Boron tribromide → 2,4,4-trimethyl-4H-3,1-benzoxazin-5-ol

Participants

Reaction Steps

5-Methoxy-2,4,4-trimethyl-4H-3,1-benzoxazine (Intermediate 201, 342 mg, 1.67 mmol) was dissolved in DCM (7 mL) and 1M BBr3 solution in DCM (1.67 ml, 1.67 mmol) was added. After 1.5 h at room temperature the mixture was heated to reflux and after 6 hours at reflux, some more 1M BBr3 solution in DCM (1.67 ml, 1.67 mmol) was added leaving the mixture at reflux overnight. The reaction mixture was quenched with an aqueous saturated solution of NaHCO3 while the pH was allowed to become basic. Two phases were separated and the organic layer was washed with brine, dried over Na2SO4 and evaporated to dryness, to obtain the title compound (330 mg) as foam.

Provenance & Evidence