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A persistent perfluoroalkyl branched radical (PPFR), perfluoro-3-ethyl-2,4-dimethyl-3-pentyl, was shown to be a good source of

Reactions of bifunctional perfluoroarylsilanes, p- and m-C6F4(SiMe3)2 as well as o-BrC6F4SiMe3, with substituted perfluoroarenes having electron-withdrawing groups were investigated using NMR and density functional theory calculation techniques. The C–F bond in perfluoroarenes was activated by the para-position of an electron-withdrawing group, such as CF3, C6F5, CN, and NO2. The reaction of C6F4(SiMe3)2 mainly occurred at the para-position of the perfluoroarenes and also occurred at the ortho-position of C6F5CN and C6F5NO2. Two equivalent reactions of perfluoroarenes with bifunctional p- and m-C6F4(SiMe3)2 provided disubstituted perfluoroarenes, along with a small amount of protonated monosubstituted perfluoroarenes. The reaction of o-BrC6F4SiMe3 with the CF3- and CN-substituted pentafluorobenzenes provided unexpected coupling products between C–Br and C–F bonds, in addition to the coupling products between C–SiMe3 and C–F bonds.

International audience; The radical polymerization of styrene (St) initiated by a trifluoromethyl radical generated from a perfluorinated highly branched persistent radical (PPFR) is presented with an isolated yield above 70 %. The release of .CF3 radical occurred from a temperature above 85 °C. Deeper 1H and 19F NMR spectroscopies of the resulting fluorinated polystyrenes (CF3‐PSts) evidenced the presence of both CF3 end‐group of the PSt chain and the trifluoromethylation of the phenyl ring (in meta‐position mainly). [PPFR]0/[St]0 initial molar ratios of 3:1, 3:10 and 3:100 led to various molar masses ranging from 1750 to 5400 g mol−1 in 70–86 % yields. MALDI‐TOF spectrometry of such CF3‐PSts highlighted polymeric distributions which evidenced differences between m/z fragments of 104 and 172 corresponding to styrene and trifluoromethyl styrene units, respectively. Such CF3‐PSt polymers were also compared to conventional PSts produced from the radical polymerization of St initiated by a peroxydicarbonate initiator. A mechanism of the polymerization is presented showing the formation of a trifluoromethyl styrene first, followed by its radical (co)polymerization with styrene. The thermal properties (thermal stability and glass transition temperature, Tg) of these polymers were also compared and revealed a much better thermal stability of the CF3‐PSt (10 % weight loss at 356–376 °C) and a Tg of around 70 °C.

The conventional radical homopolymerization of TrFE initiated by a ˙CF3 radical (generated in situ from perfluoro-3-ethyl-2,4-dimethyl-3-pentyl persistent radical, PPFR) is presented. Reactions were carried out at an increasing PPFR concentration (initial [TrFE]0 : [PPFR]0 molar ratios varying from 2.5 to 20.0 mol%) to influence the molar masses (Mn, ranging between 7700 and 38 100 g mol−1). PTrFE homopolymer yields were high (76–87%). The microstructures of such synthesized PTrFEs were characterized by 1H and 19F NMR spectroscopy. The generated PTrFE chains were exclusively terminated by CF3 end-groups, as revealed by MALDI-TOF spectroscopy and NMR analysis, indicating that the ˙CF3 radicals initiated the polymerization of TrFE. The addition of the ˙CF3 radicals onto TrFE was predominantly regioselective (66%) leading mainly to a CF3–CHF–CF2–PTrFE homopolymer. Furthermore, the CF3 end group could be used as an efficient label to determine the PTrFE molar masses by 19F NMR spectroscopy that also enabled us to assess the chain defects (14%). The thermal properties of these CF3–PTrFE–CF3 polymers revealed (i) a high thermal stability (their degradation under an oxidative atmosphere started from 362 °C and ranged even up to 428 °C for higher molar masses of PTrFEs) and (ii) a semi-crystalline behavior with a crystallinity rate averaging 36%.

The reaction of hexafluoropropene trimers with Ruppert-Prakash (CF 3 SiMe 3 ) reagent gave highly congested perfluoroolefins such as the mono-trifluoromethylation products F -2,4-dimethyl-3-isopropyl-2-pentene ( P1 ) and E - and Z -forms of F -4,4-dimethyl-3-isopropyl-2-pentene ( 2 E and 2 Z ), and the bis-trifluoromethylation product F -2,4,4-trimethyl-3-isopropyl-2-pentene ( 3 ). The E -form of 2 was also comprised of two rotamers. Various aprotic polar solvents were surveyed for this reaction, and it was found that the aprotic solvent DMI has a unique solvent effect to selectively give the mono-trifluoromethylated perfluoroolefin P1 , a precursor for the persistent perfluoroalkyl radical F -3-isopropyl-2,4-dimethyl-3-pentyl, in very high yield.

Geometries of benzene complexes with C6F5X, C6H5X, and CF3X (X is I, Br, Cl, and F) were optimized, and their interaction energies were evaluated. The CCSD(T) interaction energies at the basis set limit (Eint) of C6F5X (X is I, Br, Cl, and F) with benzene were -3.24, -2.88, -2.31, and -0.92 kcal mol(-1). Eint of C6H5X (X is I, Br, and Cl) with benzene were -2.31, -1.97, and -1.48 kcal mol(-1). The fluorination of halobenzenes slightly enhances the attraction. Eint of CF3X (X is I, Br, Cl, and F) with benzene (-3.11, -2.74, -2.22, and -0.71 kcal mol(-1)) were very close to Eint of corresponding C6F5X with benzene. In contrast to the halogen bond of iodine and bromine with pyridine (n-type halogen bond acceptor) where the main cause of the attraction is the electrostatic interactions, that of halogen bond with benzene (p-type acceptor) is dispersion interaction. In the halogen bonds with p-type acceptors (halogen-π interactions), the electrostatic interactions and induction interactions are small. The overall orbital-orbital interactions are repulsive. The directionality of halogen bonds with p-type acceptors is very weak, owing to the weak electrostatic interactions, in contrast to the strong directionality of the halogen bonds with n-type acceptors and hydrogen bonds.

Hexafluoropropene trimers were reacted with C6F5Si(CH3)3 to provide not only pentafluorophenyl but also perfluorophenylene derivatives [F(C6F4)nC9F17; n=2–9] by successive pentafluorophenylation of perfluoroaryl rings. Their structures, including rotational isomers, were determined by MS, 19F and 13C–{19F} NMR spectroscopy, and/or X-ray crystallography, and were further confirmed by B3LYP-GIAO calculation of NMR shieldings. Formation of a pair of gear-meshed rotamers with clockwise and counterclockwise conformations was identified by NMR measurements for the structures having geminal (CF3)2CF groups at the C=C bond. That the predominantly formed counterclockwise rotamer was gradually converted to the clockwise rotamer over 50 days at room temperature through a synchronized movement of gears was also confirmed by NMR measurements. A comparison between the X-ray structure and B3LYP calculations showed some structural differences that arise from the crystal packing.

International audience; Results of the radical copolymerisation of chlorotrifluoroethylene (CTFE) with isobutyl vinyl ether (iBuVE) initiated by ∙CF3 radicals generated by β-scission of perfluoro-3-ethyl-2,4-dimethyl-3-pentyl radical (PPFR) at 90 °C in a batch reactor are reported. 19F NMR spectroscopy enabled the assessment of the molecular weights of the poly(CTFE-alt-iBuVE) copolymer by end-group analysis. It was found that, at low initiator concentrations (≤ 10 mol%), the ∙CF3 radicals preferably attack the vinyl ether monomer to initiate chain propagation and produce alternating poly(CTFE-alt-iBuVE) copolymers. At initiator ratios of 20 mol%, 19F NMR signals in the CF3 region other than the expected CH2-CF3 are observed and are attributed to ∙CF3 addition patterns due to kinetic effects brought on by monomer solubility. The molecular weights for the copolymer produced from 1%, 5%, and 10% PPFR were found to be 340 000, 237 000 and 122 000 g∙mol-1, respectively. The copolymer produced from 20% PPFR was oligomeric in nature with a molecular weight of 18 000 g∙mol-1.

Perfluoro-3-ethyl-2,4-dimethyl-3-pentyl radical (PPFR) is a persistent radical stable at room temperature, but easily decomposes at 90 °C to produce a CF3 radical which is able to react with a variety of aromatic compounds to afford the corresponding trifluoromethyl derivatives, usually as mixtures of regioisomers in good to excellent overall yields.

Charge transfer interaction of a persistent perfluoroalkyl radical, perfluoro-3-ethyl-2,4-dimethyl-3-pentyl (PFR-1), with benzene and methyl substituted benzenes (toluene, m -xylene, mesitylene), 1-decene, and diethyl ether was investigated by UV–vis spectrophotometric measurement. It was found that the aromatic and olefinic π-electrons and also the unshared electron pair of ether can interact with the low-lying radical orbital of PFR-1 through CT complex formation. The Beer's law was confirmed in the range of 5–20 mM of PFR-1 for the aromatics and 5–40 mM for 1-decene and diethyl ether. The red shift of λ max occurred with increasing number of methyl substituents on the benzene ring.

The origin of the attraction in charge-transfer complexes (a p-hydroquinone-p-benzoquinone complex and benzene complexes with benzoquinone, tetracyanoethylene and Br2) was analyzed using distributed multipole analysis and symmetry-adapted perturbation theory. Both methods show that the dispersion interactions are the primary source of the attraction in these charge-transfer complexes followed by the electrostatic interactions. The natures of the intermolecular interactions in these complexes are close to the π/π interactions of neutral aromatic molecules. The electrostatic interactions play important roles in determining the magnitude of the attraction. The contribution of charge-transfer interactions to the attraction is not large compared with the dispersion interactions in these complexes.

Gas-phase acidities of polyfluorinated hydrocarbons have been determined by measuring proton-transfer equilibria and by computing the free energies of deprotonated carbanions and the corresponding neutrals. An excellent linear relationship between acidities and the accumulated inductive effects of fluorine atoms contained in a molecule was observed for the perfluoroalkyl-substituted neopentanes, (Rf 1)(Rf 2)(R f 3)CCH3, and polyfluorinated bridgehead carbon acids where the contribution of negative hyperconjugation of the CβF bond to the stability of the conjugate anions is absent or negligibly small. On the basis of this relationship, the extent of β-fluorine negative hyperconjugation involved in acidities of polyfluorinated hydrocarbons could be evaluated quantitatively. The negative hyperconjugation was found to be negligibly small in the stable tertiary polyfluorinated carbanions while in the less stable primary and secondary carbanions the contribution of this effect is present certainly, indicating that the negative fluorine hyperconjugation is complementary to the stabilization by the accumulated inductive effect of fluorine atoms. The extent of negative hyperconjugation was found to increase in order of CF3CH2- < C2F5CH 2- C3F7CH2 < i-C 3F7CH2-, being qualitatively consistent with the elongation of the CβF bond by deprotonation. The effect of α-fluorine on acidity was found to change complicatedly with the carbanion, e.g., the a-fluorine substitution in CF3CH3 strengthens acidity, no effect in (CF3)2CH2, and strengthens again acidity in (i-C3F 7)2CH2. Such varying effect of a-fluorine in the polyfluorinated hydrocarbons would be caused by a subtle balance of effective electronegativity of an anionic center carbon, a varying pp lone pair repulsion depending on the net negative charge at the formal charge center carbon, and the change in ability of β-F negative hyperconjugation caused by α-F substitution. © 2014 The Chemical Society of Japan.

Chirally switchable Ni(II) and Pd(II) complexes were synthesized and fully characterized by X-ray crystallography and additionally by spectroscopic means (NMR and MS). The syntheses and characterization of their ligands are also reported. It was found that control of the stereochemical preference between (S*,S*) and (S*,R*) diastereomers by substituent modification of the ligand sidearms was possible in the solid state with the preferred atomic coordinations of the sidearms consistent with expectations based on the electron-withdrawing properties of the substituent -o-CF3 group. The dilemma arising in terms of assigning the absolute configuration descriptors resulting from selecting between strictly following only the covalent bonds of the ligand and disregarding the nature of the bonds altogether and thus bringing the coordinate bonds into consideration to determine the stereochemical priority sequence is hereby resolved by declaring that the latter option is to be preferred. The results obtained here provide a clear indication that sidearm substitution of the Ni(II) and Pd(II) complexes need not disturb macromolecular stereochemical arrangements leading to quasidiastereomeric relationships. This permits the design of molecular systems sensitive to external stimuli with predictable macromolecular structure.

This work demonstrates that self-disproportionation of enantiomers via achiral chromatography can be recommended as inexpensive and general method for optical purification of enantiomerically enriched compounds. In particular, the advantage of this approach over conventional recrystallization is that it can be used for both crystalline as well as liquid compounds. Chirality, 25:365-368, 2013. © 2013 Wiley Periodicals, Inc.

International audience; Batch radical homopolymerization of vinylidene fluoride (VDF) and its copolymerizations with seven fluorinated comonomers such as H2CCRACF3 (where RA stands for H, F, CO2R (R = H or tBu) or F2CCFRB (RB: H, CF3, OCF3) initiated by *CF3 radical generated from a perfluoro-3-ethyl-2,4-dimethyl-3-pentyl persistent radical (PPFR) are presented. That highly perfluorinated branched radical itself was unable to directly initiate the copolymerization in contrast to the generated trifluoromethyl radical that was successful. The microstructures of the resulting PVDFs, poly(VDF-co-H2CCRACF3) or poly(VDF-co-F2CCFRB) (co)polymers were assessed by 19F and 1H NMR spectroscopy. 19F NMR spectra displayed a quintet centered at −61 ppm assigned to a CF3 end-group which enabled one to determine both the molecular weights of the resulting (co)polymers and the amounts (numbers and molar percentages) of these above comonomers. In all cases, the regioselective radical addition of *CF3 onto the methylene site of VDF was noted as well as for 3,3,3-trifluoropropene. In addition, the 19F NMR spectra showed the absence of signals attributed to PPFR or its derivatives. According to [PPFR]o/([VDF]o + [comonomers]o) initial molar ratios, this novel initiating system could produce high molecular weight-fluoropolymers (up to 200 000 g*mol−1). The lower that ratio, the higher their molecular weights as well as the higher their thermal stability (a 10% weight loss under air was noted at 425 °C). Although the kinetics of radical copolymerization were not studied, the presence of branched persistent radical did not disturb the reactivities of the comonomers and it was not involved in the primary recombination of radicals in the termination step of the polymerization while the macromolecular recombination was favored. For an initial PPFR concentration lower than 1 mol %, a feed ratio of ca. 20 mol % of 2-trifluoromethacrylic acid, MAF (or tert-butyl 2-trifluoromethacrylate, MAF−TBE) led to alternated poly(VDF-alt-MAF or MAF−TBE) copolymers. High yields (90%) of copolymers based on VDF and 2,3,3,3-tetrafluoroprop-1-ene, hexafluoropropylene (HFP), or perfluoromethyl vinyl ether (PMVE) comonomers were achieved while those from MAF, MAF−TBE, trifluoroethylene, and 3,3,3-trifluoropropene were fair to satisfactory. As expected, for a reasonable amount of HFP and PMVE inserted in the copolymers (>18 mol %), elastomers endowed with low Tg values (−35 and −42 °C, respectively) were produced. In addition, the higher the content of VDF, the lower the Tg, though the presence of tBu from MAF−TBE slightly increased the Tg values. Copolymers containing MAF or MAF−TBE exhibited poor thermostability (that arises from the decarboxylation and isobutylene elimination from MAF or MAF−TBE, respectively) in contrast to the other VDF-containing copolymers that showed decomposition from 250 °C under air.

Methacrylic monomers with biphenyl cores and those with fluorinated substituents were copolymerized to afford fluorinated composites having good mechanical properties and inertness. Adding a large amount of silica fillers to the polymer precursors followed by molding and complete thermal curing gives polymer composites that can be used as an artificial tooth material with improved durability and anti-fouling properties.

International audience; The synthesis of ω-iodo and telechelic diiodovinylidene fluoride (VDF)-based (co)polymers by iodinetransfer polymerization (ITP) of VDF initiated by a trifluoromethylradical (generated by perfluoro-3-ethyl-2,4-dimethyl-3-pentyl persistent radical, PPFR) is presented. Reactions werecarried out in the presence of different chain transfer agents(CTAs, such as trifluoroiodomethane, 1,4-diiodoperfluorobutane,and molecular iodine) with/without tert-butyl 2-trifluoromethacrylate(MAF-TBE). Experimental conditions (natureof the solvents and CTAs, time, temperature, and initial[VDF]0:[CTA]0:[initiator]0 molar ratios) were varied toinfluence the yield of the reaction (up to 86%), the molar masses (Mn), dispersity values (Đ), chain end functionalities, andmicrostructures of the obtained polymers. Detailed kinetics study enabled to confirm the well-controlled polymerization: (i)synthesis of iodinated polymers with different molar masses (Mn,SEC = 1110−5800 g mol−1) and low Đ values (≤1.30), justsimply by varying the [VDF]0:[CTA]0 initial molar ratio; (ii) linear increase of Mn versus conversion, maintaining low Đ values(≤1.28); (ii) the presence of favored -CH2CF2-I end functionality up to 80% monomer conversion. The compositions andmicrostructures of all the obtained copolymers were characterized by 1H and 19F NMR spectroscopies. Deeper mechanisticinvestigation of the ITP of VDF initiated by •CF3 radical from PPFR was carried out. In the presence of CF3I as the CTA, thecompetitive presence of CF3 end group in CF3-PVDF-I was evidenced to arise from the CTA and showed a negligible amount ofCF3-PVDF oligomer dead chains initiated from •CF3 radical from PPFR. Very low chain defects (due to reversed -CH2CF2-CF2CH2- and -CF2CH2-CH2CF2- in VDF-VDF dyads, even the absence of such a later one) led to high melting points(161−173 °C) of the resulting polymers, as revealed by differential scanning calorimetry. The thermal stability of the polymersincreased with higher Mn values reaching 270 °C under air, while for copolymers containing MAF-TBE, the degradation occurredfrom 170 °C attributed to the release of isobutene from the tert-butyl side groups.

International audience; A persistent perfluoroalkyl radical (PPFR), perfluoro-3-ethyl-2,4-dimethyl-3-pentyl, is shown to be a good source of *CF3 radicals; a useful radical for initiating the polymerization of vinylidene fluoride (VDF). NMR characterizations of the resulting PVDF homopolymers shows that polymerization of VDF was exclusively initiated by *CF3 radicals, as evidenced from the thermal decomposition of PPFR at T > 80 °C. The addition of *CF3 radical onto VDF is regioselective leading to CF3-CH2-CF2-PVDF and the α,-trifluoromethyl groups act as an efficient label to assess the molecular weights of the resulting PVDFs by 19F NMR spectroscopy. No evidence was found about the presence of the initial persistent radical attached onto the macromolecular chains. Various [PPFR]0 / [VDF]0 initial molar ratios lead to CF3-PVDF-CF3 of various molecular weights ranging from 4,100 to 7,500 g.mol-1. When that ratio decreases, both the molecular weights and the thermostability of these original PVDFs polymers increases.

The geometries and interaction energies of complexes of pyridine with C(6)F(5)X, C(6)H(5)X (X = I, Br, Cl, F and H) and R(F)I (R(F) = CF(3), C(2)F(5) and C(3)F(7)) have been studied by ab initio molecular orbital calculations. The CCSD(T) interaction energies (E(int)) for the C(6)F(5)X-pyridine (X = I, Br, Cl, F and H) complexes at the basis set limit were estimated to be -5.59, -4.06, -2.78, -0.19 and -4.37 kcal mol(-1) , respectively, whereas the E(int) values for the C(6)H(5)X-pyridine (X = I, Br, Cl and H) complexes were estimated to be -3.27, -2.17, -1.23 and -1.78 kcal mol(-1), respectively. Electrostatic interactions are the cause of the halogen dependence of the interaction energies and the enhancement of the attraction by the fluorine atoms in C(6)F(5)X. The values of E(int) estimated for the R(F)I-pyridine (R(F) = CF(3), C(2)F(5) and C(3)F(7)) complexes (-5.14, -5.38 and -5.44 kcal mol(-1), respectively) are close to that for the C(6)F(5)I-pyridine complex. Electrostatic interactions are the major source of the attraction in the strong halogen bond although induction and dispersion interactions also contribute to the attraction. Short-range (charge-transfer) interactions do not contribute significantly to the attraction. The magnitude of the directionality of the halogen bond correlates with the magnitude of the attraction. Electrostatic interactions are mainly responsible for the directionality of the halogen bond. The directionality of halogen bonds involving iodine and bromine is high, whereas that of chlorine is low and that of fluorine is negligible. The directionality of the halogen bonds in the C(6)F(5)I- and C(2)F(5)I-pyridine complexes is higher than that in the hydrogen bonds in the water dimer and water-formaldehyde complex. The calculations suggest that the C-I and C-Br halogen bonds play an important role in controlling the structures of molecular assemblies, that the C-Cl bonds play a less important role and that C-F bonds have a negligible impact.

The biomimetic transamination of fluorinated carbonyl compounds, represent the most methodologically concise and general- ized approach to the family of fluorine-containing amines and amino acids. Such amino compounds are of critical importance in the me- dicinal, bioorganic, biochemistry research and pharmaceutical industry. This review summarizes all of the synthetically and methodol- ogically important achievements in the field published to date. The review consists of two major parts summarizing the literature methods on biomimetic transamination of fluorine-free carbonyl compounds and the authors' own results on the application of this bio-inspired approach to fluorinated derivatives. Discussion on each particular method includes synthetic opportunities, limitations, practicality and efficiency of the synthetic procedures.

A novel styrenic monomer having hexafluoropropene trimer on the benzene ring was prepared. The highly fluorinated monomer was polymerized to yield a white powdery polymer, which was soluble in fluorinated solvents and had resistance to usual organic solvents, good water repellency, and low refractivity. In contrast to common fluoropolymers having linear-fluorinated side-chains, the polymer has a characteristic high glass transition temperature. Thus, the fluorinated polymer and copolymer with styrene are suitable for applications at elevated temperature. The polymers can replace the conventional fluorinated polyacrylates, which are used in large quantity as repellents with potentially generating perfluorooctanoic acid in the environment.

Pentafluorophenylation of perfluoroarenes with C 6 F 5 Si(CH 3 ) 3 was investigated by using NMR and MALDI–TOF–MS techniques. Successive multiple pentafluorophenylation easily occurred not only on the para -position but also on the ortho -positions to provide perfluorinated p -phenylene and m -phenylene compounds. The perfluoroarenes having electron-withdrawing substituents provided oligo- to poly-(phenylene)s depending on the added amounts of C 6 F 5 Si(CH 3 ) 3 , while the perfluoroarenes having electron-donor substituents gave H(C 6 F 4 ) n F polymers produced from C 6 F 5 H, which was the decomposed product of C 6 F 5 Si(CH 3 ) 3 .

Binuclear square planar Ni(II) complexes are described, formed by two tridentate ligands with two imine-nitrogens coordinating two nickel atoms. Such complexes are synthetically readily available with great structural variety and present new types of ridge-tile-like chiral compounds that are reasonably stable in the appropriate "bent" conformation. Enantiomerically pure samples of these compounds have been obtained for the first time using HPLC with a chiral stationary phase. Absolute configurations and chiroptical properties are fully characterized by ECD, VCD, ORD spectroscopy, and theoretical calculations. These new compounds with ridge-tile-like chiral topology are configurationally reasonably stable [DeltaG(double dagger) = 121.4 kJ mol(-1), t(1/2) = 14.9 h (78 degrees C, ethanol)], and therefore their chemistry, physical properties, and applications can be systematically studied.

The presented results convincingly demonstrate that self-disproportionation of enantiomers via sublimation is substantially more complex phenomenon then was previously believed. We demonstrate that the racemic form of isopropyl 3,3,3-trifluoro-2-hydroxypropanoate (1) sublimed faster regardless of the starting enantiomeric composition of the enantiomerically enriched mixtures studied in the range from 20.8, 36.8, 58.7 to 79.4% ee. This preferential sublimation of the racemic form allowed for, the most possibly simple, preparation of optically pure samples of compound 1. In this work we also suggest some general experimental procedures, which may be easily used to facilitate the interpretation of the data collected in different laboratories.

This study present a full account of continuous-flow reaction conditions for biomimetic reductive amination of fluorinated carbonyl compounds to corresponding amines and amino acids of biomedical importance. We demonstrate that simple silica-adsorbed DBU can be used as efficient catalysts for on-column 1,3-proton shift reaction, a key transformation in the biomimetic reductive amination process. This new on-column process features operationally convenient conditions, higher chemical yields, enantioselectivity and purity of the corresponding products as compared with traditional in-flask reactions. Moreover the removal of base-catalyst, the most delicate problem of the in-flask reactions, is not an issue in the on-column process, as the silica-adsorbed DBU or polymer-bound guanidine remains on the column and can be reused. This feature renders the overall process substantially more economical and synthetically efficient, in particular, for large-scale synthesis of the corresponding fluorinated amines and amino acids target.

Room temperature fluorine electron nuclear double resonance (ENDOR) has been successfully observed for several superstable fluorocarbon radicals ·C(C2F4R)(i-C3F7)2 in solution. Three radicals were employed in which CF3, F, and O-c-C6F10SO3C2F5 were introduced as R, and all the hyperfine couplings (hfcs) obtained by ENDOR were assigned with the help of ESR simulation and ab initio MO calculation. In case of ·C(i-C3F7)3 large 13C and considerable β-fluorine couplings suggest the nonplaner arrangement for the central and three carbons at the β-position, in spite of the fact that all the methyl fluorine show the same hfc. Therefore, a rapid puckering motion along the C3 axis together with the methyl rotation should average the hfc’s of the 18 fluorine nuclei to give the same value. When one of the CF3 groups is substituted with an F nucleus, the five CF3 groups give two hfc values, suggesting some dynamics still exists for the molecular frame. When a large group, O-c-C6F10SO3C2F5, is substituted for CF3, all the five CF3 groups become nonequivalent and the ENDOR signal becomes intensive and sharp even at 290 K, indicating that the molecular frame becomes rigid. The relation between the ENDOR spectra of these systems and the intramolecular dynamics is discussed.

Purpose To develop new methods that can estimate the influences of manufactured nanomaterials on biological systems, the in vivo pulmonary reducing ability of mice that had received inhalation exposures to NiO or C60 nanoparticles was investigated using a 700 MHz electron paramagnetic resonance (EPR) spectrometer. Materials and Methods NiO or C60 suspensions were atomized and mice in exposure chambers inhaled the resulting aerosol particles for 3 hours. The exposure conditions, number-based geometric average diameters, and the average number concentration were precisely controlled at almost the same levels for both NiO and C60 nanoparticles. Two days or 2 weeks after exposure, an EPR study was conducted noninvasively. Temporal changes in EPR signal intensity at the target area (ie, lung field) were obtained by the region-selected intensity determination (RSID) method. Results NiO nanoparticles significantly suppressed pulmonary reducing ability 2 days and 2 weeks after exposure, but C60 nanoparticles had no such effect. Conclusion This is the first in vivo estimation of the reducing ability in experimental animals exposed to manufactured nanoparticles. J. Magn. Reson. Imaging 2009. © 2009 Wiley-Liss, Inc.

This study has demonstrated that conceptually new continuous-flow reaction procedure for biomimetic transamination of perfluoroalkyl-containing ketones is substantially more efficient as compared with conventional in-flask approach, allowing preparation of the target fluorinated amines with generally improved chemical yields and enantioselectivity.

Selected-region intensity determination (SRID) is a method for obtaining the temporal changes in electron paramagnetic resonance (EPR) signal intensity from a selected region without complicated procedures used in the previous imaging method. We used an in vivo 700 MHz radiofrequency EPR spectrometer equipped with a bridged loop-gap resonator and the SRID method to perform temporal EPR measurements of the lung area of mice which had received a nitroxide radical (3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl) administration via the intravenous route. The half-life and initial level of nitroxide radical in the lung or the mediastinum were calculated from temporal changes in the signal intensity. A mathematical model was devised to determine the nitroxide radical concentration in the lung, which is connected to other organs via the circulatory system. Using this model and the results of the EPR measurements, the degrees of influence of the nitroxide reduction in the lung and other organs were simulated. It was found that the reaction rate (=log2/half-life) obtained from the lung mainly reflected the reduction of nitroxide radical there.

Although it is thought that perfluoro-2,4-dimethyl-3-isopropyl-3-pentyl (PFR-2) is a candidate for electron paramagnetic resonance (EPR) imaging agents because of its high stability, no study has been made yet on the EPR imaging of PFR-2. In this study, EPR imaging of a phantom including PFR-2 and mice that had received PFR-2 was performed by an in vivo EPR imaging system operating at an EPR frequency of 700 MHz equipped with a bridged loop-gap resonator (inner diameter, 41 mm; axial length, 10 mm). Because PFR-2 is insoluble in water, it was dissolved in perfluorocarbon. The PFR-2 solution was put in cylindrical sample tubes with various inner diameters, and these sample tubes were placed together in a larger cylindrical sample tube filled with a physiological saline solution, which was used as a phantom. The spatial resolution was estimated to be about 3 mm on the basis of EPR imaging of the phantom. EPR images of mice that had received a PFR-2 injection via the intraperitoneal route indicated that PFR-2 remained in the peritoneal cavity even 2 days after the injection. This finding suggests that it is possible to perform EPR imaging of experimental animals using PFR-2 as an imaging agent which persists in a biological system.

大気中に放出されたフロンはオゾン層の破壊や地球温暖化を招く. こうした地球環境への影響を抑止するための措置として, フロンの回収, 移送, 無害化処置が行われている. すなわち, 回収業者がフロンをボンベに回収し, そのボンベを破壊業者まで陸送し, 無害化処理する. こうしたフロンの集約処理過程には移送に伴う危険性や費用が発生する. 一方, その場で分散処理する方法があれば, 移送に伴う危険性がなく, またその費用も削減され, 安全かつ総合的にコストを下げることが可能になる. 本研究では, 分散処理が可能なオンサイト型フロン分解装置を開発した. 具体的にはアークプラズマを用いた分解装置の最適化と電極の長寿命化を検討し, 装置重量が400kgのオンサイト型装置の開発に成功した. さらに, アークプラズマの欠点である電極の消耗を最小限に抑え, 電極を交換せずに長時間安定してフロンを分解することを可能とした. また, 環境省の排ガス・排水基準値もクリアし, ダイオキシン類が発生しないことも確認した.

A novel styrene monomer with a highly branched perfluoroalkenyl group was readily prepared in good yield from hexafluoropropene trimer and hydroxystyrene. The fluorinated monomer radically polymerized yielded a white powdery polymer which was soluble in fluorinated solvents and had good water repellency. The polymer had a unique high glass transition temperature despite the introduction of perfluorinated groups. The monomer was copolymerized with styrene, and their monomer reactivity ratios were determined.

Methylated, highly branched fluoroolefins were prepared by treatment of hexafluoropropene trimers with CH3Li and CH3MgBr. Their structures, which included some rotational isomers, were determined by NMR and GC-MS and were further confirmed by B3LYP-GIAO calculation of NMR shieldings. Of the seven methylated fluoroolefins isolated in pure states, three were shown to be mixtures of pairs of conformational isomers. The methylated fluoroolefins containing two bulky geminal substituents such as (CF3)2CF and (CF3)2CCH3 showed gear-meshed conformations in which the two bulky substituents were conformationally locked. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Trimethylamine N-oxide and iodosylbenzene were found to be useful reagents for the epoxidation of tri- and tetra-substituted perfluoroalkenes in good to excellent yields. A catalytic epoxidation method was also developed by coupling this reaction with the N-oxidation of trimethylamine by hydrogen peroxide or perbenzoic acid.

The addition reactions of F-carboxylic acids to terminal and cyclic olefins and of F-alkanoyl halides to cyclic ethers has been found to be useful for preparing F-carboxylic esters of sec-alcohols and ω-haloalkyl alcohols, respectively. Both types of reaction can be performed under solvent-free conditions and no accompanying by-products are formed; in some cases a 100% atom efficiency was achieved.

The C−X (X = C, O, N, S, Br) bond dissociation enthalpies (BDEs) of perfluoroalkanes, perfluoroethers, perfluorotrimethylamine, perfluorodimethyl sulfide, and trifluoromethyl bromide were evaluated by the G2, G2MP2, and G2MS methods. Perfluoroethers had high BDEs of the C−O bond because of the strong negative hyperconjugation between the CF3 group and lone pair orbitals of oxygen. The BDEs of CF3−X bonds could be used as an index of the fire suppression ability.

The reactions of F -(5,6-dihydro-2 H -1,4-oxazine) and F -(3,4-dihydro-2 H -pyrrole) were investigated using two series of reagents: one is the polyfluoroalkylating agent RfOSO 2 CF 3 and the other is the (polyfluoroalkoxy)trimethylsilane RfOSi(CH 3 ) 3 . Systematic study with polyfluoroalkyl groups such as CF 3 CH 2 , C 2 F 5 CH 2 , CHF 2 CH 2 , and (CF 3 ) 2 CH revealed that the regio-chemistry, isomer distribution, product distribution between mono-, di-, and tri-substituted products and even the reaction pathways were subtly changed by the structure of these fluoro substituents as well as by the reagent stoichiometry. A notable substitution effect was found in the reaction of F -(5,6-dihydro-2 H -1,4-oxazine): substitution at the 3-position prevented the N -polyfluoroalkylation by CF 3 CH 2 OSO 2 CF 3 . No particular difference was found between the two different heterocyclic systems in contrast with the reaction of these heterocyclic systems with C 6 F 5 Si(CH 3 ) 3 . The discussion about the reaction mechanisms for both reagents are included.

The title reactions were achieved in the presence of a fluoride anion: the reaction of perfluoro-(5, 6-dihydro-2H-1, 4-oxazine)(1)with an equal amount of trimethyl(pentafluorophenyl)silane(3)provided not only a monosubstituted compound but also di and trisubstituted compounds, while the reaction of 1 with three molar excess of 3 only gave trisubstituted compounds. A significant heterocyclic ring effect was observed: the reaction of perfluoro-(3, 4-dihydro-2H-pyrrole)(2)with 3 mainly gave a dimer of 2 with a trace amount of a monosubstituted compound.

This study demonstrated that alkylation of chiral glycine Schiff base 3 with chloride 4 can be efficiently conducted in acetonitrile as a solvent using commercial-grade potassium tert -butoxide as a base. High reaction rate (1 h) chemical (>90%) and stereochemical (>95% de) outcomes of the alkylation step render this procedure reliable and operationally convenient for multi-gram synthesis of enantiomerically pure amino acid 1 . Due to the simplicity of experimental procedures and commercial availability all reagents involved, this procedure can be easily reproduced in regular biochemistry laboratories allowing for systematic biological studies and medicinal applications of compound 1 .

This paper reviews the synthesis of unnatural chiral β-fluoroalkyl β-amino alcohols, with an emphasis on their biological activity and pharmaceutical applications.

Series of amino alcohols including 2-( N,N -dialkylamino)ethanols, 3-( N,N -dimethylamino)propanol and 4-( N,N -dimethylamino)butanol were subjected to electrochemical fluorination. In the case of 2-( N,N -dialkylamino)ethanols, the F -(2- N,N -dialkylamino)acetyl fluorides were obtained in fair to good yields. Yields of each target compound were strongly dependent on the kind of the dialkylamino group. Cyclic amines having an N -(2-hydroxylethyl) group afforded the corresponding F -[ N -( c -alkylamino)-substituted acetyl fluorides]. Their yields were generally better than those of acyclic analogs. Several 2-( N,N -dialkylamino)ethanols and 3-( N,N -dimethylamino)propanol were converted into the corresponding trimethylsilylethers, aminoalkyl methyl carbonates and bis-aminoalkyl carbonate, respectively, and they were subjected to fluorination for a comparison of the yield with that obtained from that of the parent aminoalcohol.

The reactivity of persistent perfluoroalkyl radical, perfluoro-3-ethyl-2,4-dimethyl-3-pentyl ( 1 ), with various electron-donating reagents was investigated. It is revealed that 1 which is robust under oxidative conditions is rather vulnerable under reductive conditions. Thus, Lewis bases such as triethylamine and triphenylpnictogens (Ph 3 Pn, Pn=N, P, As, Sb, Bi) and some soft anions such as iodide or tetraphenyl borate reacted with 1 to give perfluoro-3-isopropyl-4-methylpent-2-ene ( 2 ) quantitatively. Even very weak Lewis bases such as diethyl ether and diethylsulfide also reacted with 1 to give 2 and additionally a hydrido product, perfluoro-3-ethyl-3- H -2,4-dimethylpentane ( 4 ). Hydrogen gas did not react with 1 at all without a catalyst, but in the presence of metal Pd adsorbed on charcoal, smoothly reacted to give 2 in quantitative yield. Metal hydrides such as LiAlH 4 , NaBH 4 , NaH, BH 3 (THF complex), Bu 3 SnH, Me 2 PhSiH reacted with 1 to give 2 and 4 . That an electron transfer mechanism is operating in the formation of 2 is obvious, but not conclusive in the formation of 4 .