α, α’-Benzylidene bis(4-hydroxycoumarin) derivatives were readily prepared in a few minutes with good yields through the reaction of an aromatic aldehyde and 4-hydroxycoumarin in aqueous media in the presence of catalytic tris(hydrogensulfato) boron [B(HSO_4)_3]. α, α’-Benzylidene bis (4-hydroxycoumarin) derivatives were prepared prepared in a few minutes with good yields through the reaction of an aromatic aldehyde and 4-hydroxycoumarin in aqueous media in the presence of catalytic tris hydrogensulfato boron [B ( HSO_4) _3].