Catalysis continued protocols

One of the most attractive features of the IL/CO2 approach to homogeneous catalysis is the development of continuous processes [7]. Consequently it needs to be demonstrated that the combination of a suitable IL and compressed CO2 can offer more potential for process optimisation than just a simple protocol for batch-wise catalyst recycling. As an example we were able to activate, tune and immobilise Ni catalyst 13 in a continuous-flow system for the hydroviny-lation of styrene (Scheme 3). Styrene is co-dimerised with ethene yielding 3-substituted 1-butenes [26,27]. We could show that this powerful carbon-carbon bond-forming reaction can be achieved with high enantioselectivity in batch-wise operation and in continuous-flow systems. 

Asymmetric pericyclic reaction represents one of the most straightforward protocols to access enantioenriched cyclic compounds and triggers continuing interest in organic synthesis. Fruitful results have been achieved by the catalysis of chiral metal complexes over the past decades [1], On the other hand, recently small organic molecules have also contributed a lot to this area owing to the rapid development of asymmetric organocatalysis [2]. 

Ag [39], or Au catalysis [40], most protocols continue to call for significant excess ofthe starting alkane relative to oxidant ((5 100 equiv) and the reactions are often limited in scope to benzylic or allylic positions and cyclic ethers. Readily available iminoiodi nanes of formula Phi = NR (R = Ts, Ns) are generally utilized as the source of nitrogen, but the employment of commercially available chloro or broma mine T [34, 37, 41 44] or arylazides [35, 45] has also been reported. 

Another highly efficient protocol for the hydroformylation consists in the combination of an ionic liquid with a solid support material (Figure 6.1). This process denominated supported ionic liquid phase (SILP) catalysis is a concept that combines the advantages of ionic liquids with those of heterogeneous support materials and allows the use of fixed-bed reactors for continuous reactions. 

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