Fluorinated Side Chains Research Articles

Synthesis of Amino Acids with Modified Principal Properties. 1. Amino Acids with Fluorinated Side Chains.

Synthesis of Amino Acids with Modified Principal Properties. 1. Amino Acids with Fluorinated Side Chains.

Temperature dependent conformers of perfluorocyclohexylethers

Temperature dependent high resolution 19F NMR spectroscopic investigations of perfluorocyclohexylmethylether ( 1), perfluorocyclohexylethylether ( 2), and perfluorocyclohexyl-(2-N-morpholino)-ethylether ( 3) revealed in each case the occurrence of two conformers, one clearly prevalent at a lower temperature and the other at a higher one. The low-temperature conformers show nearly identical differences of the 19F chemical shifts between axial and equatorial F, which closely resemble the value for perfluorocyclohexane. Also, the 2 and 6 F atoms with a chemical shift difference of about 17.2 ppm are closely related to the F in perfluorohexane, indicating only a small influence of the OCF 3, OC 2F 5, and OC 2F 4N(C 2F 4) 2O groups on the ring F compared to R F, R FOR′ F, or N(R F) 2. The high-temperature conformers of 1, 2 and 3 show much smaller differences of 19F chemical shifts of corresponding axial and equatorial F atoms, and again the 2- and 6-positions behave in this respect like the 3-, 5-, and 4-positions. In the case of the ethers the oxygen atom acts as a ‘spacer’, separating the fluorinated ring from the fluorinated side chain groups.

Structure and wettability of methacrylic polymers with fluorinated side chains

Surface properties of methacrylic homopolymers and copolymers with a random distribution of pendant perfluorinated groups R F  C nF 2n+l have been studied. These polymers are obtained by radical polymerization in solution or emulsion of fluorinated monomers (M F) CH 2  C (CH 3) CO 2 (CH 2) 2 R F with various hydrogenated comonomers (M H). Surface tensions are estimated according to the length of R F groups (n = 4, 6, 8), the fluoromonomer concentration [ M F ] in copolymers and the chemical structure of comonomers M H (MMA, BMA …), by different methods: Zisman's ( γC), geometric and harmonic mean approximation. Wettability measurements can provide useful information about the structure of polymeric surfaces. The tensiometric method used for wetting measurements reveals an abnormally large hysteresis effect between advancing and receding contact angles when the polymer surface is in contact with water. This effect is markedly decreased by the length of the R F group from n = 4 or 6 to 8 and by the concentration of fluoromonomer units in copolymers. The evolution of the surface properties of the polymer in contact with a polar liquid (water) can be explained by the reorganization and the reorientation of hydrophilic moieties of the macromolecules at the interface. At the polymer — air interface the fluorinated chain packing control the surface wettability. Hydrophilic ester groups of methacrylic units are buried in the bulk of the polymer, thus the polymer surface is different from its bulk. The evolution of surface energy cannot be explained by adsorption or absorption of water. A study by DSC has therefore been undertaken to correlate hysteresis with the potential organization of R F groups at the polymer — liquid interface and crystallinity of fluoropolymers.

Liquid-crystalline polysiloxanes with fluoro-substituted side chains

Abstract Sixteen new side chain liquid polysiloxanes, either homopolymers derived from poly(hydrogenmethyl)siloxane or copolymers derived from poly(hydrogenmethyl-dimethylsiloxane), are reported with side chains carrying fluoro-substituents. The known effects of fluoro-substitution in low molar mass liquid crystals are strongly echoed in the polymeric analogues and interesting comparisons are made between homo- and co-polymers carrying the same fluorinated side chains.

Amikacin analogs with a fluorinated amino acid side chain.

The synthesis and biological activity of kanamycin A derivatives with an omega-amino-alpha-fluoroalkanoyl side chain on the 1-amino group are described. The fluorinated amino acids (4) for the side chain were prepared by fluorination of the alpha-hydroxy esters (2) with diethylaminosulfur trifluoride (DAST) with accompanying the Walden inversion. The reaction products varied with the amino protective groups employed, chain length of the alkanoic acids and the presence or absence of base. The fluorinated side chain was introduced to 1-free-NH2 kanamycin A (12) by the conventional active ester method and subsequent deblocking reactions afforded the desired final products (13-17). Of the derivatives prepared, 1-N-[(S)-4-amino-2-fluorobutyryl]kanamycin A (2'''-deoxy-2'''-fluoroamikacin, 14) showed the best overall activity profile, nearly the same as that of amikacin. Preparation and antibacterial activity of several aminoglycoside antibiotics with the 1-N-(S)-4-amino-2-fluorobutyryl side chain are also discussed.

ChemInform Abstract: Syntheses of New Aromatic Compounds with Fluorinated Side Chains and Their Chemical Reactivity.

AbstractReaction of the bromodifluoromethylbenzoles (III), readily prepared from the aldehydes (I) via the intermediates (II), with the nucleophiles (IV), (VI), (VIII) or the Ag salts (X) or (XII) provides the products shown in the scheme.

ChemInform Abstract: Aromatic Compounds with Fluorinated Side Chains

ChemInform Abstract: Aromatic Compounds with Fluorinated Side Chains

A new lanthanide paramagnetic shift reagent containing fully fluorinated side chains

This work describes the application of a new europium complex, europium decafluoroheptanedione, to the clarification of complex NMR spectra, i.e., it reports a new paramagnetic shift reagent. This new reagent is superior to the older, partially fluorinated complex, Eu(fod) 3, in that there is no interference from side-chain protons of the shift reagent, itself. Furthermore, due perhaps to the smaller bulk of this new reagent, relative to Eu(fod) 3, larger shifts are observed for the protons remote from the complexing site of the substrate. We also qualitatively describe the shift capacities of other lanthanide decafluoroheptanediones.

Polyurethanes with long fluorinated side chains

AbstractCopolymer triols were prepared from propylene oxide and glycidyl (α,α,ω‐trihydrododecafluoroheptyl) ether or pentadecafluoroheptylepoxyethane. Cationic polymerization was used and block copolymers were obtained in the molecular weight range of 1,000 to 3,000. These copolymer triols were reacted with an 80/20 mixture of 2,4‐/2,6‐tolylene diisocyanate, giving polyurethanes with the same polymer backbone as the conventional polyurethanes based on polyoxypropylene triols and tolylene diisocyanate. It was found that these polyurethanes, containing between 0% and 45% fluorine, showed increasing adhesion to anodized aluminum with increasing urea bond content of the polymer. However, the fluorine content did not show the expected effect on adhesion. Isothermal gravimetric analysis showed that the heat stability of the fluorourethanes was lower than for conventional urethanes on a weight basis, only because the segments split off in heat degradation were heavier for the fluorourethane. This phenomenon might possibly also apply to urethanes with a fluorinated backbone. On a mole basis fluorourethanes might be as stable as nonfluorourethanes. It was also found that the thermostability, as measured by weight loss, increased with an increasing degree of crosslink density in the polymers.

The synthesis of vinyl naphthalenes with fluorinated side chains

Methods for the synthesis of β-fluoro-α-vinyl naphthalene and α-difluoromethyl-α-vinylnaphthalene were developed.