Process for producing 2-methoxybenzanthrones

A process for producing a 2-methoxybenzanthrone, starting with 1-aminoanthraquinone of the formula I ##STR7## or the corresponding anthraquinone-1-diazonium salt, wherein R.sub.1, R.sub.2 and R.sub.3 independently of one another are each hydrogen or chlorine, or the hydroxyl, methoxy or benzamido group, in which process the starting compound is reacted to give the anthraquinone-1-diazonium salt, this in its turn is reacted in a Meerwein reaction with a propene derivative of the formula ##STR8## wherein Z is an electron-attracting substituent, and the reaction product is then cyclised in an alkaline reaction mixture to obtain 2-hydroxybenzanthrone, the hydroxyl group of which is methylated, by reaction with the reaction medium, to yield 2-methoxybenzanthrone, the said process being characterised in that it is performed, without isolation of the intermediates, in a dimethylalkanephosphonate, of which the alkane radical has 1-4 C atoms.