Synthesis
In a 1 L round-bottom flask equipped with a magnetic stir bar and 5.00 g (23.8 mmol) of 2,6-dichloro-5-fluoronicotinic acid, methanol (240 mL) and N,N-diisopropylethylamine (8.30 mL (48.0 mmol)) were added. 500 mg of palladium on carbon (10 wt%) was carefully added to the solution. The resulting reaction mixture was purged with hydrogen and placed in an atmosphere of H2 (1 atm) using a balloon. The reaction mixture was stirred at ambient temperature for 12 hours, then filtered through diatomaceous earth. The filtrate was concentrated under vacuum to approximately 25 mL and diluted with approximately 250 mL of Et2O. The resulting precipitate (DIPEA/HCl salt) was filtered through a Buchner funnel, and the filtrate was concentrated under vacuum to give 3.2 g (98%) of a yellow oily 5-fluoronicotinic acid.
Figure 5. Synthetic route of fluoronicotinic acid
