Boron Trichloride → 6-Acetyl-2,3,-dihydro-7-hydroxy-4-methyl-4H-1-benzopyran
Reaction equation
[C:1]([C:4]1[C:5]([O:15]C)=[CH:6][C:7]2[O:12][CH2:11][CH2:10][CH:9]([CH3:13])[C:8]=2[CH:14]=1)(=[O:3])[CH3:2].B(Cl)(Cl)Cl>C(Cl)Cl>[C:1]([C:4]1[C:5]([OH:15])=[CH:6][C:7]2[O:12][CH2:11][CH2:10][CH:9]([CH3:13])[C:8]=2[CH:14]=1)(=[O:3])[CH3:2]Participants
4
Procedure
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 35.4 g of product mp 91°-96°. A recrystallisation from ethanol gave the title compound, mp 101°-105°.