Ethanol → Ethyl 3-bromo-2-ethoxytetrahydro-3-furoate

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

To a nitrogen-purged, 1000-mL, four-neck, round-bottom flask equipped with a thermocouple/thermowell, Dry Ice/acetone bath, addition funnel, condenser, and magnetic stirrer was charged 200 mL of ethanol, 142.12 g (1.00 mole) of ethyl 2,3-dihydro-4-furoate, and 93.0 g (1.11 mole) of sodium bicarbonate. The slurry was cooled to about 0° C. then 159.1 g (0.995 mole) of bromine was added dropwise from the addition funnel over 75 minutes at a temperature of -3 to 30° C. After 15 minutes the bath was removed and the light yellow slurry allowed to warm to room temperature over about two hours. The mixture was filtered and the solids rinsed with ethanol. Solvent was stripped from the filtrate by rotary evaporation at up to 45° C. (70 mm). To the concentrated product was added 100 mL of water. The layers were separated and the aqueous layer extracted with 50 mL of dichloromethane. The organic layers were combined and washed with 100 mL of water containing 0.23 g of sodium thiosulfate then with 100 mL of 5% aqueous sodium bicarbonate. The organic layer was dried with anhydrous magnesium sulfate, then filtered and concentrated by rotary evaporation at up to 45° C. (70 mm). The resulting crude product weighed 270.5 g and contained 5.4 weight percent dichloromethane by NMR (theory 267.12 g, 95.8% yield). A portion of this crude product (71.01 g) was distilled using a 10-inch Vigreux column at 3 mm. The product fraction was collected at 101 to 102° C. The yield of distilled ethyl 3-bromo-2-ethoxytetrahydro-3-furoate was 56.63 g (80.8%). The identity of the product was confirmed NMR and mass spectrometry.

Herkunft & Nachweise