3-bromo-7-hydroxy-4-methyl-2H-chromen-2-one

Preparation

Synthesis of 3-bromo-7-hydroxy-4-methyl-2H-chromen-2-one: 4-Methyl-7-hydroxy coumarin was added to acetic acid and stirred for 40 min. Potassium bromate was added to the reaction mixture stirred for 90 min to dissolve completely. Potassium bromide was charged and further stirred for 2 h. The reaction mixture was poured into cold water and stirred for half an hour, filtered and washed with water and recrystallized using ethanol.

Synthesis

General procedure for the synthesis of 3-bromo-7-hydroxy-4-methyl-2H-chromen-2-one from 7-hydroxy-4-methyl-2H-chromen-2-one: N-bromosuccinimide (0.98 g, 5.5 mmol) was slowly added to 7-hydroxy-4-methyl-2H-chromen-2-one (0.88 g, 5.0 mmol) in PEG-400 ( 10 g) in suspension. The reaction mixture was stirred for 3 h at room temperature. Subsequently, the reaction mixture was diluted with brine (100 mL) and extracted with dichloromethane (3 x 80 mL). The organic phases were combined, dried with anhydrous sodium sulfate and concentrated under reduced pressure to remove the solvent. The crude product was purified by column chromatography (elution gradient: ethyl acetate in hexane from 5% to 30%). A light yellow solid product was obtained in a yield of 0.45 g in 35% yield. The spectral data of the product were in agreement with those reported in the literature [16].

References

[1] Tetrahedron Letters, 2006, vol. 47, # 49, p. 8693 - 8697
[2] Synthetic Communications, 2009, vol. 39, # 2, p. 215 - 219
[3] Synthetic Communications, 1996, vol. 26, # 5, p. 887 - 892
[4] Indian Journal of Chemistry - Section B Organic and Medicinal Chemistry, 1999, vol. 38, # 11, p. 1242 - 1247
[5] Synthetic Communications, 1993, vol. 23, # 20, p. 2821 - 2826