ピラゾールアントロンの二三の誘導体の合成ならびにその環化

概要

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Though a pyrazole hydroazine vat dye (1) was formed by the direct cyclization of pyrazoleanthrone with 1-amino-2-bromoanthraquinone, the yield was as low as 10%. I, however, was obtained in 58% over-all yield in a two -step synthesis via cyclization of the intermediate, 2-(1-amino-2-anthraquinonyl)-pyrazoleanthrone, in pyridine-methanol containing potassium hydroxide . 2-(2-Aminophenyl)-pyrazoleanthrone was also readily cyclized into a pyrazole hydroazine compound . Similar reactions using 2-(3-pyrazoleanthronyl)-pyrazoleanthrone and 3-anilino - pyrazoleanthrone, however, failed to take place. It is assumed that the cyclization reaction proceeds through a link formation between a -NH anion formed as shown below and a carbonium cation induced by the electron withdrawing effect of the carbonyl group in the pyrazoleanthrone ring.
社団法人有機合成化学協会の論文