The data reported in this paper demonstrate that great care must be taken when choosing an appropriate catalyst for a given metathesis reaction. First-generation catalysts were found to useful the of sterically unhindered substrates. Second-generation (under optimised conditions) showed good excellent activities toward hindered and electron-withdrawing group (EWG)-substituted alkenes do not react using first-generation complexes. A strong temperature effect was noted on all reactions tested....

Preparation of novel, highly water soluble Ru complexes, which contain quaternary ammonium chloride tags is presented. The "on-site" quaternisation method can be used to obtain polar metathesis catalysts in an easy and efficient manner. Application profiles three representative are described.

A 95% yield in the cross metathesis of acrylonitrile with a model olefin is achieved at 25 degrees C only 3 mol % new air-stable ruthenium catalyst 1f shown enclosed structural diagram. Even more remarkable are performances its boosted version 1g incorporating an electron-withdrawing group. Both these enhanced versions Hoveyda readily available from Grubbs second generation precatalyst upon reaction styrenyl ether end group which has been functionalized by ester function. The latter acts as...

Abstract A study concerning the effect of using a fluorinated aromatic solvent as medium for olefin metathesis reactions catalysed by ruthenium complexes bearing N‐heterocyclic carbene ligands is presented. The use hydrocarbons (FAH) solvents standard commercially available pre‐catalysts allows substantially higher yields desired products to be obtained, especially in case demanding polyfunctional molecules, including natural and biologically active compounds. Interactions between FAH...

Aromatic fluorinated hydrocarbons, used as solvents for olefinmetathesis reactions, catalysed by standard commercially available Ru precatalysts, allow substantially higher yields to be obtained, especially of challenging substrates, including natural and biologically active compounds.

Abstract Structural modifications of the Hoveyda–Grubbs ruthenium metathesis complex via electronic and structural withdrawing chelating alkoxy ligand were investigated. By decreasing donor properties oxygen atom, an acceleration in catalytic activity was achieved based on facilitation initiation step. Conformational constraints ether linkage led to unexpected disturbance geometry a vast improvement activity.

The series of upgraded Grubbs/Hoveyda second-generation catalysts (H2IMes)(Cl)2Ru═C(H)(C6H4OR) (E2 (71% yield), R = CH(Me)(C(O)OMe); M2 (58% CH(C(O)OMe)2; Kme2 (88% CH2C(O)Me; Ket2 (63% CH2C(O)Et); C2 C(Me)CN) were prepared by the reaction Grubbs catalyst (H2IMes)(Cl)2Ru(CHPh)(PCy3) (G2) with appropriate ortho-substituted ether H(Me)C═CHC6H4OR in presence CuCl as a phosphine scavenger. X-ray structures these complexes reveal that terminal oxygen ester, ketone, or malonate group installed...

A small family of olefin metathesis catalysts bearing a polar quaternary ammonium group is described. The presence this allows for efficient separation ruthenium impurities after the reaction. Application 9 and 11 leads to organic products high purity, which exhibit surprisingly low contamination levels (usually below 5 ppm) simple inexpensive purification step.

This account describes the discovery and development of efficient electron-withdrawing group activated Hoveyda–Grubbs catalysts, including a nitro-substituted catalyst their applications in syntheses complex molecules. 1 Introduction 2 EWG-Activated Complexes 2.1 The Discovery Story Behind It 2.2 Nitro-Substituted Catalyst 2.3 pH-Responsive Catalysts 2.4 Fine-Tuning EWG Fragment 3 Applications Preparation Compounds Biological Relevance 3.1 Synthesis BILN 2061 4 Concluding Remarks

ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTOrtho- and Para-Substituted Hoveyda−Grubbs Carbenes. An Improved Synthesis of Highly Efficient Metathesis Initiators†Robert Bujok, Michal Bieniek, Marek Masnyk, Anna Michrowska, Agata Sarosiek, Halszka Stȩpowska, Dieter Arlt, Karol GrelaView Author Information Institute Organic Chemistry, Polish Academy Sciences, Kasprzaka 44/52, Warsaw, 01-224, Poland, LIGAND Chemie GmbH, Papenhauser Str. 10, Lemgo, D-32657, Germany, Institut für Organische der...

A new, practical large-scale preparation of the second-generation Hoveyda−Grubbs complex 3b from its first-generation congener 3a is described. The novel benzylidene−ligand exchange reaction between and substituted 1-isopropoxy-2-propenylbenzenes leads to synthetically useful 5-NO2- 4-Et2N-substituted Hoveyda-type olefin metathesis catalysts.

This personal account describes the development and fine-tuning of pH-neutral quaternary-ammonium-tagged ruthenium-based complexes, their use as versatile catalysts for olefin metathesis, application that transformation in synthesis complex molecules.

Abstract X‐Ray photoelectron spectroscopy (XPS) was applied to six selected ruthenium precatalysts. The XPS data obtained were compared against reactivity and structural results. confirmed some dependencies such as the electron‐donor properties of substituents at center. Additionally, combined with results explain differences between character Grubbs Hoveyda catalysts. It found that changing PCy 3 ligand O i Pr (PCy =tricyclohexylphosphane, Pr=isopropoxy) has a major influence on relative...

Ruthenium-based catalysts bearing quaternary ammonium groups in their N-heterocyclic carbene (NHC) fragments and different counter-ions were synthesised tested various olefin metathesis transformations.

Catalytic cross-metathesis of commercial divinyl sulfone allowed direct access to novel (E)-alkenylvinyl sulfones and (E,E)-dialkenyl with excellent stereoselectivity. These compounds are useful building blocks, e.g., in the synthesis substituted thiomorpholine 1,1-dioxide derivatives. [reaction: see text]

The influence of microwave and ultrasonic irradiation on the performance ammonium-tagged Ru-based catalysts in olefin metathesis transformations aqueous media was studied. Differences catalytic activity correlation with nature present counter ion size N -heterocyclic carbene (NHC) ligand were revealed. presented methodology allows for preparation a variety polar non-polar products under environmentally friendly conditions.

Synthesis of five Electron Withdrawing Group (EWG) activated Hoveyda-Grubbs' catalysts containing thioperfluoroalkyl, sulfone and ketone functions is reported. The catalytic activity these was well correlated with the σp values Hammett constants for respective EWGs. Importantly, one new gave good results in synthesis a macrocyclic precursor anti-HCV agent BILN2061.