Reaction Steps
A solution of 4′-methoxybenzyloxychalcone (13) (300 mg, 0.489 mmol) in aqueous HCl (2 M, 16 mL) and ethanol (66 mL) was heated at reflux for 1 h. The mixture was cooled to room temperature, and evaporated in vacuo to approximately half the volume. The resultant suspension was filtered to afford the crude deprotected chalcone (14) as a dark yellow solid. The deprotected chalcone was dissolved in 1,4-dioxane (4.8 mL), ethanol (6 mL) and NaOH (5.4% w/v, 1.9 mL) and the resultant solution was cooled in an ice bath and H2O2 (30%, 0.3 mL) was added. The solution was stirred at 0° C. for 2 h, and subsequently at room temperature overnight. The solution was then acidified with 2 M HCl and the precipitate that formed was filtered, and then recrystallised from THF/petroleum spirits to afford the flavonol (15) as a yellow solid (136 mg, 55%), m.p. 229-230° C. Anal. Calcd. for C31H25NO6: C, 73.36; H, 4.96; N, 2.76. Found: C, 73.38; H, 4.98; N, 2.68%. 1H NMR (399.7 MHz, d6-DMSO) δ 2.09 (s, 3H, CH3); 5.21, 5.24 (2 s, 2×2H, 2×CH2); 7.26 (d, 1H, J5′,6′ 8.8 Hz, H5′); 7.33-7.52 (m, 11H, 2×Ph); 7.71 (d, 1H, J7,8 9.2 Hz, H8); 7.84-7.92 (m, 3H, H2′,6′,7); 8.40 (d, 1H, J5,7 2.4 Hz, H5); 9.48 (br s, 1H, OH); 10.27 (s, 1H, NH). 13C NMR (100.5 MHz, d6-DMSO) δ 24.03 (1C, CH3); 69.91, 70.43, 112.65, 112.69, 113.79, 118.89, 121.38, 121.91, 124.06, 125.32, 135.91, 136.88, 137.08, 138.14, 145.14, 147.77, 149.77, 150.42 (18C, Ar); 168.59, 172.47 (2C, 2×C═O).
