Acetic Anhydride → 8-Bromo-2H-1-benzopyran-3(4H)-one

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Reaction Steps

The 8-bromo-3-chromanol was oxidized in small portions (400 mg, 1.7 mmol) in order to achieve better total yields. Dry pyridine (1.1 ml) was added to CH2Cl2 (60 ml), dried over P2O5 and CrO3 (0.69 g, 6.9 mmol) and molecular sieves were added to that solution. After 15 min the chromanol was added together with acetic anhydride (0.66 ml). The mixture was stirred for 10 min and then passed with suction through a column containing SiO2 (10 g), eluting with CH2Cl2. The collected eluate was evaporated and toluene was added after each evaporation (2-3 times), leaving the pure 8-bromo-3-chromanone (200 mg). GC/MS showed M+ /M+2 at m/e=226.25(89%)/228.25(82%).

Provenance & Evidence