Neutral p-cymene ruthenium complexes with P-stereogenic monophosphines. New catalytic precursors in enantioselective transfer hydrogenation and cyclopropanation

Grabulosa, Arnald; Mannu, Alberto; Mezzetti, Antonio; Muller, Guillermo

doi:10.1016/j.jorganchem.2011.09.015

Cited by 35 publications

(46 citation statements)

References 51 publications

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“…The solvents were purified by standard procedures and distilled under nitrogen. 1 H, 13 C, and 31 P NMR spectra were recorded using the following spectrometers: Varian XL-500, Mer-400 MHz, Varian Inova 300 and Bruker DRX-250, using CDCl 3 as a solvent unless otherwise specified. Chemical shifts were reported downfield from standards.…”

Section: Methodsmentioning

confidence: 99%

“…The intense inhibition of triphenylphosphine is likely to be due merely to its ability to block coordination positions at the Ru atom, and prevent decoordination of PPh 3 . Additionally, we have recently reported chirality transfer to 1-phenylethanol from neutral complexes of the type C bearing P-stereogenic monophosphines [13], showing that the chiral phosphine remains coordinated to the Ru centre, at least throughout the catalytic cycle.…”

Section: The Mechanism Of Thmentioning

confidence: 99%

“…In contrast to the extensive literature regarding the mechanism of TH with Ru complexes bearing chiral diamines and/or diphosphines [4,5,[21][22][23][24][25], there are only a handful of reports [10,12,13] with hints about the mechanism of TH with precursors of the type C. Taking into account the mechanism of TH with bidentate ligands and the strong tendency of ruthenium to form compounds with Ru H bonds, it seems reasonable to assume that the catalytically active species are ruthenium hydride complexes formed under catalytic conditions [7,8,26]. The absence of any X-H (X = N, O, S) fragment in the complex suggests that the H transfer from the donor (2-propanol) to the acceptor (acetophenone) is promoted by the metal through stepwise coordination of both donor and acceptor to the metal centre through an inner-sphere mechanism [22].…”

Section: The Mechanism Of Thmentioning

confidence: 99%

“…Li and coworkers [12] have recently reported very good activities of [RuCl 2 ( 6 -benzene)(PAr 3 )] complexes (Ar = Ph, p-An and p-CF 3 Ph) in the reduction of the same substrate. Almost at the same time, some of us [13] reported the successful enantioselective reduction of acetophenone using several [RuCl 2 ( 6 -p-cymene)(P*)] containing optically pure diarylic P-stereogenic phosphines P*. Some of these complexes showed good activities and moderate enantioselectivities.…”

Section: Introductionmentioning

confidence: 99%

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Neutral η6-arene ruthenium complexes with monodentate P-donor ligands

Grabulosa

Mannu

Alberico

et al. 2012

Journal of Molecular Catalysis A: Chemical

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Section: Methodsmentioning

confidence: 99%

Section: The Mechanism Of Thmentioning

confidence: 99%

Section: The Mechanism Of Thmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Neutral η6-arene ruthenium complexes with monodentate P-donor ligands

Grabulosa

Mannu

Alberico

et al. 2012

Journal of Molecular Catalysis A: Chemical

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“…Reduction of acetophenone in enantioselective fashion was described by Grabulosa et al [55] and Aznar et al [56] employing several catalytic precursors of the family [RuCl 2 (η 6 -p-cymene)(P*)] stabilized by P-stereogenic monodentate ligands. These P-stereogenic ligands can be obtained in pure chiral form through the Evans [53], or the Jugé-Stephan [57][58][59] methods.…”

Section: Th Catalyzed By Ru-arene Complexes Stabilized By Phosphinesmentioning

confidence: 99%

Transfer Hydrogenation from 2-propanol to Acetophenone Catalyzed by [RuCl2(η6-arene)P] (P = monophosphine) and [Rh(PP)2]X (PP = diphosphine, X = Cl−, BF4−) Complexes

2020

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The reduction of ketones through homogeneous transfer hydrogenation catalyzed by transition metals is one of the most important routes for obtaining alcohols from carbonyl compounds. The interest of this method increases when opportune catalytic precursors are able to perform the transformation in an asymmetric fashion, generating enantiomerically enriched chiral alcohols. This reaction has been extensively studied in terms of catalysts and variety of substrates. A large amount of information about the possible mechanisms is available nowadays, which has been of high importance for the development of systems with excellent outcomes in terms of conversion, enantioselectivity and Turn Over Frequency. On the other side, many mechanistic aspects are still unclear, especially for those catalytic precursors which have shown only moderate performances in transfer hydeogenation. This is the case of neutral [RuCl 2 (η 6 -arene)(P)] and cationic [Rh(PP) 2 ]X (X = anion; P and PP = monoand bidentate phosphine, respectively) complexes. Herein, a summary of the known information about the Transfer Hydrogenation catalyzed by these complexes is provided with a continuous focus on the more relevant mechanistic features. Abstract:The reduction of ketones through homogeneous transfer hydrogenation catalyzed by transition metals is one of the most important routes for obtaining alcohols from carbonyl compounds. The interest of this method increases when opportune catalytic precursors are able to perform the transformation in an asymmetric fashion, generating enantiomerically enriched chiral alcohols. This reaction has been extensively studied in terms of catalysts and variety of substrates. A large amount of information about the possible mechanisms is available nowadays, which has been of high importance for the development of systems with excellent outcomes in terms of conversion, enantioselectivity and Turn Over Frequency. On the other side, many mechanistic aspects are still unclear, especially for those catalytic precursors which have shown only moderate performances in transfer hydeogenation. This is the case of neutral [RuCl2( 6 -arene)(P)] and cationic [Rh(PP)2]X (X = anion; P and PP = mono-and bidentate phosphine, respectively) complexes. Herein, a summary of the known information about the Transfer Hydrogenation catalyzed by these complexes is provided with a continuous focus on the more relevant mechanistic features.The possibility to reduce ketones to alcohols in an enantioselective way through ATH represents a milestone in the asymmetric catalysis, as chiral alcohols are employed as intermediates, as well as end-products in many industries, including fragrancies and pharmaceutics [2]. In addition, the protocol can be extended to a general C=X polar substrate (X = O, N), allowing the synthesis of chiral alcohols [2], amines, and many corresponding derivatives [3].Recent applications of such protocol have allowed the valorization of biomass by extracting lignin [4], or for the production of biofuels [5].Historically, a ...

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Asymmetric Cyclopropanation

2017

Asymmetric Synthesis of Three‐Membered Rings

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Neutral p-cymene ruthenium complexes with P-stereogenic monophosphines. New catalytic precursors in enantioselective transfer hydrogenation and cyclopropanation

Cited by 35 publications

References 51 publications

Neutral η6-arene ruthenium complexes with monodentate P-donor ligands

Neutral η6-arene ruthenium complexes with monodentate P-donor ligands

Transfer Hydrogenation from 2-propanol to Acetophenone Catalyzed by [RuCl2(η6-arene)P] (P = monophosphine) and [Rh(PP)2]X (PP = diphosphine, X = Cl−, BF4−) Complexes

Asymmetric Cyclopropanation

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