Condensation of 4-ethylaniline (I) with propiolactone (II) produces the beta-aminoacid (III). Intramolecular Friedel-Crafts cyclization of (III) by means of polyphosphoric acid leads to the quinolinone (IV). Then, electrophilic iodination of (IV) by using iodine monochloride provides the intermediate (V)
Displacement of 2-chloro-4-ethoxyquinoline (VI) with 1,3-propanediamine (VII) affords the aminoquinoline (VIII). Subsequent acidic hydrolysis of (VIII) provides quinolinone (IX). Finally, reductive condensation between amine (IX) and ketone (V) in the presence of NaBH3CN leads to the target disubstituted propanediamine