Journal
CHEMISTRY-A EUROPEAN JOURNAL
Volume 16, Issue 1, Pages 254-260Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.200901501
Keywords
heterogeneous catalysis; hydrogen transfer; magnesium oxide; monoalkylation; palladium
Categories
Funding
- Direccion General de Investigacion Cientifica y Tecnica of Spain [MAT22006-14274-C02-01]
- Generalitat Valenciana [PROMETEO/2008/130]
- Fundacion Areces
- Consejo Superior de Investigaciones Cientificas
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It has been found that a bifunctional metal Pd/base (MgO) catalyst performs the selective monoalkylation of amines with alcohols. The reaction goes through a series of consecutive steps in a cascade mode that involves: 1) the abstraction of hydrogen from the alcohol that produces the metal hydride and the carbonyl compound; 2) condensation of the carbonyl with the amine to give an imine, and 3) hydrogenation of the imine with the surface hydrogen atoms from the metal hydride. Based on isotopic and spectroscopic studies and on the rate of each elementary step, a global reaction mechanism has been proposed. The controlling step of the process is the hydride transfer from the metal to the imine. By changing the crystallite size of the Pd, it is demonstrated that this is a structure-sensitive reaction, whereas the competing processes that lead to subproducts are not. On these bases, a highly selective catalyst has been obtained with Pd crystallite size below 2.5 nm in diameter. The high efficiency of the catalytic system has allowed us to extend the process to the one-Pot synthesis of piperazines.
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