[O:1]=[C:2]1[CH:6]([C:7]([OH:9])=[O:8])[CH2:5][CH2:4][N:3]1[C:10]1[CH:15]=[CH:14][CH:13]=[C:12]([C:16]([F:19])([F:18])[F:17])[CH:11]=1.S(Cl)(Cl)=O.[CH2:24](O)[CH3:25]>>[CH2:24]([O:8][C:7]([CH:6]1[CH2:5][CH2:4][N:3]([C:10]2[CH:15]=[CH:14][CH:13]=[C:12]([C:16]([F:17])([F:19])[F:18])[CH:11]=2)[C:2]1=[O:1])=[O:9])[CH3:25]A mixture of 2-oxo-1-(3-trifluoromethyl-phenyl)-pyrrolidine-3-carboxylic acid obtained in step 1 (0.7 g, 2.56 mmol), thionyl chloride (0.36 g, 3.0 mmol), and ethanol (10 ml) were heated at 55-60° C. for 2 hours. The mixture was cooled and solvent was removed. The residue was dissolved in ethyl acetate (20 ml). The organic layer was washed with sat. NaHCO3 and saturated brine solution, dried over Na2SO4 and evaporated to obtain 2-oxo-1-(3-trifluoromethyl-phenyl)-pyrrolidine-3-carboxylic acid ethyl ester as a yellow oil (0.5 g, 65%).
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