Trichloroacetic acid, CCl3COOH, efficiently catalyzed the reaction of an aromatic aldehydes and 4-hydroxycoumarin in aqueous media
under mild conditions to afford the corresponding α,α-benzylidene bis(4-hydroxycoumarin) derivatives in high yields. Ceric sulfate,
(Ce(SO4)2.4H2O), has also been used as another solid catalyst for this reaction.
Key words: 4-hydroxycoumarin, biscoumarin, trichloroacetic acid, ceric sulfate.
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