Acceptorless Amine Dehydrogenation and Transamination Using Pd-Doped Hydrotalcites

Diana Ainembabazi, Nan An, Jinesh C. Manayil, Karen Wilson, Adam F. Lee*, Adelina M. Voutchkova-Kostal

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

The acceptorless dehydrogenation of acyclic secondary amines is a highly desirable but still elusive catalytic process. Here we report the synthesis, characterization, and activity of Pd-doped hydrotalcites (Pd-HTs) for acceptorless dehydrogenation of both primary and secondary amines (cyclic and acyclic). These multifunctional catalysts comprise Brønsted basic and Lewis acidic surface sites that stabilize Pd in 0, 2 + , and 4 + oxidation states. Pd speciation and corresponding catalytic performance is a strong function of metal loading. High activity is observed for the dehydrogenation of secondary aliphatic amines to imines, and N-heterocycles, such as indoline, 1,2,3,4-tetrahydroquinoline, and piperidine, to aromatic compounds. Oxidative transamination of primary amines is achieved using low Pd loading (0.5 mol %), without the need for oxidants. The relative yields of secondary imines afforded are consistent with trends for calculated free energy of reaction, while yields for transamination products correspond to the electrophilicity of primary imine intermediates. Reversible amine dehydrogenation and imine hydrogenation determine the relative selectivity for secondary imine/amine products. Poisoning tests evidence that Pd-HTs operate heterogeneously, with negligible metal leaching. Catalysts retain over 90% of activity over six reuse cycles, but do suffer some selectivity loss, attributed to changes of Pd phases.

Original languageEnglish
Pages (from-to)1055-1065
Number of pages11
JournalACS Catalysis
Volume9
Issue number2
Early online date20 Dec 2018
DOIs
Publication statusPublished - 1 Feb 2019

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© 2018 The Authors CC BY-NC-ND 4.0

Keywords

  • acceptorless dehydrogenation
  • amine dehydrogenation
  • amines
  • heterogeneous catalysis
  • hydrotaclite
  • palladium
  • transamination

Cite this

Ainembabazi, D., An, N., Manayil, J. C., Wilson, K., Lee, A. F., & Voutchkova-Kostal, A. M. (2019). Acceptorless Amine Dehydrogenation and Transamination Using Pd-Doped Hydrotalcites. ACS Catalysis, 9(2), 1055-1065. https://doi.org/10.1021/acscatal.8b03885