PURPOSE: To obtain an anthraquinone compd. useful for production of dyes, paper pulp or hydrogen peroxide from phthalic anhydride and a benzene deriva tive without the need for executing sepn. and recovery of an intermediate prod uct which leads to a cost increase over the entire part of a process.

CONSTITUTION: The objective compd. is advantageously obtd. by treating a reaction mixture contg. a catalyst mixture of HF/BF3 (molar ratio) = preferably about 2 to 12, more preferably about 4 to 10 at a ratio of BF3 = at least 3 mol for each 1 mol of the compd. of formula II preferably for 5 to 60 minutes at a first temp. of about max. one hour at a temp. of about -6 to 30°C, more particularly 0°C, then treating the mixture at a temp. higher than the first temp., more preferably at a temp. of 40 to 70°C at the time of producing the compd. of formula III by reacting the compd. of formula I (R1, R2 are each H, a 1 to 6C linear or branched alkyl) with the compd. of formula II (R3, R4 are each H, a 1 to 6C linear or branched alkyl) in the reaction mixture described above by using these compds. at a ratio of 0.9 to 1.2 mol the former for each 1 mol of the latter.