General procedure for the synthesis of 3-(benzyloxy)-2-methyl-4H-pyran-4-one from 3-(benzyloxy)-2-methyl-4H-pyran-4-one: To a solution of 3-(benzyloxy)-2-methyl-4H-pyran-4-one (13.8 g, 0.064 mol) in ethanol (25 mL) was added aqueous ammonia solution (50 mL), and the reaction was carried out at reflux overnight. After completion of the reaction, the solvent was removed by distillation under reduced pressure. The residue was dissolved in water and the pH was adjusted with concentrated hydrochloric acid to 1. The resulting aqueous phase was washed with ethyl acetate (3 x 25 mL), followed by adjusting the pH with 2 M sodium hydroxide solution to 10. The aqueous phase was then extracted with chloroform (3 x 1 L), and the organic phases were combined, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The crude product was recrystallized with a solvent mixture of methanol/ether to give brown cubic crystals with a melting point of 162-164 °C. The product was extracted with chloroform (3×L) and dried with anhydrous sodium sulfate. The yield was 75%. The product was characterized by 1H NMR (CDCl3): δ 2.15 (3H, s, CH3), 5.03 (2H, s, CH2Ph), 6.35 (1H, d, J = 6.9Hz, 5-H), 7.25-7.31 (5H, m, Ph-H), 7.39 (1H, d, J = 6.9Hz, 6-H). The molecular formula is C13H13NO2.
