Selective Synthesis of Imidazo[4,5‑f]- and Imidazo[4,5‑h]quinoline N‑Oxides via Base-Catalyzed Cyclization of ortho-Nitroalkylaminoquinolines

We report an efficient base-catalyzed cyclization of readily available ortho-nitroalkylaminoquinolines for the synthesis of a series of imidazo-[4,5-f]-quinoline and imidazo-[4,5-h]-quinoline N-oxides. Using alkali metal alkoxides in anhydrous alcohol, we achieved good to excellent yields (up to 92%) of various N-oxides, allowing the corresponding N-oxidation products to be obtained selectively. The method is suitable for a wide range of substituents (except tertiary amines). This protocol opens a direct route to new, previously inaccessible imidazo-[4,5]-quinoline N-oxide derivatives, opening the way for future pharmacological studies, given their purine-like structures and potential therapeutic applications.