6-Bromo-2,3-dihydro-4H-chromen-4-one

93670-18-9

49660-57-3

3-(4-Bromophenoxy)propionic acid (150 g, 0.61 mol) was slowly added to 1.0 liter of concentrated sulfuric acid at room temperature with continuous stirring for 1 hour. Upon completion of the reaction, the mixture was carefully poured into 500 g of ice water, whereupon a white solid precipitated. The white solid was separated by filtration and dried naturally in air. The crude product was purified by recrystallization using ethanol, resulting in 89 g (64% yield) of the target compound 6-bromobenzodihydropyran-4-one as a white solid.