Pierre H. Dixneuf

Direct Arylation of Arene C−H Bonds by Cooperative Action of NHCarbene−Ruthenium(II) Catalyst and Carbonate via Proton Abstraction Mechanism

Direct functionalization of sp2 C−H bonds via ortho diarylation of 2-pyridyl benzene with arylbromides was achieved using ruthenium(II) catalysts containing a RuCl2(NHC) unit and generated from [RuCl2(arene)]2 and two types of NHC precursors, pyrimidinium and benzimidazolium salts, in the presence of Cs2CO3. DFT calculations from RuCl2(NHC)(2-pyridylbenzene) show that a proton abstraction mechanism, on cooperative actions of both the coordinated base and the Ru(II) center, is favored via a 13.7 kcal·mol-1 exothermic process affording an orthometalated intermediate with a 2.009 A Ru−C bond.

Renewable materials as precursors of linear nitrile-acid derivatives via cross-metathesis of fatty esters and acids with acrylonitrile and fumaronitrile

The cross-metathesis of fatty acids and esters, as renewable raw materials, with acrylonitrile and fumaronitrile is presented. The cross-metathesis reactions of both terminal and internal double bond containing compounds were performed using a ruthenium catalyst and led to bifunctional nitrile-esters or nitrile-acids with high conversions. The tandem ruthenium catalysed cross-metathesis and hydrogenation provide precursors of aminoacid monomers for the production of polyamides from renewable resources.

Sequential Synthesis of Furans from Alkynes: Successive Ruthenium(II)‐ and Copper(II)‐Catalyzed Processes

Step in time: 2,5-Disubstituted furans can be prepared from terminal alkynes in one pot using two successive catalytic reactions (see scheme; p-TSA = para-toluenesulfonic acid). First, a 1,3-dienyl alkyl ether is produced by the dimerization of a terminal alkyne and addition of an alcohol catalyzed by [RuCp*(NCMe)(3)][PF(6)]. Then, consecutive hydrolysis and cyclization catalyzed by CuCl(2) provides the 2,5-disubstituted furan.

Organometallic chemistry of arene ruthenium and osmium complexes

Publisher Summary This chapter focuses on the organometallic chemistry and new aspects of arene ruthenium and osmium complexes. It explores that arene ruthenium and osmium complexes play an increasingly important role in organometallic chemistry. They appear to be good starting materials for access to reactive arene metal hydrides or 16-electron metal (0) intermediates that have been used recently for carbon-hydrogen bond activation. Various methods of access to cyclopentadienyl, borane, and carborane arene ruthenium and osmium complexes have been reported. Recently, from classic organometallic arene ruthenium and osmium chemistry has grown an area making significant contributions to the chemistry of cyclophanes. These compounds are potential precursors of organometallic polymers, which show interesting electrical properties and conductivity. The possibility of coordination of a two-electron ligand, in addition to arene, to the ruthenium or osmium atom provides a route to mixed metal or cluster compounds. Cocondensation of arene with ruthenium or osmium vapors has recently allowed access to new types of arene metal complexes and clusters. It reviews that arene ruthenium and osmium appear to be useful and specific catalyst precursors, apart from classic hydrogenation, for carbon–hydrogen bond activation and activation of alkynes; such compounds may become valuable reagents for organic syntheses.

First ring-opening metathesis polymerization in an ionic liquid. Efficient recycling of a catalyst generated from a cationic ruthenium allenylidene complex

Ring-opening metathesis polymerization (ROMP) of norbornene was carried out in a biphasic medium consisting of the ionic liquid [bdmim][PF6] and toluene with a cationic ruthenium allenylidene precatalyst. The ionic liquid contained the ruthenium allenylidene complex and toluene dissolved the formed polymer. Both the catalyst and the ionic liquid were reused several times and led to very good polymer yields.

Synthesis and catalytic properties of N-functionalized carbene complexes of rhodium(I) and ruthenium(II)

Abstract Imidazolidin-2-ylidene derivatives of rhodium(I) and ruthenium(II), having 2-methoxyethyl substituent on the N-atom, [Rh(L)Cl(PPh3)2], [Rh(L)CI(COD)] or [Ru(L)Cl2(arene)] ( L 1 = CN ( Me ) CH 2 CH 2 N ︹ CH 2 CH 2 OMe and L 2 = CN ( CH 2 CH 2 OMe ) CH 2 CH 2 N ︹ CH 2 CH 2 OMe ) have been prepared by treatment of [RhCl(PPh3)3], [RhCI(COD)]2 or [RuCl2(arene)]2 with the N-functionalized electron-rich olefins L1 = L1 or L2 = L2. All of the new carbene rhodium(I) or ruthenium(II) complexes have proved to be effective catalysts for the cyclopropanation reactions of diazoalkane derivatives with styrene and the rhodium(I) precursors lead to the highest catalytic activity.

Diethyl carbonate as a solvent for ruthenium catalysed C–H bond functionalisation

The ruthenium catalysed direct functionalisation of arene C–H bonds by aryl halides is reported. Reactions were performed in diethyl carbonate (DEC) instead of N-methylpyrrolidone (NMP), the solvent of choice used in most ruthenium catalysed C–H bond transformations. The use of diethyl carbonate facilitates the workup procedure thus reducing the amount of waste water. The slight loss of activity due to the use of diethyl carbonate is counterbalanced by the improvement of the catalyst efficiency achieved by a judicious choice of additives. Several arenes containing an N-heterocycle as a directing group have been diarylated.

First ruthenium complexes with a chelating arene carbene ligand as catalytic precursors for alkene metathesis and cycloisomerisation

Electron-rich carbene precursors 2 and 3, containing the imidazolidin-2-ylidene moiety with one (2) and two (3) pendent N-(2,4,6-trimethylbenzyl) groups, on reaction with [RuCl2(arene)]2 lead to ruthenium(II) complexes 5 and 6 containing the chelating 8-electron mixed arene–carbene ligand; the X-ray diffraction crystal structure of RuCl2{η1-CN[CH2( η6-2,4,6-Me3C6H2)]CH2CH2N(CH2CH2OMe)} 6, was established. These complexes are precursors of the unstable ruthenium-allenylidene intermediates 7 and 8, but are active catalysts either for selective catalytic alkene metathesis or cycloisomerization, depending on the nature of the 1,6-diene.

Synthesis of enol esters from terminal alkynes catalyzed by ruthenium complexes

Abstract Regioselective enol ester formation results from the addition of saturated and unsaturated carboxylic acids to phenylacetylene in the presence of RuCl 3 , RuCl 3 /2PR 3 or RuCl 2 (PMe 2 )(arene) catalysts.

Ruthenium–alkylidene catalysed cross-metathesis of fatty acid derivatives with acrylonitrile and methyl acrylate: a key step toward long-chain bifunctional and amino acid compounds

The ruthenium catalysed cross-metathesis of fatty-esters arising from plant oils with acrylonitrile is presented. The resulting linear nitrile ester products have potential as new intermediates for polyamides synthesis. A series of commercially available catalysts are able to promote the transformation of methyl 10-undecenoate 1, dimethyl octadec-9-en-1,18-dioate 5 and methyl ricinoleate 9 with acrylonitrile and a protocol based on the slow addition of catalyst allowed TONs as high as 1900 (92% yield) to be reached for cross-metathesis with acrylonitrile. These cross-metathesis conditions have been applied to methyl acrylate and TONs up to 7600 were obtained.