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  • 1970-1974  (3)
  • 1965-1969  (8)
  • 1935-1939
  • 1890-1899
  • 1800-1809
  • 1971  (3)
  • 1965  (8)
  • 1890
  • 1809
  • 1803
  • Heterocycles
  • Synthetic methods
  • 1
    Electronic Resource
    Electronic Resource
    Progress in the Hetaryne FieldHetarynes, Part 15.-Part 14, see ref. [15].Dedicated to Professor Wilhelm Klemm on the occasion of his 75th birthday (1971)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 10 (1971), S. 20-33 
    Details
    ISSN: 0570-0833
    Keywords: Hetarynes ; Heterocycles ; Alkynes ; Arynes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: During recent years, instead of concentrating on the detection of the intermediacy of new hetarynes, as they did between 1958 and 1964, workers in this field have been more concerned with the critical sifting and checking of the earlier work. Special interest has been shown in the relation between structure and reactivity in the hetarynes. It has been shown that in addition to the elimination-addition mechanism (EA; hetaryne intermediate), other reaction paths (anomalous addition-elimination mechanism [AEa] and “Reinecke mechanism”) are possible for nucleophilic cine-substitutions on hetaryl halides. The use of deuterated hetaryl halides has proved very valuable for the elucidation of the mechanism of nucleophilic substitutions. Even where substitution mechanisms are superimposed on one another the occurrence of a hetaryne intermediate can be detected by a technique known as the “base competition method”. A five-membered hetaryne (4,5-didehydro-1-methylimidazole) has been detected for the first time by this method with a probability that borders on certainty. Selectivity determinations have shown that the replacement of a CH group in 1,2-didehydrobenzene and in 1,2-didehydronaphthalene by an N atom distinctly increases the reactivity to bases. According to EHT (Extended Hückel Theory) calculations, the as yet hypothetical 2,3-didehydropyridine is richer in energy than 3,4-didehydropyridine, this agrees more closely with the experimental findings than the opposite result obtained from simple MO calculations. Besides cine-substitution (1,2 shift), tele-substitution (1,3-shift) has also been observed on reaction of hetaryl halides (pyridine, quinoline, and pyrimidine systems) with bases. An EA mechanism (via m-didehydrohetarenes) and an AEa mechanism are considered as alternatives for the tele-substitution.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197100201
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  • 2
    Electronic Resource
    Electronic Resource
    New Methods for the Synthesis of Vinyl Azides (1971)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 10 (1971), S. 98-104 
    Details
    ISSN: 0570-0833
    Keywords: Vinyl azides ; Azides ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A critical survey of synthetic approaches to vinyl azides is presented, focusing especially on stereo- and regiochemical problems. The com bined procedure of azidohalogenation of olefins followed by dehydrohalogenation, leads to regiospecific and, in the case of ionic additions, also to stereospecific formation of vinyl azides. Nucleophilic substitutions by azide ions on activated olefinic halides result in β-azidovinyl ketones, esters, nitriles, etc., and proceed predominantly with retention of configuration about the C=C bond. The known synthetic methods leading to α-azidovinyl ketones and esters give rise to the thermodynamically more stable trans-vinyl azides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197100981
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  • 3
    Electronic Resource
    Electronic Resource
    Valence Isomerism in Selected Heterocyclic Systems (1971)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 10 (1971), S. 11-20 
    Details
    ISSN: 0570-0833
    Keywords: Valence isomerization ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Valence isomerization and the phenomenologically related principle of valence tautomerism, as they apply to several nitrogen-containing heterocyclic systems, are discussed herein. Attention is called first to 1H-azepines and the reluctance of such substances to isomerize to azanorcaradienes. The role of homo-1H-azepines in this context is then briefly outlined. Azocines (azacyclooctatetraenes) are seen to occupy an interesting position in the sense that pronounced shifts in the position of equilibrium (from almost entirely monocyclic to virtually completely bicyclic) occur with substitutional alterations of various types. The capability of azabullvalenes for degenerate valence isomerization is the next presented, and contrast is made with the properties of benzazabullvalenes and an azasemibullvalene derivative.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197100111
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  • 4
    Electronic Resource
    Electronic Resource
    Isonitrile Syntheses (1965)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 472-484 
    Details
    ISSN: 0570-0833
    Keywords: Formamides ; Synthetic methods ; Isocyanides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In spite of the large number of reactions which involve the formation of isonitriles, the only preparative routes to these compounds, until recently, were the classical isonitrile syntheses discovered about one hundred years ago by Gautier and Hofmann. These methods are not generally applicable, and give satisfactory yields only in exceptional cases. Isonitriles have recently become readily available by the elimination of water from N-substituted formamides, using acyl halides of Group IV-;VI elements in the presence of bases as dehydrating agents. A dehydrating system with a particularly wide range of application consists of phosgene with tertiary amines. This system generally provides the easiest and most productive route to isonitriles, particularly where large quantities (〉 1 mole) are to be prepared.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196504721
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  • 5
    Electronic Resource
    Electronic Resource
    New Reactions of Alkylidenephosphoranes and their Preparative Uses. Part I: The Acid-Base Character of Phosphonium Salts and AlkylidenephosphoranesParts II and III will appear shortly in this journal. (1965)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 583-587 
    Details
    ISSN: 0570-0833
    Keywords: Alkylidenephosphoranes ; Phosphonium salts ; Synthetic methods ; Phosphoranes ; Ylides ; Alkenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phosphonium salts may be regarded as Bronsted acids, and alkylidenephosphoranes as the conjugate bases. Compounds of the two classes exist in equilibrium with each other. Phosphonium salts and alkylidenephosphoranes can be obtained by this “transylidation”. Other methods are also given for the preparation of members of both classes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196505831
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  • 6
    Electronic Resource
    Electronic Resource
    New Reactions of Alkylidenephosphoranes and their Preparative Uses. Part II. Alkylidenephosphoranes and Halogen CompoundsFor Part I see Angew. Chem. 77,609 (1965), Angew. Chem. internat. Edit. 4, 583 (1965). Part III will appear shortly in this journal. (1965)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 645-660 
    Details
    ISSN: 0570-0833
    Keywords: Alkylidenephosphoranes ; Phosphonium salts ; Synthetic methods ; Phosphoranes ; Ylides ; Alkenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of alkylidenephosphoranes with compounds containing halogens can be used to prepare ylides, which can be converted in to useful products, e.g. by hydrolysis, by thermal decomposition, or by other reactions. Examples of such products are ketones including cyclic, unsaturated, and branched-chain ketones (including cyclic, unsaturated, and branched-chain ketones), carboxlic esters (including those of unsaturated, branched- chain, polyenecarboxylic, acetylenecarboxylic, and allenecarboxylic acids), and aldehydes.
    Additional Material: 10 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196506451
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  • 7
    Electronic Resource
    Electronic Resource
    The Hetarynes (1965)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 543-557 
    Details
    ISSN: 0570-0833
    Keywords: Hetarynes ; Heterocycles ; Alkynes ; Arynes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Investigations carried out during the last six years have shown that, as in the case of benzene, an extra bond can be introduced into heteroaromatic rings. Since this possibility does not appear to be confined to exceptional cases, the heterocyclic arynes (hetarynes) promise a much wider variety than the carbocyclic arynes. Hetarynes occur mainly as intermediates in nucleophilic substitutions on halogenated heterocyclic compounds. Since the replacement of a CH group in dehydrobenzene by a nitrogen atom and the condensation of benzene rings have stabilizing effects, the stability of hetarynes is expected to increase with the number of N atoms and with the number of condensed aromatic rings.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196505431
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  • 8
    Electronic Resource
    Electronic Resource
    New Reactions of Alkylidenephosphoranes and their Preparative Uses IIIFor Part I, see Angew. Chem. 77, 609 (1965) Angew. Chem. internat. Edit. 4, 583 (1965); for Part II, see Angew. Chem. 77, 651 (1965); Angew. Chem. internat. Edit. 4, 645 (1965).. Alkylidenephosphoranes and Reagents Containing Multiple Bonds (1965)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 830-838 
    Details
    ISSN: 0570-0833
    Keywords: Alkylidenephosphoranes ; Phosphonium salts ; Synthetic methods ; Phosphoranes ; Ylides ; Alkenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A few examples of preparatively useful syntheses using alkylidenephosphoranes and substances containing a C—N or C—C double bond are the preparations of olefins, allenes, pyran derivatives, and cyclopropane derivatives. Olefins, ketones, and monocyclic compounds can be obtained by autoxidation of alkylidenephosphoranes; α, β-dioxo compounds (including cyclicones) can be prepared by oxidation with peroxy-acids. Alkylidenephosphoranes can also be used for the synthesis of azines and Schiff bases. Of the many possibilities offered by the Wittig reaction, only the preparation of tritiated aldehydes and olefins will be considered.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196508301
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  • 9
    Electronic Resource
    Electronic Resource
    New Methods in the Chemistry PyridazonesPublished on the occasion of the 100th anniversary of the establishment of Badische Anilin- & Soda-Fabrik AG., on April 6th, 1965. (1965)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 292-300 
    Details
    ISSN: 0570-0833
    Keywords: Pyridazones ; Heterocycles ; Mucochloric acid ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new synthesis of mucochloric acid by chlorination of butynediol has facilitated the preparation of a series of 4,5-dichoropyridazones. The high reactivity of these compounds has been investigated and applied in several ways. New classes of compounds, some with biological activity, were obtained by displacement of the chlorine atoms. New heterocyclic systems were prepared by condensation and rearrangement reactions.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196502921
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  • 10
    Electronic Resource
    Electronic Resource
    The Use of Silylation in Organic SynthesesThe articles of the previous three series have been collected and published in three volumes in German by Verlag Chemie, Weinheim, Bergstr. (Germany); and in English by Academic Press, New York-London. (1965)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 417-429 
    Details
    ISSN: 0570-0833
    Keywords: Silylation ; Synthetic methods ; Trimethylsilyl group ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The term silylation is used to denote the introduction of a triorganosilyl moiety, especially the trimethylsilyl species, into organic compounds. - Silylated amino acids and sugars are particularly suitable for the syntheses of peptides and saccharides, respectively, since the silyl group can be cleaved off readily under mild conditions. Many diamines undergo ring closure, e.g. with phosgene, only after silylation. - O-silylated lactim ethers (i.e. cyclic imino ethers) are converted into N-alkyl derivatives by alkyl halides. Compounds with a strongly polarized Si—C bond may be used for chain extension. Silyl esters of halogeno fatty acids yield lactones with silver cyanate. - Trimethylsilyl azide is thermally very stable and behaves like organic azides. It reacts with acetylenic compounds, trialkylphosphines, and triarylphosphines to yield silylated triazole derivatives, trialkylphosphines N-silylimines, and triarylphosphines to yield silylated triazole dervatives, trialkylphosphine N-silylimines, and triarylphosphine N-silylimines, respectively, from which the silyl groups can be removed under mild conditions.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196504171
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  • 11
    Electronic Resource
    Electronic Resource
    Heterocycles Containing Phosphorus (1965)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 4 (1965), S. 1023-1038 
    Details
    ISSN: 0570-0833
    Keywords: Heterocycles ; Phosphorus ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of heterocycles containing phosphorus is described. The chemical behavior of ring systems containing trivalent phosphorus is mainly determined by their phosphine character; heterocyclic behavior in the ordinary sense is shown by rings containing functional groups. Syntheses and reactions of cyclic compounds of pentavalent and hexavalent phosphorus are particularly interesting.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.196510231
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