General procedure for the synthesis of 1-amino-2-naphthalenecarboxylic acid from 1-nitro-2-naphthalenecarboxylic acid: 1-nitro-2-naphthalenecarboxylic acid (17.3 g), acetic acid (2 g), and a Pd/C catalyst (1.83 g, 10 wt% Pd) were suspended in THF (339 mL) in reactor A. The reaction was carried out in the same manner as the reaction. The reaction mixture was degassed and pressurized with hydrogen (25 psig). The mixture was stirred and reacted for 10 hours under hydrogen atmosphere. Upon completion of the reaction, the reaction mixture was filtered through diatomaceous earth (6 g) and the filter cake was washed with THF (51 mL). The combined filtrates were concentrated to about 40 mL and then cooled at 0-5 °C. Water (143 mL) was added to the concentrate to induce crystallization of the product. 1-Amino-2-naphthalenecarboxylic acid was isolated by filtration, washed with water (100 mL), and dried to give 13.35 g of product in 92.2% yield, 99.5% liquid phase purity (LCAP), and 98.7% wt. purity.
