- Ru/SiO2 Catalyst for Highly Selective Hydrogenation of Dimethyl Malate to 1,2,4-Butanetriol at Low Temperatures in Aqueous Solvent
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Catalytic selective hydrogenation of esterified malic acid to produce 1,2,4-butanetriol (1,2,4-BT) using H2 as the reducing reagent suffers from the low 1,2,4-BT selectivity. Here, Ru/SiO2 catalyst was employed for selective hydrogenation of dimethyl malate (DM) to produce 1,2,4-BT, which gave abnormal high DM conversion (100%) and 1,2,4-BT selectivity (92.4%) in aqueous solvent at 363?K, especially, the 1,2,4-BT yield even is higher than the optimal catalyst reported (Ru-Re, 79.8%). The reaction pathways for the DM hydrogenation on Ru/SiO2 were also proposed, suggesting that extremely high 1,2,4-BT selectivity require for the much high hydrogenation rates at low temperatures, where side-reaction transesterification rates are relatively low. The extremely high hydrogenation activity and 1,2,4-BT selectivity on Ru/SiO2 in aqueous solvent at low temperatures arise from that H2O may coordinate to Ru2+ and prevent the reduction of Ru2+ to Ru under high H2 pressure. Ru/SiO2 surface presents abundant Ru2+ in aqueous solvent, can activate H2 through heterolytic cleavage mode to form hydride, which can significantly increase hydrogenation rates of C = O groups at low temperatures. In addition, the activity and 1,2,4-BT selectivity on Ru/SiO2 catalyst only reduced by 2.3% and 2.6%, respectively over a period of 550?h. Graphical Abstract: [Figure not available: see fulltext.]
- Chen, Can,Jiang, Junxiang,Li, Guangci,Li, Xuebing,Wang, Da,Wang, Zhong,Yu, Pei
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- Vanadium-catalyzed asymmetric oxidation of α-hydroxy esters using molecular oxygen as stoichiometric oxidant
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A vanadium-catalyzed method for the oxidative kinetic resolution of α-hydroxyesters, using oxygen as the terminal oxidant, is described. The catalyst is generated in situ from vanadium(V) tri-iso-propoxyoxide in combination with a tridentate ligand derived from 3,5-di-tert-butylsalicylaldehyde and (S)-tert-leucinol. The reaction allows for the enantioselective synthesis of both aromatic and aliphatic secondary alcohols, including those containing olefins and alkynes. Copyright
- Radosevich, Alexander T.,Musich, Christine,Toste, F. Dean
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p. 1090 - 1091
(2007/10/03)
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