To a solution of 18.0 g (49.3 mmol) of methyl 4-(cyclopropylmethyl)-2-(difluoromethyl)-5-(2-methoxyethenyl)-6-(trifluoromethyl)-3-pyridinecarboxylate (example 127 of U.S. Pat. No. 6,169,432) in 250 ml of ether was added 7.9 g (49.4 mmol) of bromine. The reaction mixture was stirred at room temperature for 2 h and to the mixture was added 6.8 g of freshly ground potassium carbonate and 100 ml of methanol. The reaction mixture was stirred for another 45 min and was washed with water and brine. The organic layer was dried (MgSO4), filtered through celite, and concentrated in vacuo. The residue was kugelrohr distilled and the distillate was purified by chromatography (7% EtOAc in hexane) to give 18.7 g (80% yield) of 1:1 mixture of methyl 5-(1-bromo-2,2-dimethoxy-ethyl)-4-(cyclopropylmethyl)-2-(difluoromethyl)-6-(trifluoromethyl)-3-pyridinecarboxylate and product. HPLC purification (10% EtOAc in hexane) gave 4.1 g of the desired product as a colorless oil which crystallized and was recrystallized from hexane to give crystals, mp 79-79.5° C.
