bluuebunny/crossref_metadata_2025 huggingface dataset:
Photochemie substituierter Cycloheptatriene. XII. Dualfluoreszenz von 1‐Aryl‐4‐(p‐dimethylaminophenyl)‐cycloheptatrienen
Authors: Abraham W. , Kupfer M. , Kreysig D.
Published: December 2004

Photochemistry of Substituted Cycloheptatrienes. XII. Dual Fluorescence of 1‐Aryl‐4‐(p‐dimethylaminophenyl)‐cycloheptatrienes

Diarylcycloheptatrienes 1 in solution show two fluorescences originating from two different excited states. The ratio of intensities of the two fluorescences depends on the excitation energy. Two alternatives are discussed as the origin of the dual fluorescence: conformers in the ground state or an adiabatic photoreaction, respectively. The two emissions are ascribed to different geometries of the seven‐membered ring. Despite the different excitation spectra the dual fluorescence of the compounds 1 is explained as an excited state property of a single absorbing species, and not as two ground state species giving rise to the two fluorescence bands.
Phosphororganische Antioxidantien. II. Kinetik und Mechanismus der Zersetzung von Alkylhydroperoxiden durch Esteramide der phosphorigen‐ und Phosphorsäure
Authors: Rüger C. , Arnold D. , Schwetlick K.
Published: December 2004

Organophosphorus Antioxidants. II. Kinetics and Mechanism of the Decomposition of Alkylhydroperoxides by Esteramides of Phosphorous and Phosphoric Acid

The reaction mechanism of 2‐amido‐1,3,2‐benzodioxaphospholes (1) with cumyl and t‐butylhydroperoxide has been studied kinetically by means of 31P‐n.m.r. and e.p.r. spectroscopy and high pressure liquid chromatography. 1 reacts with cumyl hydroperoxide to give the corresponding 2‐oxides (2) which with more hydroperoxide and/or water form the phosphate esters 7 and 8. These acidic phosphates decompose cumyl hydroperoxide catalytically giving phenol and acetone.

All amides (1) react with t‐butyl hydroperoxide stoichiometrically to give t‐butanol.

The ionic mechanism of hydroperoxide decomposition is accompanied in a minor proportion by a homolytical one.
Semiempirical and ab initio Calculations on the Tautomerism of Pyrazolin‐5‐ones in the Gas Phase and in Solution
Authors: Krebs C. , Förster W. , Köhler H.‐J. , Weiss C. , Hofmann H.‐J.
Published: December 2004

Semiempirische und ab initio Berechnungen zur Tautomerie von Pyrazolin‐5‐onen in der Gasphase und in Lösung

Es werden die Ergebnisse einer durchgehend theoretischen Behandlung der Tautomeriegleichgewichte von Pyrazolin‐5‐onen vorgestellt. Der Formalismus beinhaltet die Berechnung der potentiellen Energie mit Hilfe des MNDO‐, STO‐3G‐ und 4‐31 G‐Verfahrens, die statistisch‐thermodynamische Behandlung der Gleichgewichte unter Zugrundelegung des MNDO‐Kraftfeldes und die Abschätzung des Lösungsmitteleinflusses mit Hilfe verschiedener klassischer und quantenchemischer Reaktionsfeldmodelle.
Ionisation von Triphenylmethylbromid in Nitromethan
Authors: Heublein Günther , Bauerfeind Dietmar
Published: December 2004

Ionisation of Triphenylmethylbromide in Nitromethane

Dissolving triphenylmethylbromide in nitromethane leads to the formation of HBr which complicates conductivity and spectroscopic measurements of carbenium ion absorption. As a result of addition of bromide ions (as tetraethylammonium bromide = Et4NBr) the triphenylmethylabsorption totally disappeares. It can be concluded that Ph3CBr in nitromethane is partially present in form of free (solvated) ions. The carbenium ion concentration has been determined as a function of gross concentration and temperature.
Zur Temperatur‐ und Viskositätsabhängigkeit der Fluoreszenzquantenausbeuten von donator‐substituierten 4′‐Diphenylphosphinyl‐trans‐stilbenen in wenig viskosen Lösungsmitteln unterschiedlicher Polarität
Authors: Gloyna D. , Alder L. , Repke D.
Published: December 2004

The Dependence of Fluorescence Quantum Yields of Donor Substituted 4′‐Diphenylphosphinyl trans‐Stilbenes on Temperature and Viscosity in Low Viscous Solvents of Different Polarity

The dependence of fluorescence quantum yields of donor substituted 4′‐diphenylphosphinyl trans‐stilbenes 1 on temperature was investigated between 15–65°C in toluene and n‐propanol. It is concluded that the fluorescence quantum yield dependence on temperature is due to the dependence of nonradiative deactivation on solvent viscosity. The nonradiative deactivation is attributed to the ethylene bond rotation in 1. The rotation around the ethylenic bond and the fluorescence are the two most important deactivation processes detected up to now for the first excited singlet of 1 in liquid solution.
Umsetzung von α‐Cyano‐β‐aryl‐acrylsäure‐ethylestern mit Hydrazin, eine Retro‐Knoevenagel‐Reaktion
Authors: Geissler G. , Hippius M. , Tomaschewski G.
Published: December 2004

Reaction of α‐Cyano‐β‐aryl Acrylic Acid Ethylesters with Hydrazine, a Retro‐Knoevenagel‐Reaction

We tried to obtain 4‐cyano 5‐aryl pyrazolidones‐(3) 3a, b and related azomethine imines 4a, b. However the reaction of α‐cyano β‐aryl acrylic acid ethylesters 2a, b with hydrazine yields the familiar cyano acetic acid arylidene hydrazides 5a, b by cleavage of the carbon‐carbon double bond. 5a, b react with pyrene‐1‐aldehyde to 7a, b. Formation of 5a, b is proved by an independent synthesis. 5a, b and 7a, b are investigated by mass spectrometry.
Synthese und Struktur neuer 1‐Imino‐1λ4,2,4,6‐thiatriazine
Authors: Fischer E. , Rembarz G. , Teller M.
Published: December 2004

Synthesis and Structure of Novel 1‐Imino‐1λ4,2,4,6‐thiatriazines

O,O′‐Dimethyldiisobiurete 1 is cyclisized with N‐arylsulfonyl sulfinyl amines 4a–c to 1λ4,2,4,6‐thiatriazines 9a–c. The reaction with corresponding sulfur diimides 7a–c leads to identical 1λ4,2,4,6‐thiatriazines 9a–c. Methylation products from 9c with diazomethane are isolated by column chromatography. The cyclization mechanism with a substituted imido sulfurous diamide intermediate is discussed.
Eigenschaften und thermische Reaktionen von Komplexen der Arendiazoniumsalze mit Kronenethern
Authors: Becker H. G. O. , Israel G. , Kalauch Angelika , Pfeifer D.
Published: December 2004

Properties and Thermal Reactions from Complexes of Arene Diazonium Salts with Crown Ethers

In contrast to 18‐crown‐6, the substituted crown ethers Benzo‐18‐crown‐6, Dibenzo‐18‐crown‐6, and Naphtho‐18‐crown‐6 form in solution complexes with p‐CH3C6H4N2+BF4‐characterized by a broad charge transfer absorption up to 550 nm. The formation constants lg Kc are 2,32 2,16 and 1,44 for Benzo‐, Dibenzo‐, and Naphtho‐18‐crown‐6, respectively. Formation enthalpy ΔH = −7,5 kJ/mol and entropy ΔS = +18 J/K mol are measured in the case of p‐ClC6H4N2+BF4− and Dibenzo‐18‐crown‐6 (20°). Kc depends on substituents in the arene ring of the diazonium salt; ϱ = +0,8. Thermal dediazoniation in the presence of Crown ethers results in high yields of the corresponding arene. This is explained by a fast radical chain reaction between the diazonium salt and the polyether (Meerwein‐Reduction).
Zur Isomerisierung von Benzilphenylosazonen in Gegenwart von Säuren
Authors: Spassov A. W. , Christova N. I.
Published: December 2004

Isomerisation of Benzilphenylosazones in the Presence of Acids

Isomerisation process of the three stereomeric benzilphenylosazones (Z,Z E,E and Z,E) in a melt of trichloracetic acid and in an ethylacetate solution of conc. sulfuric acid is studied. It is established that the convertion runs irreversibly to the stable E,E‐isomer at low acid concentration. The process is reversible at high acid concentration and the equilibrium state depends on this concentration.
Cyclisierungsreaktionen β,γ‐ungesättigter Kohlensäurederivate. VII. Synthese eindeutig N‐acylierter Thiazolidin‐2‐one und Oxazolidin‐2‐one
Authors: Widera R. , Mühlstädt M.
Published: December 2004

Cyclization Reactions of β,γ‐Unsaturated Derivatives of Carbonic Acid. VII. Synthesis of Unequivocal N‐Acylated Thiazolidine‐2‐ones and Oxazolidine‐2‐ones

A new synthetic route to N‐acylated thiazolidine‐2‐ones and oxazolidine‐2‐ones is reported: The reaction of carboxylic acid chlorides with 2‐alkoxy‐2‐thiazolines (1, 2) or ‐2‐oxazolines (3) yields unequivocal N‐acylated thiazolidine‐2‐ones (4–6) or oxazolidine‐2‐ones (7). Bifunctional acid chlorides, e.g. oxalyl chloride or thiophosgene yield compounds 11 and 12.
Über die Nitril‐Carboxamid‐Umlagerung und die Heterocyclenbildung aus 2‐Cyancyclohexenylharnstoff
Authors: Bischoff Christian , Schröder Edith
Published: December 2004

The Nitrile Carboxamide Rearrangement and the Formation of Heterocycles via Cyano‐cyclohexenyl‐urea

Anthranilic amide and cyanogen bromide form Cyano‐phenyl‐urea (7) via Nitrile Carboxamide Rearrangement. Cyclisation of cyano‐cyclohexenyl‐urea (4) yields 4‐amino‐2,3,5,6,7,8‐hexahydroquinazolin‐2‐one (10). 4 and amines form N‐cyano‐cyclohexenyl‐N'‐alkyl‐ureas (11a–e) or 3‐alkyl‐4‐amino‐hexahydroquinazolin‐2‐ones (12a–g). 4 and α‐aminoacids yield octahydro‐imidazolo‐quinazolindiones (14a–b). Oxo‐cyclohexane‐2‐carboxamide (1) and amino benzimidazole form hexahydrobenzimidazo‐quinazolinone 17.
On the Interpretation of the Solvent Influence on Spectroscopic and Photophysical Parameters by means of multiparameter models
Authors: Kupfer M. , Abraham W.
Published: December 2004

Zur Interpretation des Lösungsmitteleinflusses auf spektroskopische und photophysikalische Parameter mittels Mehrparametermodellen

Die Anwendung von Mehrparametermodellen nach Kamlet und Taft auf die Solvatochromie von Absorption und Fluoreszenz sowie auf photophysikalische Parameter wird durch Beispiele aus der Literatur und durch eigene Beispiele demonstriert.

Dabei werden besonders spezifische Wechselwirkungen zwischen Substrat und Lösungsmittel diskutiert. Mit Hilfe der Regressionskoeffizienten von multiplen Korrelationen lassen sich Beziehungen zwischen der Struktur der Substrate und dem Ort der spezifischen Wechselwirkungen herstellen.

Die Beschreibung dynamischer Prozesse gelingt mit der Einführung eines zusätzlichen Viskositätsparameters, der auf der scheinbaren Arrheniusschen Aktivierungsenergie der Lösungsmittelviskosität beruht.
Elektrochemie organischer Kationen. Arylsubstituierte Tropyliumsalze
Authors: Dreher B. , Abraham W. , Pragst F.
Published: December 2004

Electrochemistry of Organic Cations. Arylsubstituted Tropylium Salts

The electrochemical behaviour of some mono‐ and diarylsubstituted tropylium perchlorates in acetonitrile was investigated and is discussed in connection with their u. v.‐vis absorption spectra.
Festphasensynthese von Oligodesoxyribonucleotiden an Polystyren‐Teflon‐Trägern nach der Diestermethode
Authors: Birch‐Hirschfeld E. , Weiss R. , Rosenthal A. , Cech D.
Published: December 2004

Phosphodiester Solid Phase Synthesis of Oligodeoxyribonucleotides on Polystyrene‐Teflon‐Supports

Phosphodiester solid phase method on two different polystyrene‐teflon‐supports has been applied for for the rapid synthesis of the hexanucleotides d(TCTAGA), d(TGTCAA), d(TTGACA) and the octanucleotides d(CATTATAC) and d(GTATAATG)

Als Abkürzungen für die Nucleinsäurebausteine und deren Schutzgruppen wurden die von der IUPAC‐IUB Commission on Biochemical Nomenclature (CBN) empfohlenen Regeln verwendet, vgl. Hoppe‐Seyler's Z. Physiol. Chem. 351, 1055 (1970); außerdem wurden abgekürzt:

DEAE = O‐(Diethylamino)ethyl, HPLC = Hochdruckchromatographie, O.D.E. = optische Dichteeinheit [17], TEAB = Triethylammoniumbicarbonat, TFA = Trifluoressigsäure, Tris = α,α,α‐Tris‐(hydroxymethyl)‐methyl‐amin

, respectively. In the case of hexanucleotides a polymeric support with 90 mg polystyrene/g support has been used. The octanucleotides were prepared using a 180 mg polystyrene/g support. The yields of all oligonucleotides were 42–51%/condensation step.
Komplexchemisches Verhalten von N‐substituierten 2‐(oHydroxyphenyl)‐Δ2‐imidazolinen als Metallextraktionsmittel
Authors: Beger J. , Wagner G. , Dinjus U. , Görls H. , Uhlig E. , Sieler J.
Published: December 2004

The Coordinative Behaviour of N‐Substituted 2‐(Δ2‐Imidazolin‐2‐yl)‐phenols as Metal Extractants

N‐Substituted 2‐(Δ2‐imidazolin‐2‐yl)‐phenols (R4NNOH) are obtained by the reaction of N‐alkyl diaminoethane‐1, 2 and 2‐hydroxybenzoic acid esters. In contrast to many other copper(II) complexes with the donor set N2O22−(A), the species Cu(R4NNO)2(B) are easily soluble in nonpolar solvents. The reason is the monomeric square‐planar structure of B, which differs from the polymeric distorted octahedral structure of A.

The two maxima in the vis‐spectra of Cu(R4NNO)2 and Ni(R4NNO)2 are assigned to the 3 dxy → 3 dx2‐y2 and the 3 dxz, 3 dyz → 3 dx2‐y2 electron transitions. The shift of these maxima, which is connected with the dissolution in chloroform, is explained by the formation of hydrogen bonds between the solvent and the N‐alkylated nitrogen atoms of the ligands.

1H‐n. m. r.‐spectra and solubility of the ligands and the crystal structure of Cu[(C4H9)NNO]2 are described.
Desaktivierungsverhalten von Arenen und Heteroarenen. XXXVI. Zum Lösungsmittel‐ und Temperatureinfluß auf das Desaktivierungsverhalten von 9, 9′‐Bis(acridizinium‐yl) bei hohen Konzentrationen
Authors: Bendig J. , Helm S. , Kreysig D. , Schmidt H.
Published: December 2004

Deactivation Behaviour of Arenes and Heteroarenes. XXXVI. The Solvent and Temperature Dependence of Deactivation Behaviour of 9, 9′‐Bis(acridizinium‐yl) at High Concentration

At room temperature the geometrical structure of the fluoresceing singlet state of 9, 9′‐bis(acridizinium‐yl) is determined by the solvent. In solvents of the type A (water, methanol, acetonitril) a plain S1‐state emits, in the case of the solvent type B (ethanol, propanol‐(2)) the S1‐state is twisted. Both excited states have different emission spectroscopical properties.

At high concentration (c ≥ 10−4 mol l−1) in the case of the solvent type B a new emission band is observed, and the monomer emission is quenched. This new band is interpreted as a fluorescence from a molecular associate in the excited state. The intensity of this associate band is increasing with decreasing temperature. It is shown that this band is the result of molecular association in the ground state. From the photochemical irradiation it follows that only in the case of the solvent type B a photocycloaddition is possible. The plain S1‐state does not react.
Stereochemische Untersuchungen heterocyclischer Verbindungen. XII. Kristall‐ und Molekülstruktur von 1‐(2‐Amino‐1‐cyano‐2‐thio‐ethylen)pyridiniumyliden
Authors: Fischer E. , Knippel M. , Wollin K.‐M. , Kálmán A. , Argay Gy.
Published: December 2004

Stereochemical Investigations of Heterocyclic Compounds. XII. Structural Investigations of 1‐(2‐Amino‐1‐cyano‐2‐thio)ethene Pyridinium Ylides

Two isomerization processes were found by 1H‐d‐n. m. r. characterized by ΔG* = 67 ± 4 KJ/mol for E‐ Z‐isomerization and ΔG* = 46 ± 5 KJ/mol for the hindered rotation of the pyridine substituent in 1a. The structure of 1b was solved by direct method. Crystals are monoclinic space group P21/n, a = 13.682(3), b = 9.452(1), C = 19.713(6) Å, β = 96.42(2)°, V = 2533.3 Å3, Dx = 1.328 Mg · m−3, Z = 8. Both E‐ and Z‐isomeres of 2b are found in the crystal lattice. The aminoC distance with 1.369 (1,387) Å is shorter than the theoretical single bond distance. The formal CC double bond with 1.377 (1.391) Å is considerably longer than 1.337 Å observed in the some alkenes.
The Electrochemical Synthesis of Benzindoles from aminonaphthalenes in the presence of arsonium ylide
Authors: Rastogi Ravi , Zutshi Kamala
Published: December 2004

Die elektrochemische Synthese von Benzindolen aus Aminonaphthalenen in Gegenwart von Arsoniumyliden

Die elektrochemische Synthese von 2‐Aryl‐1 H‐benz[g]indolen (3a–c) und 2‐Aryl‐3 H‐benz[e]indolen (4a–c) aus methanolischer Lösung von 1‐ oder 2‐Aminonaphthalenen in Gegenwart von kathodisch gebildeten Arsoniumyliden (2a–c) wird beschrieben.

Die optimalen Synthesebedingungen werden diskutiert.magnified image
13C‐NMR‐Spektroskopie von bromierten 3‐Keto‐ und 3β‐Acetoxy‐5α‐cholestan‐Verbindungen
Authors: Römer J. , Scheller D.
Published: December 2004

13C‐NMR Spectroscopic Investigations of Brominated 3‐Keto‐ and 3β‐Acetoxy‐5α‐cholestane Derivatives

The chemical shifts of some brominated 3‐keto‐ and 3β‐acetoxy‐5α‐cholestane derivatives are determined. The substituent effects of bromine atoms on chemical shifts (SCS) and their additive behaviour, especially γ‐SCS, are discussed.
Analytische Probleme der Reaktion zwischen polymergebundenen Phosphinen und Methyliodid
Authors: Paetzold E. , Oehme G. , Pracejus H.
Published: December 2004

Analytical Problems of the Reaction between Polymer Supported Phosphino Groups and Methyl Iodide

A series of different crosslinked styrene‐divinylbenzene‐copolymers bearing diphenyl phosphinomethyl groups was reacted with methyl iodide in ethanol. The quaternization has been controlled by elementary analysis of P and I and by ir spectroscopy using a key band at 1123/cm. The spectroscopic method gave satisfactory results with sample amounts of 5 mg polymer in KBr discs. In resins containing up to 7% divinylbenzene the methylation was almost quantitative within 1 h refluxing. However, in highly crosslinked polymers ( > 10% DVB) containing residues of free chloromethyl groups and intraresin quaternized phosphino groups we observed side reactions in boiling ethanol. These could be avoided by performing the methylation in toluene at room temperature.
3‐Amino‐thieno[2,3‐b]furane und 3‐Amino‐thieno[3,2‐b]furane
Authors: Gewald K. , Bellmann P.
Published: December 2004

3‐Amino‐thieno[2,3‐b]furans and 3‐Amino‐thieno[3,2‐b]furans

The O‐alkylation of 2‐hydroxy‐thiophene‐3‐carbonitriles (1) with α‐bromocarbonyl compounds yields the 2‐alkoxy‐thiophene‐3‐carbonitriles (2a–f) among them 2‐benzoylmethoxy‐thiophene‐3‐carbonitriles (2a–c) which undergo Thorpe‐Ziegler‐cyclization to form the 3‐amino‐2‐benzoyl‐thieno[2,3–b]furans (3) in low yields. The 2‐acyl‐3‐amino‐thieno[3,2–b]furans and ethyl 3‐amino‐thieno[3,2–b]furan‐2‐carboxylates (6) are synthesized in similar manner from 3‐hydroxy‐thiophene‐2‐carbonitriles (4) and α‐halogencarbonyl compounds via 3‐acylmethoxy‐ and 3‐ethoxycarbonylmethoxy‐thiophene‐2‐carbonitriles (5) with high yields.
Reactions of [2.2]paracyclophanes in melts. I. Reaction of [2.2]Paracyclophane‐4,5,12,13‐tetra‐carboxylic Acid Dianhydride with phenylacetic acid and N‐aryl carbamates
Authors: Mourad Aboul‐Fetouh E. , Nour‐El‐Din Ahmed M.
Published: December 2004

Reaktionen von [2.2]Paracyclophanen in Schmelzen. I. Reaktion von [2.2]Paracyclophan‐4,5,12,13‐tetracarbonsäuredianhydriden mit Phenylessigsäure und N‐Arylcarbamaten

The parent hydrocarbon [2.2] paracyclophane (1) exhibits transanular electronic interaction and the two benzene rings behave as dependent π system towards the chemical reactions [1a–c]. We wish to study the effect of transanular electronic interaction on the chemical behaviour of the an hydride moity in 2[2a–d]. It has been reported that 2 is less reactive in comparison with phthalic anhydride, since an attempted conversion of 2 into a tetraester failed [2b] magnified image

The reaction in melts between phtahlic anhydride, pryomillitic acid dianhydride (3) and carbamates yields the corresponding imides [3].
Kinetische Untersuchungen über die Autoxidation von Olefinen
Authors: Futu‐Tangu M. , Lawson E. , Pritzkow W. , Voerckel V.
Published: December 2004

Kinetic Studies on the Autoxidation of Olefins

The oxidabilities \documentclass{article}\pagestyle{empty}\begin{document}$ {{{\rm k}_{\rm p} } \mathord{\left/ {\vphantom {{{\rm k}_{\rm p} } {\sqrt {2{\rm k}_{\rm t} } }}} \right.\kern-\nulldelimiterspace} {\sqrt {2{\rm k}_{\rm t} } }} $\end{document} at 50°C were determined for 37 olefins, using chlorobenzene as the solvent and azodiisobutyronitril as the initiator. In the group of acyclic aliphatic olefins the oxidability rises with increasing number of alkyl groups bound to the double bond. This is also true for cyclic olefins, but in this case the ring size has also a great influence on the oxidability. So the oxidability decreases from five‐ring to eight‐ring cycloolefins. Particularly high oxidabilities are found in the case of olefins in which a phenyl group is attached directly to the CC‐double bond.
Partialsynthesen von Cardenoliden und Cardenolid‐Analogen. VIII. Lactonring‐alkylierte Cardenolide
Authors: Streckenbach Barbara , Franke Peter , Hintsche Rainer , Portius Hans Joachim , Repke Kurt R. H.
Published: December 2004

Partial Syntheses of Cardenolides and Cardenolide Analogues. VIII. Lactone Ring‐Alkylated Cardenolides

Base‐catalyzed alkylation of digitoxigenin (1), digitoxin (2), digoxigenin (3), and gitoxigenin‐3,16‐diacetate (4) with allyl bromide, allyl chloride or n‐propyl bromide in DMF resulted in the formation of the 22‐allyl‐, 21ξ,22‐diallyl‐, 22‐propyl‐, and 21ξ,22‐dipropyl‐derivatives 5–14, respectively.

The determination of the molecular biological activity of the derivatives yielded valuable information.
Zur Zuordnung der 13C‐NMR‐Spektren von Steroiden mit A,B‐ und C,D‐trans‐ und ‐cis‐verknüpften Ringen Eine Anwendung der „attached proton test”︁‐Technik zur Baugruppenanalyse
Authors: Zeigan D. , Radeglia R. , Engelhardt G.
Published: December 2004

On the Assignment of the 13C‐N.M.R. Spectra of Steroids with A,B‐ and C,D‐trans‐ and cis‐Joined Rings. An Application of the Attached Proton Test Technique to the Analysis of Building Groups

A modified single‐pulse attached proton test technique is used for an unequivocal assignment of the 13C‐n.m.r. signals to the building groups CHn (n = 0,1,2,3) of the steroid skeleton of 5α‐ and 5β‐cholestane as well as 14α‐ and 14β‐estratriene‐3‐methylether. It is shown that the different γ‐effects of selected carbon atoms of steroids with cis‐ and trans‐connected rings open a simple way to ascertain the configuration of the ring connection.
Formylation Products of Thioamides. IV. Reactions of 3‐Dialkylamino‐ and 3‐Hydroxythioacrylamides with Amines ‐ Synthesis of 3‐Aminothioacrylamides, 5‐Aminopyrazoles and 3‐Aminoisothiazolium Salts
Authors: Liebscher Jürgen , Areda Alemayehu , Abegaz Berhanu
Published: December 2004

Formylierungsprodukte von Thioamiden. IV. Reaktionen von 3‐Dialkylamino‐und 3‐Hydroxythioacrylamiden mit Aminen – Synthese von 3‐Aminothioacrylamiden, 5‐Aminopyrazolen und 3‐Aminoisothiazoliumsalzen

3‐Hydroxythioacrylsäureamide (5) oder 3‐Dialkylaminothioacrylsäureamide (4) bzw. deren Salze (3) werden von Aminen oder Hydrazinen leicht in 3‐Position unter Substitution angegriffen, wobei 3‐Aminothioacrylsäureamide (6) gebildet werden. Über die Zwischenstufe der 6 sind in Abhängigkeit vom Substituenten in 3‐Position entweder durch Oxydation 5‐Aminoisothiazoliumsalze (7) oder durch intramolekularen nucleophilen Angriff am Kohlenstoffatom 1‐Aminopyrazole (10) erhältlich.
Über die Pyrolyse von Pent‐1‐en‐4,4,5,5,5‐d5
Authors: Kopinke F.‐D. , Bach G. , Ondruschka B. , Zimmermann G.
Published: December 2004

On the Pyrolysis of Pent‐1‐ene‐4,4,5,5,5‐d5

The distribution of deuterium in the main products of thermal decomposition of pent‐1‐ene‐4,4,5,5,5‐d5 at 550 to 650°C was studied and interpreted. The results include conclusions on kinetic isotope effects, on relative reactivities of different C‐H‐bonds, on the proportion of terminal and nonterminal addition of methyl radicals, and on the importance of a radical isomerisation reaction. It was shown that the molecular decomposition (Retro‐En‐Reaction) cannot successfully compete with the radical way in the temperature range above 600°C
1H‐NMR‐spektroskopische Untersuchungen an substituierten Crotonsäure‐ und Dithiocrotonsäureestern
Authors: Michalik M. , Kreutzmann J.
Published: December 2004

1H‐NMR Spectroscopical Investigations on Substituted Crotonates

3‐Amino‐2‐cyanocrotonates 2 and ‐dithiocrotonates 3 have been characterized by n.m.r. spectroscopy. The data obtained are compared with those of acrylates 1. The COOR and CSSR groups are investigated with respect to their electron withdrawing effect and formation of intramolecular hydrogen bonds.
Photochemische Primärprozesse von Xanthenfarbstoffen. III. Blitzlichtspektroskopische Untersuchungen zum Einfluß von kationischen Mizellen auf die Photoredoxprozesse von Selenopyronin
Authors: Ortmann W. , Kassem A. , Fanghänel E.
Published: December 2004

Photochemical Primary Processes of Xanthene Dyes. III. Investigations of the Influence of Cationic Micelles on the Photoredox Processes of Selenopyronine by Flash Excitation

Cationic micelles have no influence on the decay of the triplet state of selenopyronine (3F+). The products of photoredox reactions 3F+ + 3F+ (F+) → F· + F and 3F+ + DABCO → F· + DABCO live longer in the presence of the cationic micelles. The reason for the change of the lifetime is a separation of the photoredox products by micelles. F. is stored in the interior of the micelles. The positively charged F and DABCO are repelled from the micelles and the electron back transfer is hindered.
Eine neue Synthese für 6H‐1,3‐Thiazine
Authors: Schulze K. , Richter C. , Richter F. , Mrozek E. , Weisheit R. , Achenbach F.
Published: December 2004

A New Synthesis of 6H‐1,3‐Thiazines

A new method for the synthesis of 1,3‐thiazines is described. The addition of nucleophiles to γ‐isothiocyanatoallylchlorides (1a‐j) leads to functionalisation and subsequent cyclisation (nucleophilic cyclofunctionalisation). Reaction of secondary amines or alcohols under catalysis by tert. amines gives numerous 2‐dialkylamino‐ (3a‐w) or 2‐alkoxy‐6H‐1,3‐thiazines (4a‐p).
Ringöffnungs‐ und SubstitutionsReaktionen von 4,4‐Dihalogen‐pyrazolin‐5‐onen durch Nucleophile
Authors: Kirschke Klaus , Lutze Gerhard , Schmitz Ernst
Published: December 2004

Ring Opening and Substitution Reactions of 4,4‐Dihalo‐pyrazolin‐5‐ones with Nucleophiles

1‐Aryl‐4,4‐dihalo‐3‐methyl‐pyrazolin‐5‐ones (1a–c) undergo ring opening with alkoxides and form alkyl 3‐arylazo‐2‐halo‐2‐butenoats (2a–d). Analogous reactions take place with ammonia and amines.

4‐Nitro‐phenoxide reacts with substitution of both halogens to the 4,4‐bis(4‐nitro‐phenyl)‐compound (5).

Phenols are selectively orthobrominated by the title compounds 1a and b.
Selectivity in the Oxidation of Aliphatic Ketones by thallic sulphate in aqueous medium
Authors: Pechál Miroslav , Strašák Milan
Published: December 2004

The effects of temperature, structure and sulphuric acid concentration on the selectivity of the oxidation of aliphatic ketones (R1COR2) (1a–g) by thallic sulphate have been investigated. With increasing temperature the quantity of internal α‐hydroxyketone (3a–d) decreases and the quantity of 1‐hydroxyketone (2a–d) increases in the oxidation of methyl alkyl ketones (R2>CH3) (1a–d). The same concerns to the oxidation products of hexan‐3‐one (1e): 2‐hydroxy‐hexan‐3‐one (2e) and 4‐hydroxy‐hexan‐3‐one (3e), respectively. “The inverse selectivity temperature” (IST) for oxidation of linear methyl alkyl ketones (1a–c) and hexan‐3‐one (1e) has been found. With the use of the linear free‐energy relationship it has been found that the selectivity of the reaction decreases with increasing the polar and steric effects of substituents R1, R2. With increasing the sulphuric acid concentration the selectivity of the oxidation of methyl alkyl ketones (1a, 1d) increases.
Theoretical description of solvent effects. X. Theoretical investigation of the Tautomerism of Nucleic Acid Bases of biological importance in the gas phase and in solution
Authors: Bartzsch C. , Weiss C. , Hofmann H.‐J.
Published: December 2004

The tautomerism of the nucleic acid bases cytosine and adenine and some of their derivatives is investigated by means of semiempirical MO methods. The influence of the solvent is estimated using various versions of the reaction field model. In the cases under investigation here, the medium influence does not favour “rare” tautomeric forms having other coding properties in DNA replication process than the “normal” nucleic acid base tautomers. Thus, the probability of their participation in spontaneous mutations seems to be very low.
Diels‐Alder‐Reaktionen. IX. Über Bildung und Thermolyse der isomeren Tricyclopentadiene
Authors: Ramhold K. , Moll K. K. , Roschka E. , Zimmermann G. , Krukowka Th. Smola L.
Published: December 2004

Diels‐Alder‐Reactions. IX. On the Formation and the Thermolysis of Isomeric Tricyclopentadienes

The formation of isomeric tricyclopentadienes by codimerisation of cyclopentadiene with endo‐ and exo‐dicyclopentadiene between 100 and 140°C in the liquid phase, and the retrodiene reaction of the main isomeres of the tricyclopentadiene fraction by gas phase thermolysis were studied kinetically between 230 and 310°C. The rate constants and the parameters of activation were determined.
Photochemical Dediazoniation of Arene Diazonium Salts sensitized by zink meso‐tetraphenyl porphyrin
Authors: Becker H. G. O. , Lehmann T. , Schütz R.
Published: December 2004

Photoexcited zink tetraphenylporphyrin (ZnTPP) reacts with arene diazonium salts via electron transfer according to the oxidation mechanism. This is proved by ESR spectroscopy of ZnTPP+ formed and the fact that N2 and ZnTPP+ are formed in a molar ratio.

Due to very different life‐times of1(ZnTPP)* and 3(ZnTPP)* it is possible to differentiate between singlet and triplet electron transfer reactions using different diazonium salt concentrations. In this way, the respective quenching constants are determined by means of flash spectroscopy.

Due to electron back transfer the singlet reaction at high concentrations of diazonium salts (0.1M) is inefficient (quantum yield 0.1), whereas back electron transfer is symmetry‐forbidden in the triplet reaction which, therefore, proceeds with high quantum yields, mearly reaching the ISC quantum yield.

From differences between the triplet quenching constants determined by flash spectroscopy and from product quantum yields, respectively, and from corresponding kinetic models it is concluded that the triplet reaction proceeds via a reversibly formed triplet exciplex.

Complexes of meso tetraphenyl porphyrin containing Pb(II), Sn(IV), Mn(II), Ni(II), Cu(II) and Fe(III), respectively, have lower sensitization activities decreasing in the order, given in the text.
Elektrochemische Reduktion und Azokupplung kernchlorierter p‐Dimethylaminobenzendiazoniumsalze Hammett‐Korrelationen
Authors: Fanghänel E. , Kriwanek J. , Ortmann W. , Bagal I. L. , Lebedeva N. W. , El'cov A. V.
Published: December 2004

Electrochemical Reduction and Azo‐coupling of Ring Chlorinated p‐Dimethylaminobenzenediazonium Salts. Hammett‐Correlations

The polarographic half‐wave potentials of ring halogenated 4‐dimethylaminobenzenediazonium salts (6a–6j) can be linearly correlated with the total σ‐constants Σσkorr (E1/2 = (0.25 Σσkorr + 0.33) V; r = 0.995), if for the dimethylamino group of the 3‐ or 3,5‐halogenated derivatives corrected σ′p‐constants are used. The Σσkorr‐values determined can be used to correlate the influence of substituents on the azo‐coupling kinetics (lg k/k0 = 2.46 Σσkorr; r=0,988).
Zur Bildung von Ethoxy‐hydrochinazolinon durch Reaktion von Estercarbonylsauerstoff mit Cyan‐enamin
Authors: Bischoff Christian , Schröder Edith
Published: December 2004

Formation of Ethoxyhydroquinazolinone by Attack of an Estercarbonyloxygen at a Cyano Group

By the reaction of ethyl‐2‐oxo‐cyclohexanecarboxylate with cyan amide 4‐ethoxyhexahydroquinazolin‐2‐one (12) is formed. Butyl‐2‐oxo‐cyclopentanecarboxylate and cyan amide yield butyl‐3‐cyanamino‐cyclopent‐1‐en‐carboxylate (14). 2‐Oxocyclohexane‐carboxamide (1) and ethyl‐cyanoacetate form with sodiumhydroxide 4‐cyano‐octahydroisoquinolin‐1, 3‐dione (17) and with ammonium acetate ethyl cyclohexylidene‐cyanoacetate‐2‐carboxamide (18). 18 and ammonia, hydrazine, or cyclohexylamine form the salts of cyanohydroquinazolindione 20a–c, respectively.
Untersuchungen zur Hydrolysestabilität von 4‐Arylmethyliden‐2‐pyrazolin‐5‐onen
Authors: Fanghänel E. , Akhlaq M. S. , Grossmann N.
Published: December 2004

Investigations on the Hydrolytic Stability of 4‐Arylmethylidene‐2‐pyrazolin‐5‐ones

The 4‐Arylmethylidene‐2‐pyrazoline‐5‐ones S are not stable under aqueous alkaline conditions. By the substitution of R3 with electron donor substituents S reacts preferably yielding aldehyde A and 2‐pyrazoline‐5‐one P, while with electron acceptor substituents S forms 4,4′‐aryl‐methylidene‐bis‐2‐pyrazoline‐5‐one B. The intermediate of hydrolysis is 4‐(arylhydroxymethyl)‐2‐pyrazoline‐5‐one SOH.

The second order rate constants of the reaction of S with hydroxidions and with 2‐pyrazoline‐5‐ones P− are determined. The dependence of the hydrolytic decomposition of S on the pH vaue substituents and temperature is suitable for the intermediate formation of SOH.
Substituenteneffekt und Mechanismus der thermischen Rücktautomerisierung belichteter Salicylidenaniline
Authors: Grummt U.‐W.
Published: December 2004

Substituent Effect and Mechanism of the Thermal Retautomerization of Flashed Salicylidene Anilines

V‐shaped Hammett plots are obtained with a series of p‐substituted salicylidene anilines for the relaxation rate of their phototautomers. This is interpreted by a change‐over in the mechanism from O‐protonation (donor substituents) to NH‐deprotonation (acceptor substituents) as rate determining initial steps in alcoholic solvents. The observed acid and base catalysis strongly support the assumption of an o‐quinoid geometry of the phototautomer.
Synthese von 2,4‐Bisalky(aryl)amino‐6‐cyanamino‐1,3,5‐triazinen
Authors: Freiberg Renate , Bulka Ehrenfried
Published: December 2004

Synthesis of 2,4‐Bisalkyl(aryl)amino‐6‐cyanamino‐s‐triazines

Reaction of 2,4‐bisalkyl(aryl)amino‐6‐chloro‐s‐triazines with disodiumcyanamide to 2,4‐bisalkyl(aryl)amino‐6‐cyanamino‐s‐triazines (3a–g) strongly depends on the solvent used. In dimethylformamide by‐products predominate. The best results are found in dimethylsulphoxide.
Zur Telomerisierung von Isopren mit Palladium‐Komplexen bei niedriger Temperatur
Authors: Berger R. , Gaube W.
Published: December 2004

On the Telomerization of Isoprene at Low Temperature

The telomerization of isoprene was carried out by means of a catalyst system of Pd(acac)2/PPh3 and complexes of the type Pd(acac)2 · L (L = PPh3; py; NHEt2) at 298 K. The reaction in methanol gave 8‐methoxy‐2, 7‐dimethyl‐octa‐1, 6‐diene (3a), 8‐methoxy‐3, 7‐dimethyl‐octa‐1, 6‐diene (4a) and oligomer products. 2, 7‐Dimethyl‐octa‐1,3, 7‐triene (1), 8‐i‐propoxy‐2, 7‐dimethyl‐octa‐1, 6‐diene (3b) and oligomer products were obtained in i‐PrOH. During the reaction a formation phase of the catalyst was observed.
Acetals and Ethers. XVI [1] Hydrolysis of 2‐[2‐(ω‐Hydroxyalkoxy)alkyl]‐substituted 1,3‐Dioxolanes and 1,3‐Dioxanes in Aqueous Solution of Hydrochloric Acid
Authors: Piasecki Andrzej
Published: December 2004

The rate constants of hydrolysis of 2‐[2‐(ω‐hydroxyalkoxy)alkyl]‐substituted 1,3‐dioxolanes and 1,3‐dioxanes (1–6) in aqueous HCl solution were determined. For two selected acetals, the parameters of active complexes were also evaluated. The acetals studied were found to be more stable than 2‐alkyl‐substituted 1,3‐dioxolanes and 1,3‐dioxanes. The presence of ether‐oxygen in β‐position with respect to the acetal grouping in molecules of 2‐[2‐(ω‐hydroxyalkoxy)alkyl]‐substituted 1,3‐dioxolanes and 1,3‐dioxanes was the stability determining factor.
An Improved Synthesis of 1,4‐Benzo‐ and 1,4‐Naphthoquinones Bearing Active Substituents
Authors: Syper Ludwik , Kloc Krystian , Młochowski Jacek
Published: December 2004

The synthesis of 1,4‐benzoquinones and 1,4‐naphthoquinones 3a–j carrying substituents such as methoxyl, ally or oxiranyl was substantially improved. The 1‐methoxy‐4‐methoxy‐methyloxy 2a–d, g–k or 1,4‐bis(methoxymethyloxy) derivatives 2e‐f were used, as a substrates instead of 1,4‐dimethoxy derivatives 1a–j hitherto used and they were oxidized with silver(II) dipicolinate. Among numerous examples, the synthesis a of new analog of ubiquinone 3d with the oxiranyl substituent, being a new bioactivated alkylating agent, is reported.
Elektrochemische Spaltung von 3‐Halogen‐1,2,4‐thiadiazolen zu Cyanimidothiocarbonaten
Authors: Rüttinger H.‐H. , Walek W. , Matschiner H.
Published: December 2004

Electrochemical Cleavage of 3‐Halogen‐1,2,4‐thiadiazoles to Cyanimidothiocarbonates

3‐Halogen‐1,2,4‐thiadiazole‐5‐sulfenylchlorides (5a‐j) are easily accessible by the halogenation of eyanimidodithiocarbonates (1). As electrophilic synthetic building blocks they react with basic olefines or electron‐rich aromates to the corresponding alkylthio‐or arylthio derivatives. The electrochemical reduction of these compounds led to substituted cyanimidomithiocarbonates (7a‐e), not being accessible otherwise.
Studies on the Regioselectivities in the Oxidation of Simple Alkyl Aromatic Hydrocarbons by Molecular Oxygen
Authors: Pritzkow Wilhelm , Thomas Gerda , Willecke Lothar
Published: December 2004

The products of the autoxidation of various simple alkyl aromatic hydrocarbons were reduced by LiAlH4, and the alcohols formed were determined by gas chromatography. In the cases of 2‐phenylbutane, 3‐phenylpentane, and 2‐p‐tolylbutane a considerable fragmentation of the intermediate tertiary alkoxy radicals was proved. On the basis of the analytical results relative reaction rates of the various C–H‐bonds in the hydrocarbons studied were calculated. It is shown that the attack at C–H bonds which are not activated by the aromatic nucleus cannot be neglected and may be of great importance for the kinetics of the oxidation of alkyl aromatic hydrocarbons.
Synthesen von C‐Nucleosiden und C‐Nucleosidanaloga. IV. Darstellung und Charakterisierung von 5(S)‐bzw. 5(R)‐Tetrahydroxybutyl‐3‐methyl‐1,3‐oxazolidinen
Authors: Börner A. , Kristen H. , Peseke K. , Michalik M.
Published: December 2004

Syntheses of C‐Nucleosides and Analogs of C‐Nucleosides. IV. Preparation and Characterization of 5(S)‐ and 5(R)‐Tetrahydroxybutyl‐3‐methyl‐1,3‐oxazolidines

1‐Deoxy‐1‐methylamino‐D‐hexitols 1,2,3 react with ketendithioacetals 4 to give the acyclic C‐nucleosides 5,6 and 7. The structure of the compounds were verified by means of periodate oxidation and spectroscopic investigations. Some properties of the acyclic C‐nucleosides were investigated by acetalation reactions on the tetrahydroxybutyl chain.
NMR‐study of the stereochemistry and dynamic behaviour of thioacrylamides
Authors: Kleinpeter E. , Tadesse Tsegaye , Abegaz Berhanu
Published: December 2004

Several model thioacrylamides, Me2NCH = C(R)C(S)NMe2 (R = H, Ph — 2a, b) and (p)MeOC6H4NHCHC(R)C(S)NMe2 (R = H, Ph — 3a, b) have been synthesized. The 1H‐n.m.r. spectra have been taken for discussing the E/Z‐isomerism of the thioacrylamides and the assignment further strengthened by an added LIS‐study. The 2‐unsubstituted compounds have been found to exist exclusively in preferred configurations/conformations: 2a — E(s‐cis); 3a — Z(s‐cis); the 2‐phenylsubstituted analogs are of divergent behaviour: in 2b the C(S)NMe2 moiety is found to be twisted out of the common plane, and 3b prefers the flat s‐trans conformations (E(s‐trans) ⇌ Z(s‐trans)). The compounds show restricted rotations about C1, N‐ and C3, N‐partial double bonds. The corresponding rotational barriers, determined as ΔG‐values by dynamic n.m.r. spectroscopy, are discussed with respect to (i) the resonance branch at C1, (ii) the influence of substituents, and (iii) the effect of steric hindrance in the thioacrylamide moiety generally.
Komplexkatalyse mit Technetiumverbindungen: Hydroformylierung mit Technetiumcarbonyl‐Katalysatoren
Authors: Kaden L. , Lorenz B. , Wahren M.
Published: December 2004

Complex Catalysis with Technetium Compounds. Hydroformylation with Technetiumcarbonyl Catalysts

The hydroformylation reaction of cyclohexene (1), propene (2) and 1‐octene (3) was studied using Tc2(CO)10 and Tc(CO)10/P(n‐C4H9)3, resp., as catalysts in solution. For comparison experiments have also been made with Mn2(CO)10, Mn2(CO)10/P(n‐C4H9)3 and Re2(CO)10/P(n‐C4H9)3 as catalysts for the hydroformylation of 1.

There is always a competition between hydrogenation and hydroformylation.

Tc2(CO)10/P(n‐C4H9)3 gave the best results in activity and selectivity within the subgroup VII complexes studied, but is a rather poor catalyst compared with the cobalt or rhodium compounds.
Synthesis of (3′,3′‐Dimethyloxiranyl)quinones and (Dimethylacetyl)quinones as Potential Cytostatics
Authors: Kloc Krystian , Młochowski Jacek , Syper Ludwik , Mordarski Marian
Published: December 2004

1,4‐Benzoquinones and 1,4‐naphthoquinones carrying 3′,3′‐dimethyloxiranyl, dimethylacetyl or oxiranylmethyloxy substituents (1, 2 or 3) have been synthesized. The methods presented involved epoxidation of a sterically overcrowded double bond as a crucial step for synthesis of (3′,3′‐dimethyloxiranyl)quinones 1. Reaction of aryllithium derivatives with 2‐chloro‐2‐methyl‐propanol unexpectedly led to (dimethyl)acetylarenes 11 subsequently oxidized to (dimethylacetyl)‐quinones 2. High cytotoxicity of 1 against KB cells has been revealed contrary to significantly lower activity of 2 and 3. The structure‐activity relationship was discussed in terms of current theory of biologically activated alkylating agents.
Synthese und spektrale Charakterisierung von blauen Benzenazofarbstoffen
Authors: Thiel W. , Mayer R. , Jauer E.‐A. , Modrow H. , Dost H.
Published: December 2004

Synthesis and Spectral Characterization of Blue Azo Dyes of the Benzene Series

53 Donor‐acceptor substituted azo dyes of the benzene series were prepared by diazonium‐coupling reactions (1 a–s) or halogen‐cyanide exchange (→2 a–x, 3 a–j). Described are the preparation of the amines 4 a–m and the coupling compounds 5 a–t and the procedure of diazotizing and coupling.

The colouristic and spectroscopic data show that compounds of the general formula 1 are excellent brilliant blue azo dyes useful for dyeing polyester material.
Tautomerism in 6‐Arylpyridazin‐3(2H)‐thiones and some of their reactions
Authors: Shams Nabil A. , El‐Kafrawy A. F. , El‐Sawy O. M. , Fekry Ismail M.
Published: December 2004

6‐Arylpyridazin‐3(2H)‐thiones exist mainly, if not entirely, in the thione form (1). This was shown by spectroscopic studies on some of these compounds and their substitution products either on the nitrogen or on the sulphur [in the mercaptopyridazine form (2)]. However, the reacting tautomer of these compounds was found to be dependent upon the basicity of the reaction medium. Selected 6‐arylpyridazin‐3(2H)‐thione derivatives react with formaldehyde and sec‐amines to give N‐2‐aminomethyl derivatives (8) [thione form (1)]. On the other hand oxidation and alkylation reactions gave disulphides (10) and S‐alkyl derivatives (7) [mercapto form (2)].
Pyryliumverbindungen. 33 [1] 2‐Dialkylamino‐2H‐thiopyrane aus 2,4,6‐Triaryl‐thiopyryliumsalzen
Authors: Zimmermann Thomas , Fischer Gerhard W.
Published: December 2004

Pyrylium Compounds. 33. 2‐Dialkylamino‐2H‐thiopyrans from 2,4,6‐Triaryl‐thiopyrylium Salts

2,4,6‐Triaryl‐thiopyrylium salts 7 react with dialkylamines in diethyl ether to give stable crystalline 2‐dialkylamino‐2H‐thiopyrans 8, the structure of which is in accordance with their u.v., n.m.r. and mass spectra. The chemical properties of 8 parallel those of structurally analogous 2‐alkoxy‐ and 2‐dialkylamino‐2H‐pyrans and 2‐alkoxy‐2H‐thiopyrans. Thus, on heating 2‐dimethylamino‐2,4,6‐triphenyl‐2H‐thiopyran (8a) with methanol the corresponding 2‐methoxy‐2H‐thiopyran 9 is formed. Nitromethane and ethyl cyanoacetate give rise to ring transformations yielding 1,3,5‐triphenyl benzene (10) and 2,4,6‐benzonitrile (11), respectively. From 8a electrophiles (e.g. mineral acids, methyl iodide, benzoyl chloride) regenerate the initial thiopyrylium system by taking over the dialkylamino group.
Umsetzung von Bromderivaten des 6β‐Bromcholest‐4‐en‐3‐ons mit NaBH4 und 13C‐NMR‐spektroskopische Charakterisierung der Reduktionsprodukte
Authors: Römer J. , Scheller D. , Grossmann G.
Published: December 2004

Reaction of Bromo Derivatives of 6β‐Bromocholest‐4‐en‐3‐one with NaBH4 and 13C‐NMR Spectroscopic Characterization of the Reduction Products

Bromo derivatives of 6β‐bromcholest‐4‐en‐3‐one (1a–f) were reduced with sodium borohydride. The main product of the reduction of 2α,6β‐dibromcholest‐4‐en‐3‐one (1b) was 2α‐bromocholesterol (2b). In other cases the corresponding derivatives of 6β‐bromocholest‐4‐en‐3β‐ol (3a) were formed. The chemical shifts of all new products were determined. They confirmed the structure of these new compounds.
Partialsynthesen von Cardenoliden und Cardenolid‐Analogen. X. Synthese 22‐O‐substituierter Cardenolide sowie Untersuchungen über den oxidativen Abbau von Cardenoliden mit Kaliumpermanganat
Authors: Lindig Claus
Published: December 2004

Partial Syntheses of Cardenolides and Cardenolide Analogues. X. Synthesis of 22‐O‐Substituted Cardenolides and Studies on the Oxidative Degradation of Cardenolides with Potassium Permanganate

The stereoisomeric 20,22‐dihydroxy‐cardanolides 2a and 3a as well as the oxalic acid half ester of the 3β‐acetoxy‐14,21‐dihydroxy‐5β,14β‐pregnan‐20‐one (4a) and 3β‐acetoxy‐20‐oxo‐5β,14β‐pregnane‐21,14‐lactone (5) were identified as intermediates of oxidative degradation of digitoxigenin 3‐acetate with potassium permanganate.

2a and 3a, after selective acylation in 22‐position, were converted to the 22‐acyloxy‐cardenolides 7a and 7b via dehydration or acetoxyelimination after selective acetylation of the 20‐hydroxy group. Saponification of both 7a and 7b yields the very stable 22‐hydroxy‐cardenolide 8a.

The molecular biological activities of the 22‐substituted cardenolides were investigated and discussed.
Phosphororganische Antioxidantien. IV. Chemisch induzierte Polarisation von 31P‐Kernen in der Reaktion cyclischer Phosphite mit Hydroperoxiden
Authors: König T. , Grossmann G. , Schwetlick K. , Rüger C.
Published: December 2004

Organophosphorus Antioxidants. IV. Chemical Induced Polarization of 31P Nuclei in the Reaction of Cyclic Phosphites with Hydroperoxides

31P‐n.m.r. CIDNP is observed in the reactions of cyclic o‐phenylene and ethylene phosphites with hydroperoxides. Polarized phosphorus nuclei appear especially in the phosphonate and phosphate regions. Application of Kaptein's rule shows that these products are cage or escape products of secondary or tertiary radical pairs. Solvent molecules are involved in the formation of the tertiary radical pairs.

The concentration of the products formed from polarized 31P nuclei is very low.
The Oxidation of Primary Trimethylsilyl Ethers to Aldehydes – a selective conversion of a primary hydroxy group into an aldehyde group in the presence of a secondary hydroxy group
Authors: Mahrwald Rainer , Theil Fritz , Schick Hans , Schwarz Sigfrid , Palme Hans‐Joachim , Weber Gisela
Published: December 2004

Secondary trimethylsilyl ethers (2a–d) are not affected by Collins reagent in dichloromethane at 0°C. Primary trimethylsilyl ethers (4a–e), however, are smoothly oxidized to aldehydes (5a–e) under these conditions. In agreement with these observations trimethylsilylated diols or polyols with primary and secondary trimethylsilyloxy groups (6–9) are oxidized selectively by Collins reagent to trimethylsilyloxy aldehydes (10–13).
Studies on the kinetics of the Hydrolysis of Some Substituted Benzylidene Benzoichydrazide with differential pulse polarography
Authors: Kamal M. M. , Temerk Y. M. , Ahmed M. E. , Ahmed Z. A.
Published: December 2004

The kinetics of the hydrolysis of some substituted benzylidene benzoichydrazide 1a–e in 40% (v/v) ethanol buffer mixture have been investigated by differential pulse polarography. The mechanism of the hydrolysis in acidic buffer solutions is discussed.

The catalysis by H⊕ involves the conversion of the hydrazide compound to its conjugated acid in a rapid preequilibrium step followed by a slow attack of water. The effects of pH, water, organic solvents and molecular structure on the reaction rate and the activation are investigated.