The general procedure for the synthesis of 2,2-difluoro-1,3-benzodioxole-5-carboxylic acid from methyl 2,2-difluorobenzo[d][1,3]dioxole-5-carboxylate is as follows:
Step 2. A solution of methyl 2,2-difluorobenzo[d][1,3]dioxole-5-carboxylate (1.4 g, 6.48 mmol) and sodium hydroxide (830 mg, 20.75 mmol) in methanol (30 ml) was stirred at room temperature overnight. After completion of the reaction, the reaction mixture was concentrated under vacuum and subsequently dissolved in water (20 ml). The pH of the aqueous solution was adjusted to 3 with 3N HCl, at which point a precipitate was produced. The precipitate was collected by filtration to afford 2,2-difluorobenzo[d][1,3]dioxole-5-carboxylic acid as a white solid (1.2 g, 92% yield).
Product characterization data: 1H-NMR (300 MHz, DMSO) δ 13.23 (s, 1H, COOH), 7.85 (s, 1H, Ar-H), 7.53 (d, J=1.5 Hz, 1H, Ar-H), 7.53 (d, J=9.0 Hz, 1H, Ar-H).
![methyl 2,2-difluorobenzo[d][1,3]dioxole-5-carboxylate](/CAS/GIF/773873-95-3.gif)
