C([N-]C(C)C)(C)C.[Li+].[F:9][C:10]1[CH:15]=[CH:14][CH:13]=[C:12]([F:16])[N:11]=1.Cl[C:18]([O:20][CH3:21])=[O:19].O>O1CCCC1>[F:9][C:10]1[C:15]([C:18]([O:20][CH3:21])=[O:19])=[CH:14][CH:13]=[C:12]([F:16])[N:11]=1To a stirred solution of 91 ml (0.182 mol) of 2.0 molar lithium diisopropylamide (in hexanes) in 200 mL dry tetrahydrofuran cooled to -70° under nitrogen was added dropwise a solution of 20.0 g of 2,6-difluoropyridine (0.174 mol) in 75 mL dry tetrahydrofuran such that the temperature was maintained below -60°. The solution was stirred at -70° for 3 hours and was then added via a cannula to a solution 21.7 g (0.230 mol) of methyl chloroformate in 100 mL dry tetrahydrofuran cooled to -70° under nitrogen. After stirring another hour at -70°, the mixture was poured into water and extracted with ether. The combined organic layers were washed with brine, dried over magnesium sulfate, and evaporated to a semisolid which was purified by flash chromatography to afford 13.0 g (43%) orange oil: NMR (CDCl3, 200 Mhz) 3.95 (3H, s), 6.9 (1H, m), 8.5 (1H, m); IR (neat) 1745, 1730, 1610, 1415, 1290 cm-1.
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