A mixture of ethyl 2-[(2′-cyano-3-fluorobiphenyl-4-yl)methyl]-3-oxohexanoate (408 g) and N-(1,4-dioxaspiro[4.5]dec-8-yl)-4H-1,2,4-triazol-3-amine (125 g) were dissolved in N,N-diethylaniline (1.5 L) at 160° C. (internal temperature). A solution of 1,8-diazabicyclo[5.4.0]undec-7-ene (38 mL) in N,N-diethylaniline (400 mL) was added dropwise over 30 min, and the mixture was stirred at 180° C. (internal temperature) for 22 hr. The reaction mixture was cooled to room temperature, and ethyl acetate (1 L) and 3M hydrochloric acid (1 L) were added. The mixture was transferred into a separatory funnel with ethyl acetate (2 L) and 3M hydrochlorid acid (1 L). The organic layer was successively washed with 3M hydrochloric acid (2 L) twice and brine (2 L), dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The obtained residue was purified by silica gel chromatography to give the title compound as a brown solid (246 g, 84%).
