Boron tribromide → (S)-5-amino-2'-bromo-4'-fluoro-2,6-dihydrospiro[[1,4]oxazine-3,9'-xanthen]-7'-ol

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Reaction Conditions

Reaction Steps

In a 500-mL flask, (S)-2′-bromo-4′-fluoro-7′-methoxy-2,6-dihydrospiro[[1,4]oxazine-3,9′-xanthen]-5-amine (0.676 g, 1.719 mmol) was suspended in DCM (50 mL). The suspension was cooled to 0° C., and boron tribromide (1.0 M in DCM; 5.16 mL, 5.16 mmol) was added. After 1.5 h, excess boron tribromide was quenched with saturated aqueous NH4Cl (18 mL) and aqueous NH4OH (2 mL). The aqueous phase was separated and extracted further with 5% MeOH-DCM (3×50 mL). The organics were combined, washed with brine (15 mL), dried over sodium sulfate and concentrated to afford 604 mg of (S)-5-amino-2′-bromo-4′-fluoro-2,6-dihydrospiro[[1,4]oxazine-3,9′-xanthen]-7′-ol which was used in the next step without further purification.

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