Halogen exchange, using supported

Table 12. Synthesis of Fluorinated Aromatics through Halogen Exchange Using Potassium Fluoride Catalyzed by Polymer-Supported Aminopyridinium Salts ...

Polymer-supported catalysts, especially those based on polystyrene resins, have been used on many occasions but they also suffer from low thermal stability as well as high cost and a tendency to swell in solvent.147,148 Simple physisorbed supported PTCs can be prepared by the incipient wetting method. In this way, alumina-supported phosphonium compounds have been prepared and used to catalyse various halogen exchange reactions in the gas phase along with various other nucleophilic substitutions (Figure 4.24). 

The synthesis of polymer-supported crown ethers and the use of the latter as immobilized phase transfer catalysts in the halogen exchange reaction of 1-bromo-octane with potassium iodide has been reported. ... 

Silicon linker 76 was used for direct loading of aromatic compounds to supports for the assembly of pyridine-based tricyclics (Scheme 39) [87], Following the initial coupling of an aromatic bromide to the resin by halogen/metal exchange in the presence of tert-butyl lithium, a... 

Several patents report the use of calcium fluoride supported on potassium fluoride or calcium fluoride itself for halogen-fluorine exchange.4-6 These products obtained are useful in the pharmaceutical and agrochemical industries. 

Much early work [21] involved the use of silver(I) fluoride, conveniently prepared from the oxide or carbonate with 40% hydrogen fluoride, for the exchange of single halogen atoms in alkyl halides [22] and other systems [23]. The use of calcium fluoride as a solid, inert support may increase the reactivity of silver fluoride [24] (Figure 3.1). 

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