Aluminium lithium hydride → tert-butyl N-[2-(3,5-difluorophenyl)-1-oxopropan-2-yl]carbamate

To a stirred solution of tert-butyl 2-[(tert-butoxycarbonyl)amino]-2-(3,5-difluorophenyl)propanoate from Step B (2.00 g, 5.60 mmol) in THF (20 mL) at −78° C. was added LiAlH4 (5.60 mL of a 1 M solution in THF, 5.60 mmol), dropwise. The reaction mixture was stirred at −78° C. for 6 h, then quenched with EtOAc (5.6 mL), then H2O (15.6 mL), then 1 N aqueous NaOH (5.6 mL), then EtOAc (17 mL). The reaction mixture was warmed to ambient temperature, stirred for 1 h, filtered, and extracted with EtOAc (2×40 mL). The organic extracts were dried over Na2SO4, filtered, and concentrated in vacuo to afford the title compound in sufficient purity for use in the next step. MS: m/z=186 (M−CO2C4H7).