Trifluoroacetic acid → (2S,4R)-methyl 4-(2-chlorophenylsulfonyl)pyrrolidine-2-carboxylate

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Reaction Steps

To an ice cold solution of (2S,4R)-4-(2-chloro-benzenesulfonyl)-pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester 2-methyl ester (2.97 g, 7 mmol; example 14) in dichloromethane (25 ml) was added trifluoroacetic acid (2.82 ml, 37 mmol) under an argon atmosphere. The reaction mixture was stirred for 14 h at ambient temperature. The solvent was removed under reduced pressure. The residue was dissolved in iPrOAc (200 ml) and cooled to 0° C. Saturated aqueous sodium carbonate solution (100 ml) was carefully added and the layers were separated. The aqueous layer was extracted two more times with iPrOAc, the combined organic layers were washed with ice water and brine and dried over sodium sulfate. The solvent was removed under reduced pressure to give the title compound (1.8 g, 7 mmol; 81%) as red oil which was sufficiently pure to be used in the next step. MS (ESI): m/z=304.1 [M+H]+.

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