Sodium hydride (60% dispersion in oil, 2.16 g, 54.1 mmol) was added to anhydrous THF (50 mL) and cooled to 0° C. under nitrogen. Di-tert-butyl malonate (4.65 g, 24.8 mmol) was added dropwise and the reaction mixture was stirred 15 min and allowed to warm to RT. The reaction was cooled to 0° C. and 3-chloro-5-[(2,3-difluoro-6-nitrophenyl)oxy]benzonitrile (7.0 g, 22.5 mmol) was added dropwise in a minimal amount of THF. The reaction was allowed to warm to RT and stirred for 3 h then 10% aqueous citric acid (50 ml) and EtOAc (50 mL) were added. The layers were separated and the aqueous layer was extracted with EtOAc (2×50 mL). The organic extracts were combined, washed with brine, dried over Na2SO4, filtered and evaporated to afford the title compound as an oil. 1H NMR (400 MHz, DMSO-d6): 6 ppm 8.13 (dd, 1H), 7.84 (d, 1H), 7.65 (dd, 1H), 7.59-7.61 (m, 1H), 7.56-7.59 (m, 1H), 5.10 (s, 1H), 1.40 (s, 18H). MS: m/z 507.2 (M+1).
