The general procedure for the synthesis of 2,3-dihydro-1,4-benzodioxane-5-carboxylic acid from 2,3-dihydrobenzo[b][1,4]dioxane-5-carboxaldehyde was as follows: 2,3-dihydrobenzo[b][1,4]dioxane-5-carboxaldehyde (0.500 g, 3.04 mmol) was dissolved in acetone (10 mL) and mixed with an aqueous solution of sulfamic acid at 0-5 °C ( 0.455 g, 4.5 mmol) was mixed and stirred. After the reaction mixture was stirred for 20 minutes, aqueous sodium chlorite (0.421 g, 4.5 mmol) was added and the reaction was continued for 18 hours at room temperature. After completion of the reaction, the reaction mixture was concentrated under reduced pressure and quenched with water. The resulting solid was collected by filtration and dried under vacuum to afford the target product 2,3-dihydro-1,4-benzodioxane-5-carboxylic acid (0.332 g). The product was characterized as follows: 1H NMR (DMSO-d6): δ 4.27 (s, 4H), 6.84 (t, J = 7.2 Hz, 1H), 7.02 (d, J = 7.8 Hz, 1H), 7.20 (d, J = 7.5 Hz, 1H), 12.5 (bs, 1H); MS [M + H]+: 181.12.
