Cyclization of 2-chloro-3-((4-(hexyloxy)phenyl)amino)naphthalene-1,4-dione obtained from the reaction of 2,3-dichloro-1,4-naphthoquinone with 4-(hexyloxy)aniline by sodium azide in N,N-dimethylformamide (DMF) at 90-95 degrees C gives 2-(hexyloxy)benzo[b]phenazine-6,11-dione. This is a remarkable example of a general procedure to prepare functionalized benzo[b]phenazine-6,11-dione derivatives. The structure of the title compound was confirmed by single crystal X-ray diffraction analysis. The compound, C22H20N2O3, crystallizes in the sp. gr. PZ = 2. Both O atoms and one of N atoms are involved in hydrogen bonds forming a network. Besides, there is offset stacking interaction between the planes of polycyclic systems with interplanar distance of 3.383 angstrom.