Diethyl Carbonate → 6,8-Dibromo-4-hydroxy-2H-1-benzopyran-2-one

Participants

Reaction Conditions

Reaction Steps

A solution is prepared of diethylcarbonate (62.5 mmol, 7.6 mL) in 150 mL of toluene to which is added NaH (37.5 mmol, 1.5 g of 60% dispersion in mineral oil) in portions. To this solution is added, dropwise, 3′,5′-dibromo-2′-hydroxyacetophenone (12.5 mmol, 3.67 g) in 50 mL of toluene. The reaction is heated to 105° C. overnight, cooled to ambient temperature, 100 mL of 1N NaOH, is added and the reaction is stirred vigorously for 5 hrs at ambient temperature. The layers are separated and the aqueous layer is washed with EtOAc 2×. The combined organic layers are washed with H2O 1×. The combined aqueous layers are acidified to pH 2 with conc HCl to form a precipitate that is filtered and is washed with H2O. The solid material is dissolved in ACN/H2O and speed vacced to dryness to afford the title compound as a light tan solid (0.737 g, 18%). 1H NMR (DMSO-d6, 300 MHz) δ 12.98 (1H, br s), 8.18 (1H, d, J=2.25 Hz), 7.90 (1H, d, J=2.25 Hz), 5.64 (1H, s); MS (ESI, Pos.) calcd for C9H4Br2O3 m/z [M+H]=318.9, found 318.9.

Provenance & Evidence