Synthetic studies on pyrroloquinolines. Part III. Improved synthesis of 7-chloro-2,3-dihydro-4-methoxy-1H-pyrrolo[2,3-b]quinoline and its conversion into 3a,10b-diazacyclopenta[jk]phenanthrene derivatives

Abstract

3-(2-Aminoethyl)-7-chloro-4-methoxy-2-quinolone (7) was prepared by methylation of 7-chloro-4-hydroxy-3-(2-pnthalimidoethyl)-2-quinolone and removal of the phthaloyl group. Cyclization of the 3-(2-acetamidoethyl) derivative (9) gave, after hydrolysis, the pyrrolo[2,3-b]quinoline (12). An addition reaction with ethyl acrylate followed by reduction with aluminium hydride led to the pyrroloquinolin-1-ylpropanol (14), which was cyclized to the diazacyclopenta[jk]phenanthrene (16)via the quaternary salt (15). Hydrolysis of compound (16) gave the 6-ketone (17), whose structure was confirmed by its n.m.r. spectrum.