Unexpected Results of a Turnover Number (TON) Study Utilising Ruthenium-Based Olefin Metathesis Catalysts

Maechling, Simon; Zaja, Mirko; Blechert, Siegfried

doi:10.1002/adsc.200505053

Cited by 50 publications

(30 citation statements)

References 38 publications

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“…These precatalysts however showed activity at room temperature in alkene metathesis reactions [2,8,9]. Although they perform excellent at room temperature, they have a relatively short catalytic lifetime.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Application of Novel Ruthenium Catalysts for High Temperature Alkene Metathesis

et al. 2017

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Four pyridinyl alcohols and the corresponding hemilabile pyridinyl alcoholato ruthenium carbene complexes of the Grubbs second generation-type RuCl(H 2 IMes)(OˆN)(=CHPh), where,1-phenyl methanolato and 1-(2 -pyridinyl)-1-(2 -methoxyphenyl),1-phenyl methanolato, are synthesized in very good yields. At high temperatures, the precatalysts showed high stability, selectivity and activity in 1-octene metathesis compared to the Grubbs first and second generation precatalysts. The 2-/4-chloro-and 4-methoxy-substituted pyridinyl alcoholato ligand-containing ruthenium precatalysts showed high performance in the 1-octene metathesis reaction in the range 80-110 • C. The hemilabile 4-methoxy-substituted pyridinyl alcoholato ligand improved the catalyst stability, activity and selectivity for 1-octene metathesis significantly at 110 • C.

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Section: Introductionmentioning

confidence: 99%

Synthesis and Application of Novel Ruthenium Catalysts for High Temperature Alkene Metathesis

et al. 2017

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“…[1] Nevertheless, optimization studies of the RCM with respect to catalyst loading and reaction conditions are scarce, [2] and, especially, the formation of tetrasubstituted double bonds in such reactions remains difficult and leaves room for improvement. Five-and six-membered ring cyclizations forming tetrasubstituted double bonds, which benefit by the Thorpe-Ingold effect, have met with some success.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Ring‐Closing Metathesis: Inert Gas Sparging and Microwave Irradiation

et al. 2005

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A systematic study of a ring-closing metathesis towards a tetrasubstituted double bond as part of a seven-membered ring in a 5.7.5-tricyclic guaianolide system is described. By combining two techniques, namely sparging an inert gas through the solution together with dielectric heating via microwave irradiation a high-yielding ring-closing metathesis reaction in this particularly challenging case was achieved. The results obtained compare favorably with conventional heating conditions or with microwave irradiation in a closed system. The key aspects seem to be that rapid microwave irradiation diminishes catalyst decay by allowing the required high reaction temperature to be reached quickly and homogeneously and thereby providing enough energy for a successful metathesis reaction, while inert gas sparging is purging off evolving ethylene to shift the equilibrium to the product.

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“…Under these homogeneous conditions, substrates with a variety of substituents were metathesized to form five-, six-, and sevenmembered cyclic products (Table 2). High conversion was consistently achieved with traditional non-polar substrates, except for diallyldiphenylsilane (14). Water-soluble substrates such as 11 and 16-a putative model for peptide substrates-were more challenging, requiring increased catalyst loading and organic cosolvent concentrations for high conversion.…”

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confidence: 98%

Olefin Metathesis in Homogeneous Aqueous Media Catalyzed by Conventional Ruthenium Catalysts

2007

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Olefin metathesis in aqueous solvents is sought for applications in green chemistry and with the hydrophilic substrates of chemical biology, such as proteins and polysaccharides. Most demonstrations of metathesis in water, however, utilize exotic complexes. We have examined the performance of conventional catalysts in homogeneous water-organic mixtures, finding that the second-generation Hoveyda-Grubbs catalyst has extraordinary efficiency in aqueous dimethoxyethane and aqueous acetone. High (71-95%) conversions are achieved for ring-closing and cross metathesis of a variety of substrates in these solvent systems.As a highly effective means for creating carbon-carbon bonds, olefin metathesis is a privileged reaction in the armamentarium of synthetic and polymer chemists. 1 Readily available and highly active ruthenium catalysts 1-4 have popularized metathesis chemistry in organic solvents ( Figure 1). 2,3 On the other hand, metathesis in aqueous solvents largely remains the domain of catalysts designed expressly for use in water (Figure 2). 4,5,6 Despite the allure of aqueous olefin metathesis for biological applications 7 and green chemistry, 8 the synthesis of these water-soluble ligands and complexes imposes barriers to their wider use. Developing aqueous reaction conditions suitable for catalysts such as 1-4 is an alternative approach. In the initial work with well-defined catalysts in aqueous systems, Grubbs and coworkers performed ring-openingmetathesis polymerization (ROMP) with 1 in aqueous emulsions, 9 a method that allowed Kiessling and coworkers to synthesize biologically active glycopolymers. 10 For ringclosing metathesis (RCM) and cross metathesis (CM), Blechert and coworkers employed commercially-available 2 and complex 6c, a relative of commercially-available 4, in watermethanol and water-DMF mixtures. 6 Although they achieved high conversion in the ringclosure of N-tosyldiallylamine (8) in 3:1 water/methanol and 3:1 water/DMF over an extended reaction time of 12 h, these reactions were not accomplished in homogenous systems: neither the substrate nor the catalyst was dissolved completely in the aqueous phase. In most cases raines@biochem.wisc.edu. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript detailed in their report, the ruthenium complex was only sparingly soluble in the aqueous reaction mixture.Metathesis in homogeneous aqueous systems would likely be faster and more versatile than in these heterogeneous systems. An effective system for metathesis with commercially available catalysts in homogeneous aqueous media would not only make this chemistry more accessible, but also highlight the limitations of the standard catalysts in water, informing catalyst-design efforts. Yet, reports of the use of common metathesis catalysts in an aqueous context are limited. For these reasons, we chose to test the capabilities of catalysts 1-4 in homogeneous aqueous media, and we report the results of our exploration herein. First, we screened various organic solvents as co-s...

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Unexpected Results of a Turnover Number (TON) Study Utilising Ruthenium-Based Olefin Metathesis Catalysts

Cited by 50 publications

References 38 publications

Synthesis and Application of Novel Ruthenium Catalysts for High Temperature Alkene Metathesis

Synthesis and Application of Novel Ruthenium Catalysts for High Temperature Alkene Metathesis

Optimization of Ring‐Closing Metathesis: Inert Gas Sparging and Microwave Irradiation

Olefin Metathesis in Homogeneous Aqueous Media Catalyzed by Conventional Ruthenium Catalysts

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