24265-23-4

29943-42-8

24265-23-4

Step 2: 4.79 g (30.0 mmol) of bromine was slowly added dropwise to 78 ml of anhydrous dichloromethane solution containing 8.52 g (27.5 mmol) of triphenyl phosphite at -60 °C. Subsequently 4.5 ml (32.5 mmol) of triethylamine was added and 2.5 g (25.0 mmol) of tetrahydro-4H-pyran-4-one dissolved in 2 ml of dichloromethane was added slowly dropwise. The reaction mixture was slowly warmed to room temperature over a period of about 5 hours and stirring was continued at room temperature for 1 hour. Upon completion of the reaction, all volatile components were removed using a rotary evaporator. The crude product was initially purified by silica gel column chromatography (silica gel 100 g, dichloromethane as mobile phase). After solvent evaporation, the product was further purified by bulb tube distillation (pressure: 8 mbar; temperature: up to 120 °C). Finally, 2.51 g (62% yield) of 4-bromo-3,6-dihydro-2H-pyran was obtained. The structure of the product was confirmed by 1H-NMR (400 MHz, CDCl3, δ/ppm): 6.07 (m, 1H), 4.13 (m, 2H), 3.83 (m, 2H), 2.55-2.50 (m, 2H) and GC/MS (Method L, ESIpos): rt = 2.32 min, m/z = 162/164 [M]+.