General procedure for the synthesis of 6-aminobenzo[d][1,3]dioxole-5-carboxylic acid from methyl 6-aminobenzo[d][1,3]dioxole-5-carboxylate: Sodium hydroxide (2.95 g, 73.8 mmol) was added to water (75 mL), and stirred until completely dissolved. Methyl 6-aminobenzo[d][1,3]dioxole-5-carboxylate (12.0 g, 61.5 mmol) was then added and the reaction mixture was heated to 90°C and stirred for 2 hours. After completion of the reaction, the reaction mixture was cooled with ice water and the pH was adjusted to 2 with concentrated hydrochloric acid to precipitate a solid. The mixture was stirred thoroughly and filtered, the filter cake was washed with water and dried to give 6-aminobenzo[d][1,3]dioxole-5-carboxylic acid (7.2 g, 65% yield).
