Three examples of the work undertaken at the Institut de Recherches sur la Catalyse for the selective preparation of fine chemicals in polyphasic media are presented and discussed: 1. diastereoselective hydrogenation of 1,2-disubstituted arenes to cyclohexyl derivatives, 2. chemoselective oxidation of anilines, and 3. regioselective alkoxycarbonylation of styrene derivatives to 2-arylpropionic eaters. Factors influencing the selectivity of these reactions are discussed in the light of concepts from molecular chemistry.