Ruthenium-Catalyzed Metathesis Reactions in Organic Synthesis

Well-defined ruthenium carbene complexes of type 1 introduced by Grubbs et al. are among the most popular and useful metathesis catalysts known to date. They combine a high activity with an excellent tolerance towards polar functional groups and provide access to carbo- and heterocycles of almost any ring size by ring closing metathesis (RCM) of diene substrates. This includes even medium-sized and macrocyclic rings. The design and mode of action of these and related catalysts will be outlined and their performance will be illustrated by some selected applications to the synthesis of complex natural products. Moreover, some promising developments concerning a new generation of ruthenium-based catalysts (i.a. the allenylidene complexes 2), as well as recent advancements related to the use of supercritical carbon dioxide (scCO2) as reaction medium for RCM, will be discussed