Step 2: 3-(3,4-difluorophenoxy)propionic acid (0.50 g, 2.5 mmol) was mixed with trifluoromethanesulfonic acid (5.0 mL, 56 mmol) and the reaction was stirred at room temperature for 18 hours. Upon completion of the reaction, the mixture was slowly poured into ice water (30 mL) to quench the reaction. The precipitated solid was collected by filtration to afford the target product 6,7-difluorobenzodihydropyran-4-one (370 mg, 81% yield) as a white solid. Mass spectrometric analysis showed m/z 185 [M + H]+ (electrospray ionization) with a retention time of 1.76 min (Analytical Method 1).
