Amino alcohol effects on the ruthenium(II)-catalysed asymmetric transfer hydrogenation of ketones in propan-2-ol

Takehara, Jun; Hashiguchi, Shohei; Fujii, Akio; Inoue, Shin‐ichi; Ikariya, Takao; Noyori, Ryoji

doi:10.1039/cc9960000233

Cited by 333 publications

(200 citation statements)

References 8 publications

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“…1, 4 and Ru-H Fig. 1, 5 by a bifunctional transfer of a hydride and a proton effects the oxidation of alcohols and reduction of ketones (5,11,(15)(16)(17)(18)(19)(20).…”

mentioning

confidence: 99%

Transient Ru-methyl formate intermediates generated with bifunctional transfer hydrogenation catalysts

Perry

Brownell

Chingin

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Desorption electrospray ionization (DESI) coupled to high-resolution Orbitrap mass spectrometry (MS) was used to study the reactivity of a (β-amino alcohol)(arene)RuCl transfer hydrogenation catalytic precursor in methanol (CH 3 OH). By placing ½ðp-cymeneÞ RuCl 2 2 on a surface and spraying a solution of β-amino alcohol in methanol, two unique transient intermediates having lifetimes in the submillisecond to millisecond range were detected. These intermediates were identified as Ru (II) and Ru (IV) complexes incorporating methyl formate (HCOOCH 3 ). The Ru (IV) intermediate is not observed when the DESI spray solution is sparged with Ar gas, indicating that O 2 dissolved in the solvent is necessary for oxidizing Ru (II) to Ru (IV). These proposed intermediates are supported by high-resolution and high mass accuracy measurements and by comparing experimental to calculated isotope profiles. Additionally, analyzing the bulk reaction mixture using gas chromatography-MS and nuclear magnetic resonance spectroscopy confirms the formation of HCOOCH 3 . These results represent an example that species generated from the (β-amino alcohol)(arene)RuCl (II) catalytic precursor can selectively oxidize CH 3 OH to HCOOCH 3 . This observation leads us to propose a pathway that can compete with the hydrogen transfer catalytic cycle. Although bifunctional hydrogen transfer with Ru catalysts has been well-studied, the ability of DESI to intercept intermediates formed in the first few milliseconds of a chemical reaction allowed identification of previously unrecognized intermediates and reaction pathways in this catalytic system. organometallic catalysis | reaction intermediates | ruthenium | kinetics C atalytic transfer hydrogenation (CTH) is an efficient method for the enantioselective reduction of multiple bonds (e.g., C═O and C═NR) in chemical and pharmaceutical syntheses (1-4). Typically, a hydrogen donor such as isopropanol is used as a convenient reducing agent and is oxidized to its corresponding ketone (5). As a catalytic version of the classical MeerweinPondorf-Verley reduction/Oppenaur oxidation (6-10), CTH provides a mild method for both ketone reduction and alcohol oxidation. Previous studies show that methanol (CH 3 OH) can serve as a hydrogen donor for (arene)Ru complexes ligated by β-amino alcohols (11), but the nature of the oxidized products from CH 3 OH has not been previously characterized (12). Additionally, some Pd and Ru (13, 14) catalysts can oxidize CH 3 OH to methyl formate (HCOOCH 3 ), but selective oxidation to methyl formate has not been observed previously for a transfer hydrogenation catalysis. Fig. 1 shows the mechanism proposed by Kenney, Heck, Walgrove, and Wills (15) for CTH when Fig. 1, 1 is treated with β-amino alcohol ligands in the presence of a base. Ligation of the cymene dimer Fig. 1, 1 with ligand Fig. 1, 2 generates the Ru-Cl catalyst precursor Fig. 1, 3, which undergoes dehydrohalogenation to form the Ru-amide Fig. 1, 4. An outer-sphere concerted hydrogen transfer of α-C─H to Ru and ─O─H t...

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“…1, 4 and Ru-H Fig. 1, 5 by a bifunctional transfer of a hydride and a proton effects the oxidation of alcohols and reduction of ketones (5,11,(15)(16)(17)(18)(19)(20).…”

mentioning

confidence: 99%

Transient Ru-methyl formate intermediates generated with bifunctional transfer hydrogenation catalysts

Perry

Brownell

Chingin

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…7) Hashiguchi et al, 1995;Takehara et al, 1996). After this milestone discovery a large number of related or novel ligands and catalysts for ATH have been developed that display a broad substrate scope and provide optically active alcohols in a high enantiomeric purity Everaere et al, 2003;Gladiali et al, 2006).…”

Section: Ru- Rh-and Ir-catalyzed Hydrogenation and Transfer Hydrogenmentioning

confidence: 99%

Asymmetric Hydrogenation and Transfer Hydrogenation of Ketones

Štefane¹,

Požgan²

2012

Hydrogenation

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“…A number of ligands have been developed for use in organometallic ATH reactions , which include diamines such as TsDPEN 1, [3] 2, [4a-c] 3, [4d] and 4. [5] Complexes of β-Amino alcohols [6][7][8] such as 5-9 are capable of reducing ketones with high enantioselectivities when used with iPrOH as the hydrogen donor. Ligands include 6 7 and the 2-azanorboronyl methanols 8 and 9.…”

Section: Introductionmentioning

confidence: 99%

Application of Proline‐Functionalised 1,2‐Diphenylethane‐1,2‐diamine (DPEN) in Asymmetric Transfer Hydrogenation of Ketones

Manville

Docherty²,

Padda³

et al. 2011

Eur J Org Chem

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Amino alcohol effects on the ruthenium(II)-catalysed asymmetric transfer hydrogenation of ketones in propan-2-ol

Cited by 333 publications

References 8 publications

Transient Ru-methyl formate intermediates generated with bifunctional transfer hydrogenation catalysts

Transient Ru-methyl formate intermediates generated with bifunctional transfer hydrogenation catalysts

Asymmetric Hydrogenation and Transfer Hydrogenation of Ketones

Application of Proline‐Functionalised 1,2‐Diphenylethane‐1,2‐diamine (DPEN) in Asymmetric Transfer Hydrogenation of Ketones

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