Water → 2,6-Difluoro-nicotinic acid methyl ester

Participants

Reaction Steps

To 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.

Provenance & Evidence