Ruthenium-based olefin metathesis

Imidazole-containing reagents have found useful applications in a variety of organic transformations. A second generation of ruthenium-based olefin metathesis catalysts... 

Synthesis and Activity of a New Generation of Ruthenium-Based Olefin Metathesis Catalysts Coordinated with 1,3-Dime-sityl-4,5-dihydroimidazol-2-ylidene Ligands, M. Scholl, S. Ding, C.W. Lee, et al, Org. Lett. 1999, 7, 953-956. 

Ferulic acid, a phenolic acid that can be found in rapeseed cake, has been used in the synthesis of monomers for ADMET homo- and copolymerization with fatty acid-based a,co-dienes [139]. Homopolymerizations were performed in the presence of several ruthenium-based olefin metathesis catalysts (1 mol% and 80°C), although only C5, the Zhan catalyst, and catalyst M5i of the company Umicore were able to produce oligomers with Tgs around 7°C. The comonomers were prepared by epoxidation of methyl oleate and erucate followed by simultaneous ring opening and transesterification with allyl alcohol. Best results for the copolymerizations were obtained with the erucic acid-derived monomer, reaching a crystalline polymer (Tm — 24.9°C) with molecular weight over 13 kDa. 

S. T. Nguyen, R. H. Grubbs, and J. W. Ziller, Synthesis and Activities of New Single-Component, Ruthenium-Based Olefin Metathesis Catalysts, J. Am. Chem. Soc. 115, 9858-9859 (1993). 

M. Scholl, T. M. Trnka, J. P. Morgan, and R. H. Grubbs, Increased Ring Closing Metathesis Activity of Ruthenium-Based Olefin Metathesis Catalysts Coordinated with Imidazolin-2-ylidene Ligands, Tetrahedron Lett. 1999, 2247-2250. 

Scholl, M., Ding, S., Lee, C.W., and Grubbs, R.H. 1999. Synthesis and activity of a new generation of ruthenium-based olefin metathesis catalysts coordinated with l,3-dimesityl-4,5-dihydroimidazol-2-ylidene ligands. Org Lett 1, 953-956. 

A family of phosphine-free ruthenium-based olefin metathesis catalysts has been developed over the last few years. First, work done independently by Hoveyda and Blechert resulted in the H2Mes isopropoxybenzylidene (4b), a highly active air-stable ruthenium (pre)catalyst for olefin metathesis (Scheme 4). Hoveyda described (4b) as a recyclable monomeric catalyst also with high activity for ring-opening, ring-closure, and cross metathesis that tolerates... 

Olefin metathesis has been extensively written on in both books and journals [1-10]. This chapter will focus on ADMET. Of particular interest are the issues of catalysis, mainly functional group tolerance, kinetics, and mechanistic details. The development of late-transition metal catalysts has enormously expanded the scope of ADMET, so particular attention will be given to the well-defined ruthenium-based olefin metathesis catalysts. Pertinent information pertaining to catalysts of Group VI metals will also be provided. Important procedural aspects of ADMET will be presented in conclusion. 

Catalyst Structure and Cis-Trans Selectivity in Ruthenium-based Olefin Metathesis... 

Catalyst Structure and Cis-Trans Selectivity in Ruthenium-based Olefin Metathesis 33 2.4 Z-selective Ru-based metathesis catalysts 2.4.1 Thiophenolate-based Z-selective catalysts... 

A few examples of polymer supported olefin metathesis have been reported recently. Hoveyda formed styrenyl ether complexes of several ruthenium-based olefin metathesis catalysts that were then incorporated into a dendrimer structure (273) (Scheme 23), reporting good conversions over 6 cycles albeit with diminishing ruthenium content. Yao used a similar chelating ligand to incorporate olefin... 

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