To a suspension of 3,4-dichloroisothiazole-5-carboxylic acid (0.15 g, 0.76 mmol) in oxalyl chloride (2 mL) was added a catalytic amount of dimethylformamide (2 drops) and the mixture was heated to 80° C. and stirred for 2 h. The excess oxalyl chloride was removed on the rotary evaporator. Meanwhile, 5-fluoro-2-(4-fluorobenzyloxy)-pyrimidin-4-ylamine (0.17 g, 0.68 mmol) was dissolved in THF (1 mL), treated with LiHMDS (1M in THF, 0.76 mL, 0.76 mmol) and stirred for 10 min. The freshly prepared 3,4-dichlorothiazole-5-carbonyl chloride*, dissolved in THF (1 mL), was added and the reaction was capped and stirred for 12 h. The reaction was diluted with water and the target compound was extracted with CH2Cl2 (3×5 mL). The combined extracts were dried over MgSO4 and then evaporated under reduced pressure. The mixture was eluted with CH2Cl2 through an anionic-exchange solid phase extraction column and then further purified by reverse-phase chromatography to give 3,4-dichloroisothiazole-5-carboxylic acid [5-fluoro-2-(4-fluorobenzyloxy)pyrimidin-4-yl]amide (0.035 g, 12%) as a tan solid: mp 87-90° C.; 1H NMR (400 MHz, DMSO-d6) δ 11.78 (s, 1H), 8.67 (s, 1H), 7.51-7.48 (m, 2H), 7.24-7.19 (m, 2H), 5.25 (s, 2H); MS (ESI) m/z 417 (M+H)+, 415 (M−H)−. *Nagata, T.; Kogure, A.; Yonekura, N.; Hanai, R.; Kaneko, I.; Nakano, Y. JP 2007211002 A
