To a deoxygenated solution of compound 2-bromo-4-nitroaniline (9.43 g, 43.7 mmol), methyl 2,2-dimethylbut-3-ynoate (5.00 g, 39.7 mmol), CuI (754 mg, 3.97 mmol) and triethylamine (8.03 g, 79.4 mmol) in toluene/H2O (100/30 mL) was added Pd(PPh3)4 (6.17 g, 3.97 mmol) under N2. The mixture was heated at 70° C. and stirred for 24 h. After cooling, the solid was filtered off and washed with EtOAc (50 mL×3). The organic layer was separated and the aqueous phase was washed with EtOAc (50 mL×3). The combined organic layers were dried and evaporated under reduced pressure to give a residue, which was purified by column chromatography on silica gel (petroleum ether/ethyl acetate=10/1) to obtain methyl 4-(2-amino-5-nitrophenyl)-2,2-dimethylbut-3-ynoate (900 mg, 9%). 1H NMR (400 MHz, CDCl3) δ 8.17 (d, J=2.8 Hz, 1H), 8.01 (dd, J=2.8, 9.2 Hz, 1H), 6.65 (d, J=9.2 Hz, 1H), 5.10 (brs, 2H), 3.80 (s, 3H), 1.60 (s, 6H).
