Ruthenium catalysis reduction

Rhodium (2J) and ruthenium are excellent catalysts for the reduction of aromatic rings. It is with these catalysts that the best chance resides for preservation of other reducible functions (2,10,13,18,41,42,52). Rhodium (41) and ruthenium (45) each reduced methylphenylcarbinol to methylcyclohexyl-carbinol in high yield. Palladium, on the other hand, gives ethylbenzene quantitatively. Water has a powerful promoting effect, which is unique in ruthenium catalysis (36). 

The ruthenium-catalyzed reduction of polar bonds using H gas, rather than a sacrificial reductant such as isopropanol, is an atom-economical reaction that has been thoroughly explored. A key discovery by our laboratory was that neutral, stmctur-ally characterized metal-amido complexes such as 11 (Scheme 7) could cleave H heterolytically to yield the fran -dihydride complex 12, and that these are crucial intermediates during catalysis.R - Once the H-N-Ru-H moiety is in place, proton and hydride can then be transferred to the substrate. Having methyl groups instead of hydrogens on carbons alpha to the amido group (beta to the ruthenium) in this case and in the case of 1 (Scheme 4) was important to allow the isolation of an amido... 

Reactions of arenes carrying a coordinating substituent with alkenes may give alkylated derivatives when catalysed by ruthenium biscarboxylate complexes. Experiments with deuterium-labelled compounds indicate that carbon-hydrogen metallation is reversible, so that reductive elimination from intermediates such as (90) is rate determining. Carboxylate-assisted ruthenium catalysis also allows the reaction of 2-arylpyridines with methylenecyclopropane to give derivatives, (91), in which the cyclopropane ring is conserved. ... 

Nomura, K. (1995) Efficient selective reduction of aromatic nitro-compounds by ruthenium catalysis under CO/H2O conditions, / Mol. Catal. A - Chem., 95,203-10. 

Kejrwords Dynamic kinetic asymmetric transformation (DYKAT) Dynamic kinetic resolution (DKR) Hydrogenation Imine reduction Ketone reduction Mechanism of carbonyl reduction Mechanism of imine reduction Mechanism of dUiydrogen activation Ruthenium catalysis Shvo s catalyst Transfer hydrogenation... 

Two mechanistic pathways, which differed in the way of ruthenium-mediated initial cleavage of formyl C-H or amido N-H bond, were proposed for the catalytic cycle. As shown in Scheme 7.3, an irreversibly cleavage of formyl C-H bond by the active ruthenium complex was followed by reversible insertion of the olefin into the Ru-H bond, which afforded either six-membered or seven-membered ruthenacycle. After reductive elimination, indolin-2-ones or 3,4-dihydroquinolin-2-one was formed. According to isotopic studies, pathway leading to six-membered lactams is postulated to be less favored. Another cyclization process initiated by Ru-catalyzed oxidative addition of formyl N-H bond (Scheme 7.4) was similar to Carreira s proposal for their hydrocarbamoyla-tion reaction of allylic formamides under similar ruthenium catalysis conditions [7]. The 6-endo cyclization process is proposed to be favored under the catalytic system B. 

Montagut-Romans A, Boulven M, Lemaire M, Popowycz F. Efficient C-3 reductive alkylation of 4-hydroxycoumarin by dehydrogenative oxidation of benzybc alcohols through ruthenium catalysis. New J Chem. 2014 38 1794-1801. 

Recently, Dong et al. reported a multicatalytic cascade reaction combining Pd, acid, and Ru catalysis [11]. By coupling palladium-catalyzed oxidation, acid-catalyzed hydrolysis, and ruthenium-catalyzed reduction, the elusive anti-Markovnikov olefin hydration was formally achieved, affording primary alcohols from waters and aryl-substituted terminal alkenes (Scheme 9.8). 

Chiral amino alcohols are common structures in drug molecules for example, y-secondaiy aminoalcohols are key intermediates in the synthesis of several pharmaceuticals, examples of which are shown in Scheme 14.12. Zhang has shown that Rh-DuanPhos catalysts can be used to synthesise these key intermediates directly via asymmetric hydrogenation of the p-secondary amino ketone. Application to the synthesis of the antidepressant duloxetine is shown in Scheme 14.12. It should be noted that, to date, ruthenium catalysis has not been successfully applied to the reduction of secondary amino substrates a tertiary amino group is required resulting in a less efficient synthesis requiring extra S3mthetic steps. ... 

Binary systems of ruthenium sulfide or selenide nanoparticles (RujcSy, RujcSey) are considered as the state-of-the-art ORR electrocatalysts in the class of non-Chevrel amorphous transition metal chalcogenides. Notably, in contrast to pyrite-type MS2 varieties (typically RUS2) utilized in industrial catalysis as effective cathodes for the molecular oxygen reduction in acid medium, these Ru-based cluster materials exhibit a fairly robust activity even in high methanol content environments of fuel cells. 

Cofacial ruthenium and osmium bisporphyrins proved to be moderate catalysts (6-9 turnover h 1) for the reduction of proton at mercury pool in THF.17,18 Two mechanisms of H2 evolution have been proposed involving a dihydride or a dihydrogen complex. A wide range of reduction potentials (from —0.63 V to —1.24 V vs. SCE) has been obtained by varying the central metal and the carbon-based axial ligand. However, those catalysts with less negative reduction potentials needed the use of strong acids to carry out the catalysis. These catalysts appeared handicapped by slow reaction kinetics. 

Annual Volume 71 contains 30 checked and edited experimental procedures that illustrate important new synthetic methods or describe the preparation of particularly useful chemicals. This compilation begins with procedures exemplifying three important methods for preparing enantiomerically pure substances by asymmetric catalysis. The preparation of (R)-(-)-METHYL 3-HYDROXYBUTANOATE details the convenient preparation of a BINAP-ruthenium catalyst that is broadly useful for the asymmetric reduction of p-ketoesters. Catalysis of the carbonyl ene reaction by a chiral Lewis acid, in this case a binapthol-derived titanium catalyst, is illustrated in the preparation of METHYL (2R)-2-HYDROXY-4-PHENYL-4-PENTENOATE. The enantiomerically pure diamines, (1 R,2R)-(+)- AND (1S,2S)-(-)-1,2-DIPHENYL-1,2-ETHYLENEDIAMINE, are useful for a variety of asymmetric transformations hydrogenations, Michael additions, osmylations, epoxidations, allylations, aldol condensations and Diels-Alder reactions. Promotion of the Diels-Alder reaction with a diaminoalane derived from the (S,S)-diamine is demonstrated in the synthesis of (1S,endo)-3-(BICYCLO[2.2.1]HEPT-5-EN-2-YLCARBONYL)-2-OXAZOLIDINONE. 

Most of the catalysts employed in PEM and direct methanol fuel cells, DMFCs, are based on Pt, as discussed above. However, when used as cathode catalysts in DMFCs, Pt containing catalysts can become poisoned by methanol that crosses over from the anode. Thus, considerable effort has been invested in the search for both methanol resistant membranes and cathode catalysts that are tolerant to methanol. Two classes of catalysts have been shown to exhibit oxygen reduction catalysis and methanol resistance, ruthenium chalcogen based catalysts " " and metal macrocycle complexes, such as porphyrins or phthalocyanines. ... 

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