1,4-Benzodioxane-6-carboxylic acid

29668-44-8

4442-54-0

General procedure for the synthesis of 1,4-benzodioxane-6-carboxylic acid from 1,4-benzodioxane-6-carboxaldehyde: To a 20 mL methanol solution of urea-hydrogen peroxide complex (1:1) (6 g, 63.4 mmol) and aldehydes 3a-f (4.28 mmol) in stirring was added an aqueous NaOH solution (1.6 mL, 6 M solution). The reaction mixture was refluxed and stirred for 1 h at room temperature, followed by the addition of urea-hydrogen peroxide complex (1.5 g, 15.85 mmol) and continued refluxing for 30 min. Upon completion of the reaction, the mixture was cooled to room temperature and the pH was adjusted to 3 with 18% aqueous HCl. The precipitates were collected by filtration, washed with 2 x 50 mL of ice water and dried to give 4a-f (82-94% yield) as an off-white solid. For compound 4e, the reaction mixture was cooled at room temperature and the pH was adjusted to 3 with 18% HCl aqueous solution. methanol was removed by evaporation and the mixture was subsequently diluted with 30 mL of water and extracted with CHCl3. The organic phase was washed with water and the solvent was evaporated and dried.