Filtration, polymer-bound species

The polymer-bound species, a catalyst, a product, or a by-product, can be separated from the reaction mixture. Macroscopic solids and gels can usually be separated from liquids by filtration. Soluble polymers and colloids can be separated from low molecular weight compounds by ultrafiltration. Colloids can be coagulated and filtered. The functionalized polyethylenes described by Bergbreiter in chapter 2 are soluble hot and insoluble cold so that they can be filter. ... 

In the course of developing the diene cyclooligomerization and hydrogenation catalysts described above, we recognized that soluble polymers could also be used in such multi-step processes. However, unlike the case with two different polystyrene-bound species, the use of one soluble and one insoluble polymer bound species would enable the facile isolation of the product and each catalyst or reagent. Flotation techniques can be used to separate two insoluble polymers from one another. However, separation of a soluble polymer from an insoluble one would be simpler since it would only involve a filtration step. Kinetic isolation of each polymer-bound species would be possible even with one soluble polymer-bound species because of the diffusional constraints associated with soluble macromolecules. 

This multi-step, one-pot process was taken further by integration of a third supported reagent for the sequential preparation of 3,5-diphenylpyrazole (Scheme 2.17). Following the previously established procedure, acetophenone was deprotonated and acylated to afford the 1,3-dicarbonyl species. This intermediate was easily separated from the spent polymers by filtration and passed without isolation into a suspension of the resin bound hydrazine salt (9), affording the desired pyrazole in 91% yield. In a subsequent publication, the authors reported that the depleted polymeric reagents from the first step of the conversion (i.e. (7) and (8)) were recovered and separated via a selective flotation procedure, enabhng them to... 

---