Hydrofluoric Acid → 7,8-Dichloro-3,4-dihydro-2H-1-benzopyran-4-one
Reaction equation
[Cl:1][C:2]1[C:13]([Cl:14])=[CH:12][CH:11]=[CH:10][C:3]=1[O:4][CH2:5][CH2:6][C:7]([OH:9])=O.F>>[Cl:14][C:13]1[C:2]([Cl:1])=[C:3]2[C:10]([C:7](=[O:9])[CH2:6][CH2:5][O:4]2)=[CH:11][CH:12]=1Participants
3
Procedure
500 mg of 3-(2,3-dichlorophenoxy)propionic acid, is stirred in 50 ml. of liquid hydrogen fluoride surrounded by a solid carbon dioxide/acetone bath. This slurry is allowed to stir overnight without replenishing the cooling bath. The hydrogen fluoride is removed by a stream of air. The residual solid was then dissolved in ether and washed with 10% aqueous sodium carbonate solution. The organic layer is dried over anhydrous magnesium sulphate and the solvent is evaporated to give the required chromanone with sufficient purity.
Workup
- customThe hydrogen fluoride is removed by a stream of air
- dissolutionThe residual solid was then dissolved in ether
- washwashed with 10% aqueous sodium carbonate solution