A solution of 3-chloro-4-hydroxy-5-methyl-phenyl)-acetic acid methyl ester (6b) (909 mg, 0.004 mol) in anhydrous dimethyl sulfoxide (8 mL) under argon at room temperature was treated with 3,6-dichloro-4-isopropyl pyridazine (7) (1.2 g, 0.006 mol), anhydrous potassium carbonate (1.15 g, 0.008 mol) and copper (I) iodide (239 mg, 0.001 mol). The reaction mixture was heated to 90° C. overnight. At this time, the reaction mixture was cooled to room temperature, poured onto a 1N aqueous hydrochloric acid solution and was extracted with ethyl acetate. The organics were washed with a saturated aqueous sodium chloride solution, dried with magnesium sulfate, filtered and concentrated under vacuum. The resulting residue was purified by column chromatography using silica gel eluted with 10% ethyl acetate in petroleum ether to afford [3-chloro-4-(6-chloro-5-isopropyl-pyridazin-3-yloxy)-5-methyl-phenyl]-acetic acid methyl ester (8b) (1.2 g, 78%) as a yellow solid; EI(+)-HRMS m/z calcd for C17H18Cl2N2O3 (M+) 369.0767, found 369.0766. Molecular Weight=369.2506; Exact Mass=368.0694
