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

To a cooled solution of 0.55 mL of 1M boron tribromide (5.8 mmol) in 2 mL dichloromethane, 0.8 g (2.5 mmol) of 3-cyclohexyl-5-[2-(3,4-dimethoxy-phenyl)-vinyl]-[1,2,4]oxadiazole (compound of Example 60) dissolved in 8 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 with 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 washed with 10 mL of 10% sodium chloride solution. The organic layer was distilled to obtain a crude residue, which was purified by column chromatography (silica gel, chloroform-methanol) to yield the title compound.