Biomedical subjects
Walter Leitner
Publications and source records attributed to Walter Leitner.
Baeyer-Villiger oxidation in compressed CO2.
The aerobic Baeyer-Villiger oxidation of a wide range of ketones, both cyclic and acyclic to the corresponding esters or lactones can be efficiently carried out in compressed carbon dioxide in the presence of an aldehyde as co-reductant.
Biocatalysis in ionic liquids: batchwise and continuous flow processes using supercritical carbon dioxide as the mobile phase.
A new and environmentally benign protocol for enzymatic reactions in ionic liquids is described using supercritical CO2 as the mobile phase; the products are obtained in solvent-free form and the enzyme/ionic liquid mixture can be recycled in batchwise or continuous flow operations.
Selective oxidation of cyclooctane to cyclootanone with molecular oxygen in the presence of compressed carbon dioxide.
The oxidation of cyclooctane (1) to cyclooctanone (3) with molecular oxygen and acetaldehyde (2) as a co-reductant occurs efficiently in the presence of compressed CO2. Up to 20% yields of 3 are obtained under optimised multiphase conditions.
Highly enantioselective nickel-catalyzed hydrovinylation with chiral phosphoramidite ligands.
Readily available chiral phosphoramidites are a promising class of ligands for nickel-catalyzed asymmetric hydrovinylation of vinyl arenes. Cooperative effects are operative when ligands with more than one element of chirality are used. Choosing the proper stereochemistry in each part of the modular ligand system leads to high chemoselectivities and excellent enantioselectivities up to 94%. Moreover, the catalysts derived from these ligands proved extremely efficient and remarkably robust performing up to 8300 catalytic turnovers at an initial turnover frequency beyond 1000 h-1. The large potential for structural variation and their straightforward synthesis make the phosphoramidites currently the best lead structure for catalyst development in this field.
Supercritical carbon dioxide as a green reaction medium for catalysis.
Carbon dioxide in its liquid or supercritical state (scCO(2)) has a prodigious potential as an environmentally benign reaction medium for sustainable chemical synthesis. Since the mid-1990s, rapidly increasing research efforts have shown that scCO(2) can replace conventional and potentially hazardous solvents in a wide range of processes. There is also increasing evidence that the application of scCO(2) can broaden the scope of catalytic synthetic methodologies. On the basis of the experience in our laboratories, this report analyzes the impact of scCO(2) on green organometallic catalysis.
Activation, Tuning, and Immobilization of Homogeneous Catalysts in an Ionic Liquid/Compressed CO(2) Continuous-Flow System This work was supported by the Max Planck Society, the DFG (Gerhard-Hess-Award to W.L.), and the Fonds der Chemischen Industrie. The fruitful input of Dipl.-Chem. Heike Stemmer and Dr. Andreas Wegner (both Mülheim) during the early phase of the project is gratefully acknowledged.
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