Trifluoroacetic acid → 5-(S)-azidomethyl-3-(4'-carboxy-3'-fluorophenyl)oxazolidine-2-one

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Reaction Steps

60% TFA in DCM (5 mL) was added to 5-(S)-azidomethyl-3-[4′-tert-butoxycarbonyl-3′-fluorophenyl]oxazolidine (0.336 g, 1 mmol), and the solution kept at r.t. for 1 h. Solvents were removed in vacuo to afford 5-(S)-azidomethyl-3-[4′-carboxy-3′-fluorophenyl-]oxazolidine-2-one dried (0.280 g, 99%). N-Trimethylsilyl-N,N-diethylamine (0.23 mL, 1.2 mmol) was added to above product in dry dichloromethane (3 mL) under nitrogen atmosphere, and the solution stirred for 15 min. Solvents and excess reagent were removed in vacuo, and residue dissolved in dichloromethane (4 mL). The solution was cooled to about 0° C., and oxalyl chloride (1.5 mmol, 0.13 mL) was added dropwise, followed by catalytic N,N-dimethylformamide (about 0.01 mL). The mixture was allowed to warm up to r.t. (room temperature), and stirred at r.t. for another 2 h. Solvents were removed in vacuo to afford the product as a white solid. Yield 0.292 g (98%).

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