反应详情

温度

80 °C

Into a solution of 2.23 g of racemic-ethyl 6-hydroxychroman-2-carboxylate in 30 ml of acetic acid was introduced a stream of boron trifluoride gas at 20°-25° C. A cold water bath was used during the introduction of the gas (30-45 minutes) to control the temperature of the exothermic reaction. The cold bath was removed and the reaction mixture was heated at 80° C. for 5 hours; then the reaction mixture was cooled and carefully poured into a mixture of saturated bicarbonate and ice, and the product was extracted with 1:1 tetrahydrofuran-ether. The crude material obtained after evaporation of the solvent was chromatographed on a silica gel column to yield 1.6 g (60%) of racemic-7-acetyl-6-hydroxy-3,4-dihydro-2H-1-benzopyran-2-carboxylic acid ethyl ester as a viscous oil.

1. customA cold water bath was used during the introduction of the gas (30-45 minutes)
2. customthe temperature of the exothermic reaction
3. customThe cold bath was removed
4. temperaturethen the reaction mixture was cooled
5. additioncarefully poured into a mixture of saturated bicarbonate and ice
6. extractionthe product was extracted with 1:1 tetrahydrofuran-ether
7. customThe crude material obtained
8. customafter evaporation of the solvent
9. customwas chromatographed on a silica gel column