3-Amino-2-naphthoic acid → 3-Fluoronaphthalene-2-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

3-Amino-2-naphthoic acid (40.4 g, 216 mmol) was placed in 200 mL concentrated HCl. At 0° C., the slurry was stirred vigorously using a mechanical stirring blade. To it was added a cold solution of sodium nitrite (29.8 g, 432 mmol) in 70 mL water. After completion, the cold slurry was stirred for 30 minutes at 0° C. To it was added cold tetrafluoroboric acid (48 wt. % in water, 56 mL, 432 mmol). After stirred at 0° C. for 30 minutes, the solid was filtered using a Buchner funnel. The soild cake was carefully rinsed with cold water (10 mL ×2), cold tetrafluoroboric acid (10 mL ×2) and cold ethanol (5 mL ×2). The solid was dried in vacuuo. It was then placed in 300 mL xylene and refluxed overnight. Xylene was removed on rotovap. The residue was acidified to pH 1 with aq HCl and taken into EtOAc. It was washed with brine (×2), dried, evaporated to give 3-fluoro-2-naphthoic acid (32.6 g, 78%). ES-MS: (M+H)+191.

Provenance & Evidence