FC(F)(F)S([O-])(=O)=O.[Mg+2].FC(F)(F)S([O-])(=O)=O.[O:18]1[CH2:20][C@H:19]1[C:21]([O:23][CH3:24])=[O:22].[CH2:25]([OH:27])[CH3:26]>C(Cl)Cl>[CH2:25]([O:27][CH2:20][C@H:19]([OH:18])[C:21]([O:23][CH3:24])=[O:22])[CH3:26]Magnesium trifluoromethanesulphonate (11.85 g, 36.73 mmol) was added in one portion to (S)-methyl oxirane-2-carboxylate (15.0 g, 146.93 mmol) and ethanol (10.29 ml, 176.32 mmol) cooled to 10° C. The resulting suspension was stirred at 10° C. for 20 minutes, allowed to warm to ambient temperature and then warmed to 50° C. for 30 hours. The mixture was allowed to cool and diluted with 9:1 DCM:ether (75 mL), filtered through Celite and washed through with 9:1 DCM:ether (3×50 mL) and evaporated. The residue was purified by flash silica chromatography, elution gradient 10 to 50% Et2O in DCM to give methyl (2S)-3-ethoxy-2-hydroxypropanoate (11.6 g, 53%). 1H NMR (400 MHz, CDCl3) δ 1.19 (3H, t), 3.00 (1H, d), 3.47-3.58 (2H, m), 3.72 (2H, d), 3.81 (3H, s), 4.23-4.34 (1H, m).
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