摘要:

Cyclization Reactions of β,γ‐Unsaturated Derivatives of Carbonic Acid. XI. Investigation of Stereochemistry of the Cyclofunctionalization of β,γ‐Unsaturated Carbamic Acid EstersN, N‐Disubstituted β,γ‐unsaturated urethanes1have been cyclized to 3,5‐disubstituted oxazolidine‐2‐ones3by aromatic sulfenyl chlorides2. The stereochemistry of the products and the cyclofunctionalization reactio

ISSN:0021-8383    

DOI:10.1002/prac.19863280302

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

Reaction of (2‐Alkoxy‐vinyl)hetero‐methiniminium Salts with C‐Nucleophiles — an Approach to Functionalized Pyrylium SaltsThe O‐alkylation products2of 2‐acyl‐1‐chloro‐enamines1(X = Cl) or acylketene‐S, N‐acetales1(X = SCH3) respectively react with cyanoactivated methylene compounds3under C,C‐bond formation. The reaction products4have been converted into functionally substituted pyrylium salts5by acidic treatment. Limitations of the synthet

ISSN:0021-8383    

DOI:10.1002/prac.19863280303

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

3,3‐Bis[alkylthio]‐2‐phenylacrylaldehydes as Building Sets for Thiophenes and PyrazolesAlkylation of the dithiolate2either with methyliodide and α‐CH‐acid halogenated compounds R2CH2X or only with the latter reagent yields ketene S,S‐acetals3. Base catalyzed cyclization of3leads to the thiophenes4Reaction of 3,3‐bis[methylthio]‐2‐phenylacrylaldehyde3fwith hydrazine affords a mixture of aldehydrazone5and aldazine6. The pyrazole7ais obtained by refluxing5in 1‐butanol. Mass spectra of the pyrazoles7b, cand reaction of3fwith aniline prove the attack of a nucleophile on the formyl

ISSN:0021-8383    

DOI:10.1002/prac.19863280304

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

Synthesis and Conformation of Some Dioxaspiranes with Bicyclo [2.2.2]octane SystemBy condensation of 7,7‐bis‐(bromomethyl)‐2,3,5,6‐dibenzo‐bicyclo[2.2.2]octane with different diols, three new “bridge‐spiranes”1, 2and3were obtained. On the basis of1H‐n.m.r. spectra and the respective topic relations of the hydrogen atoms the dominant conformations of heterocyclic rings in these compounds h

ISSN:0021-8383    

DOI:10.1002/prac.19863280305

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

Abstract3‐Oxo‐2,3,5,6,7,8‐hexahydro‐s‐triazolo[4,3‐a]pyrimidine(5)was synthesized and its reactivity towards acylating reagents was examined. The assignment of tautomeric structures based on n.m.r. spectral data i

ISSN:0021-8383    

DOI:10.1002/prac.19863280306

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

Preparation and Properties of Hexasubstituted BenzenesHexasubstituted benzenes are of potential interests as polypodands, host molecules and disc‐like molecules. They are prepared by catalytic cyclotrimerization of disubstituted alkynes1–8or by nucleophilic substitution of bromine in hexakis (bromomethyl)benzene9–17. The different methods of preparation were compared. The new hexasubstituted benzenes were characterized by some chemical and physical prope

ISSN:0021-8383    

DOI:10.1002/prac.19863280307

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

Oxidative Coupling of 5‐Aminopyrazoles with p‐PhenylenediaminesBy oxidative coupling of 5‐amino‐3‐methyl‐1‐phenyl‐pyrazole4with N,N‐diethyl‐p‐phenylenediamine the 4‐(4‐N,N‐diethylamino‐phenylimino)‐3‐methyl‐1‐phenyl‐2‐pyrazolin‐5‐imin5is formed.5is oxidized very easily to the 1H‐pyrazolo[3,4‐b]quinoxaline6a. The Z/E‐isomerism of the azomethine dye is investigated by dynamic n.m.r.‐spectroscopy. 1H‐Pyrazolo[3,4‐b]quinoxalines(6a–d)are also formed by reaction of 1,3‐

ISSN:0021-8383    

DOI:10.1002/prac.19863280308

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

Liquid‐crystalline Heterocycloalkanes. II. Syntheses and Liquid‐crystalline Properties of Substituted 1‐PhenylpiperazinesSeveral homologous series of the 1,4‐disubstituted piperazines of the general formulas4a—1, 6a—k, 7a, b, 8a—rwere synthesized. Most of the new substances are liquid crystalline. Besides nematic phases also smectic phases of the types A, B and E exist, which was proved by texture and miscibility studies.Die Palette kristallin‐flüssiger Substanzen wurde in den letzten Jahren durch die Verwendung von Cyclohexan und Sechsringheterocycloalkanen als Strukturfragmente in Flüssigkristallmolekülen [2, 3] bedeutend erweitert. Diese Verbindungen besitzen meistens breite kristallin‐flüssige Existenzgebiete, niedrige Viskositätswerte und günstige dielektrische Eigenschaften. Sie sind daher gegenwärtig unentbehrliche Bestandteile der Flüssigkristallgemische in allen LCD‐Anzeigesystemen.Besonders intensiv wurden Flüssigkristalle, die den 1,3‐Dioxanring enthalten, synthetisiert und die physikalisch‐chemischen Eigenschaften untersucht [1 4–10]. Die einfache Synthese der 1,3‐Dioxane aus 2‐substituierten Propan‐1,3‐diolen und Aldehyden ermöglicht eine große Variationsbreite im Substituentenmuster. Die Untersuchungen bestätigten, daß analog den Cyclohexanderivaten nur die trans‐isomeren 1,3‐Dioxane zur Au

ISSN:0021-8383    

DOI:10.1002/prac.19863280309

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

Pyrylium Compounds. 31. Reaction of 3‐Alkyl‐2,4,6‐triarylpyrylium Salts with 1,3‐Diketonates: A Method for the Preparation of 3‐Acylsubstituted BenzophenonesReaction of 3‐alkyl‐2,4,6‐triarylpyrylium salts with 1,3‐diketones in the presence of one equivalent of triethylamine or potassium tert‐butoxide does not lead — as originally suspected — to the primary adducts of 2H‐pyran structure6, but to the open‐chain valence isomers7. Treatment of the latter with one equivalent of tert‐butoxide in tert‐butyl alcohol gives the same 3‐alkyl‐2,4,6‐triarylacetophenones9which are obtained directly from5, 1,3‐diketones and two equivalents of potassium tert‐butoxide. However, on treating7with aqueous ethanolic sodium hydroxide 3‐acylsubstituted benzophenones10are formed in good yields. The reaction sequence5→7→10can also be performed through a one‐pot‐procedure. — The i.r., u.v., n.m.r. and mass spectrosco

ISSN:0021-8383    

DOI:10.1002/prac.19863280310

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

Pyrylium Compounds. 32. 2‐Methoxy‐2H‐thiopyrans from 2,4,6‐Triaryl‐thiopyrylium SaltsReaction of 2,4,6‐triarylthiopyrylium salts1with sodium methoxide in absolute methanol yields isolable 2‐methoxy‐2H‐thiopyrans2, the structure of which was proved spectroscopically. Using the 2,4,6‐triphenyl derivative2aas model compound, the behaviour of the 2‐methoxy‐2H‐thiopyran system towards some nucleophiles and electrophiles was studied. Thus, on heating with ethanol the 2‐ethoxy‐2H‐thiopyran3is formed. Nitromethane and ethyl cyanoacetate react with2ain the presence of triethylamine to give 2,4,6‐triphenylbenzene (6) and 2,4,6‐triphenylbenzonitrile (7), respectively. Electrophiles (e. g. mineral acids or acyl halides) regenerate from2athe starting thiopyrylium system; the same principle underlies the formation of 2,4,6‐triphenylthiopyrylium perchlorate (1a) and 2‐methoxy‐3‐methyl‐2,4,6‐triphenyl‐2H‐pyran (5) from2aa

ISSN:0021-8383    

DOI:10.1002/prac.19863280311

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY