Novel Reactions in the Anthraquinone Series

Abstract

NOVEL substitution and elimination reactions were noted when 1-nitroanthraquinone-2-carboxamide (I), m.p. 315°, was refluxed with excess of cyclohexylamine alone for 16 h; the products were separated and purified by chromatography in benzene on alumina. Thus, in addition to the expected bluish-red 1-cyclohexylaminoanthra-quinone-2-carboxamide (II) (38 per cent yield), m.p. 223°, formed by replacement of the labile nitro group, three other compounds were separated: in order of increasing adsorption the red 1-cyclohexylaminoanthra-quinone (III) (3.5 per cent), m.p. 145°–146°, formed by elimination of the carboxamide group, the orange 1-aminoanthraquinone-2-cyclohexylcarboxamide (IV) (4.7 per cent) m.p. 289°–290°, suggesting the reducing action of cyclohexylamine and the blue l,4-bis-cyclohexylamino-anthraquinone-2-carboxamide (V) (4.4 per cent), m.p. 276°. Mixed m.p. determinations and thin-plate Keiselgel chromatography of these three compounds with the appropriate authentic synthesized samples confirmed their identity. 1-Cyclohexylammoanthraquinone-2-cyclo-hexylcarboxamide, m.p. 174°–175°, was not isolated from the reaction products.