Fluorinated side chains

The use of highly fluorinated side-chain groups that are insulated from reaction centers in order to exploit their unique influence upon the solubility properties of the molecule without affecting the chemistry of the functional groups has spawned a new subfield of fluorine chemistry... 

Macromolecules have also been specifically designed and synthesized for use as emulsifiers for lipophilic materials and as stabilizers in the colloidal dispersion of lipophilic, hydrocarbon polymers in C02. We have demonstrated the amphiphilicity of fluorinated acrylate homopolymers, such as PFOA, which contain a lipophilic, acrylate like backbone and C02-philic, fluorinated side chains (see Fig. 3) [103]. It has been demonstrated that a homopolymer which physically adsorbs to the surface of a polymer colloid prevents agglomeration by the presence of loops and tails (see Fig. 4) [113]. The synthesis of this type of... 

Two independent screens have been developed to investigate the effects of fluorinated building blocks on the interactions of the dimeric peptide assembly. The impact of fluorine side chain substitutions on the stability of coiled coil folding has been studied using temperature-dependant CD spectroscopy. The second screen is based on the ability of a-helical peptides to self-replicate. Thus, peptide... 

Alkylation of the partial steroid structure 8 proceeds very similarly5. Alkylation with the fluorinated side chain (( )-9 is claimed to proceed with less than 5% of the (20S)-isomer. 

Figure 1.42 Befloxatone fluorinated side chain synthesis.

At the beginning of the 20th century, arenes carrying fluorinated side chains were made from (trichloromethyl)benzene (benzotrichloride, 12). Unexpectedly perhaps, this was a facile exchange. Proceeding stepwise, it went to completion, and full fluorination could be achieved even using antimony(III) fluoride alone. 

Among all remaining monomers, those containing (per)fluorinated side chains such as fluorinated acrylates, vinyl ethers or esters, maleimides and styrenic monomers are also very interesting and have been studied in (co)telo-merisation. Most of them have been previously reviewed [15]. However, they are not mentioned in this chapter. 

The trifluoromethyl group is the most prominent fluorinated side chain. An excellent review on all aspects of the introduction of the trifluoromethyl group into organic compounds is available (92T6555). The trifluoromethyl group can be introduced as radical, nucleophilic and electrophilic species as well as by functional group transformations. 

The production of quaternary centers was also utihzed by Kosugi to develop a synthesis of mesembrine [132]. Lactones bearing fluorinated side-chains are also available by this methodology [133]. The lactonization of a 50 50 mixture of cyclohexylsulfinyl butenolides has been examined. It was expected that a mixture of bis-lactones would be produced in 50 50 ratio. Instead, an 80 20 mixture of dichloro bis-lactones was obtained and, dehalogenation with Ra - Ni gave the lactone shown as the major isomer of a 95 5 mixture [133] (Scheme 19). 

Comilescu, G., Hadley, E. B., Woll, M. G., et al. (2007) Solution structure of a small protein containing a fluorinated side-chain in the core. Protein Science, 16(1), 14—19. 

Table II lists the positions and relative intensities of the main absorption bands of the sodium salt of Nafion, together with the best available assignments to vibrational modes of the structural components of Nafion the fluorinated hydrocarbon main chain, the ether-linked fluorinated side-chains, the ionic end groups -S03 Na+ and water of hydration.

Poly(acrylates) and (alkyl acrylates). - Structured nanopore films of poly(styrene-block-methyl methacrylate) copolymers have been made with controlled spectral sensitivity, such that each block is sensitive to a specific degradation wavelength. In copolymers of 2,2,2-trifluoroethyl methacrylate with vinyl ethers, the photosensitivity is controlled by the vinyl ether units. Photodegradation occurs at the tertiary positions of the ether units followed by lactone formation and chain scission processes. Furthermore, the fluorinated side chains have been found to inhibit cyclization reactions. 

Stability, but the origin of this behavior is still unknown. One possible explanation involves the close-packing nature of fluorined side chains, which may provide a kinetic barrier to oxidation. Asymmetric NTCDIs with alkyl and fluoroalkyl sidechains have also been synthesized (46i-461). The highest mobility obtained with an alkyl version (46i) was 3 x 10" cm V s under vacuum and 2 x 10" cm V s with a fluoroalkyl derivative (46j).[271]... 

Therefore, this chapter presents preliminary evidence indicating the effect and interrelationship between primary and secondary molecular motions on thrombogenesis, independent of morphological order and/or crystallinity. The polymer selected for this study was an amorphous elastomeric hydrophobic polymer of poly[(trifluoroethoxy) (fluoroalkoxy)phosphazene] (PNF) I (5, 6). The salient aspects of this polymer are that (1) the onset of the secondary molecular motions occurs between -160° and - 120°C (2) the side chain motion can be altered by irradiation (ultraviolet, electron beam, or gamma) (3) no apparent ultrastructure morphology exists (4) the side chains can be derivatized (5) and (5) the polymer can be readily coated onto our extracorporeal test shafts (7) and irradiated accordingly. Additionally, contact angle measurements of the homopolymer (8) and the PNF (9), 19.7 and 15.0 dyn/cm2, respectively, indicated that the fluorinated side chains comprised the surface to be interfaced in the extracorporeal blood studies. 

Several fluorinated monomers have been polymerized via homogeneous cationic polymerization in compressed carbon dioxide. For example, vinyl ethers with fluorinated side chains were polymerized in SCCO2 at 40 °C using adventitious water initiation with ethylaluminum dichloride as the Lewis acid coin-... 

The reason why only the fluorinated ester drops spread over one of the fluorinated coatings can be explained by mutual attraction promoted by the structural and chemical affinity of the two fluorine-containing organic compounds. It had been established [5] that the fluorinated side chains of polymer S are sterically less closely packed and have more freedom of rotation than those of polymer A they may thus permit some lateral penetration of the closely related fluoro chains of the glutarate ester, whereas polymer A with its tight array of side chains is impervious to such penetration. The fluorinated ester exerts a slight solvent action on polymer S, but not on polymer A, when the polymer is totally immersed in the ester for periods longer than 10 days at ambient temperature, or 2 days at 50°C. 

Condensation of pyrroles with carbonyl compounds under Lewis acid catalysis followed by oxidation provides an efficient route to the porphyrin ring system. This has been effectively used to prepare polyfluorinated porphyrins from 3-fluoro and 3,4-difluoropyrroles, as well as pyrroles substituted with fluorinated side chains in these positions. For example, DiMagno and coworkers extended their studies of highly electron-deficient porphyrins to a series of 2,3,7,8,12,13,17,18-octafluoro-5,10,15,20-tetraarylporphyrins 96, including the perfluorinated compound, by BFs-catalyzed condensation of 3,4-difiuoropyrrole with benzaldehydes followed by dichloro dicyano quinone (DDQ) oxidation (Fig. 3.46). A similar approach was used by Leroy and coworkers. ... 

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