Potassium Carbonate → Ethyl 7-(4-carbamoyl-2-nitrophenoxy)-6-chlorochroman-4-carboxylate

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To a stirred solution of ethyl 6-chloro-7-hydroxychroman-4-carboxylate (6.40 g, 24.9 mmol) and 4-chloro-3-nitrobenzamide in N,N′-dimethylformamide (75 mL) at ambient temperature was added potassium carbonate (8.61 g, 62.3 mmol). An argon balloon with purge valve was attached, and the stirred mixture was evacuated and purged 5 times with argon. The mixture was stirred in an oil bath at 90° C. under argon. After 15 hours the reaction mixture was cooled to ambient temperature, then poured into a reparatory funnel containing water (1000 mL) and the extracted with ether (2×1000 mL). The organic layers were combined and dried over sodium sulfate, then evaporated to give 10.5 g of brown semi-solid. The crude material was purified by silica gel column chromatography, eluting with 99/1 chloroform/methanol followed by 98/2 chloroform/methanol to provide the desired product (7.74 g, 74%).

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