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Aqueous hydrogen peroxide (30% w/v, 4 mL) was added to an ice-cold suspension of 5′-acetamido-2′-hydroxychalcone (5) (2.00 g, 7.11 mmol) and 1 M NaOH (20 mL) in ethanol (60 mL). The mixture was allowed to warm to room temperature and was vigorously stirred overnight. The mixture was acidified with 1 M HCl and the precipitate formed was collected by filtration to afford the flavonol (6) as a bright yellow powder (1.04 g, 50%), m.p. 241-242° C. 1H NMR (399.7 MHz, d6-DMSO) δ 2.10 (s, 3H, CH3); 7.48-7.59 (m, 3H, H3′,4′,5′); 7.73 (d, 1H, J7,8 9.2 Hz, H8); 7.89 (dd, 1H, J5,7 2.8, J7,8 9.2 Hz, H7); 8.21 (app. d, 2H, J=7.6 Hz, H2′,6′); 8.44 (d, 1H, J5,7 2.8 Hz, H5), 9.60 (br s, 1H, OH); 10.28 (s, 1H, NH).

1. customthe precipitate formed
2. filtrationwas collected by filtration