An Efficient Synthesis of 6-Nitro- and 6-Amino-3H-imidazo[4,5-b]pyridines by Cyclocondensation of 1-Substituted 1H-Imidazol-5-amines with 3-Nitro-4H-chromen-4-one - Ostrovskyi, Dmytro; Iaroshenko, Viktor O.; Petrosyan, Andranik; Dudkin, Sergii; Ali, Iftikhar; Villinger, Alexander; Tolmachev, Andrei; Langer, Peter (Synlett, 2010)