Selective homogeneous hydrogenation of biogenic carboxylic acids with [Ru(TriPhos)H]+: a mechanistic study
| Autor: | Markus Hölscher, Barthel Engendahl, Walter Leitner, Frank M. A. Geilen, Jürgen Klankermayer |
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| Rok vydání: | 2011 |
| Předmět: |
chemistry.chemical_classification
Ketone Carboxylic acid Protonation Succinates General Chemistry Biochemistry Aldehyde Triphos Catalysis Levulinic Acids chemistry.chemical_compound Lactones Colloid and Surface Chemistry chemistry Ethers Cyclic Levulinic acid Organic chemistry Ruthenium Compounds Hydrogenation Lactone |
| Zdroj: | Journal of the American Chemical Society. 133(36) |
| ISSN: | 1520-5126 |
| Popis: | Selective hydrogenation of biogenic carboxylic acids is an important transformation for biorefinery concepts based on platform chemicals. We herein report a mechanistic study on the homogeneously ruthenium/phosphine catalyzed transformations of levulinic acid (LA) and itaconic acid (IA) to the corresponding lactones, diols, and cyclic ethers. A density functional theory (DFT) study was performed and corroborated with experimental data from catalytic processes and NMR investigations. For [Ru(TriPhos)H](+) as the catalytically active unit, a common mechanistic pathway for the reduction of the C═O functionality in aldehydes, ketones, lactones, and even free carboxylic acids could be identified. Hydride transfer from the Ru-H group to the carbonyl or carboxyl carbon is followed by protonation of the resulting Ru-O unit via σ-bond metathesis from a coordinated dihydrogen molecule. The energetic spans for the reduction of the different functional groups increase in the order aldehyde < ketone < lactone ≈ carboxylic acid. This reactivity pattern as well as the absolute values are in full agreement with experimentally observed activities and selectivities, forming a rational basis for further catalyst development. |
| Databáze: | OpenAIRE |
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