Abstract
The NH acidity of pyrrolanthrone in dimethyl sulfoxide and the COOH acidity of pyrrolanthrone-1-carboxylic acid exceed the acidities of indole and indole-2-carboxylic acid by 6 and 2.5 orders of magnitude, respectively; this is due to the electron-acceptor effect of the condensed anthrone ring. A quantitative estimate of the effect of substituents in the 1 position on the NH acidity indicates that the bonds in the pyrrole fragment are localized to a significant degree; the C1-N bond approaches a single bond, and the C1-C10b bond consequently approaches a double bond. The effect on the NH acidity of NO2 and NH2 groups located in the anthrone fragment (in the 5 position) is examined.
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Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1659–1661, December, 1979.
Original article submitted April 5, 1979.
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Kazankov, M.V., Sadovykh, E.G. & Korolev, B.A. Acidic properties and structure of pyrrolanthrones. Chem Heterocycl Compd 15, 1334–1337 (1979). https://doi.org/10.1007/BF00514738
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DOI: https://doi.org/10.1007/BF00514738