Hydrazine hydrate (1:1) → (S)-5-(aminomethyl)-3-(3-fluoro-4-iodophenyl)oxazolidin-2-one

A solution of (5R)-2-[3-(3-fluoro-4-iodo-phenyl)-2-oxo-oxazolidin-5-ylmethyl]-isoindole-1,3-dione (1021, 23.3 g, 50.0 mmol) in ethanol (EtOH, 150 mL) was treated with hydrazine monohydrate (12.52 g, 12.1 mL, 250 mmol, 5.0 equiv) at 25° C., and the resulting reaction mixture was warmed up to reflux for 2 h. White precipitates were formed while the reaction mixture was refluxed. When TLC and HPLC showed that the reaction was complete, the reaction mixture was cooled down to room temperature before being quenched with H2O (100 mL). The white precipitates were totally dissolved when water was introduced into the reaction mixture and a homogeneous solution was generated. The aqueous solution was then extracted with CH2Cl2 (3×200 mL), and the combined organic extracts were washed with H2O (2×100 mL) and saturated NaCl aqueous solution (100 mL), dried over MgSO4, and concentrated in vacuo. The residue was further dried in vacuo to afford the crude (5S)-5-aminomethyl-3-(3-fluoro-4-iodo-phenyl)-oxazolidin-2-one (1022, 16.0 g, 16.8 g theoretical, 95.2%) as white powders, which were found to be essentially pure and was directly used in the subsequent reactions without further purifications. For 1022: C10H10FIN2O2, LCMS (EI) m/e 337 (M++H).