The advent of well-defined catalysts for olefin metathesis which combine high activity, durability, and excellent tolerance towards polar functional groups has revolutionized the field. The past decade has seen the rapid embrace of these reagents as tools for advanced organic and polymer chemistry and the success of this development is witnessed by a plethora of elegant applications to the synthesis of natural and nonnatural products. This review article provides an overview of these developments and intends to familiarize the reader with some very recent advances which hold the promise to expand the scope of the reaction even further. Moreover, the positive impact of metathesis on the fundamental logic of retrosynthetic planning is demonstrated by means of typical examples. Finally, it will be shown that metathesis is by no means restricted to alkenes as substrates, and some comments on metathesis reactions following unconventional mechanistic pathways will also be presented.

Olefin Metathesis and Beyond

Living ring-opening metathesis polymerization

Carbon-carbon bond forming reactions remain among the most important for the synthesis of organic structures. The transition metal alkylidene-catalyzed olefin metathesis reaction (eq 1) and the related transition metal alkylidene-mediated carbonyl olefination reaction (eq 2) are two such processes. Historically, olefin metathesis has been studied extensively both from the mechanistic standpoint and in the context of polymer synthesis. In contrast, its application to the synthesis of complex organic molecules and natural products has been limited. The related reaction, transition metal-mediated carbonyl olefination, is not as extensively studied mechanistically nor in synthetic applications. Among the reasons for this
gap in methodology has been the incompatibility of traditional catalysts with the polar functional groups
typically encountered in organic synthesis.

Ring-Closing Metathesis and Related Processes in Organic Synthesis

Living ring-opening metathesis polymerization catalyzed by well-characterized transition-metal alkylidene complexes

Homogeneous Metathesis Polymerization by Well-Defined Group VI and Group VIII Transition-Metal Alkylidenes: Fundamentals and Applications in the Preparation of Advanced Materials.

Reaction of neopentylidene complexes of the type M(CH-t-Bu)(N-2,6-C6H3-i-Pr2)(OR)2 (M = W, Mo) with methyl acrylate and N,N-dimethylacrylamide to give metallacyclobutane complexes

Controlled ring-opening metathesis polymerization by molybdenum and tungsten alkylidene complexes

Reaction of Neopentylidene Complexes of the Type M(CH-tBu)(N-2,6-C6H3-iPr2)(OR)2 (M: W, Mo) with Methyl Acrylate and N,N-Dimethylacrylamide to Give Metallacyclobutane Complexes.

John S. Murdzek

Papers

Reaction of neopentylidene complexes of the type M(CH-t-Bu)(N-2,6-C6H3-i-Pr2)(OR)2 (M = W, Mo) with methyl acrylate and N,N-dimethylacrylamide to give metallacyclobutane complexes

Controlled ring-opening metathesis polymerization by molybdenum and tungsten alkylidene complexes

Reaction of Neopentylidene Complexes of the Type M(CH-tBu)(N-2,6-C6H3-iPr2)(OR)2 (M: W, Mo) with Methyl Acrylate and N,N-Dimethylacrylamide to Give Metallacyclobutane Complexes.