(601b) Efficient Microwave-Assisted Synthesis of a Series of Polyhydroxylflavones

Polyhydroxylflavones are a kind of natural products, which have significant anticancer, anti-oxidation, anti-inflammatory and physiological activity. In this paper, a series of polyhydroxylflavones were synthesized starting from substituted benzoic acid and 2-hydroxyl-4-methoxyacetophenone by acylation, esterification, Baker-Venkataraman rearrangement,cyclization and demethylation. Microwave irradiation was applied in cyclization which was the key step in synthesis of polyhydroxylflavones. The effects of the substrate concentration,reaction pressure,microwave irradiation time and catalyst concentration on the yields were investigated in microwave-assisted cyclization. The optimum conditions were obtained. The use of microwaves was found to significantly improve product yields and shorten the reaction time of cyclization. This route is eco-friendly and high selectivity. Under the optimum reaction conditions, the target products were obtained in overall yields of 40% ~ 48% and purity of more than 96%. The structures of the compounds were confirmed by IR, ¹H NMR and MS. These target compounds, such as 7,3',4'-trihydroxylflavone and 7,3',4',5'-tetrahydroxylflavone, showed a wide range of pharmacological activity and notably anti-oxidation activity.