A New Route to Cationic Half‐Sandwich Ruthenium(<scp>II</scp>) Complexes with Chiral Cyclopentadienylphosphane Ligands

Doppiu, Angelino; Salzer, Albrecht

doi:10.1002/ejic.200300934

Cited by 31 publications

(22 citation statements)

References 76 publications

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“…22 The isomerization of geraniol and nerol was investigated, and under optimized conditions, the best catalyst produced citronellal almost quantitatively albeit in very low enantiomeric excess (97% conversion, 17% ee).…”

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confidence: 99%

Platinum Metals in the Catalytic Asymmetric Isomerization of Allylic Alcohols

Mantilli

Mazet

2011

Chemistry Letters

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Past and recent advances in the metal-catalyzed asymmetric isomerization of allylic alcohols into carbonyl compounds are discussed in the present Highlight. Emphasis is placed on rhodium, ruthenium, and iridium; the only three metals that have proven successful to date for this most challenging transformation. Ç IntroductionThe metal-catalyzed asymmetric isomerization of primary and secondary allylic alcohols into the corresponding aldehydes and ketones®a reaction of both academic and industrial relevance®has attracted renewed interest in recent years. 1Because such transformations undergo refunctionalization upon isomerization, they are often described as internal redox processes and from a synthetic viewpoint, legitimately placed at the very top of the atom-economy scale (Scheme 1). 2Although a variety of transition metals displays interesting catalytic activity for the non-asymmetric isomerization of some allylic alcohols with TOF up to 62500, 3 the substrate generality remains a major limitation. In most cases, the catalytic activity tends to decrease as a function of the degree of substitution of the olefinic double bond and thus limits investigation of substrates with a prochiral double bond. Catalysts that are effective for the isomerization of primary allylic alcohols are less active for secondary allylic alcohols as is the converse. Furthermore, the lack of supporting organometallic chemistry and the limited number of thorough mechanistic studies using achiral catalysts constitute severe bottlenecks in the rationalized development of highly active and selective chiral catalysts for the related asymmetric isomerization reactions.The focus of the present Highlight is placed exclusively on chiral catalysts elaborated around rhodium, iridium, and ruthenium, three of the Platinum Metals which have been applied with various success to the asymmetric isomerization of primary and secondary allylic alcohols. Ç Primary Allylic AlcoholsThe asymmetric isomerization of primary allylic alcohols into chiral aldehydes is historically intimately linked to the related isomerization of allylic amines into chiral enamines. 46 The degree of refinement attained by this rhodium-catalyzed process in terms of activity, selectivity, generality, and practicality is exceptional and has helped defining standards of excellence; very few other catalytic asymmetric transformations have reached to date. In contrast, the asymmetric isomerization of allylic alcohols does not belong to this elite category. Because of the apparent similarity between both isomerization reactions, and the influence of the success story of the cationic [(binap)Rh] system for the isomerization of allylic amines, most of the subsequent catalysts have been designed using chiral bidentate phosphines and rhodium for the isomerization of primary allylic alcohols. The initial studies conducted in the early 80s' showed that [(binap)Rh(cod)]ClO 4 1 (cod: 1,5-cyclooctadiene) was also catalytically competent for the isomerization of primary allylic alcohols i...

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confidence: 99%

Platinum Metals in the Catalytic Asymmetric Isomerization of Allylic Alcohols

Mantilli

Mazet

2011

Chemistry Letters

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“…Fig. 2 shows sections of the one-bond (left) and 13 C, 1 H long-range (right) correlations, from which one can assign the four 13 CH and the two fully substituted carbon signals of the complexed arene moiety at d > 100 ppm. These 1 H and 13 C absorptions are all shifted to relatively low frequency, in keeping with the literature [20].…”

Section: Resultsmentioning

confidence: 99%

“…It was found to be a mixture of 9 and 10. Yield: 53.5 mg. 1 [RuCp * (tris ortho xenyl phosphite)(CH 3 CN) 2 ]PF 6 (13). A solution of tris ortho xenyl phosphite (233.2 mg, 0.433 mmol) in 3 mL acetone was added to a solution of [RuCp * (CH 3 CN) 3 ]PF 6 (104.0 mg, 0.206 mmol) in 4 mL acetone.…”

Section: Methodsmentioning

confidence: 99%

“…A variety of complexes of ruthenium continue to attract interest both for their organometallic and catalytic chemistry [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The now readily available Ru(II) salts, [Ru(Cp or Cp * )(CH 3 CN) 3 ](PF 6 ) [4e], have been widely employed as starting materials in the synthesis, study and catalytic reactions of an increasing number of half sandwich complexes.…”

Section: Introductionmentioning

confidence: 99%

“…Support for this structure comes from both the 1 H (see Fig. 4) and 13 C NMR spectra from which the characteristic low frequency chemical shifts of the complexed arene, 7 are readily measured. The similarity in parts of the 1 H spectrum of 4 and 7 is coincidental.…”

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confidence: 98%

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Reactions of Ru(Cp∗) complexes with P(o-tolyl)3

Caldwell¹,

Isseponi²,

Pregosin³

et al. 2007

Journal of Organometallic Chemistry

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Continuous‐Flow Asymmetric Hydrogenation of the β‐Keto Ester Methyl Propionylacetate in Ionic Liquid–Supercritical Carbon Dioxide Biphasic Systems

2013

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A continuous-flow process for the asymmetric hydrogenation of methyl propionylacetate as a prototypical b-keto ester in a biphasic system of ionic liquid and supercritical carbon dioxide (scCO 2 ) is presented. An established ruthenium/2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) catalyst was immobilised in an imidazolium-based ionic liquid while scCO 2 was used as mobile phase transporting reactants in and products out of the reactor. The use of acidic additives led to significantly higher reaction rates and enhanced catalyst stability albeit at slightly reduced enantioselectivity. High single pass conversions (> 90%) and good enantioselectivity (80-82% ee) were achieved in the first 80 h. The initial catalyst activity was retained to 91% after 100 h and to 69% after 150 h time-on-stream, where-as the enantioselectivity remained practically constant during the entire process. A total turnover number of~21,000 and an averaged space-time yield (STY av ) of 149 g L À1 h À1 were reached in a long-term experiment. No ruthenium and phosphorus contaminants could be detected via inductively coupled plasma optical emission spectrometry (ICP-OES) in the product stream and almost quantitative retention by the analysis of the stationary phase was confirmed. A comparison between batch-wise and continuous-flow operation on the basis of these data is provided.

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A New Route to Cationic Half‐Sandwich Ruthenium(II) Complexes with Chiral Cyclopentadienylphosphane Ligands

Cited by 31 publications

References 76 publications

Platinum Metals in the Catalytic Asymmetric Isomerization of Allylic Alcohols

Platinum Metals in the Catalytic Asymmetric Isomerization of Allylic Alcohols

Reactions of Ru(Cp∗) complexes with P(o-tolyl)3

Continuous‐Flow Asymmetric Hydrogenation of the β‐Keto Ester Methyl Propionylacetate in Ionic Liquid–Supercritical Carbon Dioxide Biphasic Systems

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