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  • 1
    ISSN: 1434-193X
    Keywords: Isocyanides ; Mesoionic compounds ; Azomethine ylides ; Cycloadditions ; Polyheterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of 5-aminothiazolium chlorides (1) bearing tethered benzene ring on N-3, C-4 or the exocyclic nitrogen atom are prepared by a three-component methodology and subjected to basic treatment. The initially generated mesoionic thiazoles 2 undergo internal 1,3-dipolar cycloaddition across the pendant olefin when the 2-allylphenyl group is connected to the endocyclic N-3. The reaction leads to the formation of original N-bridged thiazoloquinolines as a mixture of two regioisomers 3,4 which are readily separated by chromatography. The structural assignments of the cycloadducts are deduced from their spectroscopic NMR properties and unequivocally established by an X-ray diffraction analysis. Intramolecular sequence also occurs using the 2-(allyloxy)phenyl substituent on the same position to give a single regioisomeric 1,4-methanothiazolobenzoxazepine (7). On the contrary, hydrolysis and ring-opening or oxidation and rearrangement of the mesoionic intermediates are the exclusive base-promoted conversions of other thiazolium salts 1.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0947-3440
    Keywords: Nitrogen heterocycles ; Nucleophilic additions ; Electrochemistry ; C—C Bond formation ; α-Aminonitrile synthesis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrochemical cyanation of N-alkyl-substituted cyclic six-membered amines including N-alkyl-1,2,3,4-tetrahydroquinoline and N-phenylpiperidine derivatives has been investigated. The reaction gives the corresponding α-aminonitriles and was carried out at a graphite felt anode percolated with a methanolic solution of the amine, containing six equivalents of sodium cyanide per mol of substrate, and lithium acetate as the supporting electrolyte. In the case of N-substituted tetrahydroquinolines 1a-f, cyanation occurs regioselectively at the ring and the position of substitution depends on the nature of the N-alkyl substituent. The stereoselectivity of the cyanide addition was investigated using various 3-methyltetrahydroquinolines 8a-c as substrates. In all cases, the major stereoisomers 9a-c possess a cis configuration in which the 2-cyano group has an axial disposition and the 3-methyl group is equatorial. In a similar fashion, various N-phenylpiperidines substituted at the ring by either one or two methyl groups were oxidized. In all the selected amines the introduction of the cyanide group occurs stereospecifically in the position α to the nitrogen atom. The cis or trans relative configuration of the cyanated compounds is discussed separately for each substrate. It is noteworthy that in all cases the cyano group was in an axial position.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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