To a solution of pentafluoropyridine (1.9 g, 11.2 mmol) in acetonitrile (25 mL) at 0° C. was added methyl thioglycolate (1.0 mL, 11.2 mmol) and cesium carbonate (4.4 g, 13.5 mmol). The resultant mixture was allowed to warm slowly to ambient temperature and stirred for 16 hours. To the mixture was added 2-benzyloxy-5-cyanophenol (2.6 g, 11.5 mmol) and cesium carbonate (4.4 g, 13.5 mmol). The resultant mixture was stirred at 40° C. for 16 hours. The mixture was then cooled to ambient temperature and poured into 150 mL of 0.5 M aqueous KOH solution and 150 mL of ethyl acetate. The organic layer was separated and washed further with 150 mL of 0.5 M aqueous KOH solution, then brine (150 mL), dried over MgSO4, filtered, and concentrated in vacuo to afford a yellow oil. Purification by flash chromatography on silica gel afforded 2.9 g (56% yield) of 4-benzyloxy-3-[(4-(methoxycarbonylmethyl)thio-3,5,6-trifluoropyridin-2-yl)oxy]benzonitrile, a compound of formula (E), as a pale yellow oil: NMR (CDCl3) 7.5-7.0 (m, 8), 5.1 (s, 2), 3.8 (s, 2), 3.7 (s, 3) ppm.
