Boron Trichloride → 6-Acetyl-2,3,-dihydro-7-hydroxy-4-methyl-4H-1-benzopyran

Participants

Reaction Steps

The product of step (d) (57.4 g) in dry methylene chloride (500 ml) was treated with boron trichloride (61 g) in dry methylene chloride (150 ml) at -70° C. The cooling bath was removed and the reaction mixture was allowed to warm to room temperature during 1 hour. The reaction mixture was poured into water and the methylene chloride layer was separated, washed with water and dried. Evaporation of the solvent left 55.7 g of crude product; this was dissolved in ether and extracted several times with a sodium hydroxide solution. The basic extracts were acidified and the precipitated product extracted with ether, which was washed with water and dried. Evaporation of the solvent gave 36.4 g of product mp 91°-96°. A recrystallisation from ethanol gave the title compound, mp 104°-105°.

Provenance & Evidence