[OH:1][CH:2]([CH2:8][CH:9]([CH3:11])[CH3:10])[C:3]([O:5][CH2:6][CH3:7])=[O:4].[F:12][C:13]1[N:18]=[C:17]([F:19])[C:16]([F:20])=[C:15](F)[C:14]=1[F:22].C(=O)([O-])[O-].[Cs+].[Cs+].O>CN(C=O)C.C(OCC)(=O)C>[CH2:6]([O:5][C:3]([CH:2]([O:1][C:15]1[C:14]([F:22])=[C:13]([F:12])[N:18]=[C:17]([F:19])[C:16]=1[F:20])[CH2:8][CH:9]([CH3:10])[CH3:11])=[O:4])[CH3:7]To a solution of ethyl 2-hydroxy-4-methylvalerate (0.50 g, 2.5 mmol) in dry DMF (25 mL) was added pentafluoropyridine (0.31 mL, 0.47 g, 2.8 mmol) and cesium carbonate (1.1 g, 3.3 mmol). The resultant mixture was heated to 45° C. and stirred at that temperature for 10 days, then poured into 100 mL of water and 100 mL of ethyl acetate. The aqueous layer was separated and extracted with another 500 mL of ethyl acetate. The combined organic extracts were washed with water (100 mL) then brine (100 mL), dried over MgSO4, filtered, and concentrated in vacuo to afford 0.87 g (99% yield) of 4-(1-ethoxycarbonyl-3-methylbutyl)oxy-2,3,5,6-tetrafluoropyridine as a clear, yellow liquid: NMR (CDCl3) 5.2 (d, 1), 4.3-4.1 (m, 3), 2.0 (m, 1), 1.8 (m, 1) 1.3 (m, 3), 1.0 (m, 6) ppm.
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