P-Xylene → 7-Bromo-2-(4-hydroxyphenyl)-1,3-benzoxazol-5-ol

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Reaction Steps

A suspension of 2-bromo-4-methoxy-6-[(4-methoxybenzoyl)amino]phenyl 4-methoxybenzoate (42.0 g, 86.4 mmol), p-toluenesulfonic acid monohydrate (32.8 g, 172.8 mmol) and anhydrous p-xylene (800 mL) was refluxed for 1 h with continuous water removal (Dean-Stark Trap). The initial suspension turned into a brown solution at refluxing temperature. The mixture was cooled to room temperature and washed with NaOH (2N). The organic layer was dried over MgSO4. Evaporation and crystallization from acetone/ethyl ether gave an off-white solid (23.5 g, 82% yield, m.p. 139-141° C.); MS m/e 334 (M+H)+.

Provenance & Evidence