New intermediates and dyes. Part XI. Novel nucleophilic substitution and group elimination in the 2-carbamoylanthraquinone series

Abstract

During the synthesis of a series of 1-amino- and 1,4-diamino-2-carbamoyl anthraquinones, several novel elimination and substitution reactions were observed. 2-Carbamoyl-1-nitroanthraquinone (I) and cyclohexylamine gave in addition to the expected 1-cyclohexylamino-analogue (II) 1-cyclohexylaminoanthraquinone (III), 1-amino-2-cyclohexylcarbamoylanthraquinone (IV)(suggesting the reducing action of cyclohexylamine), and 2-carbamoyl-1,4-biscyclohexylaminoanthraquinone (V), derived by direct nucleophilic substitution with displacement of hydride ion. With cyclohexylamine, 4-bromo-2-carbamoyl-1-cyclohexylaminoanthraquinone (VI) gave (V) and (III), and a little 4-amino-2-carbamoyl-1-cyclohexylaminoanthraquinone. The last-named was the main product from (VI) and ammonia, but some (III) was also formed by debromination and elimination of the carboxamide group. The interaction of 2-carboxy-1-nitroanthraquinone and cyclohexylamine gave (III) and some (IV).