General procedure for the synthesis of tetrahydro-2-phenyl-4H-pyran-4-one from 2-phenyltetrahydro-2H-pyran-4-ol: A DMSO solution of 2-phenyltetrahydro-2H-pyran-4-one (615 mmol) was added slowly and dropwise to a solution of oxaloyl chloride (128 mmol) in dichloromethane (100 mL) at -78 °C. The reaction mixture was stirred at -78°C for 15 minutes before a solution of 2-phenyltetrahydro-2H-pyran-4-ol (84 mmol) in dichloromethane (50 mL) was slowly added. Stirring was continued at -78 °C for 30 min, followed by the slow addition of N,N-diisopropylethylamine (DIPEA, 78 mL) and the reaction mixture was continued to be stirred at the same temperature for 3 hours. Upon completion of the reaction, water (100 mL) and dichloromethane (200 mL) were added and stirred for 15 minutes at room temperature. The organic layer was separated and the aqueous layer was extracted twice with dichloromethane. The organic phases were combined, washed twice with water, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography using a petroleum ether solution of 50% ethyl acetate as eluent to afford the target product tetrahydro-2-phenyl-4H-pyran-4-one in 72% yield.1H NMR (D6-DMSO): δ 2.44 (1H, d), 2.65 (1H, m), 2.66 (1H, t), 2.74 (1H, m), 3.85 (1H , dt), 4.44 (1H, m), 4.65 (1H, dd), 7.40-7.30 (m, 5H).
