bluuebunny/crossref_metadata_2025_split huggingface dataset:
Massenspektrometrische Fragmentierung cis/trans‐isomerer tert. Butylcycloheptanole
Authors: Herzschuh R. , Borsdorf R. , Strüber F.‐J. 
Published: December 2004

Mass Spectrometric Fragmentation of cis‐trans Isomeric tert. ButylcycloheptanolsThe mass spectra of six cis‐trans isomeric tert. butylcycloheptanole 1–6 are discussed The fragmentation of the tert. butylcycloheptanols is similar to that observed for the corresponding cyclohexanes. The quotient \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{[{\rm M \hbox{---} M}_{\rm 2} {\rm O}]^{+ _ \bullet}}}{{{\rm M}^{{\rm +}_ \bullet}}} $\end{document} is found to be characteristic for the different geometric isomers. But the differences observed between flexible tert. butylcycloheptanols are much smaller than those calculated for the rigid tert. butylcyclohexanols.
Solvolysis of cis‐ and trans‐2‐Phenylcyclohexyl‐p‐bromobenzene Sulphonate
Authors: Youssef Abdel‐Hamid A. , Sharaf Saber M. , El Hegazy Fatma M. 
Published: December 2004

Solvolyse von cis‐ und trans‐2‐Phenylcyclohexyl‐p‐brombenzen‐sulfonatenDie Solvolyse von cis‐ and trans‐2‐Phenyl‐cyclohexyl‐p‐brombenzensulfonaten wurde in Essigsäure, wäßrigem Dioxan und wäßrigem Ethanol untersucht und mit der des Cyclohexylsulfonatesters verglichen. In Essigsäure liegt die Geschwindigkeit des cis‐Isomeren gegenüber dem trans‐Isomeren um den Faktor 5 höher, in wäßrigem Dioxan und wäßrigem Alkohol dagegen um den Faktor 10 bzw. 12.Produkte der Acetolyse sind hauptsächlich Eliminierungsprodukte (1‐ und 3‐Phenylcyclohexen 75%) und cis‐ und trans‐Acetate (25%). In wäßrigen Lösungsmitteln entstehen vorwiegend Eliminierungsprodukte (98%).Die Erhöhung der Geschwindigkeit des cis‐Isomeren gegenüber der trans‐Verbindung ist auf eine sterische Beschleunigung zurückzuführen.Ein solvatisiertes Ionenpaar wurde als Zwischenprodukt postuliert; für eine Phenylnachbargruppenwirkung ergab sich kein Hinweis.
Photochemie substituierter Cycloheptatriene. XV. Zur Charakterisierung der Elektronischen Übergänge in 1‐Aryl‐4‐(p‐dimethylaminophenyl)‐cycloheptatrienen
Authors: Abraham W. , Kupfer M. , Kreysig D. 
Published: December 2004

Photochemistry of Substituted Cycloheptatrienes. XV. About the Characterization of the Electronic Transitions in 1‐Aryl‐4‐(p‐dimethylaminophenyl)‐cycloheptatrienesThe absorption spectra of the title compounds are discussed in dependence on polarity of the solvent and its ability to form hydrogen bonds. The results suggest a hybridization of the N‐atom of the dimethylamino group between sp3 and sp2 in the ground state. Contrary to this, the nitrogen has sp2‐hybridization in the short wavelength (SE) fluorescing state. In a second fluorescence state the geometry of the seven‐membered ring should change. Therefore the viscosity of the solvents influences both the position and the quantum yield of this long wavelength emission (LE). The influence of polarity and viscosity of the solvents is described by multiple regression. The temperature dependence of fluorescence quantum yields is discussed, as well.
Bestimmung der Nullfeldparameter optisch angeregter 3(π,π*)‐Zustände ausgewählter aromatischer Systeme
Authors: Stösser R. , Thurner J.‐U. , Hanke T. , Sarodnick G. 
Published: December 2004

Determination of the Zero Field Parameters Optically Excited 3(π,π*)‐States in Selected Aromatic SystemsExperimental zero field parameters of optically excited naphthalene and quinoxaline derivatives are presented. The (D*), (D) and (E) parameters are determined by the position of the transitions by means of simple approximation formula, magnetophotoselection and simulation of spectra. Possibilities of comparison of the zero field parameters of optically excited 3(π,π*)‐states with parameters of ground state for simple aromatic hydrocarbones are presented.
1,2,3‐Triazabutadiene. XV. Einfluß der Substituenten auf die 15N‐ und 13C‐chemischen Verschiebungen in Triazabutadienen und Azobenzenen
Authors: Simova S. , Radeglia R. , Fanghänel E. 
Published: December 2004

1,2,3‐Triazabutadienes. XV. Substituent Effects on the Nitrogen‐15 and the Carbon‐13 Chemical Shifts of Triazabutadienes and AzobenzenesNitrogen‐15 and carbon‐13 chemical shifts are reported for 15N‐enriched p‐substituted triazenes 1, triazenium salts 2 and azobenzenes 3. Linear correlations between substituent induced shifts for various 15N‐ and 13C‐atoms and σ‐Hammett constants was found and discussed. The sensitivity of the chemical shifts of both nuclei to substituent effects in analogously constituted compounds are compared.
The aminolysis of carbamates. I. The Kinetics of the Aminolysis of Benzyl N‐phenylcarbamate with Ethanolamine
Authors: Löcsei Vasile , Facsko Otilia , Chirila Traian 
Published: December 2004

Aminolyse von Urethanen. I. Kinetik der Aminolyse des Benzyl‐N‐phenylurethans mit MonoethanolaminDie Kinetik der Aminolyse des Benzyl‐N‐phenylurethans im Bereich von 135 bis 165°C in Gegenwart eines Überschusses an Monoethanolamin mit und ohne Lösungsmittel (Benzylalkohol) konnte als Folgereaktion erster Ordnung erfaßt werden:

.Die Abhängigkeit der Geschwindigkeitskonstante k1 von der Monoethanolaminkonzentration weist auf eine Reaktion 2. Ordnung hin, und es wurde eine lineare Abhängigkeit der relativen Reaktivität R = k1/k2 von der Konzentration festgestellt. Der Einfluß der Temperatur auf R und die Aktivierungsenergien der beiden Reaktionsschritte wurden ermittelt.Die Analyse der Reaktanten und Zwischenprodukte erfolgte mit Hilfe der Hochdruckflüssigkeitschromatographie.Mögliche Mechanismen werden besprochen.
Untersuchungen zur Verseifung aromatischer Sulfochloride
Authors: Beck H. , Doerffel K. 
Published: December 2004

Studies on the Hydrolysis of Aromatic SulfochloridesThe hydrolysis of aromatic sulfochlorides can bei described by a second‐order law. Due to the strength of the base the constants of velocity are between 10−6 (H2O) or 103 (OH−) 1 mol −1 s−1 respectively. The reaction of benzensulfochlorides proceeds according to an addition‐elimination mechanism, whereas benzylic sulfochlorides, reacting with a strong base, proceed to an elimination‐addition mechanism.
Vinyloge Acylverbindungen. XX. Reaktivität und Toxizität arylsubstituierter β‐Chlorvinylketone, β‐Chlorvinylaldehyde und β‐Chlorvinylmethyleniminiumsalze
Authors: Fischer Gerhard W. , Jentzsch Renate , Riemer Fritz 
Published: December 2004

Vinylogous Acyl Compounds. XX. Reactivity and Toxicity of Aryl‐substituted β‐Chlorovinyl Ketones, β‐Chlorovinyl Aldehydes, and β‐Chlorovinyl Methyleniminium SaltsBased on kinetic measurements, the nucleophilic replaceability of the chlorine in aromatic β‐chlorovinyl ketones ArCO‐CH  CH‐Cl (1), isomeric β‐chlorovinyl aldehydes OCHCHC(Cl)Ar(2), and corresponding β‐chlorovinyl methyleniminium salts Me2N⊕;CHCHC(Cl)Ar X⊖ (3) is compared and related to toxicological findings. The chemical reactivity of these important synthetic building blocks increases in the order 2<1<3, the acute toxicity (24 h LD50 i. p. in the mouse) shows the graduation 2<3<1. Compounds of type 1 prove to be relatively toxic (LD50 24–42 mg/kg) and display a marked necrotic action after percutaneous absorption, whereas the aldehydes 2 have not only a minor acute toxicity (LD50 158–298 mg/kg) but also a somewhat less marked skin damaging activity. In addition, the LD50 values of selected β‐chlorovinyl carbonyl compounds are compared with those of corresponding halogen‐free compounds as well as of vinylogous carbonamidium salts ArCOCHCHN⊕R3X⊖. The latter, which can be used as synthetic equivalents of 1, differ in both the reduced acute toxicity and missing skin damaging properties.
Azomethinimine. VI. Zum thermischen Verhalten des Photochromiesystems Azomethinimin/Diaziridin, untersucht an Pyrazolidon‐(3)‐azomethiniminen und deren Photoprodukten
Authors: Geissler G. , Menz I. , Angermüller K. , Tomaschewski G. 
Published: December 2004

Azomethineimine. VI. On the Thermic Behaviour of the Photochromic System Azomethineimine/Diaziridine, Investigated by Means of the Photoproducts of Pyrazolidone‐(3)‐AzomethineiminesThe photochemically obtained cycloproducts 2 of pyrazolidone‐(3)‐azomethineimines 1 react thermically to 1 in aprotic solvents. This backreaction was investigated by following up the growth of the intensive long wave absorptionband of 1. The kinetic analysis was carried out according to SWINBOURNE [5, 6]. The thermic backreaction is accelerated by factors favouring a polarization of the CN(2)‐bond (Cδ+  Nδ−) of diaziridine 2. Such factors are polar solvents, donors in the substituent R and extensive, easily polarizable π‐electronic systems in R. The influence of substituents on the backreaction can be correlated by means of the σ+‐Hammett‐constants. For most compounds the values of EA ≈ ΔH≠, Δ≠ and ΔG≠ were determined. The possible reaction mechanism is discussed. The influence of steric factors on the thermic backreaction is regarded as a first indication of an exo‐form of the bicyclic diaziridines 2.
Azomethinimine. VII. Photochemisches und thermisches Verhalten azarylsubstituierter Pyrazolidon‐(3)‐azomethinimine
Authors: Geissler G. , Fust W. , Krüger B. , Tomaschewski G. 
Published: December 2004

Azomethineimines. VII. Photochemical and Thermic Behaviour of Azarylsubstituted Pyrazolidone‐(3)‐AzomethineiminesIn principle the photochemical behaviour of azarylsubstituted pyrazolidone‐(3)‐azomethineimines 1 does not differ from other pyrazolidone‐(3)‐azomethineimines. Except for the acridyl‐(9)‐substituted compound in aprotic solvents they react to bicyclic diaziridines 2. The quantum yield of this reaction has a value of nearly 0.3. For two of the diaziridines 2 the photochemical backreaction was realized. Results of the investigation of the thermic backreaction show the expected stability of the bicyclic diaziridines 2a–d. All the investigated compounds have a pronounced tendency towards several irreversible side reactions.
Eine einfache Methode zur quantitativen Bestimmung von Silanolgruppen
Authors: Welsch T. , Frank H. 
Published: December 2004

A Simple Method for Quantitative Determination of Silanol GroupsDie Bestimmung der Konzentration von Hydroxylgruppen auf Kieselgeloberflächen ist von großem analytischen Interesse, da diese die chromatografischen oder katalytischen Eigenschaften des Kieselgelmaterials maßgeblich beeinflussen. Dazu wurden bisher sowohl spektroskopische als auch chemische Bestimmungsmethoden angewendet [1–7], die uns jedoch aufgrund des apparativen Aufwandes bzw. der benötigten Zeit für Routineuntersuchungen als ungeeignet erschienen. Die von GALLEI [3]vorgeschlagene, gut reproduzierbare aber apparativ anspruchsvolle Variante der chemischen Umsetzung der Silanolgruppen mit Lithiummethyl und anschließender gaschromatografischer Bestimmung des gebildeten Methans wurde von uns wesentlich vereinfacht, wobei die Bestimmung der gebildeten Methanmenge volumetrisch erfolgte.
α‐Substituierte Phosphonate. 43. Synthese und Reaktivität von 1,2,3,4‐Tetrahydroisochinolin‐1‐phosphonaten
Authors: Gross H. , Ozegowski S. 
Published: December 2004

α‐Substituted Phosphonates. 43. Synthesis and Reactivity of 1,2,3,4‐Tetrahydroisochinolin‐1‐phosphonatesN‐Alkyl‐ and N‐arylsubstituted 1,2,3,4‐tetrahydroisochinolin‐1‐phosphonates 1 have been synthesized from the corresponding 3,4‐dihydroisochinoliniumbromides 7 and triethyl‐phosphite. The N‐unsubstituted 1,2,3,4‐tetrahydroisochinolin‐1‐phosphonate 10 is available starting from the 1,2,3,4‐tetrahydroisochinolin‐1‐phosphonic acid by esterification with triethylformate and splitting off the formyl group of the primarily formed N‐formyl derivative 14. – N‐Quarternated tetrahydroisochinolines 19 and the 1‐phosphorylated derivatives 17, respectively react with triethyl‐phosphite in an unexpected way by dealkylation and not by splitting off the isochinolinring. – By Horner‐synthesis with 1 the 1‐aralkylidene‐isochinolines 23 are available in moderate yields.
Prostaglandine und Prostaglandinvorstufen. VIII. Synthese von (1S, 5S)‐5‐Methyl‐2‐oxa‐bicyclo[3.3.0]octan‐3,6‐dion, einem wichtigen Zwischenprodukt für 8‐Methyl‐prostaglandin C2
Authors: Schick H. , Welzel H.‐P. , Schwarz S. 
Published: December 2004

Prostaglandins and Prostaglandin Intermediates. VIII. Synthesis of (1S, 5S)‐5‐Methyl‐2‐oxa‐bicyclo[3.3.0]octane‐3,6‐dione, an Important Intermediate for 8‐Methylprostaglandin C2The bicyclic lactone 5 is prepared by Meerwein‐Ponndorf‐Verley‐reduction of the chiral cyclopentyl acetic acid 3. The stereoselectivity of this reaction is compared with that of complex metal hydride reductions.
Elektrochemische Oxidation organischer Verbindungen in Fluorsulfonsäure. VI. Voltammetrische Untersuchungen zur Oxidierbarkeit heterocyclischer Kationen
Authors: Rudenko A. P. , Pragst F. 
Published: December 2004

Electrochemical Oxidation of Organic Compounds in Fluorosulfuric Acid. VI. Voltammetric Investigation about the Oxidability of Heterocyclic CationsThe anodic behavior of a series of pyridinium, quinolinium, isoquinolinium, pyrylium, tropylium, pyrazolium and imidazolium cations and of some of their benzoderivatives was investigated by cyclic voltammetry in HSO3F at −76°C. Because of the available very positive potential region under these conditions almost all cations were oxidized, and in many cases relatively stable dication radicals could be detected. The oxidation potential decreases with decreasing acceptor ability of the heterocyclic ring, increasing extension of the π‐electron system and increasing donor effects of substituents. There was no significant difference between the curves obtained from the N‐alkylated and the corresponding N‐protonated heterocyclic compounds, which showed that the oxidation is not coupled with the N‐deprotonation. The voltammograms of phenylsubstituted pyrylium and pyrazolium ions as well as of benzimidazolium ions display typical marks of the anodic aromatic dimerization, which hitherto seemed to have been restricted to donor substituted benzenes and π‐excess heterocycles.
Reaktionen von Aroyl(Hetaroyl)iminodithiokohlesäureestern mit Carbanionen CH‐acider Verbindungen
Authors: Richter M. , Strauss K. , Augustin M. 
Published: December 2004

Reactions of Dimethyl N‐Aroyl(Hetaroyl)carbimidodithioates with Carbanions CH‐acidic CompoundsReactions of dimethyl N‐aroyl(hetaroyl)carbimidodithioates 1 with carbanions 2 present new possibilities to synthesize 3‐acyl‐amino‐3‐methylthio‐2‐subst.‐acrylnitriles 3 by monosubstitution of methylthiogroup.The reaction of 1 with 2‐alkyl‐benzothiazolium salts 4 yield deeply coloured N‐acyl‐(2,3‐dihydrobenzothiazole‐2‐yliden) thioacetimido acid‐methylates 5 of the 2‐subst.‐benzothiazoliumperchlorates 6. The structures of the final products are determined by i.r.‐, 1H.‐n.m.r.‐ and u.v.‐spectra.
Photoinduzierte Zersetzung von Aryldiazoniumsalzen durch Metalloxalate
Authors: Baumann H. , Strehmel B. , Timpe H.‐J. , Rehorek D. 
Published: December 2004

Photoinduced Decomposition of Arene Diazonium Salts by Metal OxalatesArene diazonium salts were decomposed by the irradiation of K3[Fe(oX)3] and K3 [Co(ox)3]. The dediazonation is caused by electron transfer reactions between ·CO‐2 and in the case of the former complex also by [Fe(ox)2]2‐ ‐species. As intermediates aryl radicals were found by spin trapping with nitroso durene. The dediazonation quantum yields (0,15‐‐1,21) depend on the reduction potentials of the salts and on the oxalate concentration. By electron acceptor substituted diazonium salts the values are the same as those of the K3[Fe(ox)3]‐actinometer. In the case of p‐dialkylaminobenzene diazonium salt‐types an electron transfer takes places with ·CO‐2 only whereas the reaction with [Fe(ox)2]2− is neglectable. A Hammett‐correlation for the electron transfer of Fe(II)‐species with a ϱ‐value of 1.7 was found. The investigated systems are efficient initiators of the photopolymerization.
Zur Dehydratisierung von Harnstoffen mit Dichlorcarben im Phasentransfer‐Verfahren, ein Zugang zu substituierten Cyanamiden
Authors: Schroth W. , Kluge H. , Frach R. , Hodek W. , Schädler H. D. 
Published: December 2004

The Dehydration of Ureas by Two‐Phase Dichlorocarbene Reaction, a Synthetic Access to Substituted CyanamidesA wide variety of N,N‐disubstituted ureas are dehydrated in the CHCl3/NaOH catalytic two‐phase system under mild conditions. The sequence of urea‐transamidation and dehydration thus offers a profitable approach to aprotic cyanamides. Among various tested PT‐catalysts tertiary amines prove to be the most efficient and favourable ones. Tertiary amines may also be used advantageously in the transformation of carboxylic amides and thioamides to the corresponding nitriles. The application of the same technique is less suitable in the case of N‐mono‐substituted ureas, N,N′‐ disubstituted ureas as well as N(dialkylaminomethylidene) ureas, because consequent reactions of the primarily formed cyanamides predominate. Problems concerning the dehydration mechanism are elucidated in terms of HMO‐perturbation theory
Säurekatalysierte Umsetzungen von Aromaten mit Alkanen und Cycloalkanen. X. Alkylierungen mit Cyclohexan
Authors: Miethchen Ralf , Steege Sigrid , Kröger Carl‐Friedrich 
Published: December 2004

Acid‐catalyzed Reactions of Aromatic Hydrocarbons with Alkanes and Cycloalkanes. X. Alkylations with CyclohexaneThe complex reaction mixtures of the nonconventional alkylation of benzene with cyclohexane in the presence of Lewis/proton acids and promotors were investigated by gas‐liquid chromatography and mass spectrometry. Four representative groups of hydrocarbons were found including cycloalkylbenzenes, substituted indanes or tetralines (C12H16), C1‐C6‐alkylbenzenes and isomeric biscycloalkyls (C12H22). Their formation is interpreted as a competition between alkylation, (without or with isomerization), ringfission with cycloalkylation or fragmentation, and self‐alkylation; phenylcycloalkylcations and phenylalkylcations are the intermediates.
Konfigurative Zuordnung über sterisch definierte Epoxidringe. X. Glycidonitrile. III. Synthese von 4α‐Aryl‐2‐methyl‐1α‐oxaspiro(2,5)octan‐2‐nitrilen
Authors: Fischer F. , Palitzsch P. 
Published: December 2004

Determination of Configurations by the Aid of Sterically Corresponding Epoxides. X. Glycidic Nitriles. III Synthesis of 4α‐Aryl‐2‐methyl‐1α‐oxaspiro(2.5)octane‐2‐nitrilesThe condensation of 2‐aryl‐cyclohexanones 1a‐‐d with α‐chloropropionitrile at 80° in presence of NaH and in dimethoxyethane yields the corresponding glycidic nitriles. The configuration and the conformation of the C‐2‐isomeric 4α‐aryl‐2‐methyl‐1α‐oxaspiro[2.5]octane‐2‐nitriles 3b‐‐e have been analysed. The ratio of the resulting C‐2‐isomeric glycidic nitriles has been determined.
Dicyclopentadienoxidation. II 5. Katalysierte Flüssigphasenoxidation von Dicyclopentadien
Authors: Schnurpfeil D. 
Published: December 2004

Dicyclopentadiene Oxidation. II. Catalyzed Liquid‐Phase Oxidation of DicyclopentadieneThe liquid‐phase oxidation of dicyclopentadiene 1 by molecular oxygen was studied in the presence of MoO2(acac)2Acac‐ Acetylacetonat

as a typical epoxidation catalyst. The yield of the mono‐epoxides
2
and
3
is increased to 56,4% (uncatalyzed reaction: 43,6%). The ratio of the two mono‐epoxides is decreased to
2/3
= 2,6 in relation to the uncatalyzed reaction (
2/3
= 7,1). The influence of temperature, conversion and solvents is described. The bisepoxide
4
is formed at lower conversions than in the uncatalyzed reaction. But also at higher conversions of
1
not more than 10% of the bisepoxide
4
is formed
Zum Einfluß von Lösungsmitteln auf das VIS‐Spektralverhalten von 4′‐Dialkylamino‐α‐cyano‐stilben‐4‐diazoniumsalzen
Authors: Walkow F. , Epperlein J. 
Published: December 2004

Solvatochromism of 4′‐Dialkylamino‐α‐Cyano‐Stilbene‐4‐Diazonium‐Salts4′‐Dialkylamino‐stilbene‐4‐diazonium‐salts are deep coloured compounds and give strong solvatochromism. 4′‐Diethylamino‐α‐cyano‐stilbene‐4‐diazonium‐tetrafluoroborate was investigated in 52 different solvents and 3 binary solvent mixtures. With increasing solvent basicity the longest wave lenght absorption maximum (\documentclass{article}\pagestyle{empty}\begin{document}$ \nu^{\hspace{-5pt}\sim}_{\rm max} $\end{document}) decrease. Complex formation by crown ethers causes a decrease of \documentclass{article}\pagestyle{empty}\begin{document}$ \nu^{\hspace{-5pt}\sim}_{\rm max}$\end{document}, too. In solvents with dielectricity constants higher than about 15 dissociation effects superpose solvatochromism. The summary of experimental dates support the approach of specific nucleophilic solvatation of diazonium ions.
Photoinduzierte Elektronentransfer‐Reaktionen von Komplexen der Arendiazoniumsalze mit Kronenethern
Authors: Becker H. G. O. , Israel G. , Pefeiffer D. , Oertel Ulrike 
Published: December 2004

Photoinduced Electron Transfer‐Reactions of Arenediazonium Ions Complexed with Crown EthersThe photolysis (full light of a medium pressure Hg‐lamp) of p‐methylbenzenediazonium‐tetrafluoroborate in the presence of the crown ether 18‐crown‐6 (1) yields mainly the products of a heterolytic dediazoniation via arene cations as intermediates. The quantum yield φges of the photolysis from p‐methoxybenzenediazonium‐tetrafluoroborat in CH2Cl2 decreases in the presence of 18‐ crowns‐6 (1) from 0.66 to 0.08. In contrast to 1, the photolysis of arenediazonium salts in the presence of dibenzo‐18‐crown‐6 (3) yields mainly the products of a homolytic dediazoniation as a consequence of an electron transfer from 3 to the diazonium ion. φges of this reaction increases with decreasing wavelength of the exciting light from 0.09 (436 nm) to 0.32 (366 nm). this wavelength dependence is explained by formation of a correlated radical pair after excitation. In agreement with this situation a photo‐CIDNP‐effect is observed in the 15N‐n.m.r.‐spectra of isotopically labeled arenediazonium salts complexed by 3 and benzo‐18‐crown‐6(2). No photo‐CIDNP‐effect is observed in the presence of 1. This different behaviour of the EDA‐complexes formed by arenediazonium salts with the two different groups of crown ethers 1 and 2, 3 is discussed as a control of the electron transfer‐reaction by the structure of the frontier orbitals.
Synthese und Eigenschaften kristallin‐flüssiger Derivate des Rhodanins
Authors: Weissflog W. , Möckel P. , Kolbe A. , Kresse H. , Pelzl G. , Mohr K. , Zaschke H. 
Published: December 2004

Synthesis and Properties of Liquid Crystalline Derivatives of RhodanineSubstituted benzylidene‐rhodanines 3–8 were prepared both by condensation of 1 a–f with suitable aldehydes and by acylation of 2a–g with substituted benzoyl chlorides or cinnamoyl chlorid. The mesomorphic properties of the compounds are discussed in respect to molecular structure with the aid of i.r.‐, Raman‐ and u.v./vis‐spectra of 3d, 3k, 4, 5, 6g, 8a. We have investigated the dielectric and electrooptic behaviour of 31.
Synthese von 6‐Acetyl‐3‐alkyl‐2‐phenyl‐chromen‐4‐onen in phasentransfer‐katalysierter Baker‐Venkataraman‐Reaktion
Authors: Henning H.‐G. , Schwabe B. , Kernchen F. , Westphal G. 
Published: December 2004

Synthesis of 6‐Acetyl‐3‐alkyl‐2‐phenyl‐chromen‐4‐ones by Phasetransfer Catalysed Baker‐Venkataraman ReactionThree of the five partial steps of the Baker‐Venkataraman xssynthesis of flavones (scheme 1) can be favoured by PTC conditions. In the intermolecular O‐acylations of the 4‐hydroxyacetophenone 1 (A) and the 5‐acetyl‐2‐hydroxy‐acylophenones 3 (C), respectively, the nucleophilicity of the phenolat anions is increased by the PT catalysator. The steric and electronic effects of the substituents in the 5‐acetyl‐2‐benzoyloxy‐acylophenones 4 cause the formation of the 6‐acetyl‐flavones 6 in the phasetransfer catalysed Baker‐Venkataraman rearrangement (D) in one step and in good yields. The over‐all yields of the 1 → 6 reactions are not higher than 30% because of the limiting step (B). This Fries rearrangement of 4‐acyloxy‐acetophenones 2 affords only 32–62% of 3 under drastically enhanced conditions.