SiO2-tethered rhodium complexes deriving from Rh(CO)(2)acac and the commercially available 3-(mercapto)propyl- and 3-(1-thioureido)propyl-functionalyzed silica gel, respectively, have been used as catalysts in the hydroformylation of some functionalized olefins directed to the preparation of intermediates for valuable biologically active compounds. The oxo-reaction, catalyzed by these systems, showed a good activity, with conversion, chemo- and regioselectivity values comparable with those obtained with the well-known homogeneous rhodium catalysts. These SiO2-tethered catalytic systems showed a quite good resistance to rhodium leaching which occurred in a quite small extent. (C) 2004 Elsevier B.V. All rights reserved.