To a solution of 2-chloro-N1-(1-(4-chloro-3-fluorophenyl)-2-methylpropan-2-yl)benzene-1,4-diamine (408 mg, 1.25 mmol) in toluene (15 mL) was added trimethylaluminium (2.5 mL, 5.00 mmol, 2.0 M in toluene) dropwise under N2 and the mixture was stirred at rt for 30 min after addition was completed. A solution of (Z)-methyl 3-(2-(3-fluorophenoxy)acetamido)but-2-enoate (295 mg, 1.88 mmol) in toluene (5 mL) was added slowly and the resulting mixture was stirred at rt for 22 h. Trimethylaluminium (2.0 mL, 4.00 mmol, 2 M in toluene) was then added dropwise and the mixture was stirred at rt for 30 min. A solution of (Z)-methyl 3-(2-(3-fluorophenoxy)acetamido)but-2-enoate (295 mg, 1.88 mmol) in toluene (3 mL) was added and the mixture was stirred further for 18 h. The mixture was quenched with saturated NH4Cl aqueous solution (50 mL) and filtered and the organic phase was separated from the filtrate. The aqueous phase was extracted with EtOAc (30 mL×3). The combined organic layers were washed with brine (30 mL×2), dried over anhydrous Na2SO4 (15 g) and concentrated in vacuo. The residue was purified by a silica gel column chromatography (PE/EtOAc (V/V)=2:3) to give the title compound as a yellow solid (183 mg, 33.7%). The compound was characterized by the following spectroscopic data:
