Fluorous group

Fluorous-derivatized phosphines have also been used for Heck reactions in scCC>2 together with palladium acetate [7]. The fluorous groups improve the solubility of the catalyst in the SCF compared to nonfluorous ligands. An example of a Heck reaction that uses a fluorous-derivatized phosphine to improve the solubility of a Pd(OAc)2 catalyst is shown in Scheme 10.5. 

Modified cobalt complexes of the type frans-Co2(CO)6(phosphine)2 are promising candidates for certain transition metal-catalyzed reactions, in particular for the hydroformylation of long-chained olefins [117]. A series of complexes Co2(CO)6[P(alkyl) (aryl)m]2 (n 0,1,2,3 m S - n) was synthesized and used for solubility measurements. Since the basicity of phosphines affects the catalytic activity, use of fluorous substituents might induce unexpected changes in the activity. Therefore, also derivatives with an additional ethyl spacer between the fluorous group and the phosphine moiety were examined (Sect. 3.1). 

Ionic liquids are immiscible with many organic solvents and compounds, which lends themselves to biphasic or multiphasic catalytic reactions. Most are also immiscible with fluorous phases and some are immiscible with water. In the ideal biphasic process involving ionic liquids, a soluble polar substrate is converted to a less polar - and thus insoluble -product, which will then form a separate phase. Attaching fluorous groups to the ionic liquid cation can reverse the solubility properties. 

Fluorous reverse phase silica gel (FRPSG) has been used in the purification of synthetic DNA fragments.In solid phase DNA synthesis, truncated sequences are often separated from the desired product after deprotection using HPLC or electrophoresis. In order to perform, parallel syntheses and separations of nucleotides the trityl-on purification procedure was developed, in which a lipophilic support material is used to separate the desired and undesired product, followed by deprotection. If the protecting group is labelled with a fluorous group, fiuorous-fiuorous interactions between the FRPSG and the protected nucleotide can be used to aid separation of the aqueous mixture. 

Oligosaccharide syntheses have also been performed in parallel using a fluorous support.A benzyl-type protecting group (HfBn) used in some of these procedures is shown in Figure 7.26. The novel approach here is that the fluorous group or tag is recycled and this can be achieved fairly easily... 

In addition to the various fluorousprotecting groups designed to ease the purification of carbohydrate intermediates, a range of fluorous groups have been reported with the potential for applications in the construction of... 

Figure 1 Preparation of arylphosphines substituted with fluorous groups.

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