The reaction of terephthalic acid monomethyl ester (I) with SOCl2 in dichloromethane gives the acyl chloride (II), which is condensed with 3-(3-ethoxy-4-methoxyphenyl)-1-methylpiperidin-4-amine (III) by means of TEA in dichloromethane, yielding the corresponding amide (IV). The cyclization of (IV) by means of POCl3 in refluxing acetonitrile affords the benzo-naphthyridine (V), which is treated with diisopropylamine in methanol to provide the target diisopropyl carboxamide.