General procedure for the synthesis of 2H-pyran-3(6H)-ones from 3,6-dihydro-2H-pyran-3-ol: 3,6-dihydro-2H-pyran-3-ol (2.44 g, 24.37 mmol) was dissolved in dichloromethane (100 mL) and the solution was cooled to 0 °C. Subsequently, Dess-Martin periodinane (10.34 g, 24.37 mmol) was slowly added. The reaction mixture was slowly warmed to room temperature over a period of 5 hours. After completion of the reaction, the reaction mixture was filtered through diatomaceous earth. After concentration of the filtrate, the crude product was purified using a 100 g SNAP Biotage column (eluent: 0-80% hexane solution of ethyl acetate) to afford 2H-pyran-3(6H)-one (2.33 g, 23.75 mmol, 97% yield) as a colorless oil.1H NMR (400 MHz, CDCl3) δ ppm: 7.07- 7.17 (m, 1H), 6.15-6.25 (m, 1H), 4.39 (t, J = 2.54 Hz, 2H), 4.19 (s, 2H).
