The product from Step 1 (HCl salt, 187 mg, 0.408 mmol), HOBT (125 mg, 0.815 mmol), and EDC (156 mg, 0.815 mmol) were combined with dioxane (5 mL) and stirred for 5 min at room temperature. Formic acid hydrazide (73 mg, 1.223 mmol) and DIEA (105 mg, 0.815 mmol) were subsequently added. The reaction was stirred overnight at room temperature. The reaction was diluted with water and extracted with ethyl acetate (2×). The combined organic layers were washed with brine, dried (Na2SO4), filtered and evaporated. Column chromatography on silica (50-100% EtOAc/hexanes) afforded N′-formyl-2-methyl-2-[5-(3-methyl-5-{[4-(trifluoromethyl)pyrimidin-2-yl]amino}phenyl)-1,3-thiazol-2-yl]propanehydrazide (87 mg, 46%) as a colorless solid. MS ESI: [M+H]+ m/z 465.0.
