Asymmetric Transfer Hydrogenation of CO and CN Bonds by Tethered Rh<sup>III</sup> Catalysts

Matharu, Daljit S.; Martins, José Eduardo Damas; Wills, Martin

doi:10.1002/asia.200800189

Cited by 83 publications

(34 citation statements)

References 112 publications

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“…[4] During the past two decades, a number of catalytic systems for asymmetric hydrogenation [5] and asymmetric transfer hydrogenation [6] of this class of imines have been invented. Using the chiral titanocene developed by Buchwald and Willoughby, 1-methyl-3,4-dihydro-6,7-dimethoxyisoquinoline was hydrogenated with 98 % ee.…”

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confidence: 99%

A Highly Efficient and Enantioselective Access to Tetrahydroisoquinoline Alkaloids: Asymmetric Hydrogenation with an Iridium Catalyst

2011

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Tetrahydroisoquinolines are an important class of alkaloids displaying high bioactivities.[1] They are present in numerous natural products, and in pharmaceutical drugs and drug candidates, for example, (+)-cryptostyline II, [2a] (+)-cryptostyline III, [2a] and solifenacin (Scheme 1).[2b] Among the various synthetic methods developed in recent decades to afford enantiomerically pure tetrahydroisoquinolines, [1,3] catalytic asymmetric hydrogenation of the corresponding imines shows most promise as a highly efficient and straightforward approach. [4] During the past two decades, a number of catalytic systems for asymmetric hydrogenation [5] and asymmetric transfer hydrogenation [6] of this class of imines have been invented. Using the chiral titanocene developed by Buchwald and Willoughby, 1-methyl-3,4-dihydro-6,7-dimethoxyisoquinoline was hydrogenated with 98 % ee.[5a] Noyori and coworkers initiated research into the Ru II /TsDPEN complex for the highly enantioselective transfer hydrogenation of 3,4-dihydroisoquinolines.[6a] This system was successfully applied in the reduction of 1-(2'-NHR/NO 2 C 6 H 4 )-3,4-dihydroisoquinoline.[6b] Since then, intense research has been focused on this system and modifications have taken place on all components of this catalytic complex, such as, the diamine ligand, the transition metal center, the coordinating h-arene, and the counterion.[5h, 6c-j] Although these titanocene, Ru/ DPEN and Rh/DPEN systems addressed the reduction of 1-alkyl-3,4-dihydroisoquinolines effectively, the asymmetric hydrogenation to enantiomerically pure 1-aryl-tetrahydroisoquinolines remains a challenge, probably owing to the relatively rigid and space-demanding spatial features of these imines. For example, there is no report on the asymmetric hydrogenation of 1-phenyl-3,4-dihydroisoquinoline, a reaction which would lead to the pharmaceutical drug solifenacin (Scheme 1), and the industrial production of this particular tetrahydroisoquinoline depends on an optical resolution of the racemic mixture using tartaric acid. [7] Herein, we report the highly efficient asymmetric hydrogenation of 1-substituted 3,4-dihydroisoquinolines catalyzed by an iridium/f-binaphane complex with excellent reactivity and enantioselectivities (up to 99 % ee and TONs of up to 10 000). The combination of iridium and f-binaphane (Scheme 2) was chosen based on their outstanding performance in asymmetric hydrogenation of a variety of imines from our research.[8] Iridium/diphosphine complexes show more potential for imine reduction in the presence of various additives and possess better activities than other transition metals.[9] At the same time, f-binaphane, which is a strong electron donor and features a flexible ferrocene-based backbone, thus allowing the accommodation of a wide range of substrates around the transition metal center, has been Scheme 1. Structures of (+)-cryptostyline II, (+)-cryptostyline III, and solifenacin.Scheme 2. Structures of chiral phosphine ligands.

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A Highly Efficient and Enantioselective Access to Tetrahydroisoquinoline Alkaloids: Asymmetric Hydrogenation with an Iridium Catalyst

2011

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“…Such a ligand design is necessary because iron is easily oxidized, and the organic environment provided by the ligand should lend stability to the complex without restricting catalytic activity. The tethered ligand systems used by Wills [13] to achieve high rigidity in rhodium, ruthenium, and iridium complexes and the Cp-stabilized piano-stooltype iron complexes reported by Astruc [14] both provide precedence for a ligand system composed of alkylated cyclopentadienyl derivatives bearing chiral diamine moieties for use in a new iron-based catalyst for asymmetric reductions. The general synthetic strategy was to start with an alkylated Cp core and then add the chiral amine moiety.…”

Section: Resultsmentioning

confidence: 97%

“…Despite careful temperature control during the coupling reaction, the formation of a second unexpected and undesired exo-double-bond derivative was identified, based on a multiplet in the 1 H NMR spectrum at δ = 5.25 ppm and the corresponding signal in the 13 C NMR spectrum at δ = 109-110 ppm. At a maximum of 13 % of the overall yield, this product could not be separated from the three desired isomers (Scheme 4) which were directly reduced to the corresponding aldehydes in a single step (Scheme 5).…”

Section: Resultsmentioning

confidence: 99%

Iron(II)‐Catalyzed Asymmetric Hydrosilylation of Acetophenone

Flückiger¹,

Togni²

2011

Eur J Org Chem

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Four new ligands containing a pentasubstituted cyclopentadiene tethered to a stereogenic diamine unit have been prepared and used in the iron‐catalyzed enantioselective hydrosilylation of acetophenone. Catalytically active species have been generated in situ starting from various sources of iron. Fe(acac)2 was the catalyst precursor of choice, whereas other simple FeII or FeIII compounds resulted in significantly lower or no catalytic activity. Quantitative conversions were obtained working with 4 mol‐% Fe at room temp. and phenylsilane as the reducing agent. Under these conditions, ligand 4 afforded an enantioselectivity of 37 % ee. Attempts to isolate the single‐component Fe complexes containing ligands 3–6 have failed so far.

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“…Concerning the use of rhodium complexes derived from 1,2-diamines, compounds 51 55 and 52 56 have shown to be in general excellent catalysts in the ATH of phenones. It is remarkable that in the first case the hydrogenation of an aliphatic ketone, namely cyclohexyl methyl ketone worked properly giving 87% conv and 87% ee.…”

Section: Rhodium Catalystsmentioning

confidence: 99%

Catalytic asymmetric transfer hydrogenation of ketones: recent advances

Foubelo

Nájera

Yus

2015

Tetrahedron: Asymmetry

215

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Abstract-In this review article we will consider the main processes on asymmetric transfer hydrogenation (ATH) of ketones from 2008 up today. The most effective organometallic compounds (derived from Ru, Rh, Ir, Fe, Os, Ni, Co, and Re) and chiral ligands (derived from amino alcohols, diamines, sulphur-and phosphorous-containing compounds, as well as heterocyclic systems) will be shown paying special attention to functionalized substrates, tandem reactions, processes under nonconventional conditions, supported catalysts, dynamic kinetic resolutions (DKR), the use of water as a green solvent, theoretical and experimental studies on reaction mechanisms, enzymatic processes and finally applications to the total synthesis of biologically active organic molecules. _____________________________________________________________________________________

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Asymmetric Transfer Hydrogenation of CO and CN Bonds by Tethered Rh^III Catalysts

Cited by 83 publications

References 112 publications

A Highly Efficient and Enantioselective Access to Tetrahydroisoquinoline Alkaloids: Asymmetric Hydrogenation with an Iridium Catalyst

A Highly Efficient and Enantioselective Access to Tetrahydroisoquinoline Alkaloids: Asymmetric Hydrogenation with an Iridium Catalyst

Iron(II)‐Catalyzed Asymmetric Hydrosilylation of Acetophenone

Catalytic asymmetric transfer hydrogenation of ketones: recent advances

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Asymmetric Transfer Hydrogenation of CO and CN Bonds by Tethered RhIII Catalysts

Cited by 83 publications

References 112 publications

A Highly Efficient and Enantioselective Access to Tetrahydroisoquinoline Alkaloids: Asymmetric Hydrogenation with an Iridium Catalyst

A Highly Efficient and Enantioselective Access to Tetrahydroisoquinoline Alkaloids: Asymmetric Hydrogenation with an Iridium Catalyst

Iron(II)‐Catalyzed Asymmetric Hydrosilylation of Acetophenone

Catalytic asymmetric transfer hydrogenation of ketones: recent advances

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Asymmetric Transfer Hydrogenation of CO and CN Bonds by Tethered Rh^III Catalysts