To 3.5 ml of diisopropylamine dissolved in 20 ml of tetrahydrofuran and cooled in a -20° C. bath was added 10.0 ml of a 2.5 molar solution n-butyllithium in hexane. After stirring for 5 minutes a solution of 4.0 g of N-(4-trifluoromethoxyphenyl)-3-(4-chlorophenyl)-4-methyl-4,5-dihydro-1H-pyrazole-1-carboxamide in 10 ml of tetrahydrofuran was added and the resulting solution stirred for 15 minutes and then cooled to -78° C. To this solution was added 2.0 ml of methyl formate and, after 5 minutes, 2 ml of acetic acid was added. The reaction mixture was partitioned between diethyl ether and water and the organic layer was dried over anhydrous magnesium sulfate. The resulting solution was filtered, evaporated in vacuo to give 3.9 g of N-(4-trifluoromethoxyphenyl)-3-(4-chlorophenyl)-4-formyl-4-methyl-4,5-dihydro-1H-pyrazole-1-carboxamide. NMR and IR data were consistent with the structure.
