Ruthenium-Catalyzed Hydroformylation

A similar type of intermediate in the ruthenium-catalyzed hydroformylation was suggested by Wilkinson and co-workers (36). 

KOH Concentration Studies. The effect of KOH concentration on benzaldehyde reduction was examined, and the results are shown in Figure 2 along with our previous results for ruthenium catalyzed hydroformylation (12). 

Studies analyzing the effects of the remaining reactants, H20 and C6HsCH0 indicate that the reaction appears to be zero order with respect to both reactants. It is interesting that in previous work we also found similar behavior for H20 in ruthenium catalyzed hydroformylation (12), as did Ungermann et al. with the WGSR (14). 

The effects of changes in KOH concentration on catalyst activity for benzaldehyde reduction are complex. Figure 2 compares the present work with KOH concentration studies for ruthenium catalyzed hydroformylation ... 

Ruthenium-catalyzed hydroformylation of 1,4-dienes in the presence of amines produced eight-membered heterocycles in modest yields, and an example is presented in Scheme 67 <1999T4721>. 

Ruthenium-catalyzed hydroformylation of alkenes was also studied using charged tags [84]. A unique permanently-charged version of a self-assembling bidentate ligand (Fig. 15) was synthesized to study the catalytic mechanism. 

The hydroformylation reaction or 0x0 process is an important industrial synthetic tool. Starting from an alkene and using syngas, aldehydes with one or more carbon atoms are obtained. In almost all industrial processes for the hydroformylation of alkenes, rhodium or cobalt complexes are used as catalysts [33]. A number of studies on ruthenium complex-catalyzed hydroformylation have been reported [34]. One of the reasons for the extensive studies on ruthenium complex catalysts is that, although the rhodium catalysts used in industry are highly active, they are very expensive, and hence the development of a less-expensive catalytic system is required. Since inexpensive ruthenium catalysts can achieve high selectivity for desired u-alde-hydes or n-alcohols, if the catalytic activity can be improved to be comparable with that of rhodium catalysts, it is possible that a ruthenium-catalyzed 0x0 process would be realized. 

Laine (43-47) used potassium hydroxide to promote the catalytic activity of [Ru3(CO),2] and [H4Ru4(CO),2] for the hydroformylation of pent-1-ene. Under 64 bar of CO pressure, at 135 or 150°C, high selectivities for straight-chain aldehydes were obtained, for example, 97%. As the subsequent reduction of aldehydes to alcohols is lower, important aldol condensations occurred owing to the presence of a base in solution. Analysis of the reaction mixtures has shown that the anionic [H3Ru4(CO),2] cluster is likely to be the active species. Since this complex was recognized as the major component of the low pressure ruthenium-catalyzed water gas shift... 

Phosphonium ionic liquids have been used several times for metal-catalyzed hydroformylations. Ruthenium and cobalt metal complexes catalyze the hydroformylation of internal olefins in [ Bu4P][Br] the major products are, however, the corresponding alcohols. Rhodium-catalyzed hydroformylations were conducted in [Bu3PEt][TsO] and [Ph3PEt][TsO] melts (meltingpoints 8UC and94 C, respectively). The products were easily isolated by decantation of the solid medium at room temperature. ... 

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. 

Smejkal T, Han H, Breit B, Krische Ml (2009) All carbon quaternary centers via ruthenium-catalyzed hydroxymethylation of 2-substituted butadienes mediated by formaldehyde beyond hydroformylation. J Am Chem Soc 131 10366-10367... 

By a comparison of ligands in ruthenium-catalyzed hydroformylation based on elements of the fifth row of the periodic table, the following order of yields was found [25] ... 

Up to now, almost exclusively terminal olefins have been screened in ruthenium-catalyzed hydroformylation. One of the notable exceptions concerns early investigations of Knifton [115]. He used ruthenium carbonyl melt catalysts, wherein the ruthenium carbonyls are dispersed in quaternary phosphonium salts with a low melting point. By the addition of chelating N-donor ligands such as 2,2 -bipyridyl, -aldehydes came out. 

Ruthenium-Catalyzed Hydroformylation-Hydrogenation Tandem Reaction... 

Mitsudo and coworkers [85] screened several tertiary and aromatic A(-ligands for the ruthenium-catalyzed hydroformylation of styrene (Scheme 5.64). The highest yield of 2-phenylpropanol was observed in the presence of quinuclidine. 

Scheme 5.72 Catalytic system for the ruthenium-catalyzed hydroformylation-acetalization.

A mixed ionic liquid [bmim][a,NTf2] system was successfully used as a reaction medium for ruthenium-catalyzed hydroformylation of 1-hexene with carbon dioxide in the absence of toxic CO and any volatile organic solvents. Thus, from 20 mmol 1-hexene in [bmim][Cl,NTf2] containing 0.1 mmol Ru3(CO)i2 82% heptanal was obtained at 160°C under 40bar CO2 and 40bar H2 pressure in 10 h [70]. 

Tominaga, K.-i. Sasaki, Y. Ruthenium-Catalyzed One-pot Hydroformylation of Al-kenes using Carbon dioxide as a Reactant. J. Mol. Catal. A Chem. 2004, 220, 159-... 

The first example of homogeneous transition metal catalysis in an ionic liquid was the platinum-catalyzed hydroformylation of ethene in tetraethylammonium trichlorostannate (mp. 78 °C), described by Parshall in 1972 (Scheme 5.2-1, a)) [1]. In 1987, Knifton reported the ruthenium- and cobalt-catalyzed hydroformylation of internal and terminal alkenes in molten [Bu4P]Br, a salt that falls under the now accepted definition for an ionic liquid (see Scheme 5.2-1, b)) [2]. The first applications of room-temperature ionic liquids in homogeneous transition metal catalysis were described in 1990 by Chauvin et al. and by Wilkes et ak. Wilkes et al. used weekly acidic chloroaluminate melts and studied ethylene polymerization in them with Ziegler-Natta catalysts (Scheme 5.2-1, c)) [3]. Chauvin s group dissolved nickel catalysts in weakly acidic chloroaluminate melts and investigated the resulting ionic catalyst solutions for the dimerization of propene (Scheme 5.2-1, d)) [4]. 

Ruthenium- and cobalt-catalyzed hydroformylation of internal and terminal alkenes in molten [PBuJBr was reported by Knifton as early as in 1987 [2]. The author described a stabilization of the active ruthenium-carbonyl complex by the ionic medium. An increased catalyst lifetime at low synthesis gas pressures and higher temperatures was observed. 

Fig. 10. Proposed mechanism for the ruthenium-triphenylphosphine-catalyzed hydroformylation of olefins (36).

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