In a mixed solvent of water-acetic acid-propionic acid, 3-phenanthrol was nitrated with an equimolar amount of nitric acid at - 25 - 20°C to obtain a mixture of mononitro compounds containing a small amount of polynitro compounds. The mixture consisted of 9-nitro-3-phenanthrol, 4-nitro-3-phenanthrol, and 2-nitro -3-phenanthrol, the amount of each product being decreased in this order. Further nitration of 4-nitro-3-phenanthrol and 2-nitro -3-phenanthrol in dilute acetic acid at 1112°C gave a common product, 4, 9-dinitro-3-phenanthrol[1].
[1] E. ōta, K. Iwamoto, H. Kawashima. “Nitration of 3-Phenanthrol.” Journal of Synthetic Organic Chemistry Japan 22 1 (1969): 157–161.