摘要:

N.M.R. Spectroscopical Investigations on the Conformational Behaviour of Some 2′ ‐ and 3′‐Halogen‐substituted Pyrimidine NucleosidesA series of 2′‐ and 3′‐halogenated pyrimidine nucleosides has been synthesized and investigated by1H,13C and19F n.m.r. spectroscopy. The1H and13C chemical shifts for the positions 2′ and 3′ depend linearly but oppositely on the substituent electronegativities XR.The conformational equilibrium N ⇌ S of the nucleosides in solution is determined. An approximately linear correlation between the prefered gauche‐gauche interaction of the exocyclic CH2OH groups and the ribose N co

ISSN:0021-8383    

DOI:10.1002/prac.19833250602

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

Autoxidation of Vinylcyclopentane, Vinylcyclohexane, and 4‐Vinylcyclohex‐1‐eneThe title olefins were oxidized with molecular oxygen at 75–80°C. About 40% of the oxygen absorbed were found by iodometric titration as peroxidic oxygen. The reaction products were analyzed by a combination of chemical methods, gas chromatography, and13C‐n.m.r.‐spectroscopy.Vinylcyclopentane and vinylcyclohexane are attacked preferably at the tertiary allylic C‐H‐bonds giving almost equimolar mixtures of the corresponding allylisomeric hydroperoxides. In the case of 4‐vinylcyclohex‐1‐ene the C‐H‐bonds in position 6 are preferably attacked, but products of attack on the other allylic C‐H‐bonds also could be identified.In all cases the amount of products which could not be detected gaschromatographically was determined by balance experiments in the pr

ISSN:0021-8383    

DOI:10.1002/prac.19833250603

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

Zur Wirkung von Metallionen in der organischen Synthese. XI. Hydrolyse und Alkoholyse einiger Acylhydrazine und N‐Acyl‐N′‐arensulfonylhydrazine in Gegenwart von Kupfer (II)‐chloridDie Hydrolyse und Alkoholyse einiger Acylhydrazine und N‐Acyl‐N′‐arensulfonylhydrazine in Gegenwart von Kupfer(II)‐chlorid · 2 H2O wurden untersucht. Das Mesitylensulfonylhydrazid und die 2,4,6‐Triisopropylbenzensulfonylhydrazid‐Derivate sind reaktiver als die entsprechenden Hydrazine oder Tosylhydrazid‐Derivate.Die entsprechenden Carbonsäuren und Ester erhält man in guten Ausbeuten und unter sehr milden Bedingungen. Die vorliegende Methode ist einfach und bequem im Vergleich zu anderen Methoden. Die Reaktion verläuft wahrscheinlich über Ku

ISSN:0021-8383    

DOI:10.1002/prac.19833250604

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

AbstractBoth C‐(2‐methylphenyl)‐N‐phenyl and C‐(3‐methylphenyl)‐N‐phenyl nitrones (1a, b) reacted with N‐phenylmaleinimide and fumaronitrile to give the normal primary cycloadducts. The reaction of the two nitrones (1a, b) with 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione and diacetylacetylene afforded rearrangement products. The unexpected 1,3,4‐oxadiazolidin‐2‐ones were isolated from reaction with phenylisocyanate. In contrast, tetracyanoethylene forms charge‐transfer complexes with both nitrones instead of cycloaddition products. The structural elucidation of the reaction products was made on the bases of the elemental analysis as well

ISSN:0021-8383    

DOI:10.1002/prac.19833250605

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

A Simple Synthesis of β‐Chlorocinnamonitriles by a Modified Vilsmeier‐Haack‐Arnold‐ReactionA simple one‐pot synthesis of β‐chloro‐cinnamonitriles2can be achieved by treating acetyl arenes1first with formamide chlorides and subsequently with hydroxyl amine hydrochloride. The formamide chlorides used are conveniently prepared from an excess of dimethyl formamide and phosphoryl chloride. However it is also possible to employ other N,N‐disubstituted formamides or acid chlorides, respectively. For comparison purposes β‐chloro‐cinnamonitriles2have also been synthesized in a two‐step process. Thus 3‐aryl‐3‐chloro‐(2)‐iminium salts4are reacted with hydroxyl amine hydrochloride giving rise to 3‐chloro‐cinnamic aldoximes5. The latter compounds are dehydrated to the corresponding nitriles2by refluxing in acetic

ISSN:0021-8383    

DOI:10.1002/prac.19833250606

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

1H‐NMR Spectroscopical Investigations on Substituted Crotonates3‐Amino‐2‐cyanocrotonates2and ‐dithiocrotonates3have been characterized by n.m.r. spectroscopy. The data obtained are compared with those of acrylates1. The COOR and CSSR groups are investigated with respect to their electron withdrawing effect and formation of intramolecular hydro

ISSN:0021-8383    

DOI:10.1002/prac.19833250607

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

The Synthesis of the 2‐Desalkylcyclol of the Ergotamine‐TyperBenzyloxycarbonyl‐S‐seryl‐S‐phenylalanyl‐S‐proline‐p‐nitrophenylester is synthesized by an improved route and oxidized by lead‐tetraacetate to a mixture of the two diastereomeric (RSS, SSS) benzyloxycarbonyl‐hydroxyglycyl‐phenylalanyl‐proline‐p‐nitrophenyl‐esters. Treatment of this mixture with an aqueous potassium tartrate solution provides two epimeric cyclols (2‐benzyloxycarbonylamino‐5‐benzyl‐10b‐hydroxy‐3,6‐dioxo‐octahydro‐8H‐oxazolo[3,2‐a]‐pyrrolo‐[2,1‐c]‐pyrazines), which are separated into the aci‐form as well as into the natural form

ISSN:0021-8383    

DOI:10.1002/prac.19833250608

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

Nucleophilic Substitutions in 1,3,5‐Triazines. VII. The Kinetic and ¦ Mechanism of Cyanuric Chloride with 4′‐Substituted 4‐AminoazobenzensThe kinetic and mechanism of cyanuric chloride reaction with 4′‐substituted 4‐aminoazobenzens in dioxan‐water was studied by conductometry. An addition‐elimination mechanism with a monomolecular elimination of chlorine ion at low water concentrations or a nucleophilic attack of 4‐aminoazobenzens at high water concentration as low step has been supported

ISSN:0021-8383    

DOI:10.1002/prac.19833250609

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

Studies on Photo Fading of Tautomeric Azo Dyes. V. Oxydation of Substituted 1‐Phenylazo‐2‐naphtholes by Singlet Oxygen in a Polymeric MatrixThe logarithms of rate constants of methylene blue sensitized photolysis of substituted 1‐phenylazo‐2‐naphthols (1a–y) in polymer matrix show no linear correlationship with respect to Hammett‐δ‐constants of the substituents.The slope of the function lg k = f(δ), where k represents rate constants, differs for positive and negative δ‐values in sign but decomposition is oxydative at all substituents. It is possible to explain the nonlinear correlation, when singlet oxygen1O2attacks only the anti‐hydrazone‐tautome

ISSN:0021-8383    

DOI:10.1002/prac.19833250610

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

Photochemical Primary Processes of Xanthene Dyes. III. Investigations of the Influence of Cationic Micelles on the Photoredox Processes of Selenopyronine by Flash ExcitationCationic micelles have no influence on the decay of the triplet state of selenopyronine (3F+). The products of photoredox reactions3F++3F+(F+) → F·+ F ++·and3F++ DABCO → F·+ DABCO +·live longer in the presence of the cationic micelles. The reason for the change of the lifetime is a separation of the photoredox products by micelles. F.is stored in the interior of the micelles. The positively charged F ++·and DABCO +·are repelled from the micelles and the electron back tra

ISSN:0021-8383    

DOI:10.1002/prac.19833250611

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY