To a solution of (E)-1,1-dimethyl-2-(1,1,1-trifluoropropan-2-ylidene)hydrazine (2.256 g, 14.63 mmol) in dry THF (20 mL) at −78° C. were added n,n,n′,n′-tetramethylethylenediamine (2.190 ml, 14.63 mmol) and lithium diisopropylamide, 2.0m heptane/tetrahydrofuran/ethylbenzene (7.32 ml, 14.63 mmol) and stirred at this temperature for 30 min. A solution of (R,E)-N-(2-fluoro-1-(2-fluoro-3-methylphenyl)ethylidene)-2-methylpropane-2-sulfinamide (2.0 g, 7.32 mmol) in toluene (12 mL) at −78° C. was treated with trimethylaluminum, 2.0m solution in toluene (3.66 ml, 7.32 mmol) for 10 min and added dropwise to the solution containing the hydrazine at −78° C. The resulting mixture was stirred at this temperature for 1.5 h. The mixture was quenched with saturated NH4Cl, and extracted with EtOAc. The combined organics were dried over Na2SO4, filtered, concentrated and chromatographed on silica gel using 0-50% EtOAc/hexanes to afford a bright yellow oil as (R)-N-((Z)-4-(2,2-dimethylhydrazono)-1,5,5,5-tetrafluoro-2-(2-fluoro-3-methylphenyl)pentan-2-yl)-2-methylpropane-2-sulfinamide (5.66 g, 77% yield, combined). MS m/z=427.9 [M+H]+. Calculated for C18H26F5N3OS: 427.17.
