Synthesis and Catalytic Application of Knölker-Type Iron Complexes with a Novel Asymmetric Cyclopentadienone Ligand Design

Christian A. M. R. van Slagmaat, Khi Chhay Chou, Lukas Morick, Darya Hadavi, Burgert Blom, Stefaan M. A. De Wildeman*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

11 Citations (Web of Science)

Abstract

Asymmetric catalysis is an essential tool in modern chemistry, but increasing environmental concerns demand the development of new catalysts based on cheap, abundant, and less toxic iron. As a result, Knolker-type catalysts have emerged as a promising class of iron catalysts for various chemical transformations, notably the hydrogenation of carbonyls and imines, while asymmetric versions are still under exploration to achieve optimal enantio-selectivities. In this work, we report a novel asymmetric design of a Knolker-type catalyst, in which the C-2-rotational symmetric cyclopentadienone ligand possesses chiral substituents on the 2- and 5-positions near the active site. Four examples of the highly modular catalyst design were synthesized via standard organic procedures, and their structures were confirmed with NMR, IR, MS, and polarimetry analysis. Density functional theory (DFT) calculations were conducted to elucidate the spatial conformation of the catalysts, and therewith to rationalize the influence of structural alterations. Transfer- and H-2-mediated hydrogenations were successfully established, leading to appreciable enantiomeric excesses (ee) values up to 70%. Amongst all reported Knolker-type catalysts, our catalyst design achieves one of the highest ee values for hydrogenation of acetophenone and related compounds.

Original languageEnglish
Article number790
Number of pages24
JournalCatalysts
Volume9
Issue number10
DOIs
Publication statusPublished - Oct 2019

Keywords

  • asymmetric hydrogenation
  • homogeneous catalysis
  • iron
  • structural design
  • conformational analysis
  • NMR spectroscopy
  • DFT
  • METAL-DIENE COMPLEXES
  • CHIRAL BRONSTED ACID
  • MEDIATED 2+2+1 CYCLOADDITIONS
  • COOPERATIVE TRANSITION-METAL
  • ORGANIC-SYNTHESIS
  • ENANTIOSELECTIVE HYDROGENATION
  • TRICARBONYL COMPLEXES
  • EXCHANGE REACTION
  • CARBON-MONOXIDE
  • KETONES

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