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A solution of 16.4 g (0.2 mol) of monoethyl malonate, 0.1 g of 2,2'-bipyridyl and 175 ml of dry tetrahydrofuran was cooled to -35° under a dry nitrogen atmosphere and treated dropwise with 80 ml (0.2 mol) of a 2.5 M solution of n-butyl lithium in hexane. After the addition was complete, the reaction mixture was allowed to warm to -5° where it was treated dropwise with 80 ml (0.2 mol) of 2.5 M n-butyl lithium in hexane, titrating the final addition to a pale pink color which persisted for 5 minutes. The mixture was cooled to -78° and treated with a solution of 16.7 g (50 mmol) of 1-[[4-(1,4-dioxaspiro[4.4]non-7-yl)-2,5-difluorophenyl]carbonyl]-1H-imidazole in 100 ml of dry tetrahydrofuran. The suspension was stirred at -78° for 45 minutes, then allowed to warm to -35° and poured into a mixture of ice, water, and concentrated hydrochloric acid (17.0 ml-0.2 mole). The organic layer was separated, washed with water, 5% sodium bicarbonate, dilute hydrochloric acid, and water. After drying over magnesium sulfate, the solvent was removed in vacuo to give 13.8 g of the title compound.

1. additionAfter the addition
2. temperatureto warm to -5° where it
3. additionaddition to a pale pink color which
4. temperatureThe mixture was cooled to -78°
5. temperatureto warm to -35°
6. customThe organic layer was separated
7. washwashed with water, 5% sodium bicarbonate, dilute hydrochloric acid, and water
8. dry with materialAfter drying over magnesium sulfate
9. customthe solvent was removed in vacuo