Trifluoroacetic acid → 1-(4-(3-(4-(5-Chloropyridin-2-ylamino)phenoxy)pyrazin-2-YL)piperidin-1-YL)ethanone

A solution of tert-butyl 4-(3-(4-(5-chloropyridin-2-ylamino)phenoxy)pyrazin-2-yl)piperidine-1-carboxylate (0.14 g, 0.29 mmol) in dichloromethane (1 mL) was added trifluoroacetic acid (0.22 mL, 2.9 mmol) and stirred at room temperature for 2 h. The reaction was concentrated in vacuo, and the residue was partitioned between CH2Cl2 and aqueous saturated NaHCO3 solution. The organic layer was dried (MgSO4), filtered, and concentrated in vacuo to give a golden yellow oil. A solution of the crude golden yellow oil in CH2Cl2 (1 mL) was cooled to 0° C. and added acetic anhydride (0.041 mL, 0.43 mmol). The reaction was gradually allowed to warm to room temperature and stirred for 1 h. The reaction was diluted with CH2Cl2 and washed with aqueous saturated NaHCO3 solution. The organic layer was dried (MgSO4), filtered, and concentrated in vacuo. Flash column chromatography (20% to 70% EtOAc/Hexanes) provided a crude crop of the desired product. Further purification via reverse phase HPLC afforded 1-(4-(3-(4-(5-chloropyridin-2-ylamino)phenoxy)pyrazin-2-yl)piperidin-1-yl)ethanone as an off-white amorphous solid. MS (ESI, pos. ion) m/z: 424.9 (M+1). IC50 (uM) 0.001.