To a chilled (-78° C., dry ice-acetone) solution of ethyl 3,3-bis (4-fluorophenyl)-2-(1H-tetrazol-5-yl)-2-propenoate (2.6 g, 7.3 mmoles) [prepared in Example 2] in 20 mL of dried N,N-dimethylformamide under argon was added NaH (0.44 g, 11.0 mmoles; 60% in mineral oil) followed by reagent grade 2-iodopropane (2.0 mL, 20.0 mmoles) in one single portion. The thick reaction mixture was stirred under argon at -78° C. for 30 minutes and the mixture was allowed to warm to room temperature slowly over a period of 16 hours. Analytical TLC eluted once with 50% ethyl acetate in hexanes showed only one spot at Rf =0.86. The white suspension was diluted with 40 mL of half saturated brine followed by 20 mL of ethyl acetate. The aqueous layer was washed with ethyl acetate (2×20 mL). The organic layers were combined, dried over MgSO4 and concentrated under reduced pressure. Analytical TLC eluted four times with 8% (v/v) ethyl acetate in hexanes showed two spots at Rf =0.38 (21) and Rf =0.49 (21a). The desired products were purified by silica gel column chromatography eluted with 8% EtOAc in hexanes. The fast moving product was collected to give 1.64 g (56.5%) of the title compound. MS (CI): m/e=399 for (M+H)+.
