Lithium Aluminium Hydride and Metallic Iron: A Powerful Team in Alkene and Arene Hydrogenation Catalysis.
Angew Chem Int Ed Engl
; 62(18): e202219016, 2023 Apr 24.
Article
em En
| MEDLINE
| ID: mdl-36880503
ABSTRACT
Alkenes that normally do not react with LiAlH4 (3-hexene, cyclohexene, 1-Me-cyclohexene), can be reduced to the corresponding alkanes by a mixture of LiAlH4 and Fe0 (the iron was activated by Metal-Vapour-Synthesis). This alkene-to-alkane conversion with a stoichiometric quantity of LiAlH4 /Fe0 does not need quenching with water or acids, implying that both H's originate from LiAlH4 . The LiAlH4 /Fe0 combination is also a remarkably potent cooperative catalyst for hydrogenation of multi-substituted alkenes and benzene or toluene. An induction period of circa two hours and the minimally required temperature of 120 °C, suggests that the actual catalyst is a combination of Fe0 and the decomposition product of LiAlH4 (LiH and Al0 ). A thermally pre-activated LiAlH4 /Fe0 catalyst did not need an induction time and is also active at room temperature and 1â
bar H2 . A combination of AliBu3 and Fe0 is an even more active hydrogenation catalyst. Without pre-activation, tetra-substituted alkenes like Me2 C=CMe2 and toluene could be fully hydrogenated.
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Coleções:
01-internacional
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MEDLINE
Idioma:
En
Ano de publicação:
2023
Tipo de documento:
Article