bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthese eines im B‐Kettenbereich um 5 Aminosäuren verkürzten, in den Positionen Phe B24 und Phe B25 durch Tyrosin und Alanin substituierten Hybridinsulins
Authors: Naumann Wolfgang , Stange Hans , Losse Günter , Bilk Lothar
Published: December 2004

Synthesis of a Hybrid Insulin, Shortened in the B Chain Branch by 5 Amino Acids and Substituted in the Position Phe B24 and Phe B25 by Tyrosine and Alanine

The analogue of insulin B chain was synthesized in the protected form Z‐Phe‐Val‐Asn‐Gln‐His(Trt)‐Leu‐Cys(SEt)‐Gly‐Ser(Bzl)‐His(Trt)‐Leu‐Val‐Glu(OBzl)‐Ala‐Leu‐Tyr(Bzl)‐Leu‐Val‐Cys(SEt)‐Gly‐Glu(OBzl)‐Arg(HCl)‐Gly‐Tyr(Bzl)‐Ala‐OBzl

Nomenklatur und Abkürzungen nach den Regeln der IUPAC‐IUP‐Commission on Biochemical Nomenclature: Hoppe Seyler's Z. Physiol. Chem. 348, 256 (1967); J. Biol. Chem. 247, 977 (1972), weitere Abkürzungen: DCC =Dicyclohexylcarbodiimid, HOBt =1‐Hydroxybenzotriazol. DMF =Dimethylformamid, DMSO =Dimethylsulfoxid, B(SSO3−)2 =Insulin‐B‐Ketten‐S‐sulfonat

=Z‐1–25(Tyr24, Ala25)‐OBzl, converted into the S‐sulphonate form by deprotection and oxidative sulphitolysis, and combined with native A chain S‐sulphonate to the hybrid insulin A/B 1‐25(Tyr24, Ala25). The biological results indicate, that substitution of the amino acid Phe B24 is well tolerated, if the aromatic character of the side chain is remained.
Transannulare Reaktionen von Cycloalkenen, Cycloalkadienen und Cycloalkatrienen. VIII. Zur elektrophilen Addition von Pseudohalogenen an Cycloocta‐1(Z),5(Z)‐dien
Authors: Haufe Günter , Mühlstädt Manfred
Published: December 2004

Transannular Reactions of Cycloalkenes, Cycloalkadienes and Cycloalkatrienes. VIII. The Electrophilic Addition of Pseudohalogenes to Cycloocta‐1(Z), 5(Z)‐diene

The reaction of cycloocta‐1(Z), 5(Z)‐diene 5 with chlorothiocyanate is described. The main process is the normal anti‐addition to produce trans‐5‐chloro‐6‐thiocyanato‐(Z)‐cyclooctene 6. In addition 2,6‐dichloro‐9‐thiabicyclo [3.3.1] nonane 7 and 2,6‐dithiocyanato‐9‐thiabicyclo[3.3.1] nonane 8 are obtained as products of a transannular reaction.
1, 2, 3‐Triazabutadiene. XIV. Untersuchungen zur sauren Spaltung Z‐E‐isomerer 1‐Aryl‐3‐[3‐methylbenzthiazolinyliden‐(2)]‐ und 1‐Aryl‐3‐[1,3‐dimethylbenzimidazolinyliden‐(2)]‐triazene
Authors: Fanghänel E. , Hohlfeld J.
Published: December 2004

1,2,3‐Triazabutadienes. XIV. Investigations into the Acidic Cleavage of the Z‐E‐Isomeric 1‐Aryl‐3‐[3‐methylbenzthiazolinyliden‐(2)]‐ and 1‐Aryl‐3‐[1,3‐dimethylbenzimidazolinyliden‐(2)]‐triazenes

The rate of the acid cleavage of the Z‐E‐isomeric 1‐aryl‐3‐[3‐methylbenzthiazolinyliden‐(2)]‐ and 1‐aryl‐3‐[1,3‐dimethyl‐benzimidazolinyliden‐(2)]‐triazenes 1–5 is investigated in dependence on the substituents in the aryl and benzo residue. The Z‐isomeric triazabutadienes are cleft 103 to 105 times faster than the E‐isomers. The ρ‐values are significantly smaller than the ρ‐values of the cleavage of other triazen derivatives. This is explained by an opposite influence of substituents regarding the cleavage of the N2‐N3‐bond and the equilibrium of protonation of the triazabutadienes. Triazabutadienes with a pronounced polymethine like structure decompose more rapidly than is conformable to their σ‐values. For the E‐isomers a V‐shape of the Hammett‐correlation is found. The considerable differences in the rate of heterolysis of the Z‐E‐isomers can be used for a negatively working diazo material which is sensitive to visible light.
Über die lipophile Natur von Oxyalkylgruppen in Alkylethersulfaten
Authors: Sowada Rudolf
Published: December 2004

On the Lipophilic Nature of Oxyalkyl Groups in Alkyl Ether Sulphates

Effective carbon numbers and methylene group equivalent values for tetradecane sulphonates containing oxyalkyl groups as substituents as well as and for alkyl ether sulphates containing oxyalkyl groups in the chain have been calculated. These oxyethyl groups show lipophilic character, at least up to an oxethylation degree of 10. Via ME values effective carbon numbers, critical concentrations for micelle formation and HLB‐values for alkyl ether sulphates can be calculated. HLB group numbers depending on oxalkylation degree are tabulated; the known value of + 0,33 for OCH2CH2 is valid only for nonionic surfactants.
Synthese von β‐Nitroalkenyl‐benzylphosphorylderivaten
Authors: Czekanski T. , Witek St. , Costisella B. , Gross H.
Published: December 2004

Synthesis of β‐Nitroalkenyl‐benzylphosphorylderivatives

Starting from methoxy‐chlormethylbenzaldehydes 2 the benzylphosphonates and ‐phosphinoxides 3 A, B had been synthesized, which could be transformed via the Schiff‐bases 4 A, B to phosphorylated nitrostyrenes 5 A, B and nitropropenylbenzenederivatives 6 A, B. The phosphonoacids 3 Ad, 3 Bd and 6 Ba could be prepared from the corresponding esters by direct acidic hydrolysis or by dealkylation with trimethylsilylbromide and hydrolysis of the trimethylsilylesters respectively.
Zur Kinetik radikalischer Substitutionsreaktionen beim thermischen und initiierten thermischen Zerfall von 4‐Methyl‐pentan‐2,3‐dion
Authors: Knoll H. , Barry I. , Scherzer K.
Published: December 2004

On the Kinetics of Radical Displacement Reactions in the Thermal and Initiated Thermal Decomposition of 4‐Methyl‐pentane‐2,3‐dione

Relative rate constants of H‐abstraction and free radical displacement reactions in the thermal and initiated thermal decomposition of 4‐methyl‐pentane‐2,3‐dione have been determined between 523 and 683 K. The data are compared with previous results on other α‐diketones.
Elektronenstoßinduzierte Fragmentierung von para‐substituierten Styryl‐diphenylphosphinoxiden
Authors: Berndt K.‐G. , Gloyna D. , Henning H.‐G.
Published: December 2004

Electron Impact Fragmentation of para‐Substituted Styryl‐diphenylphosphine Oxides

Para‐substituted styryl‐diphenylphosphine oxides 1 exhibit a phosphine oxide‐like fragmentation. There are two competing ways, A and B, for electron impact fragmentation with the para‐substituent of the styrene part determining the A or B way, respectively. A styrene‐like fragmentation is to be excluded in respect to the observed mass spectra.
Reaktionen von zwitterionischen s‐Triazolo[4,3‐b]pyridazinen mit elektrophilen Reagentien
Authors: Timpe H.‐J. , Missal S. , Manzoor R. , Affi E.
Published: December 2004

Reactions of Mesoionic s‐Triazolo[4,3‐b] pyridazines with Electrophilic Reagents

The redox‐properties of zwitterionic s‐triazolo [4, 3‐b]pyridazines 1–3 depend on the heteroatom: products with S‐atoms can easily be oxidated. O‐Zwitterions 1 and 2 react with diazoniumsalts under azocoupling, while S‐zwitterions 3 lead to a dediazonation. The O‐zwitterions 1 and 2 can also be bromated, nitrated and hydroxylated electrophilicably. A reaction with dithioliumsalts is not possible. S‐Zwitterions 3 react in a more complicated way in the electrophilic reactions mentioned.
UV‐Vis‐spektroskopische Eigenschaften 3,5‐disubstituierter 1,3,4‐Oxadiazolin‐2‐imine. I. Einfluß der Substituenten und des Lösungsmittels auf die Absorption
Authors: Bendig Jürgen , Kreysig Dieter , Sauer Erika , Just Manfred
Published: December 2004

The U.V.‐vis‐spectroscopic Properties of 3,5‐disubstituted 1,3,4‐Oxadiazoline‐2‐imines. I. The Influence of the Substituents and the Solvent on the Absorption

The u.v.‐vis data of 38 derivatives of 3,5‐disubstituted 1,3,4‐oxadiazoline‐2‐imines, measured in 12 different solvents, are discussed. The long wave absorption bands have charge‐transfer character, the observed solvatochromic shifts correlate with the solvent parameter ET. The assumed intramolecular charge‐transfer upon excitation is polarized in the direction R1N3C5R2. Derivatives which are donor‐substituted in the 3‐position of the oxadiazolinimine cycle (R1) and acceptor‐substituted in the 5‐position (R2) show a typical push‐pull effect. In this case bathochromic and hyperchromic effects on the long‐wave absorption bands result. On the other hand, R1is a donor and R2is an acceptor substituent the excitation energy is increasing.
MO‐LCAO‐calculations on polymethines. XIV. Alternative Fragmentation Modes in Describing Benzenoid Chromophores
Authors: Fabian J.
Published: December 2004

MO‐LCAO‐Berechnungen an Polymethinen. XIV. Alternative Fragmentierung bei der Beschreibung benzoider Chromophore

Die Lichtabsorption donator‐acceptor‐substituierter Benzene wird allgemein an Hand des Benzenchromophors interpretiert. Ein alternatives Konzept, welches zumindest einen Teil der Verbindungen in die Betrachtung einbezieht, nimmt auf ein Polymethin‐Teilchromophor Bezug. Wie durch PPP‐Berechnungen (einschließlich Konfigurationsanalyse) an ortho‐Aminobenzonitrilen gezeigt wird, führen Donator‐ wie auch Acceptorsubstituenten in jenen Ringstellungen des ortho‐Aminobenzonitrils zu einer bathochromen Verschiebung, die im Heptamethin‐Teilchromophor ein gleichartiges Verhalten zeigen. Dieser Befund stützt die Ansicht von DÄHNE, daß sowohl die KAUFFMANNsche wie auch die CALIEZYsche Farbregel durch das Polymethinkonzept verständlich werden.

Vorhersagen werden jedoch dann schwierig, wenn Polymethinketten sehr stark in cyclische Strukturen eingeschlossen sind, wie beispielsweise im para‐Aminobenzonitril. Dann führen Donator‐ und Acceptorsubstituenten in beiden freien Ringstellungen zu einer bathochromen Verschiebung. Wie kürzlich für ähnliche Fälle in der Literatur gezeigt wurde, widerspricht dieser Befund auch den DEWAR‐KNOTTschen Farbregeln.
Reaktionen von Malonsäureethylesteraniliden mit Heterokumulenen
Authors: Rudorf W.‐D. , Koch K. , Augustin M.
Published: December 2004

Reactions of Malonanilic Acid Ethyl Esters with Heterocumulenes

Malonanilic acid ethyl esters 1 react with carbon disulfide in the presence of sodium hydride to give disodium salts 2. Treatment of 2 with an alkylation reagent yields the openchain or cyclic ketene S,S‐acetals 3 and 4, respectively. Adding only one equivalent of methyl iodide to 2 and acidifying the reaction mixture lead to the dithioesters 5. Reaction of 3 with amines or o‐amino‐thiophenol yields S,N‐ and N,N‐acetals only in some cases. S,N‐acetals 6 are further available by addition of phenyl isothiocyanate to 1 whereas N,N‐acetals are synthesized, too, by chlorination of 3 and reaction with amines. Acidifying of 11 gives the thioacetoanilides 12. Some more reactions (oxidation of 3a, d and saponification/decarboxylation of 4a) are discussed.
Steroide. LXX [1]. Stereoselektive Epoxidation von 14,15‐ungesättigten Östratrien‐3‐methylethern. Zum syn‐dirigierenden Effekt von Urethanen
Authors: Ponsold Kurt , Schubert Gerd , Wunderwald Manfred , Tresselt Dieter
Published: December 2004

Steroides. LXX. Stereoselective Epoxidation of 14,15‐Unsaturated Estratriene‐3‐methyl Ethers. On the syn‐Directive Effect of Urethanes

The stereochemistry of the epoxidation of 14,15‐unsaturated estratriene‐3‐methyl ethers with peroxyacids is examined. The influence of different 17‐substituents and of the solvent on the stereoselectivity is discussed. Whereas on epoxidation of 17β‐esters and 17β‐ethers mainly 14α, 15α‐epoxides are formed (up to 89%), the 17β‐urethane derivatives yield the 14β, 15β‐epoxides up to 87% by a syn‐directive effect.
Cobaltchelate als Hydrierkatalysatoren. Zur Reduktion von Nitro‐ zu Aminoverbindungen mit Kohlenmonoxid und Wasser als Hydriermittel
Authors: Bremer J. , Dexheimer V. , Madeja K.
Published: December 2004

Cobalt Chelate Complexes as Hydrogenation Catalysts. The Reduction of Nitro Compounds to Amines with Carbon Monoxid and Water as Hydrogenation Agent

Cobalt complexes of tetradentate chelating agents have been found to catalyse the selective homogeneous reduction of nitroaryls to amines with carbon monoxide and water at room temperature and atmospheric pressure. The cobalt complexes are highly specific. Dinitroaromatics can be reduced to the intermediate nitro amines in good yields; mixtures of nitroaryls can be reduced likewise sequentially. The reaction rate depends on the pH of the reaction solutions.
Tetrathiafulvalene. XV. Mößbauer‐spektroskopische Untersuchung von monomeren und polymeren Eisendithiolenkomplexen
Authors: Poleschner H. , Fanghänel E. , Mehner H.
Published: December 2004

Tetrathiafulvalenes. XV. Mössbauer Spectroscopic Investigation of Monomeric and Polymeric Iron Dithiolene Complexes

The Mössbauer spectra of iron bis dithiolene chelates with 1,2‐dithiole‐2‐one‐4,5‐dithiolate and 1,2‐dithiole‐2‐thione‐4,5‐dithiolate ligands are compared with those of the polymeric iron complexes with ethene tetrathiolate and tetrathiafulvalene tetrathiolate ligands. The spectroscopic results are discussed in relation to the structure of these compounds. In all investigated complexes the isomer shift shows trivalent iron ions as the main component in the samples. Whereas the monomeric complexes show a double doublet spectrum, which is unusual for iron bis dithiolene chelates, the polymeric compounds produce spectra, whose quadrupole splitting is typical for distorted octahedral coordination geometry.
Stabilität von Ionenaustauschern gegen Salpetersäure und Bestrahlung. I. Nitrosierender Abbau der Iminodiessigsäuregruppen in Chelonaustauschern
Authors: Pfrepper Gerd
Published: December 2004

The Stability of Ion Exchangers towards Nitric Acid and Radiation. I. Nitrosative Cleavage of the Iminodiacetic Acid Groups in Chelating Ion Exchangers

The behaviour of the chelating ion exchangers Wofatit MC 50, Dowex A 1 and Chelex 100 with aminoacetic acid – and iminodiacetic acid‐groups towards nitric acid in the range of the concentration 1…︁10,5 mol/l and at temperatures ⩽68°C was determined. It is found that the COOH capacity and the N content are rapidly reduced leading to the formation of CO2 and N2. If the exposure to HNO3 continues there is again a rise in the COOH capacity.

The i.r.‐ and mass spectra show that the iminodiacetic acid‐groups are destroyed by nitrosative cleavage and CHO groups result, which are then oxidized to COOH groups. The mass spectrum shows that the aminoacetic acid‐groups of the resin are nitrosated, which has also been confirmed by the use of nitric acid labelled with 15N.
Folgeprodukte halogenierter Aldehyde. XVII. Reaktionen des N‐(1,2,2,2‐Tetrachlorethyl)‐trichloracetaldimins mit Alkoholen und Mercaptanen
Authors: Zinner H. , Boede W. , Künzel H. , Leske H. , Schnell M.
Published: December 2004

Derivatives of Halogenated Aldehydes. XVII. Reactions of N‐(1,2,2,2‐Tetrachloroethyl)trichloroacetaldimine with Alcohols and Thioalcohols

Reactions of N‐(1,2,2,2‐tetrachloroethyl)trichloroacetaldimine 1 with methanol lead to 1,2,2,2‐tetrachloroethyl‐(2,2,2‐trichloro‐1‐methoxyethyl)amine 2a, N‐(2,2,2‐trichloro‐1‐methoxyethyl)trichloroacetaldimine 3a and bis‐(2,2,2‐trichloro‐1‐methoxyethyl)amine 5. After the reaction of the aldimine 1 with ethanol or propanol only the N‐(1‐alkoxy‐2,2,2,‐trichloroethyl)trichloroacetaldimines 3b, c are isolated; with thioalcohols only the N‐(1‐alkylthio‐2,2,2‐trichloroethyl)‐trichloroacetaldimines 4a–c are obtained. The aldimines 3a–c and 4b, c are decomposed on treatment with hydrochloric acid and an excess of an alcohol or thioalcohol to yield the amine hydrochlorides 6a–c, 7b, c, which are transformed into the amines 8a–c and 9b, c. From these amines the derivatives 10–15 are prepared.
Metallporphyrinkomplexe. VI, Synthese von Polymethacrylsäureestern mit kovalent gebundenem Eisen(III)‐protoporphyrin IX
Authors: Kühn M. , Wesuls E. , Mohr P. , Ristau O. , Benes M.
Published: December 2004

Metalloporphyrin Complexes. VI. Synthesis of Polymethacrylates with Covalently Bound Iron (III)‐protoporphyrin IX

Convenient synthesis of polymeric iron (III)‐protoporphyrin IX (hemin) compounds is described. The covalent linkage via the carboxylic groups of hemin is possible by the reaction of the activated ester of hemin with polymethacrylates containing aliphatic amino groups. Polymethacrylates with aromatic amino groups are suitable to immobilize the hemin via its methine bridges. The hemin‐containing polymers are characterized by visible spectra and e.p.r.‐spectroscopy.
Untersuchungen zum Mechanismus der Chlorhydrinierung von Olefinen
Authors: Buss E. , Rockstuhl A. , Schnurpfeil F. R. D.
Published: December 2004

Studies on the Mechanism of the Chlorohydrination of Olefins

We studied the rate‐determining and the product‐determining steps of the chlorohydrination of olefins with Cl2/H2O and HOCl. In competitive kinetic experiments with 3‐ethylpent‐2‐ene and cyclohexene we determined the relative rate constants krel = 1,5 (with Cl2/H2O) and krel = ∞ (with HOCl). This shows that the rate‐determining steps of the chlorohydrination with Cl2/H2O and with HOCl are different. In order to investigate the product‐determining steps we determined the proportion of alkyl‐(2‐chloroethyl)‐ethers 3 and ethylene chlorohydrine 2 in the reaction of ethylene with Cl2 and with HOCl in alcohol/water‐mixtures. The proportion of both the reaction products 3/2 was independent of the chlorinating agent used. Also the proportion of MARKOVNIKOV and anti‐MARKOVNIKOV products in the chlorohydrination of propylene with Cl2/H2O or HOCl was independent of the type of chlorinating agent. In the chlorohydrination of cyclohexene both agents (Cl2/H2O and HOCl) yielded only the trans‐chlorohydrine. From the results obtained it may be concluded that the product‐determining step of chlorohydrination is the same for both the chlorinating agents studied.
Photochemie adsorbierter Moleküle. V. ESR‐Untersuchungen von Phenylkationen bei der Photolyse von Arendiazoniumsalzen im Festkörper und im adsorbierten Zustand
Authors: Bäzold D. , Fassler D. , Kunert R.
Published: December 2004

Photochemistry of Adsorbed Molecules. V. E.S.R.‐Investigations of Phenyl Cations during Photolysis of Arendiazonium Salts in the Polycrystalline and the Adsorbed State

During photolysis of 4‐NR2‐substituted arene diazonium salts ground state triplets occur at low temperatures in the e.s.r.‐spectra with (π)5(sp2)1 configuration in the polycrystalline as well as in the adsorbed state on SiO2. The influence of anions and the reaction order of decay processes are discussed. The decay of the aryl cations were also investigated in the presence of pyrene as π‐electron donor. Reaction takes place with coadsorbed molecules and the decay mechanism changes from ionic character to radical character.
Benzalanilines and 2‐Phenyl‐indolenines ‐ characterization of their excited electronic states and interpretation of their U.V. spectra
Authors: Mehlhorn Achim , Fabian Jürgen , Perez Carlos
Published: December 2004

Benzalaniline und 2‐Phenyl‐indolenine — Charakterisierung ihrer elektronischen Anregungszustände und Interpretation ihrer UV‐Spektren

Die UV‐Spektren einiger substituierter Benzalanilin‐ und 2‐Phenylindolenin‐derivate werden unter Verwendung des PPP‐ und des CNDO/S‐Verfahrens berechnet. Die Übereinstimmung zwischen theoretischen Übergangsenergien und experimentellen Spektren ist gut, wenn man die PPP‐Methode benutzt, aber weniger befriedigend für das CNDO/S‐Verfahren. Eine Mischung zwischen nπ*‐ und ππ*‐Übergang führt zu einer Bandenaufspaltung im langwelligen Spektralbereich, wenn der Chromophor des Benzalanilins nicht‐planar wird. Die elektronischen Übergänge werden interpretiert durch PPP‐Konfigurationsanalyse der angeregten Zustände, wobei auf unterschiedliche Teilchromophore abgebildet wird. Frühere Zuordnungen werden kritisch überprüft.
Photokatalytische Systeme. XLVIII. Ungewöhnliche lichtinduzierte Redoxreaktionen von Cobalt(III)‐, Eisen(III)‐ und Kupfer(II)‐Komplexverbindungen in Gegenwart von Chromsäureestern
Authors: Hennig H. , Scheibler P. , Wagener R. , Thomas P. , Rehorek D.
Published: December 2004

Photocatalytic Systems. XLVIII. Unusual Light‐Induced Redox Reactions of Cobalt(III), Iron(III) and Copper(II) Complexes in Presence of Chromic Acid Esters

The coordination compounds[Co(NH3)5H2O]3+,[Co(NH3)4(H2O)2]3+,[Co(en)2(H2O)Cl]2+ (en = ethylendiamine), [L2(H2O)Fe‐O‐Fe(H2O)L2]4+ (L = 1,10‐phenanthroline; 2,2′‐bipyridine) and [CuL2]2+ (L = 2,9‐dimethyl‐1,10‐phenanthroline) show no or neglegible photo redox reactions upon irradiation wave‐length above 350 nm. However, in the presence of chromate(VI), water, and different alcohols like methanol, ethanol, i‐propanol and n‐propanol a very efficient light‐induced formation of cobalt(II), iron(II) and copper(I) (ϕ = 0,7; Λirr = 375 nm) can be observed together with reduced generation of chromium(III). The participation of chromium(V) in the primary step of the photolysis of chromic acid esters was shown to be the reason for these unusual light‐induced redox reactions. The coordination compounds under discussion behave as very efficient scavengers for chromium(V) connected with simultaneous reoxidation to chromate(VI) and reduction to the appropriate cobalt(II), iron(II) and copper(I) compounds. The general importance of the participation of chromium(V) in the primary step of the photolysis of chromate(VI) in non‐aqueous solvents is also shown by investigations of the photochemical behaviour of the system metal complex/CrO4—, Cr2O7—/dimethylsulfoxide. Possible mechanisms of the light‐induced reductions of the metal complexes are discussed.
Synthesen und Eigenschaften Mono‐ und diphenylsubstituierter Monothio‐β‐dicarbonylverbindungen und ihrer Nickel(II)chelate
Authors: Pulst M. , Beyer L. , Weissenfels M.
Published: December 2004

Syntheses and Properties of Mono‐ and Disubstituted Monothio‐β‐dicarbonyl Compounds and their Nickel(II) chelates

Reaction of phenylacetaldehyde with phosphorous oxichloride and dimethylformamide yielded 3‐chloro‐2‐phenyl‐propenal, which was converted into 2‐phenyl‐monothiomalonic dialdehyde 2 by treating with sodium sulfide nonahydrate. Furthermore the reactions of other mono‐ and diphenylsubstituted monothio‐β‐dicarbonyl compounds with aniline on the one side and nickel(II)acetate on the other side have been studied. It was shown, that compounds 1–6 react in different way with aniline yielding either sulfur free products or in case of 1 and 4 enaminothioketones, which are of interest as building blocks for syntheses.

In contrast to this the nickel complexes of 1–6 indicates an one another similar, typical chelate structure, which have been elucidated by u.v.‐vis‐, i.r.‐ and x‐ray photoelectron spectroscopy.
Löschung der Fluoreszenz aromatischer Urethane durch Ketone
Authors: Stumpe J. , Schwetlick K. , Kuzmin M. G.
Published: December 2004

Fluorescence Quenching of N‐Arylurethanes by Ketones

Fluorescence and photo‐Fries reaction of N‐aryl‐urethanes can be quenched by diffusion‐controlled energy transfer to biacetyl, acetone and other aliphatic ketones. Quenching of the photo reaction and fluorescence obeys the Stern‐ Volmer Equation.

The efficiency of quenching may by influenced by solvents and substituents changing the S1 energies of donors and acceptors. The identical rate constants determined by independent methods demonstrate that quenching of urethane fluorescence and photoreaction by aliphatic ketones occurs completely by singlet energy transfer.
Zur Gültigkeit des Prinzips des quasistationären Zustandes
Authors: Just G. , Bittrich H.‐J.
Published: December 2004

On the Validity of Steady State Principle

Considering the simple case

reduced concentrations were calculated by solving the exact differential rate equation by assuming a steady state and by assuming an „equilibrium”︁ between A1 and A2. In a broad field of reduced rate constants Ki/k1 the range in which these assumptions are valid within ±5% was determined for different values of time.
Chinon‐sensibilisierte photochemische Dediazonierung von Arendiazoniumsalzen
Authors: Becker H. G. O. , Jirkovsky J. , Fojtik A. , Kleinschmidt J.
Published: December 2004

Photochemical Dediazoniation of Arene Diazonium Salts Catalyzed by Quinones

The rate constants of the hydrogen abstraction of triplet‐excited p‐benzoquinone (BQ), duroquinone (DQ), p‐chlorophenyl‐p‐benzoquinone (PQ) and 2, 5‐di(p‐chlorophenyl)‐p‐benzoquinone (P2Q) from n‐heptane and acetonitrile are determined by laser flash photolysis as well as the rate constants for the reactions with oxygen.

The semiquinones formed are in equilibrium with their respective semiquinone anions; at pH 3 and pH 7, respectively, it was possible in acetonitrile/water solution to determine separately the rate constants for their disproportionation affording quinones and hydroquinones and the rate constants for electron transfer to p‐chlorbenzene diazonium tetrafluoroborate. It comes out that the electron transfer to the diazonium compound only competes favorably with the disproportionation in the case of the semiquinone anions.
Eindeutige Synthese des 4,7‐Dihydro‐4‐oxo‐1 H‐pyrazolo[3,4‐b]pyridins – Bemerkungen zur „(NC)‐Umlagerung”︁ von (2‐Alkoxycarbonyl‐vinyl‐amino)pyrazolen
Authors: Dorn Helmut , Ozegowski Rüdiger
Published: December 2004

Unambiguous Synthesis of 4,7‐Dihydro‐4‐oxo‐1H‐pyrazolo[3,4‐b]pyridine — Further Comments on the “(NC)‐Rearrangement” of (2‐Alkoxycarbonyl‐vinyl‐amino)pyrazols

4,7‐Dihydro‐4‐oxo‐1H‐pyrazolo[3,4‐b]pyridine1ais synthesized by decarboxylation of 1‐benzyl‐5‐carboxy‐4‐hydroxy‐pyrazolo[3,4‐b]pyridine4band debenzylation of 1‐benzyl‐4,7‐dihydro‐4‐oxo‐pyrazolo[3,4‐b]pyridine1bwith sodium in liquid ammonia. The product from 3‐amino‐pyrazol and methyl propiolate, formerly described as1a, obviously is the 6‐oxo isomer2a.

Use of the parameter δ13(CO) for the structural assignment of pyrazolo[3,4‐b]pyridones is only permitted, if in the corresponding media mainly the oxo‐tautomer is existing. It is again demonstrated that DMSO is often an insufficient medium.

Debenzylation of1band similar compounds with SeO2is only possible, if the α‐position of CO is blocked by a substituent. Otherwise diselenids of type6are formed. This obviously is a general reaction of cyclic lactames.

The cyclisation of (2‐alkoxycarbonyl‐vinyl‐amino)pyrazols7in acidic media, and with catalytical amounts of the corresponding amino‐pyrazols gives 6,7‐dihydro‐6‐oxo‐pyrazolo[3,4‐b]pyridines2via amino 4‐(2‐alkoxycarbonyl‐vinyl)pyrazols8, i.e. via products of an “(NC)‐rearrangement”, while by thermal cyclisation of74,7‐dihydro‐4‐oxo‐pyrazolo[3,4‐b]pyridines1are formed.
Synthesen mit 1,3‐Dithietanen. XIV. Ringumwandlungen von substituierten Dihydropyrazolo[5, 1‐b]thiazolcarbonsäureestern
Authors: Peseke K. , Vogel C.
Published: December 2004

Syntheses with 1,3‐Dithietanes. XIV. Ring Transformations of Substituted Dihydropyrazolo [5,1‐b]thiazolecarboxylates

Dihydropyrazolo[5,1‐b]thiazolecarboxylates 2 react with aliphatic amines to give dihydrothiazolo[2,3‐g][1,2,4]triazepinecarboxylates 4. Compounds 2c, d and o‐phenylenediamine, o‐amino‐phenols or o‐amino‐thiophenol afford substituted ethyl benzimidazol‐, benzoxazol‐ or benzothiazol‐2‐yl‐acetates 6. Hydrazine hydrate and compounds 2 yield derivatives of ethyl pyrazolidin‐4‐yliden‐4‐thiazoline‐5‐carboxylates 8.
Free radicals of phenothiazine and related compounds. IV. Phenothiazinyl‐ and Diphenothiazine‐ Copper Complexes as intermediates and products in the interaction of phenothiazines with copper(II) halides
Authors: Diudea Mircea V. , Silberg Ioan A.
Published: December 2004

Freie Radikale des Phenothiazins und ähnliche Verbindungen. IV. Phenothiazinyl‐ und Diphenothiazin‐Kupferkomplexe als Zwischen‐ und Endprodukte in der Reaktion von Phenothiazin mit Kupfer (II)‐halogeniden

Darstellung und Eigenschaften einiger Komplexverbindungen des 10‐Phenothiazinylradikals und deren Dimerisierungsprodukte mit Cu(I)‐ und Cu(II)‐ionen werden beschrieben.

Ein Mechanismus für die selektive Chlorierung von Phenothiazinen in Position 1 mittels CuCl2 wird diskutiert. Die Möglichkeit ähnlicher Bromierungen mittels CuBr2 wird demonstriert.
Azomethinimine. V. 1H‐NMR‐Spektren und sterischer Bau von arylsubstituierten Pyrazolidon‐Azomethiniminen
Authors: Geissler G. , Hippius M. , Tomaschewski G.
Published: December 2004

Azomethineimines. V. 1H‐N.M.R. Spectra and Steric Properties of Arylsubstituted Pyrazolidone‐Azomethineimines

From the results of 1H‐n.m.r.‐spectroscopic investigations we tried to draw conclusions regarding the steric properties of pyrazolidone‐azomethineimines 1a–k. The influence of aromatic systems on chemical shift of the methineproton of the 1,3‐dipolar centre was calculated using the ring current model. Without the twisted 9‐anthryl‐substituted compound 1f experimental results show a good correspondence to the values of chemical shift calculated for two of four possible isomeric structures.
Zur Synthese und zum Reaktionsverhalten von 2,6‐disubst.‐5‐Acyl‐4H‐1,3‐oxazin‐4‐thionen
Authors: Dehne H. , Krey P.
Published: December 2004

Synthesis and Chemical Behaviour of 2,6‐Disubst.‐5‐acyl‐4H‐1,3‐oxazine‐4‐thiones

New 2,6‐disubst.‐5‐acyl‐4H‐1,3‐oxazine‐4‐thiones 4 are synthesized by addition‐cyclocondensation reaction between 1,3‐diketones and acylisothiocyanates.

With perchloric acid ring opening of 4 takes place and N‐acyl‐acylthioacetamides 5 are obtained. The compounds 5 can be S‐alkylated by alkyl halides to form 6. 2‐Aroyl‐1‐aroylamino‐1‐arylaminoethenes 7 are prepared from 5 or 6 with primary amines. Spectroscopic measurements of 4–7 are discussed.
Reaktion von methylenaktiven Nitrilen und Cyanamid mit acylierten Enaminen
Authors: Gewald K. , Schäfer H. , Bellmann P.
Published: December 2004

Reaction of Methylene Active Nitriles and Cyanamide with Acylated Enamines

The addition products from enamines onto isocyanates and isothiocyanates, i.e. substituted β‐aminoacrylo amides 1 and thioamides 2, react with malononitrile to yield the 6‐amino‐1‐aryl‐5‐cyano‐pyridin‐2‐ones 3 and ‐thiones 4 among them 5,6,7,8‐tetrahydroisoquinolin‐1‐ones and ‐thiones. From ethyl cyanoacetate the 5‐cyano‐6‐hydroxy‐pyridin‐2‐ones 7 and from benzoyl acetonitrile the 6‐phenyl‐pyridin‐2‐ones 8 are formed. The replacement of malononitrile by cyanamide yields the 2‐amino‐3‐aryl‐pyrimidin‐4‐ones 5 and ‐thiones 6 among them 5,6,7,8‐tetrahydroquinazolin‐4‐ones and ‐thiones. The not isolated β‐acyl enamines derived from enamines and acid chlorides react with malononitrile or cyanamide to form the pyridin‐2‐ones 14 or pyrimidin‐2‐ones 15 caused by Dimroth‐rearrangement.
Untersuchungen über den Thermischen Zerfall von n‐Dodecylcyclopentan in der Gasphase
Authors: Zychlinski W. , Anders G. , Zimmermann G.
Published: December 2004

Investigations on the Thermal Decomposition of n‐Dodecylcyclopentane in the Gas Phase

In the thermal decomposition of n‐dodecylcyclopentane at 670 and 750°C in a laboratory tubular reactor mixtures of hydrogen and 57 and 113 hydrocarbons respectively are formed. The mixtures have been analyzed and identified by capillary gas chromatography and by mass spectrometry. The distribution of the reaction products is used for mechanistic discussions.
Desaktivierungsverhalten von Arenen und Heteroarenen. XXXIII. Zur statischen Löschung der Fluoreszenz von Azinium‐Anthracenen in Lösungsmitteln mit n‐Donatoreigenschaften
Authors: Bendig Jürgen , Helm Siegrun , Kreysig Dieter , Wilda Jürgen
Published: December 2004

Deactivation Behaviour of Arenes and Heteroarenes. XXXIII. Static Fluorescence Quenching of Azinium‐Anthracenes by Solvents of n‐Donor Properties

The fluorescence of azinium‐anthracenes is quenched by solvents of n‐donor properties. A model of static quenching by electron transfer is developed analogous to the dynamic process. The rates of quenching correlate with the donor properties of the solvent (ionization potential) and the acceptor properties of the fluorophor (reduction potential). In the same way as in the case of dynamic quenching this static process is characterized by a high free enthalpy of activation. The existence of a thermally induced step in the process of the electron transfer affects the temperature dependence of the fluorescence quantum yields. The analysis of this temperature dependence on the basis of an Arrhenius equation shows a linear relationship.
Neue Bifunktionelle Brückenfunktionen zur A1‐B29‐Verklammerung der beiden Insulinketten
Authors: Losse Günter , Naumann Wolfgang , Mätzler Gudrun , Richter Birgit
Published: December 2004

Novel Bifunctional Bridging Functions for A1‐B29 Crosslinking of the Two Insulin Chains

The positions A1 and B29 of the insulin molecule are crosslinked by the new bifunctional groups U and V. These insulin derivatives are convertible by oxydative sulfitolysis into A1‐B29 crosslinked hexa‐S‐sulfonates, which recombine by tributylphosphan/O2 in high yields to the A1‐B29 insulin derivatives, correctly reconstructing the disulfide system, and from which the bridging function is smoothly removable by acidolysis. The example of the bridging function U demonstrates that this principle is also suitable for the combination of both isolated single chains.
Tetrathiafulvalene. XVIII. Elektronen‐Donator‐Akzeptor‐Komplexe von Tetrathiafulvalenen (TTF) mit Tetracyanochinodimethan (TCNQ)
Authors: Schukat G. , Fanghänel E.
Published: December 2004

Tetrathiafulvalenes. XVIII. Charge‐Transfer‐Complexes of Tetrathiafulvalenes (TTF) with Tetracyanoquinodimethane (TCNQ)

TTF form CT‐complexes with TCNQ in solvents having small ET‐values, whose association constants are estimated. The energy of the absorption maximum of the CT‐complex between octamethylentetrathiafulvalene and TCNQ increases linearly with decreasing ET‐values of the solvents. In chloroform the energy of the absorption maximum of the CT‐complexes between TCNQ and tetrathiafulvalenes increases linearly with the oxidation potential of the tetrathiafulvalene.
Dreikomponentenreaktionen. XIV. 2‐Imidazoline und 1,2,4‐Triazole durch Ringschlußreaktionen von N‐(2‐Chlor‐alkyl)imidchloriden mit Hydrazin und Hydrazonen
Authors: Neumann R. , Beger J.
Published: December 2004

Three Component Reactions. XIV. 2‐Imidazolines and 1,2,4‐Triazoles by Ring Closure Reactions of N‐(2‐Chloro‐alkyl)imidchlorides with Hydrazine and Hydrazones

N‐(2‐Chloro‐alkyl)benzimidchlorides (1a and 1b) give with hydrazine in dependence on the reaction medium 1,1′‐bis(2‐imidazolines) (4), 1‐benzamido‐2‐imidazolines (5) or 1,2,4‐triazoles (6 and 7) and also N‐(2‐chloro‐alkyl)benzamides (8). From imidchlorides (1a–c) and hydrazones Schiff bases (10) of 1‐amino‐2‐imidazolines are obtained. They are not cleavable into free 1‐amino‐2‐imidazolines. magnified image
The aminolysis of carbamates. II. The Kinetics and Mechanism of the Aminolysis of Benzyl N‐phenylcarbamate with ethanolamine in aprotic solvents
Authors: Löcsei Vasile , Facsko Otilia , Chirilâ Traian
Published: December 2004

Aminolyse von Urethanen. II. Kinetik und Mechanismus der Aminolyse des Benzyl N‐phenylurethans mit Monoethanolamin in aprotischen Lösungsmitteln

Die Kinetik der Aminolyse des Benzyl‐N‐phenylurethans in Gegenwart eines Überschusses an Monoethanolamin wurde zwischen 140–160°C in zwei aprotischen Lösungsmitteln (Amin und Ether) verfolgt.

Es werden komplexe Geschwindigkeitsgesetze der Form kexp. = k Amin + k' Amin2 gefunden und mit einem E1cB‐Verlauf der Aminolysereaktion interpretiert. Ein synchroner E‐A‐Mechanismus unter Zwischenbildung eines Isocyanats wird dadurch ausgeschlossen, da die N‐methylierte Verbindung nicht reagiert.
Über Gesetzmäßigkeiten in der π‐Elektronenstruktur von heteroanalogen Polyvinylidenverbindungen
Authors: Hartmann Horst , Gutman Ivan
Published: December 2004

On Regularities of the π‐Electronic Structure of Heteroanalogous Polyvinylidene Compounds

Starting with simple forms of the equations for the eigenvalues and eigencoefficients of the π‐system of heteroanalogous polyvinylidene compounds 3 several regularities in the π‐electronic structure of these systems are derived and compared with known experimental facts. In this line several predictions are given for the properties of compounds unknown up to now.
Partialsynthesen von Cardenoliden und Cardenolid‐Analogen. VI. (20R)‐ und (20S)‐Cardanolide
Authors: Lindig Claus , Repke Kurt R. H.
Published: December 2004

Partial Syntheses of Cardenolides and Cardenolide Analogues. VI. (20R)‐ and (20S)‐Cardanolides

(20R)‐Dihydrodigitoxigenin (2) and (20S)‐dihydrodigitoxigenin (4) as well as their 3‐acetates3and5, respectively, were synthesized by catalytic hydrogenation of the appropriate cardenolides and separation by column chromatography on silica of the mixtures of stereoisomers. Hydroxymethylation of3and5followed by selective elimination yielded (20S)‐ and (20R)‐14‐hydroxy‐22‐methylene‐5β,14β‐cardanolide 3‐acetate (10and16), respectively.

The biological activities of the synthesized 20‐stereoisomeric cardanolides are investigated and discussed. Cardanolides10and16have a strong inhibitory activity on the proliferation of Ehrlich ascites carcinoma cells in suspension culture.
Partialsynthesen von Cardenoliden und Cardenolid‐Analogen. VII. Synthese A/B‐cis‐ und C/D‐cis‐verknüpfter Steroidmono‐ und ‐bis(α‐methylen‐γ‐butyrolactone)
Authors: Lindig Claus
Published: December 2004

Partial Syntheses of Cardenolides and Cardenolide Analogues. VII. Synthesis of A/B‐cis‐ and C/D‐cis‐linked Steroidal Mono‐ and Bis (α‐methylene‐γ‐butyrolactones)

The synthesis of A/B‐cis‐ and C/D‐cis‐linked steroidal mono‐ and bis(α‐methylene‐γ‐butyrolactones) 10–13, 18 and 24 by Reformatsky‐type reaction of 3β‐acetoxy‐14‐hydroxy‐5β, 14β‐androstan‐17‐one( 6), 14‐hydroxy‐5β, 14β‐androstane‐3,17‐dione (8), 3β‐acetoxy‐14‐hydroxy‐5β,14β‐pregnan‐20‐one (17) and 14‐hydroxy‐5β,14β‐pregnane‐3,20‐dione (23), respectively, with ethyl α‐(bromomethyl)acrylate is described. All steroidal lactones exhibit strong inhibitory activity on the proliferation of Ehrlich ascites carcinoma cells in suspension culture. For inhibitory activity the lactone moiety at C‐17 of the steroid molecule is more important than the lactone moiety at C–3 and C–20, respectively.
O‐ und N‐alkylsubstituierte 2‐(2′‐Hydroxyphenyl)‐benzimidazole und ‐1,3,4‐oxadiazole als Komplexbildner und Extraktionsmittel für Kupfer‐II‐ionen
Authors: Beger J. , Wagner G. , Uhlig E. , Dinjus U.
Published: December 2004

O‐ and N‐Alkylsubstituted 2‐(2′‐Hydroxyphenyl)‐benzimidazoles and ‐1,3,4‐Oxadiazoles as Complexing and Extracting Agents for Copper‐II‐Ions

2‐(2′‐Alkoxyphenyl)‐benzimidazoles1, 1‐alkyl‐2‐(2′‐hydroxyphenyl)‐benzimidazoles2, 2‐(2′hydroxy‐4′‐alkoxyphenyl)‐benzimidazoles3, 2‐(2′,4′‐dialkoxyphenyl)‐benzimidazoles4and 1‐alkyl‐2‐(2′‐hydroxy‐5′‐nitrophenyl)‐benzimidazoles7are synthesized by condensation of 2‐hydroxybenzoic acid derivatives and o‐phenylenediamine or its derivatives. Alkyl chains C4, C8or C12are introduced by alkylation before or after the ring closure in order to increase the solubility of the reagent in toluene or n‐octane. Furthermore the extraction properties of the benzimidazoles are investigated. Also some new analogous compounds of the benzothiazole and the 1,3,4‐oxadiazole series were synthesized.
Dreikomponentenreaktionen. XVI Zur Halogenierung von Alk‐1‐enen in Gegenwart von Ethylenoxid und Propylenoxid
Authors: Beger J. , Schiefer H. , Scheller D.
Published: December 2004

Three Component Reactions. XVI. Halogenation of Alk‐1‐enes in the Presence of Ethylene Oxide und Propylene Oxide

The products of the chlorination of alk‐1‐enes in the presence of ethylene oxide and propylene oxide were investigated in relation to products of the chlorination in the presence of corresponding chloroalcohols4and5. Isomers dominating in the Markovnikov orientation were found in all cases. Two of the three pairs of diastereomeric bischloropropylethers expected for the chlorination of propene in the presence of propylene oxide were identified by capillar GLC and13C n.m.r. spectroscopy.
Untersuchung der Struktur photochemisch aus Pyrazolidon‐(3)‐azomethiniminen erzeugter 1,5‐Diaza‐bicyclo‐[3,1,0]‐hexan‐2‐one mit Hilfe der LIS und der RKSA
Authors: Geissler G. , Menz I. , Köppel H. , Kretschmer M. , Kulpe S.
Published: December 2004

LIS and X‐Ray Investigations of the Structure of 1,5‐Diaza‐Bicyclo‐[3,1,0]‐hexanones‐(2) Obtained by Irradiation of Pyrazolidone‐(3)‐azomethineimines

1,5‐Diaza‐bicyclo‐[3,1,0]‐hexanones‐(2) 2 are the photoproducts of pyrazolidone‐(3)‐azomethineimines 1. Generally they can exist in the exo‐form or in the endo‐form. 1H‐n.m.r.‐measurements of 2a–d show that neither at normal temperature (298 K) nor at low temperatures (213 K) an exo/endo mixture is formed photochemically. Therefore the conclusion is drawn that the photoreaction is stereospecific. Chemical shift calculations of the methyleneprotons and the methyl‐protons in 2c and 2d using the ring current model and lanthanoide induced shifts (LIS) on 2d with Eu(fod)3 show that in solution the photoproducts have the exo‐form. These results are in agreement with results of a single‐crystal X‐ray structure analysis on 2a.
Konfigurationsbestimmung von Steroiden mit Primärer und sekundärer Aminogruppe durch Messung des Circulardichroismus der Kupfer‐Succinimidat‐Komplexe
Authors: Balint A. , Kerek F. , Ponsold K. , Schönecker B.
Published: December 2004

Configurational Assignment of Steroids with Primary and Secondary Amino Groups by CD Measurements of the Copper Succinimidate complexes

The CD spectra of the copper succinimidate complexes of 9 different steroids with a primary and 3 steroids with a secondary amino group were investigated. A good correlation between the sign of the Cotton effects in visible range and the chirality of the immediate neighbourhood of the nitrogen atom was observed. The results obey the earlier established octant rule for this chromophor.
MO‐LCAO‐Calculations on Polymethines. XXI. Electrono‐dative, electrono‐captive, and electrono‐ambident polymethine radicals
Authors: Fabian J. , Hartmann H.
Published: December 2004

[N + 1]π‐polymethine radicals with nitrogen containing terminal groups (violenes) display electron transfer reactions. Modification of the simple chain structures results in distinct changes of the molecular electronegativity and, consequently, of the redox properties. Based on the formerly defined non‐bonding singly occupied MO (SOMO) of ideal polymethines, the various polymethine derivatives are classed into electrono‐dative and electrono‐captive polymethine radicals. Electrono‐dative radicals are prone to release electrons, whereas electrono‐captive radicals are prone to accept electrons. This classification reflects experimental results presented by HÜNIGand coworkers, which have been formerly discussed in terms of aromaticity rather than of MO theory. A third class of radicals embraces compounds in which the redox properties of the simple chain polymethine radicals are less changed upon structural modification. These radicals have been termed as electrono‐ambident radicals because they are both inclined to release and to accept an electron. HÜNIGand coworkers obviously found the first representatives of this series of radicals. Electronoambident radicals also encounter in VIEHE‐type radicals suggesting a more general definition of the latter ones.
Zur palladiumkatalysierten Isoprentelomerisierung in alkoholischen Medien und deren Folgereaktionen
Authors: Gaube W. , Stegemann H.
Published: December 2004

Palladium‐Catalyzed Telomerization of Isoprene in Alcoholic Mediums and its Consecutive Reactions

The telomerization of isoprene with methanol to give dimethyloctadienylmethylethers by palladium‐containing homogenous catalysts was investigated. It was found that the primary products of the catalysis undergo different consecutive reactions catalysed by the same catalytic systems. These reactions, i.e. isomerization, ether cleavage, interchange reaction and oligomerization were investigated in greater detail. A reaction scheme is developed and discussed.
Cyansäureester. 35. Über Bildung und Folgereaktionen von N‐Cyanatophthalimid. Neue spezifisch aktivierte und blockierte Isatosäurederivate
Authors: Martin Dieter , Nadolski Karin , Gründemann Egon
Published: December 2004

Cyanic Acid Esters. 35. On Formation and Consecutive Reactions of N‐Cyanato Phthalimide. New Specifically Activated and Blocked Isatoic Acid Derivatives

Depending on the reaction conditions N‐hydroxy‐phthalimide affords on treatment with cyanogen bromide via N‐cyanato phthalimide 2 the iminocarbonate 3 and isatoic acid derivatives 7 and 16. Both the latter react with nucleophiles as isatoic acid derivatives activated on the carboxylic group and protected on the carbamic group or vice versa, furnishing N,N‐bis alkoxycarbonyl anthranilic acid amides 9, N‐alkoxycarbonyl anthranilic acid amides 12, o‐alkoxycarbonyl phenyl ureas 17 and the benzotriazepin‐2,5‐dione 14. The structures of the new compounds are proved by 1H‐n.m.r. and 13C‐n.m.r. measurements as well as independent synthesis.
Vereinfachte synthetische Wege zum Cyclol‐System von Mutterkorn‐Peptidalkaloiden
Authors: Losse Günter , Strobel Jürgen
Published: December 2004

Improved synthetic pathways to the cyclol system of ergot peptide alkaloids.

As demonstrated in the case of N‐tert. butyloxycarbonylhydroxyglycine, N‐protected 2‐hydroxy‐2‐amino acids can be directly condensed with dipeptide esters to afford tripeptide derivatives, which are activated C‐terminally and transferred into the epimers (8) and (9) of the corresponding oxacyclols. These are separated in the usual manner into the aci and the naturally occuring configuration 2R:5S:10aS:10bS. Alternatively, the epimeric cyclols may be obtained by acylation of dipeptide lactams with 2‐tert. butyloxycarbonylamino‐2‐benzyloxy‐carboxylic acids, followed by hydrogenolytic debenzylation and cyclisation of the OH‐deprotected acyl lactam.
Synthesis of Gonadoliberin, a gonadotropin releasing hormone
Authors: Rzeszotarska Barbara , Masiukiewicz Elzbieta , Kmiecik‐Chmura Halina
Published: December 2004

A simple laboratory synthesis of gonadoliberin was elaborated basing on classical solution methods and using minimal protection of side‐chain functions. In the final step a hexapeptide segment was condensed with the corresponding tetrapeptide and the obtained product was purified by a single step silica gel chromatography. The total efficiency of the whole synthesis was 15%.
Pyryliumverbindungen, XXV. Quantenchemische Berechnungen zur Valenzisomerisierung von 2‐Amino‐2H‐pyran und ‐thiopyran
Authors: Schlodder Heike , Thieme Rainer , Weiss Cornelius , Fischer Gerhard W. , Zimmermann Thomas
Published: December 2004

Pyrylium Compounds. XXV. Quantum Chemical Calculations Concerning the Valence Isomerization of 2‐Amino‐2H‐pyran and ‐thiopyran

The equilibrium 2‐amino‐2H‐pyran6⇌ 5‐amino‐2,4‐dien‐1‐one7was investigated using the semi‐empirical MINDO/3 and MNDO methods. In accordance with experimental findings for the substituted derivatives1/2a–d, the introduction of a methyl group into the position 3 of6or the exchange of oxygen by sulfur shifts the equilibrium towards the cyclic structures8and10, respectively. Polar solvents, the influence of which was estimated applying the reaction field approach as well as the solvaton theory, and entropy effects are calculated to favour the ring‐open valence isomer7. These results also correspond to experimental results.
Zur Pyrolyse unsubstituierter Cyclane – Produktbildungsselektivitäten, kinetische Parameter, mechanistische Interpretationen
Authors: Zimmermann G. , Zychlinski W. , Bach G. , Rennecke D.
Published: December 2004

On the Pyrolysis of Unsubstituted Cyclanes – Selectivity of the Formation of Reaction Products, Kinetic Parameters, Mechanistic Interpretations

The thermal decompostion of cyclopentane (1), cyclohexane (2), cycloheptane (3), cyclooctane (4), cyclodecane (5), and cyclododecane (6) was studied in a laboratoryscale metallic tubular reactor at 650 to 850°C in the presence of steam. The kinetic parameters for the overall reactions were determined and the gaseous as well as the liquid reaction products were analyzed and identified by gas chromatography or by the coupling of gas chromatography and mass spectrometry, respectively. It could be shown that from all cyclanes the isomeric α‐olefines are formed, if the conversion of the starting cyclanes is small. This supports the view that the cyclane → α‐olefin isomerization is an important initial reaction in pyrolysis of 1 up to 6. The results also demonstrate that the main pathway of degradation is a radical chain mechanism via cyclanyl radicals with β(CC) bond scission and 1.4 or 1.5‐H‐isomerization of alkenyl radicals as the most important reaction steps.