To 1.5 g of zinc dust (23.8 mmole) and 5.2 g of triphenylphosphine (20 mmole) in 20 ml of methylene chloride was added 6.8 g of carbon tetrabromide (20 mmole) after stiring for 90 minutes a solution of 3 g of N-(4-trifluoromethoxyphenyl)-3-(4-chlorophenyl)-4-formyl-4-methyl-4,5-dihydro-1H-pyrazole-1-carboxamide in 10 ml of MeCl2 is added and the mixture is stirred an additional 60 minutes. The reaction is partitioned between ether and aqueous sodium thiosulfate, dried, rotovaped and chromatographed (ether/hexane) to yield 2.0 g of N-(4-trifluoromethoxyphenyl)-3-(4-chlorophenyl)-4-(2,2-dibromovinyl)-4-methyl-4,5-dihydro-1H-pyrazole-1-carboxamide an oil. NMR data was consistent with the structure.
