An efficient, mild, and environmental friendly method has been developed for the synthesis of dicoumarols in water over Lewis and Bronsted acid catalyst sulfated titania (TiO2/SO42−). The method involves the condensation of various aromatic and aliphatic aldehydes with 4- hydroxycoumarin. It affords the corresponding product in high yield with short reaction times employing a very low loading of catalyst. The catalyst was reused several times without ...