Step C: Synthesis of 2,6-difluoro-4-methylbenzoic acid
1. silver oxide (43.8 g, 0.189 mol), water (200 mL) and sodium hydroxide (33.7 g, 0.842 mol) were added to a flask.
2. 2,6-difluoro-4-methylbenzaldehyde (29.23 g, 0.187 mol) was added in batches over 30 min.
3. intense exothermic phenomena were observed during the reaction and the color of the reaction mixture changed from black to gray.
4. The thick suspension formed was continued to be stirred for 1 hour and subsequently filtered through a Brinell funnel.
5. The filtrate was acidified to pH 2 with concentrated hydrochloric acid to produce a suspension.
6. The precipitate was collected by filtration, dissolved in ether and dried by adding anhydrous sodium sulfate.
7. The dried solution was filtered and concentrated to give a white solid product, 2,6-difluoro-4-methylbenzoic acid (17.0 g, 53% yield). 8. The product was purified by 1H-NHPA and concentrated.
8. The product was characterized by 1H-NMR (500 MHz, d6-DMSO): δ 13.7 (br.s, 1H), 7.02 (d, 2H, J = 9.3 Hz), 2.32 (s, 3H).
