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Acceptorless Amine Dehydrogenation and Transamination Using Pd-Doped Hydrotalcites
被引:41
作者:
Ainembabazi, Diana
[1
]
An, Nan
[1
]
Manayil, Jinesh C.
[2
]
Wilson, Karen
[2
]
Lee, Adam F.
[2
]
Voutchkova-Kostal, Adelina M.
[1
]
机构:
[1] George Washington Univ, Chem Dept, 800 22nd St NW, Washington, DC 20052 USA
[2] RMIT Univ, Sch Sci, Melbourne, Vic 3001, Australia
关键词:
acceptorless dehydrogenation;
amines;
amine dehydrogenation;
transamination;
palladium;
hydrotaclite;
heterogeneous catalysis;
SECONDARY-AMINES;
COUPLING REACTIONS;
AEROBIC OXIDATION;
HETEROGENEOUS CATALYST;
THERMAL-DECOMPOSITION;
NITROGEN-HETEROCYCLES;
GRAFTED HYDROTALCITE;
PALLADIUM CATALYSTS;
ANIONIC CLAYS;
IMINES;
D O I:
10.1021/acscatal.8b03885
中图分类号:
O64 [物理化学(理论化学)、化学物理学];
学科分类号:
070304 ;
081704 ;
摘要:
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 Bronsted 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.
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页码:1055 / 1065
页数:21
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