Boron tribromide → HCID 66798199, compound

Participants

Reaction Conditions

Reaction Steps

5.23 g (18.8 mmol) of 4,7-difluoro-3,8-dimethoxy-6H-benzo[c]chromene (prepared by the method of: Taugerbeck, Klasen-Memmer, WO 2004076438) are initially introduced in 70 ml of dichloromethane, and a solution of 5 ml (52.7 mmol) of boron tribromide in 10 ml of dichloromethane is added dropwise with ice cooling. After 1 h, the cooling is removed, and the batch is left to stir at room temp. for 3 h and added to ice-cold 1 M sodium hydroxide solution. The aqueous phase is separated off and extracted three times with ethyl acetate. The combined org. phases are washed with sat. sodium chloride soln. and dried over sodium sulfate. The solvent is removed in vacuo, the residue is filtered through silica gel with toluene/ethyl acetate (3:2), and the crude product is washed by stirring with hot heptane/ethyl acetate (2:1) and filtered off with suction after cooling to 8° C., giving 4,7-difluoro-6H-benzo[c]chromene-3,8-diol as colourless solid.

Provenance & Evidence