Fluorous substituent

Synthesis of benzirnidazolo[ 1,2- ][ 1,3,5]triazine bearing fluorous substituents has also been published <2000JFC105, 2000ZOR120> 2-aminobenzimidazole 238 was reacted with a perfluoroazomethine at45°C to give the product 239 in good yield (62%). 

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). 

A common feature of the solubihty curves, as outlined in Fig. 16, is the exponential increase with the pressure due to the increasing density of CO2. From the solubility measurements [125], it can be concluded that the modification of phosphines by fluorous substituents is not necessarily required to reach sufficient solubilities of the corresponding metal complexes in SCCO2. In particular, alkyl substitution on phosphorus promotes complex solubility. Additional aryl groups, e.g., in lb and 4b, cause a reduced solubility of the corresponding complexes. Moreover, trans-Co2(CO)6 (PC6H5)3 2 (7b) is completely insoluble in SCCO2. 

Recently, a combination of fluorous substituents and a sugar-derived structure allowed the preparation of the scC02-soluble copolymer 53 as a novel phase-transfer catalyst (Figure 4.8). ° Dendrimers with fluorous substituents were also prepared for the same use. ° They are soluble in dense carbon dioxide and can solubilize otherwise C02-insoluble compounds such as Pd-nanoparticles (Scheme 92). The resulting dendrimer-encapsulated Pd catalyzes the hydrogenation of styrene and the Heck reaction of phenyl iodide. 

Figure 9 Modified IBX with a fluorous substituent for its easy recovery. ...

The possible electronic influence of a fluorous pora-silyl-substituent was studied in detail using a wide range of physico-chemical techniques [19-23], sug-... 

Tin hydrides bearing highly fluorinated substituents (fluorous chemistry) were used in the radical-mediated reduction of 1-bromoadamantane. The reaction was complete within 3 min under 35 W microwave irradiation (Scheme 4.42)68. 

The first chemical modification of EMFs, the cycloaddition of disilacyclo-propane to La C82> was reported in 1995 [1]. Several other groups also reported cycloadducts of EMFs [2,3], but unambiguous structural characterization was achieved only in one study [4]. More recently, water-soluble EMFs, the Gd C6o(C(COOH)2)io cycloadduct reported by Bolskar et al. [5], have been prepared to explore their potential use as MRI contrast agents [5,6], and Shinohara et al. used fluorous biphase techniques to prepare La C82(C8F]7)2 [7]. Until this work, however, La C82(C8Fi7)2 was the only reported exohedral derivative of EMFs with atomic substituents such as H, F, Cl, or Br, or with organic substituents R having only R-CEmf single bonds. 

---