Ethyl 3-methyl-5-[4-(trifluoromethyl)phenyl]thiophene-2-carboxylate (intermediate 35, 0.100 g) and sodium bromate (0.144 g) were suspended in a mixture of cyclohexane and water (1:1 v/v, 4 ml). To this was added a solution sodium bisulfite (0.99 g) in water (1 ml). The mixture was stirred for 2 hours, quenched with 1M sodium thiosulfate solution, then extracted with ethyl acetate. The organic layer was taken and washed with water, sodium thiosulfate and dried with brine and over MgSO4 and concentrated to give the title compound as a white crystalline solid.
