Amide Ion Formation and N -Alkylation of Aminoanthraquinones in the Presence of Potassium Hydroxide in Dimethyl Sulfoxide

Abstract

Amide ions were formed by the deprotonation of the amino group of amino- and (monoalkylamino)anthraquinones in the presence of powdered potassium hydroxide in dimethyl sulfoxide (DMSO). Under a nitrogen atmosphere these amide ions changed to their radical anions. The amide ions of 1-aminoanthraquinones reacted with excess alkyl halides to yield 1-alkylaminoanthraquinones, while the N-alkylation of 2-aminoanthraquinones afforded 2-dialkylaminoanthraquinones in good yields. 2-Aminobenzophenone underwent mono-N-alkylation, while 4-aminoazobenzene and p-nitroaniline underwent di-N-alkylation. It was also found that the carbanion of DMSO easily attacked the carbonyl group of the (dialkylamino)anthraquinones.