FROM OLEFIN CYCLOPROPANATION TO OLEFIN METATHESIS THROUGH CATALYST ENGINEERING - RECENT APPLICATIONS OF OLEFIN METATHESIS TO FINE ORGANIC-SYNTHESIS AND TO POLYMER CHEMISTRY

An overview of the recent synthetic breakthroughs brought about by the discovery of new, functional group tolerant late transition metal (Rh and Ru)-based catalysts is proposed. Whereas dirhodium(II)-based comp lexes promote only carbene transfer reactions to olefins (i.e. olefin cyclopropanation), a few ruthenium-based catalysts can be engineered a nd fine tuned so as to mediate either carbene-transfer reactions or ol efin metathesis. The different outcome of the reactions can be rationa lized by the capability of the metal center to coordinate or not both the carbene and the olefin. This quite simple-minded approach indicate s that several available coordination sites at the metal center favors metathesis reactions to the prejudice of olefin cyclopropanation. Exa mples of recent applications in ring opening metathesis polymerization s and copolymerizations include the formation of postpolymers of polyd ienes, of carbohydrate-substituted polymers and of telechelic oligomer s. Application of the same ruthenium-based catalysts in ring-closing m etathesis is illustrated by the formation of crown ether analogs, of u nsaturated peptides and amino acids, of beta-lactams, and of different bicyclic systems.