Boron tribromide → 7-hydroxy-3-(4-hydroxyphenyl)-2H-chromen-2-one
Reaction equation
[OH:1][C:2]1[CH:11]=[C:10]2[C:5]([CH:6]=[C:7]([C:13]3[CH:18]=[CH:17][C:16]([O:19]C)=[CH:15][CH:14]=3)[C:8](=[O:12])[O:9]2)=[CH:4][CH:3]=1.B(Br)(Br)Br>ClCCl>[OH:1][C:2]1[CH:11]=[C:10]2[C:5]([CH:6]=[C:7]([C:13]3[CH:18]=[CH:17][C:16]([OH:19])=[CH:15][CH:14]=3)[C:8](=[O:12])[O:9]2)=[CH:4][CH:3]=1Participants
4
Reactant 2
Product 1
Reagents, catalysts & solvents 1
Procedure
4.00 g (14.9 mmol) of 7-hydroxy-3-(4-methoxyphenyl)chromen-2-one are initially introduced in 190 ml of dichloromethane, and a solution of 2.5 ml (26.3 mmol) of boron tribromide in 10 ml of dichloromethane is added with ice-cooling. The cooling is removed, and the batch is stirred overnight at room temp. The solution is added to ice-water, acidified using 2 N hydrochloric acid and extracted three times with ethyl acetate. The combined org. phases are washed with water and dried over sodium sulfate. The solvent is removed in vacuo, and the residue is recrystallised from toluene/ethyl acetate (2:1), giving 7-hydroxy-3-(4-hydroxyphenyl)chromen-2-one as yellow crystals.