Molybdenum and tungsten alkylidene

Schrock RR, Czekelius C. Recent advances in the syntheses 136. and applications of molybdenum and tungsten alkylidene and alkylidyne catalysts for the metathesis of alkenes and alkynes. 

Schrock, R.R. and Czekelius, C. (2007) Recent advances in the syntheses and applications of molybdenum and tungsten alkylidene and alkylidyne catalysts for the metathesis of alkenes and alkynes. Adv. Synth. Catal, 349, 55-77. Zhang, W. and Moore, J.S. (2007)... 

This review will focus on isolated and characterized high-oxidation state molybdenum and tungsten alkylidene and metallacyclobutane complexes. Attention will be directed largely toward monoalkoxide pyrrolide (MAP) complexes because they have yielded the majority of new results in the last several years. MAP species have been found to be especially efficient in several Z-selective olefin metathesis reactions, such as homocoupling, cross-coupling, ethenolysis, and ROMP (see Grubbs, Handbook of Metathesis, 2nd Edition, Volume 2, Chapter 7). Most of what is presented here has appeared since a review in 2009 [4]. 

Marinescu, S.C. (2011) Molybdenum and Tungsten Alkylidene Species for Catalytic Enantio-, Z-, and -Selective Olefin Metathesis Reactions. PhD thesis. Massachusetts Institute of Technology. 

Initial reports of cross-metathesis reactions using well-defined catalysts were limited to simple isolated examples the metathesis of ethyl or methyl oleate with dec-5-ene catalysed by tungsten alkylidenes [13,14] and the cross-metathesis of unsaturated ethers catalysed by a chromium carbene complex [15]. With the discovery of the well-defined molybdenum and ruthenium alkylidene catalysts 3 and 4,by Schrock [16] and Grubbs [17],respectively, the development of alkene metathesis as a tool for organic synthesis began in earnest. 

Around 1990, Richard Schrock developed versatile molybdenum and tungsten catalysts for olefin metathesis that tolerate a wide range of functional groups in the alkylidene fragments of the olefins. The Schrock catalyst shown in Figure 8-10a is now commercially available. The Schrock catalysts tend to be air- and moisture-sensitive, which limits their use in commercial processes. 

Schrock, R. R., Hoveyda, A. H. Molybdenum and tungsten imido alkylidene complexes as efficient olefin-metathesis catalysts. Angew. Chem., Int. Ed. Engl. 2003, 42, 4592-4633. 

Schrock, R. R. Recent advances in olefin metathesis by molybdenum and tungsten imido alkylidene complexes. J. Mol. Catal. A Chemical... 

Asymmetric syntheses of natural products cyclization reactions using molybdenum and tungsten imido alkylidene complexes as efficient olefin-metathesis catalysts 03AG(E)4592. 

Molybdenum and Tungsten Imide Alkylidene Complexes as Efficient Olefin-Metathesis Catalysts Schrock. R.R. Hovevda. A.H. Angew. Chem. Int. Ed. 2003, 42,4592. 

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