. (2011) The importance of the N-H bond in Ru/TsDPEN complexes for asymmetric transfer hydrogenation of ketones and imines. Organic & Biomolecular Chemistry,9 (9). pp. 3290-3294. Permanent WRAP url:http://wrap.warwick.ac.uk/40377 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher's statement:Final published version : http://dx.doi.org/10.1039/C1OB05208J A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. For more information, please contact the WRAP Team at: publications@warwick.ac.uk Ru(II) complexes of TsDPEN containing two alkyl groups on the non-tosylated nitrogen atom are poor catalysts for asymmetric transfer hydrogenation of ketones and imines; this observation provides direct evidence for the importance of the N-H interaction in the transition state for ketone reduction. CREATED USING THE RSC COMMUNICATION TEMPLATE (VER. 3.0) -SEE WWW.RSC.ORG/ELECTRONICFILES FOR DETAILS

A series of Ru(II) catalysts were prepared and tested in the asymmetric transfer hydrogenation of ketones. The catalyst containing a "4-carbon" tether gave the fastest rates of ketone reduction. This is due to both increased rate of regeneration of hydride "Ru-H" and increased rate of ketone reduction. Several classes of ketone were reduced in enantiomeric excesses of up to 97%. Substituents on the arene ring of the catalyst influence the reaction rate and enantioselectivity.

Stereochemically well-defined ruthenium(II) catalysts have been applied to the asymmetric transfer hydrogenation of a series of ketones. In one case, statistical experimental design was employed to optimize the enantiomeric excess of the product. In the case of the TsDPEN-based systems, the replacement of trans-1,2-diphenyl substitution with cis-, or deletion of one of the phenyl groups, results in significant deterioration of the enantiomeric excess. A new method is described for the synthesis of tethered amino alcohol-containing catalysts.

A series of kinetic and structural investigations on ruthenium-based catalysts for asymmetric transfer hydrogenation (ATH) of ketones are reported. A method is reported for monitoring the formation of ruthenium hydride species in real time using 1 H NMR spectroscopy.10

A series of catalysts have been prepared for use in the asymmetric transfer hydrogenation of ketones. The complexes were prepared using a [4 + 2] cycloaddition reaction at a key step in the reaction sequence. This provides a means for the synthesis of catalysts with modifications at specific sites.

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The synthesis and applications to asymmetric ketone hydrogenation of a series of novel Ru(II) catalysts is described. The design of the ligands ensures that the configuration at the metal atom is retained and cannot invert during the catalytic cycle. The catalysts generate alcohols in moderate to good enantiomeric excess and conversion.

The structure of the Ru catalysts (I) is optimized and best results are achieved for (Ia) containing a butylene tether between the arene and the diamine ligand. This agent provides the product alcohols (III), (V) and (VII) with excellent conversions and high enantioselectivities. Asymmetric reduction of cyclohexyl methyl ketone (IX) is achieved using a sterically more hindered catalyst (Id). -(CHEUNG, F. K.; LIN, C.; MINISSI, F.; CRIVILLE, A. L.; GRAHAM, M. A.; FOX*, D. J.; WILLS, M.; Org. Lett. 9 (2007) 22, 4659-4662; Asymmetric Catal. Group, Dep. Chem., Univ. Warwick, Coventry CV4 7AL, UK; Eng.) -Mischke 14-028