反应详情

2,3,4,5-Tetramethoxy-6-methylbenzaldehyde (17.3 g, 72.1 mmol), malonic acid (22.5 g, 216 mmol) and piperidine (1.7 ml) were dissolved in pyridine (50 ml). The reaction was conducted for 5 hours, while the temperature was gradually raised from 50° C. to 100° C. The solvent was removed under reduced pressure. The residue was acidfified with 2 N hydrochloric acid, extracted and concentrated. Recrystallization of the product from ethyl acetate-isopropyl ether gave 1,2,3,4-tetramethoxy-5-methylcinnamic acid (Compound 20, 14.3 g, 70%). m.p. 117°-118° C. δ 2.31 (3H), 3.78 (3H), 3.83 (3H), 3.90 (3H), 3.96 (3H), 6.59 (1H), 7.94 (1H), 11.2 (1H).

1. temperaturewas gradually raised from 50° C. to 100° C
2. customThe solvent was removed under reduced pressure
3. extractionextracted
4. concentrationconcentrated
5. customRecrystallization of the product from ethyl acetate-isopropyl ether