Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2023 Jan 6;88(1):18-26.
doi: 10.1021/acs.joc.2c00616. Epub 2022 May 18.

Parts-Per-Million of Soluble Pd0 Catalyze the Semi-Hydrogenation Reaction of Alkynes to Alkenes

Jordi Ballesteros-Soberanas  1 , Jose A Carrasco  1 , Antonio Leyva-Pérez  1
Affiliations

Parts-Per-Million of Soluble Pd0 Catalyze the Semi-Hydrogenation Reaction of Alkynes to Alkenes

Jordi Ballesteros-Soberanas et al. J Org Chem. .

Abstract

The synthesis of cis-alkenes is industrially carried out by selective semi-hydrogenation of alkynes with complex Pd catalysts, which include the Lindlar catalyst (PdPb on CaCO3) and c-Pd/TiS (colloidal ligand-protected Pd nanoparticles), among others. Here, we show that Pd0 atoms are generated from primary Pd salts (PdCl2, PdSO4, Pd(OH)2, PdO) with H2 in alcohol solutions, independently of the alkyne, to catalyze the semi-hydrogenation reaction with extraordinarily high efficiency (up to 735 s-1), yield (up to 99%), and selectivity (up to 99%). The easy-to-prepare Pd0 species hold other potential catalytic applications.

PubMed Disclaimer

Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Kinetic plots for the hydrogenation of 1 to 2 with PdCl2, Lindlar′s and c-Pd/TiS catalysts (0.0002 mol %), and PdSO4 (0.002 mol %) in ethanol (0.5M) under 5 bar of H2 at 90 °C. The reactors were previously washed with aqua regia. Solid lines represent alkyne conversion, and dashed lines represent alkene selectivity; the remaining yields pertain to the corresponding alkane.
Figure 2
Figure 2
Kinetic plots for the hydrogenation of 1 to 2 with PdCl2 (0.04 mol %) in ethanol (0.5M), by adding 1 (black lines), H2 (green lines), or 1 + H2 (orange lines) after 10 min at 30 °C. The reactors were previously washed with aqua regia. Solid lines represent alkyne conversion, and dashed lines represent alkene selectivity; the remaining yields pertain to the corresponding alkane.
Scheme 1
Scheme 1. Proposed Reaction to Generate the Catalytically Active Pd0 Species during the PdCl2-Catalyzed Hydrogenation Reaction
Figure 3
Figure 3
1H NMR of the triethylamine (TEA) methylene protons. Top: Proton shifts caused by the in situ formation of HCl after reduction of PdCl2. Bottom: Proton shifts caused by the direct addition of HCl to triethylamine solutions, at the corresponding (1:2) PdCl2/HCl stoichiometry. The amount of acid was kept constant throughout the experiment (0.9 mg PdCl2, 1 mg 37 wt % HCl in H2O), and the base was progressively added. The experiments were performed in D2O.
Figure 4
Figure 4
Alkene yields of the hydrogenation of 1 at 90 °C, and 5 bar of H2 in ethanol with PdCl2 at different loadings: 0.0004 mol % (green curve), 0.004 mol % (black curve), 0.04 mol % (orange curve). The reactors were previously washed with aqua regia. The remaining yields pertain to the corresponding alkane.
Figure 5
Figure 5
Hydrogenation of different alkynes catalyzed by the indicated amounts of PdCl2 in ethanol (0.5M) under 5 bar of H2 at 30 °C (0.04 mol % Pd) or 90 °C (0.0002 mol % Pd). The reactors were previously washed with aqua regia. Solid lines represent alkyne conversion, and dashed lines represent alkene selectivity; the remaining yields pertain to the corresponding alkane.
See this image and copyright information in PMC

References

    1. Bonrath W.; Medlock J.; Schütz J.; Wüstenberg B.; Netscher T. Hydrogenation in the Vitamins and Fine Chemicals Industry—An Overview. Hydrogenation 2012, 69–90. 10.5772/48751. - DOI
    1. Howse P. E.; Jones O. T.; Stevens I. D. R.. Synthesis of Pheromones. In Insect Pheromones and their Use in Pest Management; Springer Science & Business Media, 1998; pp 226–245.
    1. Parker G. L.; Smith L. K.; Baxendale I. R. Development of the Industrial Synthesis of Vitamin A. Tetrahedron 2016, 72, 1645–1652. 10.1016/j.tet.2016.02.029. - DOI
    1. Swamy K. C. K.; Reddy A. S.; Sandeep K.; Kalyani A. Advances in Chemoselective and/or Stereoselective Semihydrogenation of Alkynes. Tetrahedron Lett. 2018, 59, 419–429. 10.1016/j.tetlet.2017.12.057. - DOI
    1. Vilé G.; Albani D.; Almora-Barrios N.; López N.; Pérez-Ramírez J. Advances in the Design of Nanostructured Catalysts for Selective Hydrogenation. ChemCatChem 2016, 8, 21–33. 10.1002/cctc.201501269. - DOI