Recent theoretical studies by Eisenstein and co-workers present the case that high-oxidation-state complexes that bear a stereogenic metal center would be exceptionally effective olefin metathesis catalysts. First, their theoretical investigations suggest that the presence of one acceptor ligand A in V, is required in order to ensure that the metal center possesses sufficient Lewis acidity to provide effective binding to olefins.
Users may view, print, copy, download and text and data- mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use: Abstract Many biologically active macrocycles contain a C—C double bond through which various other derivatives are prepared; the stereochemical identity of the alkene or the resulting moieties can be critical to the beneficial properties of such molecules.
Catalytic ring-closing metathesis RCM is a widely employed method for the synthesis of large unsaturated rings;1,2 however, cyclizations often proceed without control of alkene stereochemistry. Utility is demonstrated by stereoselective preparation of anti-cancer epothilone C [ Ref.
As a result of efficient RCM and re-incorporation of side products into the catalytic cycle with minimal alkene isomerization, desired cyclizations proceed in preference to alternative pathways even under relatively high concentration 0.
Catalytic ring-closing metathesis RCM of alkenes is indispensable to the preparation of cyclic structures i ; it is used extensively in the synthesis of biologically active molecules ii.
RCM is broadly employed in accessing large rings, despite the lack of a reliably stereoselective variant, the availability of which would substantially enhance the value of this critical class of reactions. The absence of stereochemical control originates from the dependency of the catalytic ring closure on the energetic attributes of the product stereoisomers vs.
With small- or medium-rings, Z alkenes are generated exclusively; this is not so with sizeable rings, since, frequently, either the energy difference between the two isomeric alkenes is insufficient for achieving high stereoselectivity by thermodynamic control, or, if one isomer is adequately lower in energy, the catalyst is unable to promote facile equilibration.
The severe shortcoming in the state-of-the-art is illustrated by the two sets of non-selective catalytic RCM, shown in Fig. Efforts from several laboratories have focused on catalytic RCM for synthesis of the macrocyclic moiety of different members of the epothilone family; popular catalysts, like those derived from alkylidene 1 vii and carbenes 2a—d viiiix Fig.
Initiatives regarding nakadomarin A cf.Research Publications Review articles and patents are listed below separately.
“ Syntheses of Molybendenum Oxo Benzylidene Complexes," F.
Zhai, K. V. Bukhryakov, “Catalytic Z-Selective Cross-Metathesis with Secondary Silyl- and Benzyl-Protected Allylic Ethers. At a ratio [vinylsilane]/[total >C Cvinylsilane yielding silylated unsaturated oligomers.
Ruthenium-Catalyzed Vinylsilane Synthesis and Cross-Coupling as a Selective Approach to Alkenes: Benzyldimethylsilyl as a Robust Vinylmetal Functionality. Barry M.
Synthetic Methods Organosilicon Chemistry Boc-protected 2-pyrrolyldimethylsilanol: a potent trans β -vinylsilanecis- β-vinylsilane metathesis . Nov 03, · Synthesis of macrocyclic natural products by catalyst-controlled stereoselective ring-closing metathesis range of substrates involving reactions between an internal vinylsilane and a terminal alkene, followed by likely due to similar principles that result in stereoselective homocoupling and cross-metathesis. A new synthetic approach to 3-methylenecyclohexanols fused to five-, six- and seven-membered carbocycles through intramolecular cyclization of epoxyallylsilanes Asunción Barbero, Pilar Castreño, Francisco J. Pulido*, 15 and by cross metathesis of alkenyl epoxides and.
Trost, Selective Domino Ring-Closing Metathesis−Cross-Metathesis Reactions between Enynes and Electron-Deficient Alkenes. Frédérique Royer, Claire Vilain, . Design and Stereoselective Preparation of a New Class of Chiral Olefin Metathesis Catalysts and Application to Enantioselective Synthesis of Quebrachamine: Catalyst Development Inspired by Natural Product Synthesis.
Transmetalation between palladium(II)−vinyl complex and vinylsilane was theoretically investigated with the DFT and MP2 to MP4 methods to clarify the reaction mechanism and the reasons why fluoride anion accelerates the Pd-catalyzed cross-coupling reaction between vinyl iodide and vinylsilane.
This transmetalation occurs with a very large . Cross-metathesis (disproportionation) of vinyl-substituted silicon compounds containing methyl, alkoxyl, phenyl, trimethylsiloxyl and silatranyl groups at silicon with 1-decene occurs effectively.