Nitroxoline → 5-Amino-8-hydroxyquinoline

5-Amino-8-hydroxyquinoline was prepared by the reduction of 8-hydroxy-5-nitroquinoline (from Aldrich Chemical Co., Inc., Milwaukee, Wis.). Twenty-five grams (0.131 moles) of 8-hydroxy-5-nitroquinoline were placed in a 500 milliliter (ml) Parr bottle followed by 250 ml of glacial acetic acid and 1 g of 10% palladium carbon. The bottle was further filled with 3×105Pascals (Pa) (3 atmospheres) of hydrogen. The filled bottle was attached to the Parr shaker-type hydrogenation apparatus (from Parr Instrument Co., Moline, Ill.) and the bottle and its contents were shaken until theoretical uptake was complete (approximately 5-6 hours). Reduction of the nitro group to the amine group was verified by the theoretical uptake of hydrogen. The original pressure in the Parr reactor was 0.61 MPa (88 psi). A drop of 0.24 MPa (34.7 psi) indicated that the theoretical uptake of hydrogen had occurred. The reaction contents were filtered, and the liquors were concentrated to a black-purple tar using a rotoevaporator. To remove excess acetic acid from the 5-amino-8-hydroxyquinoline, the tar was spread onto the bottom of an aluminum pan. The pan and its contents were heated in a vacuum oven for about 16 hours until the contents (5-amino-8-hydroxyquinoline) were dry.