Reaction of ethyl (3-carboxy-8-methylquinolin-2-yl)acetate (I) with POCl3/DMF under Vilsmeier formylation conditions leads to the cyclic anhydride (II). Subsequent treatment of (II) with methylamine gives rise to the benzonaphthyridine derivative (III). After activation of acid (III) as the corresponding acyl chloride (IV) with SOCl2, condensation with N,N-dimethyl ethylenediamine (V) furnishes the title amide.