Ruthenium-catalyzed hydrogenation

Further mechanistic insights into hydrogenations catalyzed by HRuCl(PPh3)3 (7, p. 83) have been obtained indirectly, from studies on hydrogenation of some ruthenium(III) phosphine complexes (83). A frequently considered mechanism for hydrogen reduction of metal salts involves slow formation of an intermediate monohydride, followed by a faster reaction between the hydride and starting complex (/, p. 72), Eqs. (2) and (3) ... 

Fig. 3.1 G raphical illustration of numbers of reports per year versus date of publication. Data were obtained by searching the Chemical Abstracts Database using the term hydrogenation catalyzed by ruthenium complexes or osmium complexes or rhodium complexes. These are not comprehensive searches but are still representative of the activity in the field.

Enantioselective catalytic hydrogenation. The ruthenium(II) complexes of (R)- and (S)-l, bearing a chiral BINAP ligand, catalyze asymmetric hydrogenation of N-acyl-l-alkylidenetetrahydroisoquinolines to give (1R)- or (lS)-tetrahydroiso-quinolines in 95-100% ee.1 Thus the (Z)-enamide (2), prepared by acylation of 3,4-dihydropapaverine, is hydrogenated in the presence of (R)-l to (1R)-tetrahydroisoquinolines (3). The enantiomeric (lS)-3 is obtained on use of (S)-l as catalyst. 

Asymmetric reduction of carbonyl via hydrogenation catalyzed by ruthenium(II) BINAP complex. 

Noyori, R. and S. Hashiguchi, Asymmetric Transfer Hydrogenation Catalyzed by Chiral Ruthenium Complexes, Accounts of Chemical Research, 30, 97-102 (1997). 

Reduced ruthenium catalysts stored in air are usually oxidized on the surface and must be activated by prereduction with hydrogen for 1-2 h before use for hydrogenations at a low temperature and pressure. In contrast for platinum and palladium catalysts, organic as well as inorganic acids strongly poison the ruthenium catalyzed hydrogenation. Thus acetic acid should not be added or used as solvent for the hydrogenations over ruthenium, particularly under mild conditions. 

Noyori R, Hashiguchi S, Iwasawa Y. Asymmetric transfer hydrogenation catalyzed by chiral ruthenium complexes. Acc. Chem. 

Reduction of anhydrides to y-lactones. Carboxylic acid anhydrides are reduced by homogeneous hydrogenation catalyzed by this ruthenium complex... 

Hydrogenation. The ruthenium chloride complex catalyzes the stereoselective h> drogenation of simple ketones. 

The intramolecular insertion of a hydride into a coordinated olefin is a crucial step in olefin hydrogenation catalyzed by late transition metal complexes, such as those of iridium, rhodium, and ruthenium (Chapter 15), in hydroformylation reactions catalyzed by cobalt, rhodium, and platinum complexes (Chapter 16), and in many other reactions, including the initiation of some olefin polymerizations. The microscopic reverse, 3-hydride elimination, is the most common pathway for the decomposition of metal-alkyl complexes and is a mechanism for olefin isomerizations. 

Zhang, X. Guo, X. Chen, Y. Tang, Y. Lei, M. Fang, W. Mechanism investigation of ketone hydrogenation catalyzed by ruthenium bifunctional catalysts Insights from a DFT study. Phys. Chem. Chem. Phys. 2012,14,6003-6012. 

Formic acid can be used as the ultimate reducing agent in transfer hydrogenations catalyzed by the Shvo complex 1 [3, 35]. Shvo proposed that a formate complex served as a precursor to ruthenium hydride 2, which was the active reducing agent. 

Catalytic asymmetric Michael addition is an important reaction for creating carbon-carbon bonds with enantioselectivity. This reaction can be combined with other catalytic transformations to build up complex organic structures. A successful example is the enantioselective cascade Michael addition/H -hydrogenation catalyzed by ruthenium hydride borohydride complexes containing P-aminophosphine ligands 26 (Scheme 5.13) [19]. This approach has been extended to pentenones, heptenones, and nitrostyrene Michael acceptors and malonitrile Michael donors. 

Dynamic Kinetic Resolution (DKR) under Hydrogenation Conditions Ruthenium-catalyzed asymmetric hydrogenation of racemic a-substituted ketones via-dynamic kinetic resolution (DKR) is one of the elegant and powerful methods for the synthesis of chiral alcohols that simultaneously control two adjacent stereogenic centers with high levels of selectivity in a single chemical operation. This method was first reported... 

Catalysts show remarkable product variation in hydrogenation of simple nitriles. Propionitrile, in neutral, nonreactive media, gives on hydrogenation over rhodium-on-carbon high yields of dipropylamine, whereas high yields of tripropylamine arise from palladium or platinum-catalyzed reductions (71). Parallel results were later found for butyronitrile (2S) and valeronitrile (74) but not for long-chain nitriles. Good yields of primary aliphatic amines can be obtained by use of cobalt, nickel, nickel boride, rhodium, or ruthenium in the presence of ammonia (4J 1,67,68,69). 

An example of a stereoselective hydrogenation in ionic liquids was recently successfully demonstrated by Drie en-H6lscher et al. On the basis of investigations into the biphasic water/n-heptane system [51], the ruthenium-catalyzed hydrogenation of sorbic acid to cis-3-hexenoic acid in the [BMIM][PFg]/MTBE system was studied [52], as shown in Scheme 5.2-8. 

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