摘要:

AbstractManyN‐chloroalkylamines with double bond(s) dissociate homolytically to give chlorine atoms and aminyl radicals which undergo intramolecular cyclization reactions. Here, the nature of the aminyl radicals (neutral, protonated, or complexed to metal salts) appears to be important. The reactivity varies strongly from one species to another, and their selectivities can be different towards addition, substitution, abstraction, or dimerization reactions. A good synthetic tool appears to be the “complexed radical”, which is generated under mild conditions. A variety of β‐functionalized, substituted, fused, or bridged azaheterocycles with alkaloid part structures thus become easily accessible in high yields, in a regio‐ and, possibly, stereoselective manner. Many examples are discussed illustrating the synthetic possibilities, limitations, and mechanistic features of this cyclizati

ISSN:0570-0833    

DOI:10.1002/anie.198303373

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe introduction of Fourier transform methods has not only remarkably enhanced the sensitivity of high‐resolution NMR spectroscopy, thus allowing measurements to be made on less sensitive nuclei of the Periodic Table, but also has paved the way for the development of a large number of new experimental techniques. On the one hand, procedures already known have been improved and can now be performed more rapidly, and, on the other, completely new experimental approaches have become available. This situation resulted mainly from the introduction of programmable pulse transmitters and the separation of the experiment into preparation, evolution, and detection. In particular, the concept of two‐dimensional spectroscopy has opened up new possibilities important for the analysis of complicated spectra and is able to provide information previously not accessible. As elsewhere, optimum application of the techniques and correct interpretation of the results require sound understanding of the underlying physical principles. Since a rigorous mathematical treatment is complicated and does not necessarily improve the comprehensibility, this article attempts to give an illustrative presentation of the new pulse techniques within the framework of the Bloch vector model. After a short introduction covering the basic principles, one‐dimensional pulse techniques that can be applied using standard experimental equipment are dealt with. The main areas of application are signal assignment, sensitivity enhancement for measurements on less abundant nuclei, and selective excitation of individual resonances. Subsequently, the various techniques of two‐dimensional NMR spectroscopy are treated: these enable shift correlations for different types of nuclei to be made, the presentation of spin multiplets without overlap, and the analysis of geometrical relations as well as of chemical exchange ph

ISSN:0570-0833    

DOI:10.1002/anie.198303501

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe development of cultural and technical civilization has been marked with increasing interference in hydrogeochemical cycles and the production of a growing number of chemicals; this is accompanied by a growing concern on the potential adverse effects of chemicals on biological systems. Assessment of the potential toxicological and ecological effects of pollutants is of central importance. We are of the opinion that this cannot be accomplished by merely evaluating the harmfulness of a substance on the basis of toxicity tests with individual organisms and by monitoring analytically the environment for pollutants. We would like to encourage chemists to participate in the solution of ecotoxicological problems: chemodynamical concepts permit the estimation‐on the basis of physical‐chemical generalizations and with the help of compound‐specific data‐of the fate, the distribution, the potential for bioaccumulation in the food chain, and the approximate residence time of pollutants (and thus the attainable residual concentrations) in the environment and therefore to predict the relative risk of different pol

ISSN:0570-0833    

DOI:10.1002/anie.198303801

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractMethods developed for the generation and study of stable carbomonocations can also be employed for similar investigations on carbodications. Trivalent (classical) as well as hexacoordinate (non‐classical) carbodications studied under long‐lived ion conditions are reviewed with special emphasis on their structural features, and investigated primarily by1H‐ and13C‐NMR spect

ISSN:0570-0833    

DOI:10.1002/anie.198303901

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198304021

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198304031

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198304041

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe complete manuscript of this communication appears in:Angew. Chem. Suppl. 1983, 551. DOI:10.1002/anie.198305510

ISSN:0570-0833    

DOI:10.1002/anie.198304051

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198304062

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198304071

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY