Olefin metathesis, review

We will focus on the development of ruthenium-based metathesis precatalysts with enhanced activity and applications to the metathesis of alkenes with nonstandard electronic properties. In the class of molybdenum complexes [7a,g,h] recent research was mainly directed to the development of homochi-ral precatalysts for enantioselective olefin metathesis. This aspect has recently been covered by Schrock and Hoveyda in a short review and will not be discussed here [8h]. In addition, several important special topics have recently been addressed by excellent reviews, e.g., the synthesis of medium-sized rings by RCM [8a], applications of olefin metathesis to carbohydrate chemistry [8b], cross metathesis [8c,d],enyne metathesis [8e,f], ring-rearrangement metathesis [8g], enantioselective metathesis [8h], and applications of metathesis in polymer chemistry (ADMET,ROMP) [8i,j]. Application of olefin metathesis to the total synthesis of complex natural products is covered in the contribution by Mulzer et al. in this volume. 

In the March 3, 1978 issue of Chemical and Engineering News, a feature article examined activities at the forefront of inorganic chemistry. On olefin metathesis, the article states How the organometallic complexes affect the reaction is just now becoming well understood. In our review, the accent has been on aspects of olefin metathesis which are not well understood, with the hope that this will stimulate new and original work related to this remarkable reaction. 

In this chapter I will cover only well-defined or well-characterized compounds. Results will be included that have appeared since reviews in 1991 on alkylidene and metalacyclobutane complexes [41] and in 1993 on ring-opening metathesis polymerization [30], but an overview of prior results that are especially relevant to olefin metathesis in particular will also be included. (An excellent and comprehensive text also has been published recently [1].) The terms well-defined or well-characterized originally were meant to imply that the alkylidene complex is isolable and is essentially identical to that in a catalytic reaction except for the identity of the alkylidene. These terms have been watered down from time to time in the literature, even to the point where they are used to describe a catalyst that is formed from a well-characterized transition metal precursor complex, but whose identity actually is not known. In this article I... 

For a review see Ivin KJ, Mol JC (1997) Olefin metathesis and metathesis polymerization,2nd ed, Academic Press, New York... 

Olefin metathesis refers to a process in which two alkenes exchange their alkylidene fragments. This reaction has recently been reviewed [743-747]. An exciting account on the discovery of olefin metathesis has been written by Eleuterio [748]. 

For a review of asymmetric Mo-catalyzed metathesis, see Catalytic Asymmetric Olefin Metathesis, A. H. Hoveyda, R. R. ScHROCK, Chem. Eur. J. 2001, 7, 945-950 for reports on chiral Ru-based complexes, see (b) Enantioselective Ruthenium-Catalyzed Ring-Qosing Metathesis, T.J. Sei-DERS, D.W. Ward, R.H. Grubbs, Org. Lett. 2001, 3, 3225-3228 (c) A Recyclable Chiral Ru Catalyst for Enantioselective Olefin Metathesis. Efficient Catalytic Asymmetric Ring-Opening/Cross Metathesis In Air, J. J. Van Veldhuizen, S. B. 

This article presents the principles known so far for the synthesis of metal complexes containing stable carbenes, including the preparation of the relevant carbene precursors. The use of some of these compounds in transition-metal-catalyzed reactions is discussed mainly for ruthenium-catalyzed olefin metathesis and palladium-Znickel-catalyzed coupling reactions of aryl halides, but other reactions will be touched upon as well. Chapters about the properties of metal- carbene complexes, their applications in materials science and medicinal chemistry, and their role in bioinorganic chemistry round the survey off. The focus of this review is on ZV-heterocyclic carbenes, in the following abbreviated as NHC and NHCs, respectively. 

It is worthwhile commenting that the one method that has really seen an explosion in its use for heterocycle formation since the publication of CHEC-II(1996) is olefin metathesis, with the various metathesis catalysts now readily commercially available. It is beyond the scope of this review to discuss the mechanism and nature of metathesis catalysts and the reader is directed to alternative texts for this <2004CRV2199, 2004CRV2239>. 

Olefin metathesis has been extensively reviewed,6 7 14 17-32 and regular symposia have been devoted to the subject.33-37... 

For select reviews on catalytic olefin metathesis, see Grubbs RH, Chang S (1998) Tetrahedron 54 4413 Furstner A (2000) Angew Chem Int Ed 39 3012... 

A recent review of olefin metathesis is found in J. Tsuji, Transition Metal Reagents and Catalysts, Innovations in Organic Synthesis, Wiley, New York, 2000, Chapter 8, pp. 305-322. An excellent discussion of RCM is found in R. H. Grubbs and S. Chang, Recent Advances in Olefin Metathesis and Its Applications in Organic Synthesis, Tetrahedron, 1998, 54, 4413-4450. 

Olefin metathesis is also a highly versatile technique for the synthesis of polymers from renewable resources. In this respect, especially ADMET polymerization and ROMP have been used to prepare macromolecules starting from fatty acid precursors due to their inherent double-bond functionality. Nevertheless, also other feedstock and methods have been applied, as will be reviewed within this section. 

Olefin metathesis provides the principal synthetic context for metallacyclobutane reactivity this catalytic reaction proceeds by the transient, and reversible, formation of a metallacyclobutane intermediate from a metal alkylidene and an alkene. The olefin metathesis reaction has been exhaustively reviewed and is not directly discussed here... 

Enantiomerically pure olefin metathesis catalysts can be used to promote reactions whereby simple achiral substrates are transformed into more complex chiral molecules. Much like their achiral counterparts, chiral olefin metathesis catalysts can be used in three distinct fashions. Chiral metathesis reactions have been reviewed.51-53... 

Reviews on Olefin Metathesis (a) Grubbs RH (1982) In Wilkinson G (ed) Comprehensive organometallic chemistry, Pergamon, Oxford, vol 8, p 499 (b) Dragutan V, Balaban AT, Dimonie M (1985) Olefin metathesis and ring-opening polymerization of cyclo-olefins, Wiley, Chichester (c) Ivin KJ (1983) Olefin metathesis, Academic, London... 

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