A New Ring-Forming Methodology for the Synthesis of Bioactive Pyrroloquinoline Derivatives

Abstract

A new, efficient, two-step method for the synthesis of bioactive pyrroloquinolines is described. Readily available nitroquinolines, bearing the nitro moiety in the carbocyclic ring, are treated with 4-chlorophenoxyacetonitrile in the presence of potassium tert-butoxide/THF to give the analogous vicarious nucleophilic substitution products (5, 8 and 11). These, in turn, are subjected to catalytic hydrogenation to produce 1H-pyrrolo[2,3-f]quinoline (6), 3H-pyrrolo[3,2-f]quinoline (9) and 1H-pyrrolo[3,2-h]quinoline (12) in good yields and relatively short reaction times. The differential activity of two N-alkylated 1H-pyrrolo[2,3-f]quinolines (1) in cisplatin resistant cell lines compared to the corresponding parent lines suggests that these might be useful leads for developing agents for use in drug resistant diseases.