Selective demethylation of di- and tri-methoxyanthraquinones via aryloxydifluoroboron chelates. Synthesis of 4-hydroxy-1,5-dimethoxyanthraquinone and 1,4-dihydroxy-5-methoxyanthraquinone

Abstract

Methoxyanthraquinone derivatives react with boron trifluoride–diethyl ether to give mono- and bis-difluoroboron chelates which, in methanol, are converted into hydroxyanthraquinones; an extension of this method is described for the synthesis of 2-hydroxy-2′,4,4′-trimethoxybenzophenone.