Ruthenium phase-transfer conditions

In many respects the apparently analogous reduction of nitroarenes with triruthenium dodecacarbonyl under basic phase-transfer conditions is superior to that of the iron carbonyl-mediated reductions. However, the difference in the dependence of the two processes on the concentration of the aqueous sodium hydroxide and the pressure of the carbon monoxide suggests that they may proceed by different mechanisms. Although the iron-based system is most effective under dilute alkaline conditions in the absence of carbon monoxide, the use of 5M sodium hydroxide is critical for the ruthenium-based system, which also requires an atmosphere of carbon monoxide [11]. The ruthenium-based reduction has been extended to the... 

In the presence of ruthenium trichloride, alkaline sodium hypochlorite is able to oxidize methylbenzenes to benzoic acids under phase-transfer conditions at room temperature. In a recent development, selective oxidation of xylenes to toluic acids has... 

Ruthenium(III) chloride has been shown to be particularly effective with hydrogen peroxide for the oxidation of alcohols under phase-transfer conditions.204 Primary alcohols are converted to acids, allylic and secondary alcohols to ketones, and benzyl alcohols to either benzaldehydes or benzoic acids. 

Wacker oxidation. The oxidation of 1-alkcnes to methyl ketones by oxygen catalyzed by PdCk and CuCU can be carried out under phase-transfer conditions with cetyltrimethylammonium bromide or a closely related salt as the phase-transfer catalyst. Yields are in the range 50-75%. Several rhodium and ruthenium complexes can be used as the metal catalyst, but the yields are lower. 

The phase-transfer-assisted permanganate oxidation of alkynes and alkenes has been reviewed. Terminal and internal alkynes are oxidized to 1,2-dicarbonyl compounds by the combined action of diphenyl disulphide, ammonium peroxidisulphate and water or by sodium periodate in the presence of ruthenium dioxide (equation 34). Other reagents for the conversion of acetylenes into 1,2-dicarbonyl compounds are hydrogen peroxide in the presence of (2,6-dicarboxylatopyridine)iron(II), the complex oxo(A, A -ethylenebissalicylideneiminato)chromium(V) trifluoromethanesulphonate (216)and ruthenium tetroxide as a mediator in electrooxidation. l-Acetoxyalkan-2-ones 217 are obtained by the oxidation of terminal acetylenes with sodium perborate and mercury(II) acetate in acetic acid ". Terminal alkynes give a-ketoaldehydes 218 on treatment with dilute hydrogen peroxide, combined with mercury(II) acetate and sodium molybdate or sodium tungstate under phase-transfer conditions. ... 

Conjugated dienes can be selectively hydrated to ketones in the presence of cationic ruthenium complexes with bipyridyl ligands. The role of ruthenium is to catalyze the isomerization of allylic alcohols formed by the addition of water to diene. This method allows one to convert butadiene to methyl ethyl ketone in high yield [187]. Hydration of triple bonds is one of the oldest catalytic processes of organic chemistry. Though this reaction has no industrial value, it can serve as a tool of fine organic synthesis. The hydration can be catalyzed by rhodium salts under phase-transfer conditions [188]. The more exotic process of the hydrolysis of phenylacetylene to toluene and carbon monoxide catalyzed by ruthenium complex should also be mentioned [189] ... 

The Water-gas Shift Reaction.—This reaction is catalysed by M(CO) (activity M = W>Mo>Cr) in the presence of base and under phase-transfer conditions these carbonyls, in common with MS(CO)i2 (M =Ru or Os), are also active in the presence of sodium sulphide. The most active catalysts reported are Fe(CO)6 in basic methanol (turnover No. 2000 per day at 180 °C ) and Rh6(CO)i6 with diamine co-catalysts (e.g., en, turnover No. a 25 h at 100 C). Photolysis of [RuCl(CO)(bipy)a]Cl in water under CO produces COa and catalytically the CO2 is produced in a thermal step, whereas the formation of Ha is photo-initiated. Water-gas has also been used to hydroformylate pent-1-ene in the presence of ruthenium complexes similarly, water-gas is used in reaction (9), which is catalysed by a variety of Group VIII metal complexes... 

Methylbenzenes are oxidized to the corresponding benzoic acids in very high yield under phase-transfer catalytic conditions by sodium hypochlorite in the presence of ruthenium trichloride, which is initially oxidized to ruthenium tetroxide [5]. Absence of either the ruthenium or the quaternary ammonium salt totally inhibits the reaction. 

Hydride ion transfer from formic acid and its salts finds widespread application in the reduction of organic substrates, but limited use has been made of the procedure under phase-transfer catalytic conditions. However in the presence of a ruthenium complex catalyst, it is possible to selectively reduce the C=C bonds of conjugated ketones with sodium formate [11], The rate of reduction is fastest with tetrahexyl-ammonium hydrogensulphate and Aliquat the complete reduction of chalcone being effected within one hour, whereas with benzyltriethylammonium chloride only ca. 15% reduction is observed after two hours under similar conditions. 

The catalytic properties of the sulfonated diphosphine-stabilized RuNPs and sulfonated diphosphine/cyclodextrin-stabilized RuNPs were compared in the hydrogenation of unsaturated model substrates (styrene, acetophenone, and w-methylanisole) in biphasic liquid-hquid conditions (i.e., ruthenium aqueous colloidal solution and organic substrate no added solvent). Whilst all of these RuNPs displayed suitable performances in catalysis, different activities and selec-tivities were observed. This highhghted that supramolecular interactions on the metallic surface in the presence of a cyclodextrin control the catalytic reactivity of the nanocatalysts. Interestingly the CD acts as a phase-transfer promotor, which... 

Ru/tppms catalysts exhibited excellent yields (98%) in the transfer hydrogenation of unsaturated aldehydes such as cinnamaldehyde or crotonaldehyde, to the corresponding unsaturated alcohols under mild reaction conditions (30-80°C), with HCOONa in an aqueous/organic two phase system. Similarly, ruthenium modified with the water soluble, air stable phosphine 100 (pta Table 5) is an effective catalyst for the chemoselective transfer hydrogenation of a,P-unsaturated aldehydes to unsaturated alcohols using formate in an aqueous/ organic two phase system. In contrast, Rh/pta afforded the cor-... 

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