Synthesis of Compound A.6: To a solution of 2-amino-4-trifluoromethylpyridine (2.00 g, 12.3 mmol) in N,N-dimethylformamide (DMF, 4 mL) was slowly added a solution of 1,3-dichloro-5,5-dimethylglycolide (1.4 g, 7.4 mmol) in DMF (4 mL). The reaction mixture was stirred at room temperature for 2 hours. After completion of the reaction, the mixture was diluted with ether (80 mL) and washed with deionized water (10 mL). The organic phase was separated, dried over anhydrous sodium sulfate and concentrated under reduced pressure to give the crude product. The crude product was purified by fast column chromatography (eluent: 0-20% ethyl acetate/hexane) to afford compound A.6 as a light yellow oil in 65% yield.1H NMR (DMSO-d6) δ: 8.16 (s, 1H), 6.87 (s, 1H), 6.76 (br s, 1H); MS: m/z 197 [M + H]+.
