To a mixture of 3-[[2-fluoro-5-(3-fluorophenyl)phenyl]methylamino]phenol (300 mg, 0.96 mmol, 1.0 eq.) and t-BuOK (216 mg, 1.90 mmol, 2.0 eq) in DMF (3 mL) was added dropwise ethyl bromoacetate (193 mg, 128 uL, 1.20 mmol, 1.2 eq) at 0° C. The resulting mixture was stirred for 1 h at room temperature. The reaction was quenched with water and neutralized with 1 M HCl. The aqueous layer was extracted with EtOAc and the combined organic extracts were washed with brine, dried (Na2SO4), filtered and evaporated in vacuo. The residue obtained was purified by chromatography (petroleum ether: EtOAc, 4:1) to give the title compound as a colourless oil (200 mg, 52%).
