Triethylamine → Phthalidyl o-acetylsalicylate

o-Acetylsalicylic acid (18 g) and triethylamine (21 ml) were stirred at a temperature of 20°-25° C. for 30 minutes in 500 ml of acetone. When dissolution was completed, 3-bromophthalide (32 g) was added and the mixture refluxed 2 hours. The reaction mixture was then cooled to 20°-25° C. and poured into distilled water (500 ml). The resulting mixture was extracted with 200 ml of dichloromethane twice, discarding the acetone layer. After the organic solution was washed with 200 ml portions of distilled water twice, 5 g of anhydrous sodium sulfate were added and the mixture filtered. After filtration the organic filtrate was evaporated, the residue was taken up with previously warmed methanol. Decolorizing carbon (1 g) and filtering aid (1 g) were added. The methanolic solution was filtered, and the filtrate was cooled, first to room temperature, and subsequently in an ice/water bath. The solid precipitate was collected by filtration, and dried under vacuum at 40° C. to obtain a yield (83.9%; 26.2 g) of crude phthalidyl o-acetylsalicylate (m.p. 85° C.-88° C.).