Homogeneous catalysis operational scheme

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. 

There are various possible approaches for multiphase operation of homogeneous catalysis, to improve their usability and recycle processes with organic/organic, organic/aqueous, or fluorous solvent pairs (solvent combinations), non-aqueous ionic solvents, supercritical fluids, and systems with soluble polymers. Figure 2.2 reports a general scheme of the possibilities for homogeneous catalysis. 

Operational scheme of homogeneous catalysis 460 Basic reactions of homogeneous catalysis 461... 

A particularly promising concept for designing catalysts, which combine the advantages of homogeneous and heterogeneous catalysis, involves coating a solid support with a thin layer of an IL, whereby the IL forms a second phase or is immiscible with the bulk fluids phase containing the reactants and products. Such a concept may be applicable to batch operation in the slurry phase as well as continuous operation in fixed-bed reactors (Scheme 10.2) [25, 35]. The chemical... 

Kurd and coworkers developed a general method for the synthesis of N-H aziridine from unfuncionaUzed olefins under mild conditions using 0-(2,4-dinitrophenyl)hydroxylamine (DPH) via homogeneous rhodium catalysis [112]. This method is operationally simple, scalable, broad functional group tolerable, and fast at ambient temperature, furnishing N-H aziridines in good to excellent yields (Scheme 2.11). 

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