bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zur Umsetzung von n‐Alkanen mit Aluminiumnitratnonahydrat
Authors: Minkov Dimiter , Lavčieva Dimitrina , Kumanova Bogdana 
Published: December 2004

About the Reaction between n‐Alkanes and Aluminium Nitrate‐nonahydrateThe reaction between n‐alkanes (C10C13) and aluminium nitrate‐nonahydrate in the temperature range 353–403 K, time of contact 12 h and mole ratio nitrating agent: hydrocarbon from 1:2 to 2:1 was investigated.The product obtained was separated on silicagel. The fractions separated by adsorption chromatography were studied by i.r.‐ and combined GC/MS spectroscopy. Only alkyl nitrates were obtained. The oxidation processes yield aldehydes, ketones and nitrate carboxylic acids.The model reaction with n‐undecane shows that undecyl‐3‐nitrate (5), undecanal (6), undeca‐5‐on (7) and nitrate undecanic acid (8) are obtained.
Fluoreszenzlöschung und Excimerenbildung von Pyren‐3‐sulfonat in wäßrigen Lösungen von Polydimethyldiallylammoniumchlorid
Authors: Becker H. G. O. , Schütz R. , Kuzmin M. G. , Sadovsky N. A. , Soboleva I. V. 
Published: December 2004

Quenching of Fluorescence and Excimer Formation of Sodiumpyren‐3‐sulfonate in Aqueous Solutions of Polydimethyldiallylammonium ChlorideThe fluorescence spectra and lifetimes of sodium‐pyren‐3‐sulfonate have been measured in the presence of polydimethyldiallylammonium chloride. It is shown, that the excimer formation by static self‐quenching of fluorescence of the pyren‐3‐sulfonate is based on the cooperative effect of the macroion. The association constants of interaction between the aromatic compound and the polycation are determined. Presence of diazoniumcations leads to quenching of fluorescence of pyren‐3‐sulfonate in both the polyelectrolyte and aqueous phases. The quenching constants are discussed.
Reaction of Cyclohexylamine with Formaldehyde: The structure of N′,N″,N″′‐tricyclohexylhexahydro‐symtriazine
Authors: Zangrando Ennio , Poggi Gabriella , Giumanini Angelo G. , Verardo Giancarlo 
Published: December 2004

AbstractA reported preparation of 1,3‐dicyclohexyl‐1,3‐diazacyclobutane (2) is rebutted: the correct structure is that of N′,N″,N″′‐tricyclohexylhexahydro‐sym‐triazine (5), having a diequatorial‐axial conformation in the solid state, as shown by mass spectrometry and X‐ray diffraction. Theoretical calculations were carried out in order to predict the stabilities of 1,2‐ and 1,3‐diazacyclobutane (14 and 1) and their geometries.
Silylation‐Mediated Oxidation of 2,2′‐Anhydro‐5,6‐dihydro‐5‐azacytidine
Authors: Abbasi M. M. , El‐Wassimi M. T. , Osman F. H. , Kamel M. M. 
Published: December 2004

AbstractReaction of 5,6‐dihydro‐5‐azacytidine hydrochloride 1 with 2‐acetoxy‐isobutyryl chloride produced 5′‐O‐(2,5,5‐trimethyl‐1,3‐dioxolan‐4‐on‐2‐yl)‐3′‐O‐acetyl‐5,6‐dihydro‐2,2′‐anhydro‐1‐β‐D‐arabinofuranosyl‐5‐azacytosine hydrochloride 2, which upon partial hydrolysis with EtOH/HCl at 4°C gave 3′‐O‐acetyl‐5,6‐dihydro‐2,2′‐anhydro‐1‐β‐D‐arabinofuranosyl‐5‐azacytosine hydrochloride 3. The hydrolysis of 3 with EtOH/HCl at 25°C gave 2,2′‐anhydro‐5,6‐dihydro‐1‐β‐D‐arabinofuranosyl‐5‐azacytosine hydrochloride 4. Silylation oxidation of 3 and 4 with BSTFA or BSA in acetonitrile produced the N‐substituted derivatives of 1‐β‐D‐arabinofuranosyl‐5‐azacytosine 8 and 7, respectively.
The “normalizing factor” for the tomato mutant chloronerva. XXV. Synthesis of 2‐Epinicotianamine and Nicotianamine
Authors: Ripperger H. , Schreiber K. 
Published: December 2004

Abstract2‐Epinicotianamine (6) was synthesized by stepwise reductive alkylation of ethyl (R)‐2‐azetidinecarboxylate (2) with ethyl (S)‐4‐oxo‐2‐(trifluoroacetylamino)butanoate (3); nicotianamine (8) was prepared in an analogous manner from (2S,αS)‐α‐amino‐2‐carboxy‐1‐azetidine‐butanoic acid (7). 2‐Epinicotianamine and nicotianamine showed the same biological activity with regard to the phenotypical normalization of the tomato mutant chloronerva.
Darstellung und Reaktivität von 2,4‐Diamino(bis‐alkylamino)‐1,3,5‐triazin‐6‐yl‐thioharnstoffen
Authors: Freiberg Renate , Bulka Ehrenfried 
Published: December 2004

Synthesis and Reactivity of 2,4‐Diamino(bis‐alkylamino)‐s‐triazine‐6‐thioureas2,4‐Diamino‐s‐triazine‐6‐thiourea (1a) was prepared by treating cyanomelamine with hydrogen sulphide under pressure in aqueous ammonia. Addition was also performed indirectly by the reaction with thioacetamide. This method was further be used to get 2,4‐bis‐alkylamino‐s‐triazine‐6‐thioureas (1b–g). s‐Triazine‐thioureas (1a–g) were S‐alkylated with methyl iodide or benzyl chloride to the compounds 2a–f, 3a. Hantzsch thiazole synthesis of s‐triazine‐thioureas with α‐halocarbonyl derivatives gave 2,4‐diamino(bis‐alkylamino)‐6‐(thiazolamino)‐s‐triazines (5a–j, 6b, d–g, 7a–f).
Exo‐ and endohormones. X. A novel route to an isomer mixture of 7,9‐Dodecadien‐1‐yl Acetate utilizable in field attraction of Lobesia botrana males
Authors: Daradics L. , Oprean I. , Hodosan F. 
Published: December 2004

AbstractWittig condensation of (Z)‐2‐pentenylidene triphenylphosphorane (14) and 7‐tert.‐butoxy‐heptanal (13) under conditions of phase transfer catalysis and subsequent conversion into the corresponding acetate afforded a mixture of 28% 7(E),9(Z)‐dodecadien‐1‐yl acetate, the sex pheromone of Lobesia botrana, along with the other geometrical isomers and 30% unidentified by‐products. The synthons 14 and 13 were prepared starting with (Z)‐2‐butene‐1,4‐diol (1) and hexane‐1,6‐diol (9), respectively.
Darstellung neuer substituierter 1,2,4‐Triazin‐6‐carbonsäuren und 1,2,4‐Triazin‐6‐yl‐alkancarbonsäuren
Authors: Heinisch L. 
Published: December 2004

Synthesis of New Substituted as‐Triazine‐6‐carboxylic Acids and as‐Triazine‐6‐yl‐alkanoic AcidsNew substituted 3‐amino‐, 5‐amino‐ and 3,5‐diamino‐as‐triazine‐6‐carboxylic acids 4a, b, 5a, b and 6 were obtained by the hydrolysis 6‐azalumazine derivatives 3a–e. Corresponding acids of the structure 10a–d, 11a, b and 12 were synthesized from 5‐chlor‐3‐methylthio‐astriazine‐6‐carboxylic‐ester 8. The synthesis of new 3‐alkylthioderivatives of as‐triazine‐6‐yl‐acetic acid 16a–c and ‐propionic acid 18 and its hydrolysis to 3,5‐dioxotetrahydro‐as‐triazine‐6‐yl‐propionic acid 19 is reported.
Bestimmung der Extinktionskoeffizienten der Photoisomeren von 3β‐Hydroxy‐cholest‐5,7‐dien (Provitamin D3)
Authors: Gliesing S. , Reichenbächer M. , Ilge H.‐D. , Fassler D. 
Published: December 2004

Determination of the Molar Absorptivity (ε) of the Photoisomers of 3β‐Hydroxy‐cholest‐5.7‐diene (Provitamin D3)A method is described which allows the determination of the molecular absorptivity (ε) of all components in a four‐component system and is applied to the ε‐determination of the photoisomers of provitamin D3 (1): prävitamin D3 (2), lumisterol3 (3), and tachysterol3 (4). By means of irradiation with appropriate wavelengths the four‐component system is reduced to a two‐ and a three‐component system, respectively, and the unknown molar absorptivities are evaluated numerically or graphically.
13C‐NMR‐Untersuchungen an 4‐Amino‐2,6‐dialkyl‐pyrimidinen und ihren Sulfonamidderivaten
Authors: Gründemann E. , Niclas H.‐J. , Zeunter F. 
Published: December 2004

Carbon‐13 N.M.R. Studies on 4‐Amino‐2,6‐dialkyl Pyrimidines and Their Sulfonamide DerivativesCarbon‐13 n.m.r. studies on 4‐amino‐2,4‐dialkyl pyrimidines and their sulfonamide derivatives have shown that the known additivity rules for the assignment of signals are not valid. The reason is a tautomerism as demonstrated by changes of the chemical shifts of the alkyl groups. The electronic influence of substituents at the amino group on the alkyl C‐atoms are neglegible compared to changes due to tautomerism.
Revisitation of the reaction between aniline and formaldehyde. VI. The accumulated amide ester function from Addition of Carboxylic Anhydrides to N‐methyleneamines or their trimers
Authors: Giumanini Angelo G. , Verardo Giancarlo , Cauci Sabina 
Published: December 2004

AbstractSome aliphatic carboxylic anhydrides gave excellent yields of the novel addition products to both aliphatic and aromatic N‐methyleneimines, starting from their aliphatic and aromatic trimeric cyclic oligomers. A preliminary positive ion mass spectrometric study is here reported. They hydrolyze surprisingly faster than the corresponding acid amides, making necessary the intervention of a special mechanism. The reduction of the acetylamideester of cyclohexylmethyleneimine (3c) with LiAlH4 was also “abnormal”, as it yielded N‐methyl‐N‐ethylcyclohexylamine in quantitative yield.
Synthesis of Schizokinen, Homoschizokinen, Its Imide and the detection of imide with 13C‐N.M.R.‐spectroscopy
Authors: Milewska Maria J. , Chimiak Andrzej , Głowacki Zdzisław 
Published: December 2004

AbstractA new method for the synthesis of homoschizokinen 1 and schizokinen 2 is described. 2‐tert‐Butyl‐1,3‐di‐N‐hydroxysuccinimidyl citrate has been applied as the key substrate. The method excludes the possibility of imide formation. The imide of compound 1 has been obtained analogously from the active ester of the 1,3‐dioxolan‐4‐one derivative 5. It has been stated that 13C‐n.m.r. signals of the C‐3 carbon atoms enable the detection of traces of homoschizokinen 17.
Exo‐ and endohormones. XII. Synthesis of 7(E),9(Z)‐Dodecadien‐1‐yl Acetate, the sex pheromone of european grape vine moth Lobesia botrana, involving phase transfer technique
Authors: Daradics L. , Oprean I. , Hodosan F. , Serban N. 
Published: December 2004

AbstractThe synthesis of 7(E), 9(Z)‐dodecadien‐1‐yl acetate using for the olefination steps Wittig and Horner reactions under phase transfer conditions is reported. The 7(E) double bond was prepared by Horner coupling of 7‐tert‐butoxy‐heptanal (1) with 0,0‐diethylphosphonoacetate (2) in a two phase system.Wittig olefination was used to build up the 9(Z) double bond by reacting 9‐tert‐butoxy‐2‐nonen‐1‐yl‐triphenyl‐phosphonium bromide(13) with propionaldehyde under phase transfer catalytic conditions.
Experimentelle und theoretische Untersuchungen an Kohlenwasserstoffen der Formel C5H6: Pyrolyse von Cyclopenta‐1,3‐dien
Authors: Gey E. , Ondruschka B. , Zimmermann G. 
Published: December 2004

Experimental and Theoretical Investigations on Hydrocarbons of the Formula C5H6: Pyrolysis of 1,3‐CyclopentadieneThe details of high temperature chemistry of the conversion of 1,3‐cyclopentadiene (CPD) are unknown. Therefore the pyrolysis of CPD was studied under various reaction conditions in labscale dimension. The attempt to interpret the composition of the reaction products only on the basis of convenient axiomes does not seem satisfactory. For that reason heats of formation and relative stabilities for 25 closed and open shell hydrocarbons of the formula C5H6 were calculated using the MINDO/3 procedure. These enthalpy values were used to estimate heats of reactions for selected start steps of the pyrolysis of CPD. The molecular‐assisted hydrogen transfer under formation of cyclopentadienyl and cyclopentenyl radicals ought to be one of the most important reaction steps.
Nachbargruppenbeteiligung bei durch N‐Bromsuccinimid initiierten Elektrophilen Additionen
Authors: Haufe Günter , Gierscher Fritz , Köhler Günther , Schulze Klaus 
Published: December 2004

Neighbouring Group Participation in Electrophilic Additions Initiated by N‐BromosuccinimideStarting from endo‐5‐hydroxymethyl‐norbornene as well as 5‐(hydroxymethyl)‐methyl‐cyclohexene the methoxybromination procedure gives cyclic ethers by participation of the hydroxymethyl group. Unsaturated formyl compounds or their acetals, respectively by contrast, gave methoxybromination products. After oxidation of the functional groups bromo methoxy methyl carboxylates are formed depending on the molar ratio of the substrate to NBS.
Partialsynthesen von Cardenoliden und Cardenolid‐Analogen. XII. Synthese 21‐substituierter Cardenolide durch Oxidation von 17β ‐ (Fur‐3‐yl)‐Steroiden und nukleophile Substitution
Authors: Lindig Claus , Repke Kurt R. H. 
Published: December 2004

Partial Syntheses of Cardenolides and Cardenolide‐Analogues. XII. Synthesis of 21‐Substituted Cardenolides by Oxidation of 17β ‐ (3‐Furyl)‐Steroids and Nucleophilic SubstitutionOxidation of 17β‐(3‐furyl)‐5β, 14β‐androstane‐3β, 14β‐diol 3‐acetate (2b) with chromic acid yielded the 14,21‐epoxy‐cardenolide 4. After elimination of the 14β‐hydroxy group of 2b the unsaturated furyl derivative 5, when treated with chromic acid, gave a mixture of the diastereomeric unsaturated 21ξ‐hydroxy‐cardenolides 8a which were converted with N‐bromoacetamide to a mixture of the 14β, 15β‐epoxy‐21ξ‐hydroxy‐cardenolides 9a.The hydroxy‐cardenolides 8a and 9a were acetylated to the 21ξ‐acetoxy‐cardenolides 8b/8c and 9b/9c, respectively, and they reacted with primary and secondary amines to give the corresponding N‐substituted 21ξ‐amino‐cardenolides 11a‐‐11c and 12b, respectively. When reacted with p‐toluenesulfonyl chloride both 8a and 9a yielded the 21ξ‐chloro‐cardenolides 11d/11e and 12c/12d, respectively, the chlorine of which could easily be substituted by SN1‐ and SN2‐reactions.
Oligosiloxane mit funktionellen Gruppen. II Reaktion von 1,4‐Bis(trimethylsiloxy)‐but‐2‐en mit H‐Silanen in Gegenwart von Hexachloroplatin‐säure
Authors: Engelbrecht L. , Sonnek G. , Ždanov A. A. , Makarova L. I. 
Published: December 2004

Oligosiloxanes with Functional Groups. II. Reaction of 1.4‐Bis(trimethylsiloxy)‐but‐2‐ene with H‐Silanes in the Presence of Hexachloroplatinic AcidThe synthesis of silicon‐modified butane‐1.4‐diol derivatives by the hydrosilylation of 1.4‐bis (trimethylsiloxy) but‐2‐ene (1) is described. Under the conditions of the hydrosilylation 1 is isomerized with high selectivity. At a temperature above 150°C hydrosilylation and isomerization take place simultaneously.
Substituierte 5‐Imino‐3,3‐pentamethylen‐1,2,4‐thiadiazolidine durch Aminierung von Thioharnstoffderivaten
Authors: Andreae Siegfried , Schmitz Ernst 
Published: December 2004

Substituted 5‐Imino‐3,3‐pentamethylene‐1,2,4‐thiadiazolidines by Amination of Thiourea DerivativesN‐Acylthioureas 2a–b and thiosemicarbazones of aldehydes, ketones, and esters 4a–g are aminated at the potential SH‐group by 3,3‐pentamethyleneoxaziridine yielding substituted 5‐imino‐3,3‐pentamethylene‐1,2,4‐thiadiazolidines 3 and 6 the latter via the intermediates 5.The reaction of the thiosemicarbazones 4 is a very general one, but only two acylthioureas 2 could be converted into the title compounds.
1,2,3‐Triazabutadiene. XX. Untersuchungen zur Fotoisomerisierung, Fotolyse, Protonierung und sauren Spaltung von 1‐Aryl‐3‐[3‐methyl‐benzthiazolinyliden‐(2)]‐triazenen in mizellaren Lösungen
Authors: Fanghänel E. , Ortmann W. , Hennig A. 
Published: December 2004

1,2,3‐Triazabutadienes. XX. Investigations of the Photochemical Z‐E‐Isomerization, Photolysis, Protonation and Acidic Cleavage of 1‐Aryl‐3‐3‐methylbenzthiazolinyliden‐(2)‐triazenes in Micellar SolutionsThe E‐isomers of the 1‐Aryl‐3‐[3‐methylbenzthiazolinyliden‐(2)]‐triazenes are soluble in aqueous micellar solutions of sodium dodecylsulfate (NDS) and cetyltrimethylammoniumbromide (CTAB). They are fixed in the Stern region of the micelles. The Z‐isomers decompose in aqueous micellar solutions by acidic cleavage. They can be stabilized by the use of alkaline buffer solutions. The concentration of protons is higher by the factor 103 in the Stern region of NDS‐micelles than in the Stern region of CTAB‐micelles. This difference is explained by electrostatic attraction and repulsion between the protons and the micelles. The quantum yields of the photochemical isomerization in micellar solutions and in organic solvents are the same. Water soluble ionic dyes with relatively low triplet energies sensitize the photoisomerization in micellar solutions and the photostationary state is on the side of the E‐isomer.
Zur Nitrierung von 2‐Methylaminopyridin‐N‐oxid‐Derivaten
Authors: Talik Tadeusz , Talik Zofia 
Published: December 2004

Nitration of Some Derivatives of 2‐Methylaminopyridine N‐OxidesThe only stable products obtained from nitrations of 2‐methylaminopyridine N‐oxide and some derivatives, are those resulting from nitration of the pyridine ring. Thus, 2‐methyl‐aminopyridine N‐oxide 8 is nitrated under mild conditions to yield 2‐methylamino‐5‐nitropyridine N‐oxide 9, but not 2‐methylnitraminopyridine‐N‐oxide 10 is obtained.2‐Methylamino‐4‐nitropyridine N‐oxide 1 yields 2‐methylamino‐4,5‐dinitropyridine N‐oxide 2 upon nitration.Chemical reactions which relate known compounds to the new compounds obtained, confirm the assigned structures.
Untersuchungen zum UV/Vis‐Spektralverhalten von Azofarbstoffen. XX. Zum unterschiedlichen Substituenteneinfluß auf die Absorptionsmaxima von Hydrazonen und Benzendiazoniumionen
Authors: Mustroph H. 
Published: December 2004

Studies on UV/Vis Absorption Spectra of Azo Dyes. XX. On the Different Substituent Effects on the Absorption Maxima of Hydrazones and Benzenediazonium IonsPMO theory predicts that substituent effects on the absorption maxima of benzenediazonium ions are partly contrary to those in hydrazones. Therefore, it seemed likely that azo coupling products absorbing at shorter wavelengths than the parent diazonium ions should exist. This is confirmed experimentally. The hydrazones 4c and 5c absorb significantly hypsochromic than the diazonium ion 3c.
Untersuchungen zur Gegenionenstruktur bei der Kationischen Polymerisation von Isobutylvinylether mit iodhaltigen Initiatoren
Authors: Spange Stefan , Heublein Günther , Taeger Frank 
Published: December 2004

Investigations on the Counter Ion Structure of the Cationics Polymerization of Isobutylvinylether with Iodine Based SystemsThe structure of counter ions of iodine based initiators for the cationic polymerization of isobutylvinylether is elucidated by means of u.v.‐spectroscopy using as model system:
equation image
Increasing electrophilicity of the cation causes a decrease of the counter ion stability. High concentrations of iodine lead to the formation of polyiodides, as I and I, respectively.The influence on chain propagation by iodine and monomer concentration as well have been followed by GPC and u.v.‐spectroscopy. Both influences, strongly affects the propagation reaction.Triphenylmethylbromide in conjunction with iodine is a convenient initiating system, realizing a long living and transfer suppressed propagation, when solvents of higher polarity are used. An activated carbon‐halide bond is concluded to be the active species.
Untersuchungen zur Synthese und den Eigenschaften von amphiphilen Polymeren
Authors: Behrmann K. , Richter C. , Fanghänel E. 
Published: December 2004

Investigations of the Synthesis and Properties of Amphiphilic PolymersBy reaction of propylene/maleic anhydride copolymers with the sodium salt of α‐dodecyl‐ω‐hydroxy‐trioxyethylene ionic polymers with different shares of long aliphatic side chains were prepared. The properties of these amphiphilic polymers were studied. Like micelles they are able to solubilize nonpolar probe molecules (N,N‐dimethyl‐aminoazobenzene). Viscosity measurements show the dependence of the conformation of the polymeric chain in solution on the share of aliphatic side chain and the degree of protonation. The polymers from micelle‐like aggregates. It is supposed that the polymer with a high share of aliphatic side chains froms several local aggregates per polymer chain, while the polymer containing only few side chains seems to form intermolecular aggregates between different polymer chains. These investigations were performed with pyrene as probe molecule. Pyrene was also used to examine the micropolarity of the aggregates. Like polyelectrolytes the amiphilic polymers are able to cause the aggregation of opposite charged dyes (thionine).
Furylvinylhalogenide. IX. Reaktionen von β‐Fur‐2‐yl‐β‐chlor‐α‐cyanacrylsäureestern mit Aminen
Authors: Jähnisch K. , Schwertner R. S. , Seeboth R. H. 
Published: December 2004

Furylvinylhalides. IX. Reactions of β‐fur‐2‐yl‐β‐chloro‐α‐cyanoacrylates with aminesβ‐Fur‐2‐yl‐β‐chloro‐α‐cyanoacrylates 4 react with amines to yield β‐Fur‐2‐yl‐β‐amino‐α‐cyanoacrylates 5. The 1H‐n.m.r. spectra of 5 are discussed.
Zur Übertragung von Substituenteneffekten in Fluorenen und Fluorenonen
Authors: Hauser A. , Thurner J.‐U. , Hinzmann B. 
Published: December 2004

On the Transmission of Substituent Effects in Fluorenes and FluorenonesA series of 2‐ and 2,7‐substituted fluorenes (1) and fluorenones (2) were prepared either by electrophilic substitution (1c–f, h–j; 2c, d, j), reduction (1, 2k, l) or nucleophilic exchange (1g, m, n; 2m) via respective diazonium compounds as well as by oxydation (2e–h, n) of the hydrocarbons (1).The carbon‐13 n.m.r. spectra for the fluorene (1a–n) and fluorenone (2a–n) derivatives was analyzed using a dual substituent parameter (DSP) equation. The substituent chemical shifts (SCS) of the carbon atoms 4a, 4b, 7 and 4a, 4b, 7, 9 of eleven fluorenes and nine fluorenones, respectively, correlate with the 𝒻, 𝓇 substituent constants and with σI, σ ones in a satisfactory manner. The comparison indicates that the correlation with the 𝒻, 𝓇 constants yields always a higher resonance contribution than the calculation with σI, σ constants. The DSP analysis reveals that transmission of the substituent effect to the substituted ring is primarily resonance controlled while the transmission to the second ring involves a π‐bond polarization mechanism. For C‐4b in the unsubstituted ring a reversed substituent effect was found. In contrast to fluorenes in fluorenones the transmission of the substituent effect involves the carbon atom 9.
Preparative vis‐laser photochemistry. Qinghaosu‐type 1,2,4‐Trioxanes by molecular oxygen trapping of paterno‐büchi triplet 1,4‐diradicals derived from the bicyclic enol lactones Δ1,6‐ and Δ1,10‐2‐oxabicyclo[4.4.0]decen‐2‐one and p‐benzoquinone
Authors: Adam W. , Kliem Ulrike , Peters Eva‐Maria , Peters K. , von Schnering H.‐G. 
Published: December 2004

AbstractThe VIS‐laser irradiation of enol lactones 1a, b and benzoquinone in an argon atmosphere led to the fenestrane‐type oxetane 2a and the propellane‐type oxetane 2b, with regioselective preference for the acetal structure. Under an oxygen atmosphere both regioisomeric fenestrane‐type 1,2,4‐trioxanes 4a and 5a were obtained from enol lactone 1a, while no oxygen trapping to the propellane‐type trioxanes was observed with 1b. Significant quantities of photooxygenation products were obtained from both enol lactones 1a, b due to singlet oxygen derived from oxygen quenching of benzoquinone triplets. The present study demonstrates that Qinghaosu analoga are accessible via trapping of Paterno‐Büchi triplet 1,4‐diradicals by molecular oxygen.
Untersuchungen zur Reaktion von Pyrazolon‐Azomethin‐Farbstoffen mit 2‐Pyrazolin‐5‐on‐Derivaten
Authors: Kucybala Z. , Gaca J. 
Published: December 2004

Investigations on the Reaction of Pyrazolone Azomethine Dyes with 2‐Pyrazolin‐5‐one‐DerivativesThe reaction between pyrazolone azomethine dyes 1 and different 2‐pyrazolin‐5‐ones 2 was investigated. Among the reaction products compounds 5 {3,3′3″‐trimethyl‐1,1′1″‐triphenyl‐[4,4′4″‐tri‐(2‐pyrazolin‐5‐on)]} was isolated, which hitherto was unknown as a product of this reaction. A new reaction pathway is proposed.