H-Transfer reactions of internal alkenes with tertiary amines as H-donors on carbon supported noble metals

Abstract

A hydride transfer reaction with tertiary amines was observed in the presence of noble metals on a carbon support. Hydride transfer had been documented previously in terms of activated allyl-type carbon-carbon double bonds containing carbonyl derivatives in the presence of triethyl amine (conjugate reduction). The proposed mechanism is a hydride transfer reaction in which the metal serves as the reaction partner of the hydrido-metal iminium adduct formation. The saturation of a non-activated internal double bond containing compound, such as methyl oleate and trans-5-decene as substrates, was observed for the first time in this work. The pre-reduced catalyst samples showed high activity; in the presence of Pd/C, Pt/C and Rh/C partial to complete conversion was detected at 140 °C in a p-xylene solvent without molecular hydrogen. Higher molecular weight byproducts of the amines were formed, while in the case of the substrates negligible amounts of unreacted but double bond migrated species were present. There is a possibility of usage of alkyl amines other than triethylamine; thus use of tributyl-, tripentyl-, trihexylamine and N,N-diisopropylethylamine, as well as cyclic 1-ethylpyrrolidine and 1-ethylpiperidine, was investigated. Cyclic amines and diisopropyl derivatives as H sources produced the highest conversion, while amines with longer alkyl chains showed minor activity. As a clear indication of H-donation, the formation of unsaturated amine species such as 1-ethyl-pyrrole and pyridine was observed.

Hydrogen Transfer Reactions of Carbonyls, Alkynes, and Alkenes with Noble Metals in the Presence of Alcohols/Ethers and Amines as Hydrogen Donors

“…H-Transfer reactions of internal alkenes with tertiary amines on carbon-supported noble metals such as palladium, platinum, and rhodium was studied in the condensed phase [98]. The highest overall catalytic activity was observed for Pd/C (Pd/10 mol %) in the presence of N,N-diisopropylethylamine, 1-ethylpyrrolidine, and 1-ethylpiperidine, while methyl oleate and trans-5-decene were used as starting materials (Scheme 26) [98]. Scheme 26.…”

“…Triethylamine and amines with longer alkyl chain (n-butyl, n-pentyl, n-hexyl) showed minor hydrogen donation abilities. The formation of 1-ethyl-pyrrole (from 1-ethylpyrrolidine) and pyridine (from 1-ethylpiperidine) was observed, which clearly indicated that the source of the newly incorporated two hydrogen atoms was the amine [98]. Two modes of activation of the alkene were described: one possibility if the alkene competitively adsorbs on the metal with the alkyl amine Scheme 26.…”

A Heterogeneous Pt-ReOx/C Catalyst for Making Renewable Adipates in One Step from Sugar Acids

“…In addition to the advantages in DODH, isopropanol is a good hydrogen donor for the CTH reaction. CTH reactions using isopropanol as a hydrogen donor have garnered much attention as an alternative to direct hydrogenation because the hydrogen donor is easy to handle and environmentally friendly, minimizing possible hazards. − While CTH reactions have been mostly accomplished using noble-metal complexes, several effective heterogeneous catalysts for the CTH of ketone, imines, and polarized alkenes have been reported. − …”

Development of the Applications of Palladium on Charcoal in Organic Synthesis

“…The crucial hydrogenation reaction has gained increasing interest, because it is widely utilized in span from industrial materials to activated drugs synthesis . In general, there are two strategies for the hydrogenation reaction; one is the direct hydrogenation with hydrogen gas, and the other one is the convenient and powerful transfer hydrogenation, referring to the addition of hydrogen to a molecule from a non‐H 2 hydrogen source.…”