Potassium Carbonate → ethyl 6-nitro-2-(trifluoromethyl)-2H-1-benzopyran-3-carboxylate

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A mixture of 5-nitrosalicylaldehyde (4.80 g, 28.7 mmol) and ethyl 4,4,4-trifluorocrotonate (6.6 g, 39.4 mol) in anhydrous DMF was warmed to 60° C. and treated with anhydrous K2CO3 (3.90 g, 28.9 mol). The solution was maintained at 60° C. for 20 hours, cooled to room temperature, diluted with water, and extracted with ethyl acetate. The organic extracts were washed with brine, dried over anhydrous MgSO4, filtered and concentrated in vacuo to afford an oil. The oil was dissolved in diethyl ether (5 mL). Hexanes was added until the solution became cloudy. Upon standing at room temperature overnight the ester was obtained as yellow crystals (0.856 g, 7% yield). This material was of sufficient purity to be used in subsequent steps without further purification. 1H NMR (CDCl3/300 MHz) 8.15–8.19 (m, 2H), 7.74 (s, 1H), 7.09 (d, 1H, J=8.9 Hz), 5.81 (q, 1H, J=5.8 Hz), 4.29–4.39 (m, 2H), 1.35 (t, 3H, J=6.0 Hz),

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