Boron tribromide → HCID 136413223, Verbindung

To a cooled solution of 2.09 mL of 1M boron tribromide (2.0 mmol) in 2 mL dichloromethane, 0.300 g (0.9 mmol) of 5-[2-(3,4-dimethoxy-phenyl)-vinyl]-3-heptyl-[1,2,4]oxadiazole (compound of Example 51) dissolved in 1 mL of dichloromethane was added over a period of 15-20 min at −45° C. to −40° C. The reaction mixture was stirred at −45° C. to −40° C. for 30-45 min and allowed to attain a temperature of 25° C. to 30° C. slowly, over a period of 1 h. The reaction mixture was further stirred at 25° C. to 30° C. for 4-5 h. After completion of the reaction, the reaction mixture was quenched in 10 mL of chilled 5% sodium bicarbonate solution, below 20° C. (pH: 8-9). 10 mL of ethyl acetate was added to the reaction mass to dissolve the solid and stirred for 10-15 min. The organic layer was separated and the aqueous layer was washed with 10 mL of 10% sodium chloride solution. The organic layer was collected and distilled to obtain a crude residue, which was purified by column chromatography (silica gel, chloroform-methanol) to yield the title compound.