Boron tribromide → Apigenin dimethylether

Participants

Reaction Steps

To a solution of 5b (10.0 g, 32.1 mmol) in 200 mL anhydrous CH2Cl2 was added dropwise a 1 M solution of BBr3 (35.3 mL, 35.3 mmol) over 15 min at room temperature with magnetic stirring. A thick yellow precipitate formed rapidly during the addition. After stirring 5 h, the reaction was quenched by adding 200 mL EtOH, and the solvent was then evaporated in vacuo. The yellow residue was triturated with 300 mL boiling 50% EtOH. After cooling to room temperature, the yellow solid was collected on a Büchner funnel, rinsed with 500 mL 50% EtOH and air dried. Recrystallization from 1.5 L EtOH provided 8.16 g (85.4%) of the title product as fine, pale-yellow needles; mp 176-177° C. (lit.25 mp 174-175° C.); 1H NMR (CDCl3) δ 3.88 (s, 3 H), 3.89 (s, 3 H), 6.36 (d, 1 H, J=2.1 Hz), 6.48 (d, 1 H, J=2.1 Hz), 6.57 (s, 1 H), 7.01 (d, 2 H, JAB=9.0 Hz), 7.84 (d, 2 H, JAB=9.0 Hz), 12.81 (s, 1 H); EI-MS m/z 298 (M+, 100). Anal. calcd for C17H14O5: C, 68.45; H, 4.73. Found: C, 68.25; H, 4.77.

Provenance & Evidence