The general procedure for the synthesis of 1,3-benzodioxole-4-carboxylic acid from methyl benzo[d][1,3]meso-dioxole-4-carboxylate was as follows: methyl benzo[d][1,3]meso-dioxole-4-carboxylate (0.4 g, 2.22 mmol) was dissolved in methanol (8.0 mL), and 2.0 M aqueous KOH (2.2 mL) was added and stirred at room temperature. The reaction was stirred for 3 hours at room temperature. After completion of the reaction, the mixture was concentrated to about 3 mL, diluted with water (5 mL), and the pH was adjusted to ~3 with 2.0 M HCl. The precipitate was separated by filtration, washed sequentially with water and ether, and dried in vacuo to give 1,3-benzodioxole-4-carboxylic acid as a beige solid (0.38 g, 97% yield).1H NMR (400 MHz, DMSO-d6): δ = 7.28 (dd, J = 8.0, 1.2 Hz, 1H), 6.97 (dd, J = 8.0, 1.2 Hz, 1H), 6.89 (t, J = 8.0 Hz, 1H), 6.12 (s, 2H); 13C NMR (100 MHz, DMSO-d6): δ = 165.5, 148.9, 148.5, 122.9, 121.6, 113.8, 112.5, 102.1.
