Efficient RuIII-catalyzed synthesis of 9-aryl-9H-xanthene-3,6-diols as precursors to fluorones

Efficient condensation of resorcinol and various aromatic aldehydes in the presence of RuCl3·nH2O as a homogeneous catalyst under reflux conditions was investigated. It was found that a very simple method afforded good to excellent yields of the desired products.