期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 133, 期 36, 页码 14349-14358出版社
AMER CHEMICAL SOC
DOI: 10.1021/ja2034377
关键词
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资金
- Cluster of Excellence
- Excellence Initiative of the German federal and state governments
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 catalyzedtransformations 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 sigma-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 approximate to 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.
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