3-Amino-3-methylpyridine (9 mg), cesium carbonate (45 mg), Pd2(dba)3 (10 mg), and Xantphos (12 mg) were added to a dioxane (3 ml) solution containing benzyl 4-((6-chloro-5-cyano-3-fluoropyridin-2-yl)amino)-3-(1,3-dioxoisoindolin-2-yl)piperidin-1-carboxylate (37 mg), followed by microwave irradiation (Initiator™, 160° C., 10 minutes, 2.45 GHz, 0-240 W). The obtained residue was filtered through Celite and filter cake was washed with ethyl acetate. Subsequently, the solvent was distilled away from the filtrate under reduced pressure. The obtained residue was purified by silica gel column chromatography (hexane:ethyl acetate=4:1 to 1:1). Yellow oily matter of benzyl 4-((5-cyano-3-fluoro-6-((5-methylpyridin-3-yl)amino)pyridin-2-yl)amino)-3-(1,3-dioxoisoindolin-2-yl)piperidin-1-carboxylate (28 mg) was thus obtained.
