Hydrochloric Acid → 3,3-Dimethyl-2,3-dihydrobenzofuran-6-carboxylic acid

In a 50 ml pear flask containing methyl 3,3-dimethyl-2,3-dihydrobenzofuran-6-carboxylate (32 mg, 0.16 mmol) were added methanol (3 ml) and 1.0 M sodium hydroxide (6 ml, 6 mmol) solution to give a suspension. This was stirred at room temperature for 1 hour. Then 2N hydrochloride solution (3.5 ml) was added to neutralize the excess base. The acidic mixture (pH˜2) was then extracted with EtOAc twice, and the combined organic layers were dried over MgSO4, filtered and concentrated to give the desired 3,3-dimethyl-2,3-dihydrobenzofuran-6-carboxylic acid (23 mg, 77% yield) as a white flakey oily solid that was used in the next step without further purification.