Microwave-assisted efficient synthesis of polymethoxyacetophenones and natural polymethoxyflavones, and their inhibitory effects on melanogenesis

Microwave-assisted Friedel-Crafts acetylation of polymethoxybenzenes with acetic anhydride in the presence of In(CF 3 SO 3 ) 3 under solvent-free conditions was achieved rapidly to give polymethoxyacetophenones in high yields. Microwave-assisted benzoylation of 2'-hydroxypolymethoxyacetophenones with polymethoxybenzoyl chlorides, followed by the rearrangement of the resulting benzoates and the final formation of natural polymethoxyflavones was achieved rapidly and efficiently. The polymethoxyflavones showed inhibitory effects on melanogenesis in human melanoma cells.