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Step c: 4-Methoxyisoindolin-1-one (291 mg, 1.78 mmol) was dissolved in dichloromethane (20 mL) and cooled in an ice bath. A 1.0 M solution of boron tribromide in dichloromethane (3.6 mL, 3.6 mmol) was added slowly with stirring. The ice bath was removed and the reaction mixture was stirred at room temperature for 16 hours. Upon completion of the reaction, the reaction was carefully quenched by the addition of water and the mixture was extracted with ethyl acetate. The organic phases were combined, washed sequentially with water and saturated brine, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to afford 4-hydroxy-isoindolin-1-one (232 mg, 87% yield) as a beige solid.

[1] Patent: WO2004/26875, 2004, A1. Location in patent: Page 38
[2] Patent: US2004/106791, 2004, A1. Location in patent: Page 9
[3] Chinese Chemical Letters, 2012, vol. 23, # 1, p. 9 - 12