The synthesis of pyridoquinolines with dialkylaminopropylamine side chains

Several new pyridoquinolines with dimethylaminopropyl side chain including 4,7‐bis(3′‐dimethylaminopropylamino)‐1,10‐phenanthroline (1), 4,10‐bis(3′‐dimethylaminopropylamino)‐1,7‐phenanthroline (2), 4,10‐bis(3′‐dimethylaminopropylamino)‐6‐methyl‐1,7‐phenanthroline (3), 4,6‐bis(3′‐dimethylaminopropylamino)‐10‐methylpyrido[3,2‐g]quinoline (4) and 4‐(3′‐dimethylaminopropyl)pyrrolo[lmn][4,7]phenanthroline (5) have been prepared. The compounds were prepared by a multi‐step synthesis which begins with Michael type addition of dimethyl acetylenedicarboxylate or diethyl ethoxymethylenemalonate to the appropriate phenylenediamine. The enamines obtained from the Michael addition were cyclized on heating at elevated temperatures to form the corresponding pyridoquinoline‐diester‐diones. The diester‐diones were saponified decarboxylated and converted into dichloropyridoquinolines which on reaction with dimethylaminopropylamine yielded the title compounds.