Organometallic Chemistry

Selective Manganese-Catalyzed Semihydrogenation of Alkynes with in-situ Generated H2 from KBH4 and Methanol

Authors

  • Ronald Farrar-Tobar Institute of Applied Synthetic Chemistry, Vienna University of Technology ,
  • Stefan Weber Institute of Applied Synthetic Chemistry, Vienna University of Technology ,
  • Zita Csendes Institute of Applied Synthetic Chemistry, Vienna University of Technology ,
  • Antonio Ammaturo Institute of Applied Synthetic Chemistry, Vienna University of Technology ,
  • Sarah Fleissner Institute of Applied Synthetic Chemistry, Vienna University of Technology ,
  • Helmuth Hoffmann Institute of Applied Synthetic Chemistry, Vienna University of Technology ,
  • Luis Veiros Centro de Química Estrutural and Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa ,
  • Karl Kirchner Institute of Applied Synthetic Chemistry, Vienna University of Technology

Abstract

The selective semihydrogenation of alkynes with the Mn(I) alkyl catalyst fac-[Mn(dippe)(CO)3(CH2CH2CH3)] (dippe = 1,2-bis(di-iso-propylphosphino)ethane) as pre-catalyst is described. Hydrogen gas required for the hydrogenation is generated in situ upon alcoholysis of KBH4 with methanol. A series of aryl-aryl, aryl-alkyl, alkyl-alkyl and terminal alkynes were readily hydrogenated to yield E-alkenes in good to excellent isolated yields. The reaction proceeds at 90°C with catalyst loadings of 0.5 -2 mol%. The implemented protocol tolerates a variety of electron donating and electron withdrawing functional groups including halides, phenols, nitriles, unprotected amines and heterocycles. The reaction can be upscaled to the gram scale. Mechanistic investigations including deuterium labelling studies and DFT calculations were undertaken to provide a reasonable reaction mechanism showing that initially formed Z-isomer undergoes fast isomerization to afford the thermodynamically more stable E-isomer.

Content

Thumbnail image of Mn Catalyzed Semihydrogenation Alkynes.pdf

Supplementary material

Thumbnail image of Supporting information.pdf
Supporting Information
Experimental Details, NMR Spectra
Thumbnail image of coordinates DFT calculated compounds.xyz
DFT Calculations
Cartesian coordinates for DFT-optimized structures (XYZ)