Acetic Acid → racemic-7-acetyl-6-hydroxy-3,4-dihydro-2H-1-benzopyran-2-carboxylic acid ethyl ester

Participants

Reaction Conditions

Reaction Steps

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.

Provenance & Evidence