Application of Olefin Metathesis to Organic Synthesis

The design and execution of complex molecule synthesis centers upon those reactions that are truly versatile and reliable, especially those that form carbon-carbon bonds. For many decades, alkene metathesis reactions have found great application in polymer synthesis, but it has only been recently that this reaction is finding a place in the arsenal of the synthetic chemist. This new role for the olefin metathesis reaction is directly related to the recent development of stable, well-defined catalysts for this reaction. Ruthenium and molybdenum catalysts, among others, are finding wide spread use in organic synthesis. These catalysts are able to promote the exchange of two independent alkenes and result in the formation of a new olefin. The most common use for this reaction involves an intermolecular variation whereby a tethered diene is metathesized to form a cycloalkene. This ring-closing metathesis (RCM) process has been shown to be remarkably versatile and is tolerant to a wide range of accompanying functionality. RCM reactions are now widely used for the preparation of carbocyclic, azacyclic, and oxacyclic systems. This review focuses on the versatility offered by these well-defined catalyst systems and focuses on their use in the synthesis of natural and non-natural products.