Acceptorless Amine Dehydrogenation and Transamination Using Pd-Doped Hydrotalcites


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.

Publication DOI:
Divisions: College of Engineering & Physical Sciences > Energy and Bioproducts Research Institute (EBRI)
College of Engineering & Physical Sciences
Additional Information: © 2018 The Authors CC BY-NC-ND 4.0
Uncontrolled Keywords: acceptorless dehydrogenation,amine dehydrogenation,amines,heterogeneous catalysis,hydrotaclite,palladium,transamination,Catalysis,Chemistry(all)
Publication ISSN: 2155-5435
Last Modified: 18 Jun 2024 07:22
Date Deposited: 26 Jun 2019 10:14
Full Text Link: https://chemrxi ... xides/6998204/2
Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL) ... cscatal.8b03885 (Publisher URL)
PURE Output Type: Article
Published Date: 2019-02-01
Published Online Date: 2018-12-20
Accepted Date: 2018-12-16
Authors: Ainembabazi, Diana
An, Nan
Manayil, Jinesh C. (ORCID Profile 0000-0002-9864-3332)
Wilson, Karen
Lee, Adam F.
Voutchkova-Kostal, Adelina M.

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