A FACILE AND NOVEL SYNTHESIS OF 5-PHENYLIMIDAZO[4,5-C][1,8]NAPHTHYRIDIN-4(5H)-ONES

A convenient and regioselective synthesis of a new heterocycle, 5-phenyl-IH or 3H-imidazo[4,5-c][1,8]-naphthyridin-4(5H)-one 1-a or 1-b, is described. Methyl 2-anilinonicotinate 15 was transformed into the valuable intermediate, N-phenyl-3-azaisatoic anhydride 4 using trichloromethyl chloroformate (TCF). Treatment of 4 with the anion of ethyl nitroacetate gave 4-hydroxy-3-nitro-1-phenyl-1,8-naphthyridin-4(5H)-one 3. Compound 3 was chlorinated, aminated. reduced, and cyclized to afford 5-phenylimidazo[4,5-c][1,8]naphthyridin-4(5H)-one 1. Regioselective substitution at the 1 or 3-position in the imidazole moiety of 1 was achieved by minor changes of the above scheme.