摘要:

Reactions of β‐Chlorovinylaldehydes. IV. Syntheses of 2‐Formylmethylene‐2H‐1‐benzopyranes and Benzopyrylocyaninedyes from β‐Chlorovinylaldehydesα‐Alkyl‐β‐chlorocrotonaldehydes react with salicylaldehyde in methanolic solution of potassium hydroxide forming 2‐formyl‐methylene‐2H‐1‐benzopyranes1. The corresponding benzopyryliumsalts2which are easily available from1and strong acids, exist in the enolic form. They react at room temperature in alcoholic solution with elimination of ethyl formiate, yielding dark blue compounds which were identified as 2,2′‐benzopyrylotrimethincyanindyes3. The structure of3has been eluc

ISSN:0021-8383    

DOI:10.1002/prac.19783200402

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Pyrazolone Derivatives. IV. Tautomerism and Stereochemistry of 4‐Aminomethylene‐Δ2‐pyrazolinones‐(5)Tautomerism and stereochemistry of compounds of type1were investigated by1H‐n.m.r.‐ and i.r.‐spectroscopy. Dynamic1H‐n.m.r. study with15N‐labelled compounds shows, that1exist in solution as 4‐aminomethylene‐Δ2‐pyrazolinones‐(5) with strong intramolecular hydrogen bonds. Compared to 4‐unsubstituted Δ2‐pyrazolinones‐(5) polar solvents do not change the tautomeric equilibrium of1. The N‐aryl‐substituted compounds have a higher NH‐acidity than N‐alkyl‐substituted derivatives.In crystalline state the N‐alkyl‐substituted compounds1g, hexist in theE‐configuration as 4‐aminomethylene‐Δ2‐pyrazolinones‐(5) with intermolecular hydrogen bond. At higher temp

ISSN:0021-8383    

DOI:10.1002/prac.19783200403

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Pyrazolone Derivatives. V. U.V.‐Spectroscopical and Photochemical Behaviour of N‐mono and N,N‐disubstituted 4‐Aminomethylene‐Δ2‐pyrazolinones‐(5)U.V.‐spectra of N‐mono and N,N‐disubstituted 4‐Aminomethylene‐Δ2‐pyrazolinones‐(5)1a–jand their dependence on solvent and temperature are discussed. N,N‐disubstituted and N‐monosubstituted 4‐aminomethylene‐3‐methyl‐1‐phenyl‐Δ2‐pyrazolinones‐(5) show aZ‐/E‐isomerization of the exocyclic CC‐double bond at low temperatures. Compared to the N‐monosubstituted compounds the compound1jexhibits a strong interaction in theE‐configuration between the aminomethylene‐substituent and the methyl‐group at the parazolone‐ring.TheZ‐/E‐isomerization depends on solvent polarity. With increasing solvent polarity the energy of activation of

ISSN:0021-8383    

DOI:10.1002/prac.19783200404

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Pyrimidinderivate und verwandte Verbindungen. VIII. Neue Synthesemöglichkeiten für 3,5‐Diaminopyrazole, 2‐Aminopyrazolo[1,5‐a]‐pyrimidine und 5‐Aminopyrazolo‐[1,5‐a]‐pyrimidineWährend die 3,5‐Diacylamidopyrazole2a–cdurch Umsetzung von 3,5‐Diamino‐4‐phenylazopyrazolen3mit Schwefelsäure und Fettsäuren erhalten werden, entstehen die 3,5‐Diaminopyrazole1beim Erhitzen der Pyrazole3mit Schwefelsäure.2‐Amino‐6,7‐dihydro‐5‐methyl‐7‐oxopyrazolo [1,5‐a] pyrimidin (4) erhält man durch Entfernung der Phenylazogruppe des leicht zugänglichen 3‐Phenylazoderivates6.Die 5‐Aminopyrazolo [1,5‐a] pyrimidinderivate12a–cerhält man in guten Ausbeuten durch Reaktion der 5‐Aminopyrazole10a–cmit Diethyl‐β‐amino‐β‐trichloromethylenmalonat11a. Durch Reaktion vo

ISSN:0021-8383    

DOI:10.1002/prac.19783200405

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Kinetics of Hydrogen‐Deuterium‐Exchange in the Methin Chain of Simple PolymethinesSimple polymethines are deuterated in the methin chains at positions of high π‐electronic density. The rate constants of this reaction were determined by1H‐n.m.r. spectroscopy taking into account hydrolytic side‐reactions. The rate constants of the H/D exchange correlate well with the HMO localization energies at the methin atoms

ISSN:0021-8383    

DOI:10.1002/prac.19783200406

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Fatigue Products of Photochromic 2‐(2′,4′‐Dinitrobenzyl)‐pyridineUnder prolonged irradiation or frequent repetitions of its photochromic cycle, 2‐(2′,4′‐dinitrobenzyl)‐pyridine1shows fatigue phenomena both in solid state and in solution. These phenomens — yellow discoloration, depression of the melting point, decrease of band intensity of the coloured form, shorter lifetime of the coloured form — are caused by irreversible redox processes and subsequent reactions at the methylene and ortho‐nitro groups which are essential for photochromism. Azomethine2, ketone3and amine4are isolated as t

ISSN:0021-8383    

DOI:10.1002/prac.19783200407

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Absorptionsspektren einiger ChinonanileElektronenabsorptionsspektren einiger Chinonanile wurden in organischen Lösungsmitteln unterschiedlicher Polarität untersucht. Die Spektren werden in Abhängigkeit von Mediumeffekten und der Molekularstruktur diskutiert. Die pK‐Werte der Verbindungen wurden durch Spektralmessungen in Pufferlösungen durch Veränderung des pH‐Wertes bestimmt. Die wichtigsten IR‐Banden werden bezüglich der Molekularstruktur

ISSN:0021-8383    

DOI:10.1002/prac.19783200408

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Identification of Intermediates in the Photolysis of Some σ‐Alkyl Cobalt Complexes using the Technique of Spin TrappingIn the aerobic photolysis of the complexes [R1Co(chel)Y] (R1= CH3, C2H5, n‐C3H7; chel = salen, salphen; Y = H2O, C5H5N, P(C6H5)3) and [R 22Co(bipy)2]X (R2= CH3, n‐C3H7, C6H5CH2; X = ClO4, J) in chloroform alkyl‐, alkoxy and hydroxyalkyl radicals are detected using the technique of spin trapping. Moreover, in the presence of phenyl tert.‐butyl nitrone the photolysis of the ethyl and propyl complexes [RCo(chel)Y] produces the spin adduct of H at phenyl tert.‐butylnitrone. From these results we conclude that photochemically the hydridocomplexes [HCo(che

ISSN:0021-8383    

DOI:10.1002/prac.19783200409

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Reaction of Cyclobutendiones. LIII. New Heterocyclic Systems by Reaction of 4‐[‐(z)‐Benzylidenene]‐2,3‐diphenyl‐cyclobut‐2‐enone with DiazomethaneThe addition of diazomethane to stable 4‐alkylidene‐cyclobut‐2‐enones gives at the same time the 1:1 adducts2, and under elimination of 1 mole nitrogene the 1:2 adducts3respec

ISSN:0021-8383    

DOI:10.1002/prac.19783200410

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Acylketene S,S‐ and Acylketene S,N‐acetals as Buildingsets for Heterocycles: 5‐CyanopyrimidinesAcylketene S,S‐acetals1react with amidines, guanidine or S‐alkylisothioureas in the presence of triethylamine to give 4‐methylthio‐5‐cyanopyrimidines4–6. 4‐Anilino‐5‐cyanopyrimidines7have been synthesized from the acylketene‐S,N‐acetals2under similiar conditions. The treatment of1with guanidine and acetamidine, respectively, in alcoholic sodium ethoxide solution yields 4‐ethoxy‐5‐cyanopyrimidines10. The i.r.‐ and1H‐n.m.r.‐spectra of

ISSN:0021-8383    

DOI:10.1002/prac.19783200411

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY