6-Bromo-4-isochromanone

676134-67-1

676134-68-2

Step 2: A solution of bromo-2-carboxymethoxymethyl-benzoic acid in acetic anhydride (350 mL) containing potassium acetate (170 g) was heated to reflux for 2 hours. Upon completion of the reaction, the mixture was cooled to room temperature and concentrated under reduced pressure. The residue was partitioned between ethyl acetate and water to separate the phases. The aqueous phase was further extracted with ethyl acetate. All ethyl acetate phases were combined and washed with saturated sodium chloride solution and subsequently dried over sodium sulfate. The dried organic phase was filtered and concentrated to give a red semi-solid product. Purification by silica gel fast column chromatography (eluent ratio 85:15 hexane/ethyl acetate) afforded enol acetate (7.59 g, three-step overall yield 29%), which appeared as a golden syrup: 1H NMR (300 MHz, CDCl3) δ 7.37 (dd, J=8.2, 1.9 Hz, 1H), 7.19 (d, J=1.9 Hz, 1H), and 6.82 (d, J=8.2 Hz, 1H), 5.04 (s, 2H), 2.29 (s, 3H). Subsequently, the unactivated Dowex 500A OH anion exchange resin (1 g) was added one time to a methanol (50 mL) solution of enol acetate (5.95 g, 22.11 mmol) and the reaction mixture was stirred at room temperature overnight. The reaction mixture was separated by gravity filtration and the resin was washed with fresh methanol. The filtrates were combined and concentrated under reduced pressure to give 6-bromo-isochroman-4-one (4.32 g, 86% yield), which was initially a yellow oil and solidified on standing.