A solution of (R,E)-2-methyl-N-(4-(pyrimidin-5-yloxy)benzylidene)propane-2-sulfinamide (830 mg, 2.74 mmol) in DCM (6.72 mL) was cooled to −40° C. To the solution was added methylmagnesium bromide (3M in diethylether; 1.81 mL) dropwise over 10 min. Additional DCM (5 mL) were added to retain stirring. The yellow suspension was stirred at −40° C. for ˜30 min while warming to −20° C. The mixture was cooled to −40° C. and additional methylmagnesium bromide (3M in diethylether; 1.8 mL) was added. The suspension was stirred for ˜3 hour while slowly warming to −20° C. The mixture was cooled to ˜−40° C., and additional methylmagnesium bromide (3M in diethylether; 0.4 mL) was added. The suspension was stirred for 30 min and allowed to warm to −10° C. The mixture was quenched slowly over 10 min with saturated aqueous NH4Cl solution (10 mL). The mixture was diluted with saturated aqueous NH4Cl solution (30 mL) and water (15 mL). The separated aqueous phase was extract with DCM (2×75 mL). The combined organic layers were washed with brine (50 mL), dried over Na2SO4, filtered off and concentrated under reduced pressure. The residue was purified by column chouromatography [SiO2, 40 g, heptane/ethyl acetate followed by 5% MeOH in EtOAc] providing 2-methyl-N—((S)-1-(4-(pyrimidin-5-yloxy)phenyl)ethyl)propane-2-sulfinamide (55 mg; purity ˜87%) as an off-white solid. LCMS m/z 320.0 (M+H)+, Rt 0.69 min.
