Fluorous mixture synthesis examples

Apart from its use for solvation and separation of catalysts, the fluorous phase can also be used advantageously for separation processes during workup. Strategic synthesis planning is facilitated by tagging with fluorous residues to overcome the frequently limiting recovery and purification difficulties [1], As in solid-phase syntheses, an excess of components can be used to drive the reactions to completion. Side products can easily be separated if, for example, only the product is tagged with fluorous alkyl residues and therefore precipitates from the reaction mixture or is extracted with the fluorous phase. 

As well as labelling reagents permanently fluorous, Curran has also labelled substrates temporarily fluorous for multiplex synthesis. For example, a series of fluorous aryl tin substrates were prepared (Fig. 8) and used as variable pieces of a small library of Stifle couplings [86-88]. A mixture of tin reactant (32a-d, 1.2 equivalents), halide or triflate (35a-e, 2 mmol, 1 equivalent), PdCl2(PPh3)2 (2 mol%) and LiCl (3 equivalents) in THF/DMF (1/1,1 cm3) was heated at 80°C for 22 h. The reactions were carried out in groups of five by reacting one tin reactant with all five partners in separate vials simultaneously. After evaporation of the solvent, the crude... 

In addition to the en route protocol described in Section 13.2.6 for the synthesis of pas-sifloricins, the use of redundant tags for the synthesis of fused-tricyclic hydantoins is another example of FMS in which the number of fluorous tags is less than that of components in the mixture. Since molecules for FMS have fluorine atoms both on the parent structure and on the tag, each component in the mixture has different total fluorine content - even the tag may be redundant. 

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