In situ 1H-PHIP-NMR studies of the stereoselective hydrogenation of alkynes to ( E)-alkenes catalyzed by a homogeneous [Cp*Ru]+ catalyst

Schleyer, Dana; Niessen, Heiko G.; Bargon, Joachim

doi:10.1039/b007201j

Cited by 73 publications

(74 citation statements)

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“…acetylenedicarboxylic acid and its esters. 10,14,15 The same findings have now been extended to include more electronrich alkyne substrates. Table 1.…”

Section: Discussionmentioning

confidence: 51%

“…From our experiments it appears that the maximum distance for homopolarization transfer between protons is about three bonds, whereas it is five bonds for heteropolarization transfer to 13 C. From our investigations, it has become obvious that the initial proton polarization may also be transferred to other magnetically active heteronuclei, most attractively to those associated with a low value of their nucleus, i.e. to 15 N, 29 Si or other similarly 'difficult' atoms, using heteroatom PHIP at low magnetic fields.…”

Section: Discussionmentioning

confidence: 84%

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¹³C PHIP NMR spectra and polarization transfer during the homogeneous hydrogenation of alkynes with parahydrogen

Schumacher

Kohlmann

Niessen

et al. 2001

Magnetic Reson in Chemistry

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Homogeneously catalyzed hydrogenations of unsaturated substrates with parahydrogen not only lead to strong polarization signals in 1 H NMR spectra, but also can give rise to strong heteronuclear polarization, especially if the hydrogenations are carried out in low magnetic fields. As a typical example, the polarization transfer from protons to carbon nuclei during the hydrogenation of alkynes is outlined for several substrates. In systems containing easily accessible triple bonds, e.g. phenylethyne or 3,3-dimethyl-1-butyne, polarization transfer occurs to all carbon nuclei in the molecule. Accordingly, in NMR spectra recorded in situ all 13 C resonances can be observed with good to excellent signal-to-noise ratios using only a single transient. The qualitative influence of symmetry and electronic aspects of the substrate and its hydrogenation product on the efficiency of the transfer of polarization to the 13 C-nuclei are discussed.

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“…acetylenedicarboxylic acid and its esters. 10,14,15 The same findings have now been extended to include more electronrich alkyne substrates. Table 1.…”

Section: Discussionmentioning

confidence: 51%

Section: Discussionmentioning

confidence: 84%

¹³C PHIP NMR spectra and polarization transfer during the homogeneous hydrogenation of alkynes with parahydrogen

Schumacher

Kohlmann

Niessen

et al. 2001

Magnetic Reson in Chemistry

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“…For instance, Bargon et al have shown that when [Cp* Ru(alkene)] ϩ was the catalyst, non-phenyl-substituted alkynes selectively formed the (E)-alkene while phenyl-substituted alkynes did likewise at low temperature, but increasingly favoured the (Z) isomer as the temperature was raised. [38] The same group has also reported several investigations into the homogeneous hydrogenation of dehydroamino acids using parahydrogen. [39] This work included the determination of the reaction mechanism and the quantification of the reaction rate.…”

Section: Catalytic Studiesmentioning

confidence: 96%

The Study of Inorganic Systems by NMR Spectroscopy in Conjunction with Parahydrogen‐Induced Polarisation

Duckett

Blazina

2003

Eur J Inorg Chem

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The study of reaction mechanisms by NMR spectroscopy normally suffers from limitations in sensitivity that result in substantial difficulties in the detection and characterisation of reaction intermediates. One technique that can circumvent this problem is the use of para‐enriched hydrogen. Here, an overview of the developments in the study of chemical reactions using parahydrogen‐assisted NMR spectroscopy is presented, with the characterisation of a number of new hydride complexes of iridium, rhodium, ruthenium and tantalum being described. A number of studies involving transition metal clusters and catalytic applications are also considered. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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“…The reduction of acetylenedicarboxylic acid dimethyl ester and diphenylacetylene to their respective trans -alkenes has been reported with [RhH 2 (O 2 COH)(P -i -Pr 3 ) 2 ] [32] . This complex was also shown to facilitate the isomerization of cis -stilbene to trans -stilbene, though the process was around eight SO 3 ] also reduces internal alkynes to ( E ) -alkenes [34] . However, no activity was observed with terminal alkynes, possibly due to the formation of stable vinylidene complexes.…”

Section: Semi -Hydrogenationmentioning

confidence: 99%

Alkyne Reductions

Munslow¹

2008

Modern Reduction Methods

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15 IntroductionAlkynes are highly versatile building blocks for organic chemists due to the ease with which they can be modifi ed. The selective semi -hydrogenation of alkynes is an important process for the fi ne chemical industry, manufacturing of insect sex pheromones and vitamins [1] , and for industrial polymerization processes, where removal of alkynes from alkene feedstocks is crucial [2] . The hydrometallation of alkynes is perhaps the most straightforward method for the production of vinylmetal intermediates. Vinylmetal reagents are important organic intermediates that can function in oxidation and reduction reactions as nucleophiles or in Pdcatalyzed cross -coupling reactions.This chapter covers three methods for alkyne reductions: hydrogenation [3, 4] , hydroboration [5] and hydrosilylation [6] . For the hydroalumination and hydromagnesiation of alkynes, the reader is directed to the relevant sections in Chapter 18 . Their reduction with dissolved metals is discussed in Chapter 17 . Also of interest, but not discussed here, are the hydrometallation reactions including hydrostannation [7] , hydrogermylation [8] and hydroselenation [9] . HydrogenationThe addition of molecular hydrogen (H 2 ) to carbon -carbon multiple bonds has been studied extensively and is a technique frequently used by chemists [10] . The partial reduction of alkynes gives alkenes, whereas total reduction gives alkanes. Total reduction can be simply achieved by catalytic hydrogenation. Alkanes are easily obtained with palladium [11] , Raney nickel [12] or Adams ' platinum oxide [13] under low pressures of hydrogen. A number of alkynes have been fully reduced with the complexes [RhCl(PPh 3 ) 3 ] and [Ru(OAc)(PPh 3 ) 3 ] [14] . The electronrich titanium complexes [Cp 2 Ti(PhC ≡ CPh)(PMe 3 )], [(MeCp) 2 Ti(PhC ≡ CPh)(PMe 3 )]

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In situ 1H-PHIP-NMR studies of the stereoselective hydrogenation of alkynes to ( E)-alkenes catalyzed by a homogeneous [Cp*Ru]+ catalyst

Cited by 73 publications

References 8 publications

¹³C PHIP NMR spectra and polarization transfer during the homogeneous hydrogenation of alkynes with parahydrogen

¹³C PHIP NMR spectra and polarization transfer during the homogeneous hydrogenation of alkynes with parahydrogen

The Study of Inorganic Systems by NMR Spectroscopy in Conjunction with Parahydrogen‐Induced Polarisation

Alkyne Reductions

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In situ 1H-PHIP-NMR studies of the stereoselective hydrogenation of alkynes to ( E)-alkenes catalyzed by a homogeneous [Cp*Ru]+ catalyst

Cited by 73 publications

References 8 publications

13C PHIP NMR spectra and polarization transfer during the homogeneous hydrogenation of alkynes with parahydrogen

13C PHIP NMR spectra and polarization transfer during the homogeneous hydrogenation of alkynes with parahydrogen

The Study of Inorganic Systems by NMR Spectroscopy in Conjunction with Parahydrogen‐Induced Polarisation

Alkyne Reductions

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Product

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¹³C PHIP NMR spectra and polarization transfer during the homogeneous hydrogenation of alkynes with parahydrogen

¹³C PHIP NMR spectra and polarization transfer during the homogeneous hydrogenation of alkynes with parahydrogen