Acceptorless Amine Dehydrogenation and Transamination Using Pd-Doped Hydrotalcites

Ainembabazi, D, An, N, Manayil, J, Wilson, K, Lee, A and Voutchkova-Kostal, A 2019, 'Acceptorless Amine Dehydrogenation and Transamination Using Pd-Doped Hydrotalcites', ACS Catalysis, vol. 9, no. 2, pp. 1055-1065.


Document type: Journal Article
Collection: Journal Articles

Title Acceptorless Amine Dehydrogenation and Transamination Using Pd-Doped Hydrotalcites
Author(s) Ainembabazi, D
An, N
Manayil, J
Wilson, K
Lee, A
Voutchkova-Kostal, A
Year 2019
Journal name ACS Catalysis
Volume number 9
Issue number 2
Start page 1055
End page 1065
Total pages 11
Publisher American Chemical Society
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.
Subject Catalysis and Mechanisms of Reactions
Keyword(s) acceptorless dehydrogenation
amine dehydrogenation
amines
heterogeneous catalysis
hydrotaclite
palladium
transamination
DOI - identifier 10.1021/acscatal.8b03885
Copyright notice © 2018 American Chemical Society
ISSN 2155-5435
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