Ethyl formate → 7-(3-Carboxypropyl)-9-formyl-9H-fluorene-4-carboxylic acid

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Reaction Steps

In a dry argon-purged flask with a reflux condenser, 7-(3-carboxy-propyl)-4-fluorenecarboxylic acid (4.0 g, 0.0135 mol) was dissolved in anh. DMF (120 mL) at 40° C. Ethyl formate (40 mL, stored over K2CO3 anh.) was added followed by addition of potassium tert-butoxide 95% (12.8 g, 0.108 mol, added in 2 portions). The reaction was stirred at about 40° C.-50° C. for four hours with the addition of anh. DMF (80 mL), anhydrous THF (5 mL) and ethyl formate (25 mL) at various intervals to aid solubility. The reaction was then stirred another 17 hours at room temperature. The ethyl formate was evaporated at reduced pressure. The reaction was quenched with water (150 mL) and acidified to pH 2 with concentrated HCl. The product was twice extracted with ethyl acetate (600 mL then 200 mL). The combined organic layers were washed 3 times with brine, dried over sodium sulfate, filtered and evaporated to dryness. The crude product (4.7 g, ˜100%, purity 80%) contained some unreacted starting material. 1H-NMR (d6-DMSO): δ (ppm) 11.4 (s, 1H, formyl); 8.3-7.0 (m, 7H, Ar); 2.7 (m, 2H, CH2); 2.3 (m, 2H, CH2); 1.9 (m, 2H, CH2).

Provenance & Evidence