Flowthrough-reactor (PASSflow)
Transfer hydrogenation
In the shadow of solid phase synthesis, the utilization of functional polymers as reagents and catalysts have only recently gained increased interest for applications in industrial laboratories.[1] Indeed, this method shows several advantages over the conventional solution phase synthesis:
1. the ease of separation of the supported species from a reaction mixture by filtration and washing.
2. the use of excess of reagent to force the reaction to completion without causing workup problems.
3. reuse of the catalyst or of a supported reagent after regeneration.
4. their adaptability to continuous flow processes and hence use in automated synthesis.
The true justification for using solid supports in organic synthesis is automation. Current strategies of automation are based on reaction vessels such as flasks, cans or miniature vials which are employed in the batch mode.
Flowthrough-reactor (PASSflow)
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Transfer hydrogenation |
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In this report, the concept of polymer-assisted solution phase synthesis using solid phase bound reagents and catalysts and new immobilization strategies for chemically active species are brought to the attention of the audience. Besides new heterogeneous catalytic systems, a novel microreactor is presented which is constructed as a continuous flow-through system (PASSflow).[2]
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1 Selected reviews on polymer-assisted syntheses in solution: (a) A. Kirschning, H. Monenschein, R. Wittenberg, Angew. Chem. Int. Ed. Engl. 2001, 40, 650-679; (b) S. V. Ley, I. R. Baxendale, R. N. Bream, P. S. Jackson, A. G. Leach, D. A. Longbottom, M. Nesi, J. S. Scott, R. I. Storer, S. J. Taylor, J. Chem. Soc., Perkin Trans. I 2000, 3815-4195.
2 (a) A. Kirschning, C. Altwicker, G. Dräger, J. Harders, N. Hoffmann, U. Hoffmann, H. Schönfeld, W. Solodenko, U. Kunz, Angew. Chem. Int. Ed. Engl. 2001, 40, 3995-3998; (b) W. Solodenko, U. Kunz, A. Kirschning, Bioorg. Med. Chem. Lett. 2002, 12, 1833-1835.