5-Bromovanillin → 5-Bromo-3,4-dihydroxybenzaldehyde

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Reaction Steps

To a solution of the compound of Example (a) (12.1 g, 0.52 mol) in CH2Cl2 (200 mL) was added 1.0 M boron tribromide in CH2Cl2 (2.2 eq, 115 mL) at 0°. The reaction was stirred at 0° for 20 min, then at ambient temperature for 2.5 h. The reaction was then cooled to 0°, and quenched by the slow addition of methanol. The solvents were removed under reduced pressure and the trimethyl borate was removed by azeotropation with added methanol. Vacuum drying yielded a dark green-brown solid (11.51 g, 100%) which was used without further purification: MS (ES) m/z 217.2. (M+H)+.

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