Application of Ruthenium Complexes of Triazole-Containing Tridentate Ligands to Asymmetric Transfer Hydrogenation of Ketones

Abstract

Original citation:Johnson, Tarn C., Totty, William and Wills, Martin. (2012) Application of ruthenium complexes of triazole-containing tridentate ligands to asymmetric transfer hydrogenation of ketones. Organic Letters, 14 (20). pp. 5230-5233. Permanent WRAP url:http://wrap.warwick.ac.uk/55213 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:This document is the Accepted Manuscript version of a Published Work that appeared in final form in Organic Letters, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work, see http://dx.doi.org/10.1021/ol302354z 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 Received Date (will be automatically inserted after manuscript is accepted) ABSTRACTThe synthesis of a series of tridentate ligands based on a homochiral 1,2-diamine structure attached to a triazole group, and their subsequent applications to the asymmetric transfer hydrogenation of ketones, are described. In the best cases, alcohols of up to 93% ee were obtained. Although base is not required, the use of Ru3(CO)12 as metal source is essential, indicating a unique mechanism for the formation of the active catalyst.

Use of tridentate TsDPEN/pyridine ligands in ruthenium-catalysed asymmetric reduction of ketones

“…2 Recently, we found 4 that an N-tosyl-1,2-diphenyl-ethane-1,2-diamine (TsDPEN) modified with a triazole donor, 5 i.e. 2, gave good results in the reduction of ketones when used in conjunction with Ru3(CO)12.…”

“…A suggested mechanism of action for the ATH of an aryl ketone using compound 11 as the ligand is illustrated in Figure 2. 4 Initial decomposition of Ru3(CO)12 with CO release, then ligation by 11 and proton transfer forms the coordinatively saturated active species 16. Aryl ketones can be reduced by 16 via an outer sphere, concerted mechanism as shown in transition state 17.…”

“…In view of the encouraging precedents, we elected to study tridentate ligands containing pyridine groups, with regard to their efficiency when used in a novel complex with Ru3(CO)12. 4 Towards this end we first prepared (R,R)-pyridine-2-carboxylic acid [2-(toluene-4-sulfonylamino)-1,2-diphenyl-1,2-ethylenediamine]-amide 7 in 86% yield (Scheme 1) by the reaction between pyridine-2-carboxylic acid 8 and (1R,2R)-TsDPEN 1 using ethyl chloroformate.…”

Ru(II)‐η6‐benzene Complexes of Dibenzosuberenyl Appended Aroyl/Acylthiourea Ligands: In vitro Biomolecular Interaction Studies and Catalytic Transfer Hydrogenation

“…The Noyori complexes [RuCl(TsDPEN)(h 6 -p-cymene)] and [RuCl(TsDPEN)(h 6 -mesitylene)] inspired the development of TH. [13][14][15][16][17][18] Since last decade, a variety of half-sandwich ruthenium complexes have been extensively investigated in TH. [19] The [Ru(h 6 -arene)(ligand)Cl]/[Ru(h 6 -arene)(ligand)Cl 2 ] type of "piano stool" complexes exhibit the structural features which favour the sequential reactions involved in catalysis.…”

Catalytic asymmetric transfer hydrogenation of ketones: recent advances

“…When an aliphatic ketone was reduced, namely cyclohexyl methyl ketone, conversion was excellent (93%) but, as expected, enantioselectivity was very poor (13% ee). 50 …”