Synthesis of novel 2-and 8-substituted 4-amino-7-chloroquinolines and their N-alkylated coupling products

The synthesis of a series of 2- and 8-substituted 4-amino-7-chloroquinolines is presented. Starting from 4,7dichloroquinolines, the chloro in the 4-position can be effectively substituted using amino alcohols to yield novel analogues of the antimalarial (hydroxy)chloroquine. Both short-chain (2-aminoethanol) and long-chain (5-[N-ethyl-N-(2-hydroxyethyl)amino]2-aminopentane) coupling partners can be used. While ketone and nitro functionalities were found to be incompatible with the coupling conditions, electron-donating amino and dimethylamino substituents were tolerated. In addition to characterization in solution using multinuclear NMR spectroscopy and high-resolution mass spectrometry, single-crystal X-ray structures are presented of two 4,7-dichloroquinolines as well as three of the N-alkylated products including a unique species in which a pyrrole heterocycle formed at the 2-position of the quinoline subunit and a rare example of a 4-aza-1,10-phenanthroline.

Automated summary

The synthesis of novel analogues of the antimalarial (hydroxy)chloroquine was achieved through the substitution of the chloro group at the 4-position of 4,7-dichloroquinolines with amino alcohols. Short-chain and long-chain coupling partners were used, with electron-donating amino and dimethylamino substituents being tolerated. The compounds were characterized using various techniques and crystal structures of selected products were obtained.