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  • 1
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reduction of 9-cyanoanthracene by two equivalents of potassium in liquid ammonia was shown to yield the 9-cyanoanthracene dianion, whereas 1-naptho- and benzonitrile gave the cyanodihydroaryl anions corresponding to the protonation of nitrile dianions at a position para to the cyano group. The 9-cyanoanthracene dianion underwent the same transformation in the presence of a stronger protonating agent, methanol. According to 13C NMR spectral data of the generated species, the cyano group extracts the negative charge from the π-electronic system: ca 0·20:0·25 e in the case of the 9-cyanoanthracene dianion and ca 0·14:0·17 e in the case of cyanodihydroaryl anions. These estimations and the general NMR pattern of π-charge distribution in all the anionic species under investigation are in accordance with data from quantum molecular orbital calculations at the PM3 and INDO levels, being reflected by the fairly good linear relationships between the changes of ring carbon chemical shifts on going to the anionic species from the respective neutral precursors on the one hand and the calculated π-charges on the other. The para-orienting effect of the cyano group in the protonation of nitrile dianions is discussed in terms of the π-charge distribution in the starting dianion and the tendency to form a most stable cyanodihydroaryl anion isomer.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0170-2041
    Keywords: Ninhydrin ; Hydroxylamines ; Indeno[1,2-b]pyrazines ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of the ninhydrin (1) with 1,2-bishydroxylamines 2a-c affords dihydroindeno[1,2-b]pyrazine N,N′-dioxides 5a-c. The intermediates hexahydro- and tetrahydroindeno[1,2-b]pyrazines 3a and 4c, which have been isolated, are easily transformed into 5a, c. Heating of 5b, c or keeping of 5b on alumina gives indeno[1,2-b]pyrazine N-oxides 6b, c, N,N′-dioxide 7c and indeno[1,2-b]pyrazine 8. Treatment of 5b with a solution of hydrochloric acid in H2O/MeOH leads to 6b, whereas treatment of 5b with KOH furnishes mono-N-oxides 6b, 9 and dioxide 7b. Compound 8 is prepared by deoxygenation of 6b with TiCl3. The reduction of 6b with NaBH4 yields alcohol 10 and the reaction of 6b with NH2OH/AcOH gives a mixture of isomeric oximes (E)-11 and (Z)-11.
    Type of Medium: Electronic Resource
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