5,6,7,4'-Tetramethoxyflavone → Benzaldehyde, 4-(phenylmethoxy)-

Participants

Reaction Steps

Similar to the preparation of 1c, 1e (4′-benzyloxy-5,6,7-trimethoxyflavone) was prepared from 6-hydroxy-1-(4-benzyloxycinnamoyl)-2,3,4-trimethoxybenzene (6b), which, in turn, was obtained from the reaction of the acetophenone 5 and 4-benzyloxybenzaldehyde. A solution of 1e (500 mg, 1.20 mmol) in 48% HBr (5 mL) and glacial acetic acid (10 mL) was refluxed for 2 h. Then, the reaction mixture was poured onto crushed ice (ca. 100 g). The resulting precipitate was filtered and washed with water. Recrystallization from ethanol furnished compound 1f (305 mg, 85%). 1H NMR (DMSO, 200 M Hz) δ 12.63 (br s, 1H), 10.30 (br s, 1H), 8.70 (br s, 1H), 7.93 (d, J=8.8 Hz, 2H), 6.92 (d, J=8.8 Hz, 2H), 6.88 (s 1H), 6.78 (s 1H), 3.90 (s, 3H); 13C NMR (DMSO, 50 M Hz) δ 182.2 (s), 163.8 (s), 161.1 (s), 154.3 (s), 149.6 (s), 146.2 (s), 129.9 (s), 128.4 (d, 2C), 121.4 (s), 116.0 (d, 2C), 105.0 (s), 102.5 (d), 91.1 (d), 56.3 (q). The stereochemistry of compound 1f was confirmed by cosy and nosy experiments.

Provenance & Evidence