Approaches towards the preparation of 5,6,7-trimethoxyflavone (8), a key intermediate for the synthesis of baicalein, are discussed. Of the synthetic routes, the most efficient was accomplished by direct Fries acylation of trimethoxyphenol (I) with cinnamoyl chloride folIowed by oxidative cyclization of the resulting chalcone 6 with I2/DMSO in good overall yields (70%). Demethylation of 8 using 47% HBr/ AcOH readily produced baicalein. The chalcone 6 could also be prepared by Claisen-Schmidt condensation of acetophenone 2 with benzaldehyde catalyzed in alkali.
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