A solution of the dianion of ethyl acetoacetate (1.42 mL, 11.1 mmoles) in dry tetrahydrofuran (15 mL) was generated as described in Example 10 using 450 mg (11.3 mmoles) of NaH (60% in mineral oil) and 4.5 mL (11.1 mmoles) of 2.5M n-BuLi in hexane at 0° C. under argon. The orange dianion solution, after being chilled to -78° C., was transferred via a cannula into a tetrahydrofuran (15 mL) solution containing 5,5-bis(4-fluoro-3-methylphenyl)-4-(1-methyl-1H-tetrazol-5-yl)-2,4-pentadienal (2.12 g, 5.6 mmoles) at -78° C. The reaction mixture was stirred at -78° C. for 15 minutes. Analytical TLC eluted once with 50% (v/v) ethyl acetate in hexanes showed a major product at Rf =0.16. The reaction mixture was diluted with 20 mL of 1N HCl and the organic residues were extracted with ethyl acetate (30 mL×2). The organic layers were combined, dried over MgSO4 and concentrated under reduced pressure to give a pale syrup. The crude product was chromatographed on a silica gel column eluted with 35% (v/v) ethyl acetate in hexanes to give 1.39 g (48.7%) of the title compound. MS (CI): m/e=511 for (M+H)+.
