Advances in chemoselective and/or stereoselective semihydrogenation of alkynes

Swamy, K. C. Kumara; Reddy, Alla Siva; Sandeep, K.; Kalyani, A. Grace

doi:10.1016/j.tetlet.2017.12.057

Cited by 89 publications

(55 citation statements)

References 106 publications

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“…Catalytic semihydrogenation of internal alkynes is an attractive route to access different alkenes for small-scale laboratory synthesis as well as large-scale industrial processes. [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61] Controlling the stereoselectivity and avoiding the formation of over-reduced alkane products are two major challenges facing the development of such reactions. The acridine-based PNP-type ruthenium pincer complex Ru-1 was found to be a highly active catalyst for the trans-semihydrogenation of alkynes.…”

Section: Resultsmentioning

confidence: 99%

“…This translates into a TOF of more than 1000 h -1 , which, to the best of our knowledge, represents the most efficient trans-semihydrogenation of any alkyne reported to date. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61] As the reaction progressed, a clear color change from brown-red to yellow was observed, with the latter being that of Ru-1, and this visible change could be used as a reaction indicator. 7 Notably, only negligible over-reduction into alkane 3a was observed (<1 %), possibly due to the very mild conditions employed.…”

Section: Resultsmentioning

confidence: 99%

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Controlled selectivity through reversible inhibition of the catalyst: Stereodivergent semihydrogenation of alkynes

Luo

Liang

Montag

et al. 2022

Preprint

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Catalytic semihydrogenation of internal alkynes using H2 is an attractive atom-economical route to various alkenes, and its stereocontrol has received widespread attention, both in homogeneous and heterogeneous catalysis. Herein, a novel strategy is introduced, whereby a poisoning catalytic thiol is employed as a reversible inhibitor of a ruthenium catalyst, resulting in the first controllable H2-based semihydrogenation of internal alkynes. Both (E)- and (Z)-alkenes were obtained efficiently and highly-selectively, under very mild conditions, using a single homogenous acridine-based ruthenium catalyst. Mechanistic studies indicate that the (Z)-alkene is the reaction intermediate leading to the (E)-alkene, and that addition of a catalytic amount of bidentate thiol impedes the Z-E isomerization step by forming stable ruthenium thiol(ate) complexes, while still allowing the main hydrogenation reaction to proceed. Thus, the absence or presence of catalytic thiol controls the stereoselectivity of this alkyne semihydrogenation, affording either the (E)-isomer as the final product, or halting the reaction at the (Z)-intermediate. The developed system, which is also applied to the controllable isomerization of a terminal alkene, demonstrates how selective metal catalysis can be achieved by reversible inhibition of the catalyst with a simple auxiliary additive.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Controlled selectivity through reversible inhibition of the catalyst: Stereodivergent semihydrogenation of alkynes

Luo

Liang

Montag

et al. 2022

Preprint

View full text Add to dashboard Cite

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“…However, this catalytic system requires 1) lead (Pb) to suppress the activity of a palladium (Pd) catalyst, 2) quinoline for the same purpose and 3) hydrogen (H 2 ) gas as a hydrogen (electron (e − ) and proton (H + )) source. Recently, excellent catalytic systems for semihydrogenation of alkynes have been developed …”

Section: Introductionmentioning

confidence: 99%

“…Recently, excellent catalytic systems for semihydrogenation of alkynes have been developed. [3][4][5][6][7][8][9][10] A TiO 2 photocatalyst generates positive holes in the valence band and electrons in the conduction band by irradiation of UV light and these cause oxidation and reduction, respectively.…”

Section: Introductionmentioning

confidence: 99%

Accelerated Semihydrogenation of Alkynes over a Copper/Palladium/Titanium (IV) Oxide Photocatalyst Free from Poison and H₂ Gas

et al. 2020

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Selective hydrogenation of alkynes to alkenes (semihydrogenation) without the use of a poison and H2 is challenging because alkenes are easily hydrogenated to alkanes. In this study, a titanium (IV) oxide photocatalyst having Pd core‐Cu shell nanoparticles (Pd@Cu/TiO2) was prepared by using the two‐step photodeposition method, and Pd@Cu/TiO2 samples having various Cu contents were characterized by electron transmission microscopy, X‐ray photoelectron spectroscopy and UV‐vis spectroscopy. Thus‐prepared Pd@Cu/TiO2 samples were used for photocatalytic hydrogenation of 4‐octyne in alcohol and the catalytic properties were compared with those of Pd/TiO2 and Cu/TiO2. 4‐Octyne was fully hydrogenated to octane over Pd/TiO2 at a high rate and 4‐octyne was semihydrogenated to cis‐4‐octene over Cu/TiO2 at a low rate. Rapid semihydrogenation of 4‐octyne was achieved over Pd(0.2 mol%)@Cu(1.0 mol%)/TiO2, indicating that the Pd core greatly activated the Cu shell that acted as reaction sites. A slight increase in the reaction temperature greatly increased the rate with a suppressed rate of H2 evolution as the side reaction. Changes in the reaction rates of the main and side reactions are discussed on the basis of results of kinetic studies. Reusability and expandability of Pd@Cu/TiO2 in semihydrogenation are also discussed.

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“…4 In the same vein, catalytic E-selective semi-hydrogenations of alkynes using hydrogen-transfer chemistry or molecular hydrogen have been also explored. 5 Yet, this transformation remains challenging because most transition metal-catalyzed semi-hydrogenations of C-C triple bonds occur through cisselective processes and E-alkenes are only obtained upon isomerization of the initially formed Z-alkenes. In such a situation, the over-reduction of the alkene is a major limitation.…”

mentioning

confidence: 99%

Catalytic Chemoselective and Stereoselective Semihydrogenation of Alkynes to E-Alkenes Using the Combination of Pd Catalyst and ZnI₂

et al. 2018

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An efficient E-selective semihydrogenation of internal alkynes was developed under low dihydrogen pressure and low reaction temperature from commercially available reagents: Cl2Pd(PPh3)2, Zn 0 and ZnI2. Kinetic studies and control experiments underline the significant role of ZnI2 in this process under H2 atmosphere, establishing that the transformation involves synhydrogenation followed by isomerization. This simple and easy-to-handle system provides a route to E-alkenes under mild conditions.

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Advances in chemoselective and/or stereoselective semihydrogenation of alkynes

Cited by 89 publications

References 106 publications

Controlled selectivity through reversible inhibition of the catalyst: Stereodivergent semihydrogenation of alkynes

Controlled selectivity through reversible inhibition of the catalyst: Stereodivergent semihydrogenation of alkynes

Accelerated Semihydrogenation of Alkynes over a Copper/Palladium/Titanium (IV) Oxide Photocatalyst Free from Poison and H₂ Gas

Catalytic Chemoselective and Stereoselective Semihydrogenation of Alkynes to E-Alkenes Using the Combination of Pd Catalyst and ZnI₂

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Advances in chemoselective and/or stereoselective semihydrogenation of alkynes

Cited by 89 publications

References 106 publications

Controlled selectivity through reversible inhibition of the catalyst: Stereodivergent semihydrogenation of alkynes

Controlled selectivity through reversible inhibition of the catalyst: Stereodivergent semihydrogenation of alkynes

Accelerated Semihydrogenation of Alkynes over a Copper/Palladium/Titanium (IV) Oxide Photocatalyst Free from Poison and H2 Gas

Catalytic Chemoselective and Stereoselective Semihydrogenation of Alkynes to E-Alkenes Using the Combination of Pd Catalyst and ZnI2

Contact Info

Product

Resources

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Accelerated Semihydrogenation of Alkynes over a Copper/Palladium/Titanium (IV) Oxide Photocatalyst Free from Poison and H₂ Gas

Catalytic Chemoselective and Stereoselective Semihydrogenation of Alkynes to E-Alkenes Using the Combination of Pd Catalyst and ZnI₂