Published: December 2004

The Ag+‐induced α‐chloro‐aldonitrone/olefin reaction in polar solvents can proceed by substitution, thereby providing a method for the preparation of β, γ‐unsaturated aldehydes. Positional as well as configurational retention of the olefinic double bond are mechanistically significant and preparatively useful characteristics of this process. Substitution also occurs with great ease at nucleophilic aromatic nuclei; this offers a simple preparative route to certain β‐aryl‐aldehydes.

The results illustrate a general aspect of the chemistry of α‐chloro‐aldonitrones: the N‐alkenyl‐N‐alkyl‐nitrosonium‐ions derived from them can serve as preparative equivalents of the elusive corresponding α‐acyl‐carbonium‐ions.
Contribution à la phytochimie du genre Gentiana III. Etude des composés flavoniques et xanthoniques dans les feuilles de Gentiana lutea L. (2me communication)
Authors: Hostettmann Kurt , Bellmann Günter , Tabacchi Raphaël , Jacot‐Guillarmod André
Published: December 2004

The xanthone isogentisin and two flavonic heterosides (isocrientin‐4′‐O‐glucoside and isovitexin‐4′‐O‐glucoside) have been isolated from leaves of Gentiana lutea L. by means of column chromatography on polyamide. The determination of the structures and the NMR. spectra of the acetylated derivatives are reported.
Heterotricyclodecanes XVII. 2,7‐Dioxa‐twist‐4‐ene and 2,7‐dioxa‐twista‐4,9‐diene
Authors: Ackermann Peter , Ganter Camille
Published: December 2004

2,7‐Dioxa‐twist‐4‐ene (3) and 2,7‐dioxa‐twista‐4,9‐diene (6) were prepared.
Hyperfine Shifts of the 13C‐NMR. in Protoporphyrin IX Iron (III) Dicyanide and Deuteroporphyrin IX Iron (III) Dicyanide
Authors: Wüthrich Kurt , Baumann Rudolf
Published: December 2004

The 13C‐NMR. in Zn(II) (Protoporphyrin IX), Fe(III) (Protoporphrin IX) (CN)2, Zn(II) (Deuteroporphyrin IX dimethylester), and Fe(III) (Deuteroporphyrin IX) (CN)2 have been identified, and the 13C hyperfine shifts in the iron complexes evaluated. In a partial analysis of these data the parameters QH, QCCHH, and QC′CHC, which characterize the isotropic coupling through hyperconjugation between the 1H and 13C nuclei of the porphyrin side chains and the unpaired electron spin density on the aromatic ring carbon atoms, have been re‐examined. This paper is part of an investigation of the electronic states in low spin ferric hemes and hemoproteins, and the relations between the electronic structures and the biological roles of these molecules.
Synthesis of [2‐p‐Fluorophenylalanine]oxytocin and its Desamino Analogue Using the S‐Acetamidomethyl Protecting Group
Authors: Marbach Peter , Rudinger Josef
Published: December 2004

[2‐p‐Fluorophenylalanine]oxytocin (1a), desamino‐[2‐p‐fluorophenylalanine]oxytocin (1b), and desamino‐oxytocin (2) have been synthesised via intermediates containing S‐acetamidomethyl‐cysteine. The protected linear peptides were built up using both stepwise and fragment‐condensation procedures, and the S‐protecting groups were removed by iodine with simultaneous formation of the disulfide bridge. The uterotonic activities in vitro of the analogues have been determined. The close similarity of the 19F‐NMR. spectra indicates that the p‐fluorbenzyl side chain is freely exposed to the solvent in the disulfide‐bridged hormone analogues as well as in their S‐protected, acyclic precursors.
Quadricyclanes. Part I: Photoelectron spectra and electronic structure
Authors: Martin Hans‐Dieter , Heller Constanze , Haselbach Edwin , Lanyjova Zuzana
Published: December 2004

The photoelectron spectra of quadricyclane (3) and 3‐methylidene quadricyclane (4) have been measured. The results served as a basis for the elucidation of the electronic structure of these compounds, which agreed with theoretical calculations. It is found that the symmetry of the HOMO of 3 is different when compared to that of its valence isomer norbornadiene (1). The results also indicate that the structure of the highest occupied orbitals cannot be derived by only considering the Walsh‐orbitals of the two three‐membered rings. In addition one of the Walsh‐components of the four‐memebered ring has to be taken into account.
Preparation of Diazo Phenyl Sulfides. Kinetics and Mechanism of the Diazo Coupling Reaction of p‐Nitrobenzenediazo Phenyl Sulfide with β‐Naphthol under Various Conditions
Authors: Sakla Alfy Badie , Masoud Nabil Khalil , Sawiris Zaki , Ebaid Wagih Sadik
Published: December 2004

Aryldiazophenyl sulfides prepared from diazotised arylamines and thiophenol at controlled pH, are coupled with β‐naphthol yielding the corresponding azo dye.

A kinetic study of the diazo coupling reaction of p‐nitrobenzenediazo phenyl sulfide with β‐naphthol under various conditions revealed that the reaction is of first order kinetics with respect to the diazo phenyl sulfide, and that the rate of coupling measured colorimetrically is influenced by the hydrogen ion concentration and by the ionising power of the medium.
Stereochemistry of Polynuclear Cadmium(II) Thioglycolates: Crystal structure of cadmium(II) bisthioglycolate
Authors: Bürgi Hans‐Beat
Published: December 2004

Crystals of cadmiumbisthioglycolate are monoclinic, a = 10.06, b = 19.81, c = 8.74 Å, β=107.36°, space group P 21/c, Z = 4. A detailed three‐dimensional analysis shows that cadmium ions and mercaptide sulfur atoms form a two dimensional array of six‐membered and four‐membered rings (Fig. 1). All sulfur atoms bridge two cadmium ions. Of the two kinds of cadmium ions, one shows distorted tetrahedral coordination to four sulfurs, the other one distorted trigonal bipyramidal coordination (Fig. 4) to four sulfurs and to an axial alcohol oxygen atom.
The Mass Spectrometric Fragmentation of 1‐Heptyl Ions Derived from the Corresponding Halides
Authors: Fiaux André , Wirz Bernhard , Gäumann Tino
Published: December 2004

We have studied the fragmentation of 1‐heptyl ions resulting from the loss of halogen from the corresponding halide ions. All positions had been labelled with D and 13C, some positions even doubly labelled. The main processes are the loss of propene and, to a lesser extent, ethylene as neutral fragments. All carbon atoms have a definite probability of being lost with the olefin, those which are terminal having the smallest chance; this precludes an important contribution by direct scission. The source‐and the metastable‐decomposition produced much the same isotopic distribution in the fragments. The terminal hydrogen atoms also have a small chance of being rearranged, whereas those at non‐terminal positions show extensive scrambling. It seems that the fragmentation proceeds via cyclic structures which are rapidly attained and equilibrated amongst each other, but our results do not warrant suggestion of a detailed model.
Identification des composés phénoliques dans les feuilles de Homogyne alpina, Petasites albus, Petasites hybridus et Adenostyles alliariae
Authors: Schwendimann Jean‐Michel , Tabacchi Raffaele , Jacot‐Guillarmod André
Published: December 2004

Four polyphenolheterosides have been isolated from the leaves of Homogyne alpina, Petasites albus, Petasites hybridus and Adenostyles alliariae by means of thin layer and column chromatography on polyamide. Isoquercitrine (II) has been isolated from Petasites albus, Petasites hybridus and Adenostyles alliariae; Astragaline (III) from Petasites albus and Petasites hybridus; Glucoluteoline (IV) from Adenostyles alliariae and Rutine (I) from Homogyne alpina. Piceine (V) has also been isolated from Homogyne alpina.
Über stereoselektive Synthesen und Reaktionen von 5,6‐Epoxy‐perhydroisoindolinen
Authors: Achini Roland , Loosli Hans‐Rudolf , Troxler Franz
Published: December 2004

Stereo‐selective syntheses of 2,5,6‐trisubstituted perhydroisoindolines are achieved by preparation of the three diastereoisomeric 5,6‐epoxy‐perhydroisoindolines and their reactions with nucleophiles, e.g. amines. The transformation of trans‐amino alcohols obtained in this way into cis‐amino alcohols is described.
Acidities of Hydrochloric Acid in Water/Acetic Acid and in Water/Acetic Acid/Formaldehyde Mixtures: Investigations with the indicator method and with the nmr method. 31st communication on investigations in textile chemistry
Authors: Gorrie Thomas M. , Zollinger Heinrich
Published: December 2004

The NMR. chemical shift (δH) of the acidic proton in the systems HCl/H2O and HCl/H2O/HOAc was correlated with the acidity function (Ho)I determined by the indicator method. By using three indicators it could be shown that, except for solutions with very low concentrations of hydrochloric acid, the acidity function (Ho)I correlates with δH in a way which can be rationalized. Addition of 7,5% (W) formaldehyde to these systems changes (Ho)I and δH very significantly, particularly in systems with low water content. Logarithmic rate constants of cellulose formal formation in HCl/H2O/HOAc systems which do not show a linear relationship with (Ho)I, measured without presence of formaldehyde, do so if (Ho)I is measured with formaldehyde present. For these systems, however, δH is not a suitable acidity parameter.
Addition von Acetylendicarbonsäuredimethylester an Imidazole; Aminierung der Addukte: neue Synthesen von 3‐(2‐Imidazolyl)‐2‐pyridon‐4,5‐dicarbonsäureamiden und Pyrido[1,2‐a]pyrazinen
Authors: Troxler Franz , Weber Hans Peter , Jaunin André , Loosli Hans‐Rudolf
Published: December 2004

The reaction between dimethyl acetylene dicarboxylate and 2‐amino‐1‐methylimidazole affords dimethyl 2‐amino‐1‐methyl‐1,3‐diazepine‐5,6‐dicarboxylate in low yield. This 1:1 – adduct was formed by addition of the acetylenic compound to the enamine double bond of the imidazole ring followed by ring enlargement. On the other hand, 2:1 – adducts to the imine bond are isolated in moderate yield when dimethyl acetylene dicarboxylate is treated with either 1‐methyl‐2‐methylmercapto‐imidazole or 1‐methyl‐2‐methylmercapto‐imidazoline. These adducts behave differently on heating with ethylamine: the adduct of the imidazole series cyclizes to the pyridone 15 with concomittant loss of one carboxamide group whereas that of the imidazoline series forms a pyrido[1,2‐a]pyrazine derivative 20, both in high yield. The possible reaction mechanisms are discussed. 13C–NMR.‐spectroscopy and X‐ray analysis were used in the determination of several structures.
Ein neuer, ergiebiger Zugang zu Dihydroactinodiolid und α‐substituierten Furanderivaten
Authors: Von Wartburg Beat R. , Wolf Hans R.
Published: December 2004

Dihydroactinodiolid 1 is formed in high yields by oxidation of the alcohols 2 and 3 and the ether 4. Furthermore, the oxidation of the epoxy‐alcohols 13 and 14 gives rise to the formation of furancompounds (15 and 16, respectively).
Photochemische Primärreaktionen α‐verzweigter aliphatischer Ketone und Aldehyde in lösung
Authors: Blank Bernd , Henne Andreas , Fischer Hanns
Published: December 2004

UV.‐Irradiation of methyl t‐butyl ketone, di‐t‐butyl ketone, pivalaldehyde and isobutyraldehyde in benzene solution leads to chemically induced dynamic nuclear polarization (CIDNP.) of the parent compounds and of various reaction products. CIDNP.‐effects and product distributions establish type I α‐cleavage predominantly of triplet state molecules as the major primary photochemical step for all the four α‐branched carbonyl compounds. In chlorinated solvents singlet reactions interfere with the triplet processes.
Electronic States of 1,5‐Cyclooctadiyne Radical Cation and of Related Systems: The electronic structure of cis‐bent carbon‐carbon triple bonds
Authors: Bieri Gerhard , Heilbronner Edgar , Kloster‐Jensen Else , Schmelzer Andreas , Wirz Jakob
Published: December 2004

The photoelectron spectra of 1,5‐cyclooctadiyne (2) and of 1,6‐dithiacyclodeca‐3,8‐diyne (3) have been recorded. The first four (2) or six (3) PE. bands have been assigned as follows; in increasing order of ionization potentials:

The relative sequence and the positions of the PE. bands are explained in terms of through‐bond and through‐space interactions between the basis π‐orbitals and σ‐orbitals of appropriate symmetry behaviour.

An analysis of the PE. spectroscopic data for cyclooctyne (1) and for (2) indicates that a cis‐bend of the acetylene moiety by θ < 20° leads to a split in energy of the in‐plane and out‐of‐plane basis π‐orbitals which is smaller than ∽ 0.2 eV. This is in agreement with the predictions derived from semiempirical models (MINDO/2, SPINDO) and qualitative orbital arguments. However, it is shown by using orbital localization procedures, that the rationales underlying the two semiempirical models differ significantly.
Metal Complexes with Macrocyclic Ligands, V. Formation and dissociation kinetics of the pentaco‐ordinated Ni2+, Cu2+, Co2+ and Zn2+ complexes with 1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane
Authors: Hertli Liselotte , Kaden Thomas A.
Published: December 2004

The formation and dissociation kinetics of the pentaco‐ordinated Cu2+, Ni2+, Co2+ and Zn2+ complexes with 1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane (4‐MeCyclam‐14) was studied by pH‐stat techniques and spectrophotometrically. The rates of the reactions between 4‐MeCyclam‐14 and each of the four metal ions, although slower than normal complexations by a factor of 103−104, closely follow the order Cu2+ > Zn2+ > Co2+ > Ni2+, found for the rate of water exchange. This implies that beside water exchange an other constant factor plays an important role in the rate determing step. The dissociation of the pentaco‐ordinated 4‐MeCyclam‐14 complexes is acid catalyzed. The limiting rate for acid dissociation is not reached even in 2.5M HNO3 in the case of Ni(4‐MeCyclam‐14)2+. From the formation and dissociation rates stability constants have been calculated, which do not show any macrocyclic effect.
Anil‐Synthese. 11. Mitteilung. Über die Darstellung von in 4′‐Stellung substituierten 4‐Styryl‐stilben‐, 4‐(Benzo[b]furan‐2‐yl)‐stilben‐ und β‐(2‐Phenyl‐benzo[b]furan‐6‐yl)‐styrol‐Derivaten
Authors: de Buman Alain , Siegrist Adolf Emil
Published: December 2004

Schiff'sche Basen aus Stilben‐4‐carbaldehyd, 2‐(p‐Formyl‐phenyl)‐benzo[b]furan und 2‐Phenyl‐6‐formyl‐benzo[b]furan und p‐Chloranilin können mit p‐tolyl‐ bzw. methyl‐substituierten heterocyclischen und carbocyclischen Aromaten in Gegenwart von Dimethylformamid und Kaliumhydroxid bzw. Kalium‐t‐butylat in die entsprechenden Stilben‐bzw. Styrol‐Derivate übergeführt werden («Anil‐Synthese»).

Die Lage der Absorptions‐ und Fluoreszenz‐Maxima der dargestellten Grundkörper der Benzo[b]furan‐Reihe wird mit derjenigen entsprechender Stilben‐Verbindungen verglichen.
Photoinduzierte 1, 3‐dipolare Cycloaddition von 3‐Phenyl‐2H‐azirinen an Azodicarbonsäure‐diäthylester. 32. Mitteilung über Photoreaktionen
Authors: Gilgen Paul , Heimgartner Heinz , Schmid Hans
Published: December 2004

Irradiation of 2, 2‐dimethyl‐3‐phenyl‐ (1a), 2, 3‐diphenyl‐2H‐azirine (1b) or the azirine‐precursors 1‐azido‐1‐phenyl‐propene (2a) and 1‐azido‐1‐phenyl‐ethylene (2b), respectively, in benzene in the presence of azodicarboxylic acid diethylester, yields the corresponding 1, 2‐carbethoxy‐3‐phenyl‐Δ3‐1, 2, 4‐triazolines 4a–d (Scheme 1).

Refluxing 4 (a, c or d) in 0, 2–0, 4M aqueous ethanolic potassium hydroxide leads to the formation of the 1‐carbethoxy‐3‐phenyl‐Δ2‐1, 2, 4‐triazolines 6 (a, c or d). Under the same conditions 4b is converted to 3, 5‐diphenyl‐1, 2, 4‐triazole (7b, Scheme 2). In 10M aqueous potassium hydroxide solution heating of either 4 (c or d) or 6 (c or d) yields the 3‐phenyl‐1, 2, 4‐triazoles 7 (c or d).

Photolysis of 1‐carbethoxy‐5, 5‐dimethyl‐3‐phenyl‐Δ2‐1, 2, 4‐triazoline (6a) in benzene in the presence of oxygen and trifluoroacetic acid methylester gives the 5‐methoxy‐2, 2‐dimethyl‐4‐phenyl‐5‐trifluoromethyl‐3‐oxazoline (13, Scheme 5). 5, 5‐Dimethyl‐3‐phenyl‐1, 2, 4‐triazole seems to be the intermediate, which on losing nitrogen gives the benzonitrile‐isopropylide (3a).
Comparison of 13C‐ and 1H‐Magnetic Resonance Spectroscopy as Techniques for the Quantitative Investigation of Dynamic Processes. The cope rearrangement in bullvalene
Authors: Oth Jean F. M. , Müllen Klaus , Gilles Jean‐Marie , Schröder Gerhard
Published: December 2004

The potential advantages of 13C‐(1H‐noise decoupled) spectroscopy (in the Fourier transform mode) over 1H‐spectroscopy for the quantitative investigation of molecular dynamic process is discussed. The Cope rearrangement in bullvalene, an example of complex exchange of spins over different magnetic sites, has been studied by both kinds of spectroscopy as a test.
Beweis der absoluten Konfiguration der Xanthophyll‐5, 6‐epoxide (Luteinepoxide)
Authors: Cadosch Herbert , Eugster Conrad Hans
Published: December 2004

Natürliches (+)‐Xanthophyllepoxid kann, nach Umwandlung in die diastereomeren furanoiden Epoxide, mit NiO2 zu ( − )‐Loliolid abgebaut werden. Semisynthetisches Xanthophyllepoxid gibt hauptsächlich Isololiolid. Daraus folgt, dass bei der säurekatalysierten Umlagerung der 5, 6‐Epoxide an C(5) praktisch keine Inversion eintritt und dass nat. (+)‐Xanthophyllepoxid die (3S, 5R, 6S, 3′R, 6′R)‐ und synth. Xanthophyllepoxid im wesentlichen die (3S, 5S, 6R, 3′R, 6′R)‐Konfigurationen besitzen.
Sur l'amino‐5‐benzoyl‐4‐méthyl‐3‐isoxazole: synthèse et transformation en dihydro‐6,8‐diméthyl‐3,8‐phényl‐4‐7H‐isoxazolo[5,4‐e]diazépin‐1,4‐one‐7
Authors: Jaunin Roland
Published: December 2004

On treatment with ammonia and benzaldehyde the benzalisoxazolone 3 does not give the aminoketone 7 as assumed by Speroni [1] but a product which has been shown to be identical with the enamine 8 prepared by Ried & Czack [4] from ethyl oximinoacetoacetate and benziminoethyl ether. Authentic aminoketone 7 was synthesized in a three‐step procedure starting from the aminonitrile 19. Conversion of 7 into the bromacetyl derivative 23 and subsequent treatment with hexamethylene‐tetramine yielded the isoxazolodiazepine 24. Methylation of 24 with diazomethane produced predominantly the N‐methyl derivative 1 along with a small amount of the O‐methyl compound 25.
Isokinetic Relationships in Alcohol Oxidation with Chromic Acid
Authors: Müller Paul , Perlberger Jean‐Claude
Published: December 2004

The activation parameters for the oxidation of 13 secondary alcohols with chromic acid have been determined. Application of a statistical treatment of Exner [9] shows that the reactions are isoentropic with an average entropy of activation (ΔS≠) of −24.0 e. u.
Neue Derivate der 7‐Amino‐cephalosporansäure. Über die Substitution der Acetoxygruppe durch aromatische Reste. Modifikationen von Antibiotica, 11. Mitteilung [1]
Authors: Peter Heinrich , Rodriguez Hermann , Müller Beat , Sibral Walter , Bickel Hans
Published: December 2004

7‐Phenylacetamido‐3‐trifluoroacetoxymethyl‐ceph‐2‐em‐4‐carboxlic acid (7), which is easily produced from the iso‐cephalosporanic acid derivatives 4 or 6 by treatment with trifluoroacetic acid, reacts smoothly with ‘C‐nucleophiles’ to give derivatives of type 5 (Schema 1 and 2). Compounds 5 are converted into microbiologically active cephalosporins of type 8 (Table) by previously described methods.
Neue β‐Lactam‐Antibiotika. Über die Darstellung und Decarbonylierung von 3‐Formylcephem‐Verbindungen. Modifikationen von Antibiotica, 12. Mitteilung [1]
Authors: Peter Heinrich , Bickel Hans
Published: December 2004

Benzhydrylic esters of 3‐unsubstituted cephem‐4‐carboxylic acids of types 9 and 10 (Scheme 2) are prepared by decarbonylation of esters of 3‐formylcephem compounds of type 2 with tris‐triphenylphosphine‐rhodium chloride. The preparation of the starting materials 2 and 5, as well as of the nucleus 13 is described.
Terpenoids Derived from Linalyl Oxide, Part 4. The oxidation of davanone. Isolation and synthesis of the davana ethers, sesquiterpenes of Artemisia Pallens
Authors: Thomas Alan F. , Dubini Renée
Published: December 2004

The photosensitized oxygenation of the β,γ‐unsaturated ketonic sesquiterpene, davanone, is described. Treatment of davanone epoxide with an acid ion exchange resin yields a stereoisomeric mixture of the davana ethers, sesquiterpenoids containing two reduced furan rings.
The [2,3] Sigmatropic Reaction of Acetonyl Allyl Ethers, a new method for preparing certain 2‐hydroxyketones
Authors: Thomas Alan F. , Dubini Renée
Published: December 2004

A new [2] [3] sigmatropic rearrangement is described, enabling the conversion of acetonyl allyl ethers to 3‐hydroxy‐5‐en‐2‐ones.
Dediazoniations of Arene Diazonium Ions in Homogeneous Solution. Part VI: Solvolyses in 2,2,2‐trifluoroethanol/water mixtures and exclusion of a potential aryne mechanism
Authors: Burri Peter , Wahl George H. , Zollinger Heinrich
Published: December 2004

The rates and products of dediazoniation of benzenediazonium tetrafluoroborate in 2,2,2‐trifluoroethanol (TFE)/water mixtures has been determined. The results are not consistent with a mechanism in which TFE and water enter the rate‐determining part of the reaction as nucleophiles. The influence of the solvent composition on product ratios and rates is explained as a solvent effect, the formation of a (solvated) aryl cation being the rate‐determining part of the reaction. The magnitude of the preexponential factor of the Arrhenius equation is consistent with this interpretation. Since the solvolysis of p ‐chlorobenzenediazonium tetrafluoroborate in TFE yields no detectable m‐products, an aryne‐like mechanism is excluded.
On the Ring‐Expansion in Aromatic Nitrenes and Carbenes
Authors: Gleiter Rolf , Rettig Wolfgang , Wentrup Curt
Published: December 2004

The ring expansion, phenylnitrene (1) → azepinylidene (3) has been investigated using the CNDO/2 and Extended Hückel method. Both methods predict that the nitrene‐nitrogen of 1 is moving out of the molecular plane on the path of minimum energy. Whether an intermediate 2 is formed or not, the net charge during the reaction indicates that an interaction between the filled nitrene p‐orbital and an empty MO of the ring is important in lowering the transition state. The results are compared with experimental results of arylnitrenes and arylcarbenes. The rearrangement of tolylcarbenes to benzocyclobutene and styrene has been reexamined experimentally and interpreted in terms of the dynamics of the out of plane movement of the carbene during ring expansion.
Die Aufklärung der Isomerie‐Ursachen bei äquatorial koordinierten 2 : 1‐Arylazo‐Co(III)‐Komplexen mit Hilfe der kernmagnetischen Protonenresonanz
Authors: Schetty Guido , Steiner Eginhard
Published: December 2004

Von methylgruppenhaltigen o, o‐′Dihydroxy‐diarylazo‐Liganden und ihren 1 : 2‐Co(III)‐Komplexen wurden die chemischen Verschiebungen (δ) der Methylprotonensignale im 1H—NMR.‐Spektrum bestimmt. Dabei wurde festgestellt, dass der Wert der chemischen Verschiebung von der Stellung der Methylgruppe am Arylrest und von ihrer relativen Lage zum koordinierten Stickstoffatom abhängt. Durch Vergleich der erhaltenen Werte, mit denen der entsprechenden methylgruppenhaltigen o, o′‐Dihydroxy‐diarylazomethine bzw. ihrer 1 : 2‐Co(III)‐Komplexe gelang es, Regelmässigkeiten zu finden, mit deren Hilfe als Isomerieursache bei 2 : 1‐Arylazo‐Co(III)‐Komplexen wechselweises Koordinieren der beiden Stickstoffatome (Nα/Nβ‐Isomerie) bewiesen und das koordinierte Stickstoffatom bezeichnet werden konnte.

Ausserdem wurden an zwei Beispielen isomere 1 : 2‐Co(III)‐Komplexe nachgewiesen, in welchen das Metallin an das gleiche Stickstoffatom koordiniert ist, womit das frühere Postulat der Azo‐Hydroazon‐Tautomerie als eine weitere Isomerie‐Ursache in Metallkomplexen eine starke experimentelle Stütze erhalten hat.

Die Beobachtung zweier isomerer 1 : 2‐Co(III)‐Komplexe eines o, o′‐Dihydroxyazomethins legt in diesem Fall das gleichzeitige Vorliegen der Azomethin‐ und der Chinonmethidstruktur nahe.