Boron tribromide → 4-[2-(3-Pyridin-3-yl-[1,2,4]oxadiazol-5-yl)-vinyl]-benzene-1,2-diol

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Reaction Steps

To a cooled solution of 0.35 mL of 1M boron tribromide (3.7 mmol) in 2 mL dichloromethane, 0.500 g (1.6 mmol) of 3-{5-[2-(3,4-dimethoxy-phenyl)-vinyl]-[1,2,4]oxadiazol-3-yl}-pyridine (compound of Example 54) dissolved in 5 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 mixture 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.

Provenance & Evidence