A mixture of ethyl 2-(indolin-6-yl)thiazole-4-carboxylate (28D) (56 mg, 0.14 mmol), K2CO3 (22 mg, 0.16 mmol), and 4-nitrophenyl benzo[d]thiazol-2-ylcarbamate (19) (48 mg, 0.15 mmol) was heated to reflux in acetonitrile (3 mL) for 5.5 hours. The reaction mixture was cooled to rt and diluted in EtOAc (5 mL), washed with water, dried over MgSO4, filtered, and concentrated under reduced pressure. The crude material was purified by column chromatography on silica gel eluting with a gradient of PE/EtOAc (1:1), to provide 22 mg (34%) of the desired product ethyl 2-(1-(benzo[d]thiazol-2-ylcarbamoyl)indolin-6-yl)thiazole-4-carboxylate (28E): 1H NMR (300 MHz, CDCl3) δ 8.67 (1H, s), 8.12 (1H, s), 7.68 (2H, m), 7.52 (1H, m), 7.38 (1H, m), 7.25 (2H, m), 4.43 (2H, q), 4.22 (2H, m), 3.18 (2H, m) 1.45 (3H, t). LC/MS (APCI): m/z 451.1 (M+H).
