Synthesis of 4-Quinolone N-Oxides via Controlled Partial Hydrogenation of 2-Nitrobenzoyl Enamines

An operationally simple procedure for the synthesis of 2-alkyl-4-quinolone N-oxides, relying on controlled platinum-catalyzed partial hydrogenation of 2-nitrobenzoyl enamines, has been demonstrated. The P. aeruginosa metabolite 2-heptyl-4-quinolone-N-oxide (HQNO) and four analogous products have been prepared in good yield and high purity by this method.