Diethyl Carbonate → 4-Hydroxycoumarin

Participants

Reaction Steps

To a stirred suspension of sodium hydride (Aldrich, 60% dispersion in mineral oil) (1.2 g, 30.0 mmol) and diethyl carbonate (Aldrich) (5.9 g, 50 mmol) in anhydrous benzene (Aldrich) (100 mL) under a dry nitrogen atmosphere was added dropwise a solution of 5'-fluoro-2'-hydroxy-acetophenone (Aldrich) (1.54 g, 10 mmol) in anhydrous benzene. The mixture was then refluxed under a nitrogen atmosphere overnight. The reaction mixture was cooled and 50 mL 1N NaOH was added. The mixture was stirred at room temperature for 1 hour. The aqueous layer was separated and washed with ether (100 mL×2). The dark solution was acidified to pH 2 with 6N HCl. The white precipitate was collected by filtration, washed with water and dried to afford product (4) (4-hydroxy-6-fluoro-coumarin) as an off-white solid (1.38 g, 7.66 mmol, 77%). 300-MHz 1H-NMR (CDCl3) δ 5.79 (s,1H), 7.25-7.28 (m,2H), 7.52 (d,1H). Mass/EI: 179 (M-H).

Provenance & Evidence