Ruthenium-catalysed reactions hydrogenation

As an extension of this work, a total synthesis of sulfobacin A, a von Willebrand factor receptor antagonist, was reported by the same group, in 2004. The key steps of this short route to sulfobacin A involved ruthenium-catalysed asymmetric hydrogenation reactions of a /i-ketoester and a /J-keto-a-amino ester hydrochloride to afford, respectively, the corresponding enantiomerically pure S-hydroxy ester and the enantio-enriched anti -hydroxy-a-amino ester hydrochloride through DKRs (Scheme 2.15). 

Dyson, P. J., Ellis, D. J., Henderson, W., Laurenczy, G. (2003). A comjjarison of ruthenium-catalysed arene hydrogenation reactions in water and l-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids. Adv. Synth. Catal., 345,1-2, 0anuaiy 2003) 216-221, ISSN 1615-4150... 

As an alternative to the use of hydrogen gas, asymmetric ruthenium-catalysed hydrogen transfer reactions have been explored with significant success [381. 

Enantioselective reduction of acetophenone was achieved in a ruthenium-catalysed hydrogen transfer reaction using isopropanol as the hydrogen source in the presence of mono-tosylated (R, R)-diphenylethylenediamine, ephedrine or norephedrine as chiral auxiliary ligands. Under optimised conditions, ( R)-l-phenylethanol was obtained in 90% yield and 82% enantiomeric excess (ee) within 9 min. f-Butylphenylketone was reduced under similar conditions in almost quantitative yield but in moderate ee... 

Catalysis by Metal Ousters in Zeolites. There is an increasing interest in the use of metal clusters stabilized in zeolites. One objective of such work is to utilize the shape and size constraints inherent in these support materials to effect greater selectivities in typical metal-catalysed reactions. Much work has been concerned with carbon monoxide hydrogenation, and although the detailed nature of the supported metals so obtained is not well understood, there is clear evidence of chain limitation in the Fischer-Tropsch process with both RuY zeolites and with HY and NaY zeolites containing Fe3(CO)22- In the former case there is a drastic decline in chain-growth probability beyond C5- or C10-hydrocarbons depending upon the particle size of the ruthenium metal. 

The identification of catalytically active species in FTS is of fundamental importance, as an improved understanding could enable the development of catalysts with increased activity and selectivity. In cobalt- and ruthenium-catalysed FTS, metallic cobalt and ruthenium function as active catalysts. However, in iron-catalysed FTS there are several distinct species generated during the reaction. Due to the lower, or similar, activation energy for iron carbide formation in comparison to carbon monoxide hydrogenation, iron-carbide formation is typically observed in FTS. The formation of several iron-carbide phases have been observed -Fe2C/8 -Fe2.2C (hexagonal... 

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