Visible-light-induced perfluoroalkylation/arylmigration/desulfonylation cascades of conjugated tosyl amides

An effective visible-light-induced perfluoroalkylation of conjugated tosyl amides using R_f-X (X = I or Br) as the R_f source by Ir photocatalyst was disclosed. This protocol provides a new way to prepare oxindoles or α-aryl-β-fluoroalkyl amides bearing various perfluorinated moieties such as n-C₃F₇, i-C₃F₇, n-C₄F₉, n-C₆F₁₃, n-C₈F₁₇, n-C₁₀F₂₁ and CF₂CO₂Et.     

Radical homopolymerization of tetrafluoroethylene initiated by perfluorodiacyl peroxide in supercritical carbon dioxide: Reaction mechanism and initiation kinetics

Radical homopolymerizations of tetrafluoroethylene (TFE) in supercritical carbon dioxide (sc-CO₂) initiated by bis(perfluoro-2-n-propoxypropionyl) peroxide (BPPP) were conducted. Low molecular weight polytetrafluoroethylenes (PTFEs) which are widely used in diverse fields with stable end groups were successfully obtained. PTFEs were characterized by solid-state ¹⁹F NMR and FT-IR spectroscopy. From rational assignment of the characteristic signals, an overall reaction mechanism explaining the homopolymerization processes is proposed. The carboxyl radicals resulted from thermal decomposition of BPPP were completely decarboxylated to n-C₃F₇OCF(CF₃) before reacting with TFE. Additionally, a small amount of n-C₃F₇OCF(CF₃) rearranged into n-C₃F₇ with decreased rearrangement fraction from 0.11 to 0.04 when the reaction temperature was lowered from 35 to 5 °C. Initiation rate constants (k_d) were slightly increased with elevated pressure. The initiation activation energy derived from k_d is 90.3 kJ mol^?1, which is much lower than those of the other systems where nonfluorinated diacyl peroxides are used. Such mechanism and kinetics insights into the homopolymerizations of TFE in sc-CO₂ will be instructive for the syntheses of fluoropolymers with desired properties in future.     

Recent advances on synthesis of potentially non-bioaccumulable fluorinated surfactants

Fluorinated surfactants are exceptional compounds that have found many applications in everyday life. This review focuses on severe issues on the toxicity, persistency and bioaccumulation of these halogenated products, especially perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), the half-lives of which are several years in human serum. After an introduction on their productions, uses and hazards, this minireview updates non-exhaustive recent strategies of synthesis of original fluorosurfactants that may be potentially non-bioaccumulable. These routes have been devoted on: (i) the preparation of CF₃-X-(CH₂)_n-SO₃Na (with X = O, C₆H₄O or N(CF₃) and n = 8–12), (ii) the use of fluorinated polyethers (achieved either by oligomerization of hexafluoropropylene oxide (HFPO) or by ring opening cationic oligomerization of fluorinated oxetanes; (iii) the telomerization of vinylidene fluoride (VDF) with 1-iodoperfluoralkanes to produce C_nF_2n + 1-(VDF)₂-CH₂CO₂R (n = 2 or 4, R = H or NH₄), (iv) the radical telomerization of 3,3,3-trifluoropropene (TFP) with isoperfluoropropyliodide to prepare (CF₃)₂CF(TFP)_x-R_H, and (v) the radical cotelomerization of VDF and TFP, or their controlled radical copolymerization in the presence of either (CF₃)₂CFI or a fluorinated xanthate. In most cases, the surface tensions versus the surfactant concentrations have been assessed. These above pathways led to various highly fluorinated (but yet not perfluorinated) telomers or cooligomers, the chemical changes of which enabled to obtain original surfactants as novel alternatives to PFOA, ammonium perfluorooctanoate (APFO), or PFOS regarded as the PCBs of the XXIst century.     

An efficient stereoselective preparation of cis-perfluoroalkenylzinc reagents [(E)-RFCFCFZnCl] by the metallation of 1H,1H-perfluoroalkanes and their derivatization to cis-1-arylperfluoroalkenes [(Z)-RFCFCFAr]

Various 1H,1H-perfluoroalkanes (R_FCF₂CH₂F, R_F = CF₃, C₂F₅, C₄F₉, C₅F₁₁, C₆F₁₃, C₁₀F₂₁) were metallated using LDA in a THF solution of ZnCl₂ at RT or −78 °C to produce the corresponding perfluoroalkenylzinc reagents (R_FCFCFZnCl) in a cis-selective fashion. An increased yield (75–83%) and cis-selectivity (>89%) of the perfluoroalkenylzinc reagents were observed for metallation reactions performed at −78 °C. The cis selectivity was excellent for 1H,1H-perfluoroalkanes with larger R_F groups (C₄F₉, C₅F₁₁, C₆F₁₃, >96%). The cis-perfluoroalkenylzinc [(E)-R_FCFCFZnCl] reagents were coupled with aryl iodides to obtain cis-1-arylperfluoroalkenes [(Z)-R_FCFCFAr] in 71–95% isolated yields. The cis-perfluoroalkenylzinc reagents upon iodinolysis produced cis-1-iodoperfluoroalkenes [(E)-R_FCFCFI] in 68–70% isolated yield.     

High-temperature and photochemical syntheses of C60 and C70 fullerene derivatives with linear perfluoroalkyl chains

New experimental results on perfluoroalkylation of C₆₀ and C₇₀ with the use of R_fI (R_f = CF₃, C₂F₅, n-C₃F₇, n-C₄F₉, and n-C₆F₁₃), along with a critical overview of the existing synthetic methods, are presented. For the selected new fullerene (R_f)_n compounds we report spectroscopic, electrochemical and structural data, including improved crystallographic data for the isomers of C₇₀(C₂F₅)₁₀ and C₆₀(C₂F₅)₁₀, and the first X-ray structural data for the dodecasubstituted perfluoethylated C₇₀ fullerene, C₇₀(C₂F₅)₁₂, which possesses unprecedented addition pattern.     

On the kinetics of thermal electron attachment to perfluoroethers

In this Letter we report the results of the measurements of the rate coefficients for thermal attachment to several perfluoroethers namely perfluorodiglyme (C₆F₁₄O₃), perfluorotriglyme (C₈F₁₈O₄), perfluoropolyether (CF₃–(OCF(CF₃)CF₂)_n–(OCF₂)_m–OCF₃) and perfluorocrownether ((C₂F₄O)₅). Rate coefficients were obtained under thermal conditions in the temperature range 298–378 K. The increase of the rates with temperature follows the Arrhenius law and the activation energies have been obtained from the slope of the ln(k) vs. 1/T. The respective values of the rate coefficients (at 298 K) and activation energies are as follows: 7.7 ± 1.2 × 10^?11 cm³ s^?1 (0.18 ± 0.005 eV), 6.7 ± 2.1 × 10^?11 cm³ s^?1 (0.25 ± 0.004 eV), 2.1 ± 0.2 × 10^?10 cm³ s^?1 (0.16 ± 0.010 eV), 3.1 × 10^?11 cm³ s^?1 (0.27 ± 0.003 eV) for C₆F₁₄O₃, C₈F₁₈O₄, CF₃–(OCF(CF₃)CF₂)_n–(OCF₂)_m–OCF₃ and (C₂F₄O)₅.     

Synthesis of fluorine-containing symmetrical N,N-alkylidene bisamides

Fluorine-containing N,N-alkylidene bisamides RCH(NHCOR_f)₂ (R: H, Aryl; R_f: CF₃, CF₂Cl, 2,6-C₆H₃F₂) are conveniently prepared in good yields by the reaction of corresponding aldehydes with fluorine-containing amides (R_fCONH₂) in the presence of fluoroalkanesulfonic acids R_f′SO₃H(R_f′: CF₃, HCF₂CF₂, ICF₂CF₂OCF₂CF₂).     

Synthesis,X-ray structure and reactivity of μ-(CF3COO)2-[Mo(N-2,6-i-Pr2-C6H3)(CHCMe2Ph)(OOCCF3)(Et2O)]2, the first Bis(trifluoroacetate) derivative of a Schrock catalyst

Reaction of Mo(N-2,6-i-Pr₂-C₆H₃)(CHCMe₂C₆H₅)(OSO₂CF₃)(DME) (DME = 1,2-dimethoxyethane) with 2 equiv. of CF₃COOK yields μ-(CF₃COO)₂-[Mo(N-2,6-i-Pr₂-C₆H₃)(CHCMe₂Ph)(OOCCF₃)(Et₂O)]₂ (1). Compound 1 crystallizes in the orthorhombic space group Pna2₁ with a = 17.2485(3), b = 17.0336(3), c = 25.4031(5) Å, α = β = γ = 90°, V = 7463.5(2) Å³, Z = 4. In contrast to alkoxide based Schrock type initiators, 1 is virtually inactive in numerous metathesis reactions including ring-closing metathesis (RCM) and homo metathesis reactions, the cyclopolymerization of 1,6-heptadiynes, and even ring-opening metathesis polymerization (ROMP) of norborn-2-ene. However, addition of quinuclidine results in the in situ formation of 1a (Mo(N-2,6-i-Pr₂-C₆H₃)(CHCMe₂C₆H₅)(OOCCF₃)₂(quinuclidine) which displays moderate activity in ROMP, cyclopolymerization of 1,6-heptadiynes and RCM. Theoretical investigations carried out on the B3LYP/LACVP¹ level provide substantial explanation for these findings.     

Fluoroalkenyl, fluoroalkynyl and fluoroalkyl phosphines

A review of the methods available for the preparation of monodentate P(III) compounds containing fluoroalkenyl, fluoroalkynyl and fluoroalkyl groups is given. The synthesis, properties and coordination chemistry of some fluoroalkenyl- and fluoroalkynyl-containing phosphines derived from HFC-134a (CF₃CH₂F) and HFC-245fa (CF₃CH₂CH₂F) is summarised. The development of the reaction between trimethylsilyl-containing phosphines and R_fI which provides a general method by which bulky fluoroalkyl groups, such as i-C₃F₇, t-C₄F₉, c-C₆F₁₁, can be readily introduced into phosphorus(III) centres is reported. Together these methods provide a way of generating P(III) systems of the type R_3−nP(R_f)_n capable of possessing a wide range of steric and electronic properties.     

Asymmetric hydrogenation of aromatic ketones catalyzed by achiral monophosphine TPPTS-stabilized Ru in ionic liquids

Achiral monophosphine TPPTS [TPPTS: P(m-C₆H₄SO₃Na)₃]-stabilized Ru was synthesized by reduction of RuCl₃·3H₂O with hydrogen in ethanol using TPPTS as the stabilizer. The catalytic asymmetric hydrogenation of aromatic ketones using TPPTS-stabilized Ru modified by a chiral diamine (1R,2R)-DPENDS [disodium salt of sulfonated (1R,2R)-1,2-diphenyl-1,2-ethylene-diamine] was investigated in hydrophilic ionic liquid [RMIM]Ts (1-alkyl-3-methylimidazolium p-methylphenylsulfonates, R = ethyl, butyl, octyl, dodecyl, hexadecyl). Hundred percent conversion and 85.1% ee were obtained for acetophenone under optimized conditions. The resulting products can be easily separated from the catalyst immobilized in ionic liquid by simple extraction with n-hexane, and the catalyst can be reused several times without a significant loss of ee value or conversion. In particular, the addition of water can improve the catalyst performance.     

New three-dimensional (3,4)-net zincophosphites templated by linear diammonium cations: H3N(CH2)5NH3·Zn3(HPO3)4 and β-H3N(CH2)6NH3·Zn3(HPO3)4

The mild-condition syntheses, single-crystal structures and properties of H₃N(CH₂)₅NH₃·Zn₃(HPO₃)₄ and β-H₃N(CH₂)₆NH₃·Zn₃(HPO₃)₄ are reported. Both are constructed from (3,4)-nets of ZnO₄ tetrahedra and HPO₃ pyramids, sharing vertices to result in three-dimensional anionic open-frameworks. In both materials, the organic species interacts with the framework by way of N–H⋯O bonds. Crystal data: H₃N(CH₂)₅NH₃·Zn₃(HPO₃)₄, M_r = 620.22, orthorhombic, Pccn (No. 56), a = 9.5364 (9) Å, b = 21.8015 (19) Å, c = 9.1118 (7) Å, V = 1894.4 (3) Å³, Z = 4, R(F) = 0.044, wR(F²) = 0.111. β-H₃N(CH₂)₆NH₃·Zn₃(HPO₃)₄, M_r = 634.25, monoclinic, P2₁/n (No. 14), a = 8.7627 (1) Å, b = 13.8117 (2) Å, c = 16.6187 (3) Å, β = 92.680 (1)°, V = 2009.12 (5) Å³, Z = 4, R(F) = 0.072, wR(F²) = 0.187.     

Temperature dependence of the surface tension and 0.1 MPa density for 1-Cn-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate with n = 2, 4, and 6

Experimental air–liquid interfacial tension data and density data are presented for three 1-C_n-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphates (FAP), [C_nMIM][(C₂F₅)₃PF₃], with n = 2, 4, and 6, measured at atmospheric pressure in the temperature range from 267 K to 360 K using the Krűss K100MK2 tensiometer. The accuracy of the surface tension measurements was checked by employing the Wilhelmy plate and the du Noüy ring methods in parallel. The combined standard uncertainty associated with the Wilhelmy plate method is estimated to be ±0.1 mN · m⁻¹. The density data were obtained using buoyancy method with an estimated standard uncertainty less then ±0.4 kg · m⁻³ (3 · 10⁻⁴ϱ). The chloride anions decrease the density of the tris(pentafluoroethyl)trifluorophosphates of interest up to six times more effectively than they decrease the density of the imidazolium based tetrafluoroborates. A QSPR analysis of the surface tension of imidazolium based ionic liquids with BF₄, TFA, DCA, FAP, NTf₂, and PF₆ anions indicates, that the FAP ionic liquids fit well into the analyzed group of imidazolium based ionic liquids while those having hexafluorophosphate anion show anomalously high deviations of the experimental surface tension from the values predicted by the QSPR model.     

Activation process of 3-alkyl-substituted ansa-bis(indenyl) zirconocenes by MAO

The ansa-indene compound {1-Me₂Si(3-C₉H₆Et)₂} (1) was prepared by alkylation of the unsubstituted ansa-indene. This compound was converted, by reaction with nBuLi, to the dilithium compound [Li₂{1-Me₂Si(3-C₉H₅Et)₂}] (2). ansa-Zirconocene [Zr{1-Me₂Si(3-η⁵-C₉H₅Et)₂}Cl₂] (3) was prepared by the reaction of ZrCl₄ with 2 in ether/toluene at −78 °C. The molecular structure of meso-3 was determined by single crystal X-ray diffraction studies. The ansa-zirconocene 3 exhibits a greater activity in ethylene polymerization than reference complexes such as [Zr{1-Me₂Si(η⁵-C₉H₆)₂}Cl₂] and [Zr{1-C₂H₄(η⁵-C₉H₅)₂}Cl₂] and, in addition, it maintained a reasonable level of activity after 12 h of contact with MAO solution. Furthermore, the different elementary steps in the activation process of ethylene polymerization for substituted complexes [Zr{1-Me₂Si(3-η⁵-C₉H₅R)₂}Cl₂] (R = Et 3, Me 4, nPr 5 and nBu 6) by commercial methylaluminoxane (MAO) have been studied by UV–vis spectroscopy. Addition of MAO in large excess ([Al]/[Zr] = 2000) at −78 °C yields a previously unreported intermediate in the activation process of metallocenes; this intermediate has an absorption band centered at λ = 639 nm. We report here the influence of the type of catalyst, ring substitution, type of cocatalyst and addition of THF on the activation process of these metallocenes.     

Synthesis of open-framework iron phosphates, [C5N2H14]2[FeIII2F2(HPO4)4]·2H2O and [C5N2H14][FeIII4(H2O)4F2(PO4)4], with one- and three-dimensional structures

The hydrothermal syntheses and structures of two new open-framework iron phosphates, [C₅N₂H₁₄]₂[Fe^III₂F₂(HPO₄)₄]·2H₂O, I, and [C₅N₂H₁₄][Fe^III₄(H₂O)₄F₂(PO₄)₄], II, are presented. While the structure of I consist of FeO₄F₂ octahedra and HPO₄ terahedra linked to form one-dimensional structure, that of II consist of FeO₄(H₂O)₂, FeO₄(H₂O)F, FeO₄F₂ and PO₄ units connected to give rise to a three-dimensional structure. The structure of I resembles the naturally occurring mineral tancoite while II resembles the iron phosphate, ULM-12, [C₆N₂H₁₄][Fe₄(PO₄)₂F₂(H₂O)₃]. Magnetic susceptibility studies indicate anti-ferromagnetic behavior in both the compounds with T_N=200 and 175 K for I and II, respectively. Crystal data: I, monoclinic, space group=P2₁/n (no. 14). a=7.2261(6), b=16.5731(14), c=11.0847(10) Å, β=97.265(2)°, V=1316.8(2) Å³, Z=4, ρ_calc=1.952 g cm⁻¹, μ_(MoKα)=1.446 mm⁻¹, R₁=0.0448 and wR₂=0.1141 for 1882 data [I>2σ(I)]; for II, monoclinic, space group=P2₁/n (no. 14). a=9.9691(3), b=12.4013(3), c=17.3410(3) Å, β=103.762(1)°, V=2082.32(9) Å³, Z=4, ρ_calc=2.576 g cm⁻¹, μ_(MoKα)=3.162 mm⁻¹, R₁=0.0510 and wR₂=0.1064 for 2979 data [I>2σ(I)].     

Base-controlled selective construction of polysubstituted dihydrofuran and furan derivatives through an I2-mediated cyclization

A base-controlled formal [3 + 2] cycloaddition of 1,3-dicarbonyl compounds to enones via an I₂-mediated cyclization was reported. Highly functionalized dihydrofurans and furans were selectively obtained under I₂/DMAP and I₂/DBU conditions in the cyclization step, respectively.     

Fluorinated nitroxides as ESR probes of solvation

Some newly synthesized fluorinated nitroxides, such as t-butyl perfluoroalkyl nitroxides Bu^tN(O) R_f (R_f=CF₃, 5; C₂F₅, 6; n-C₃F₇, 7) and s-butyl perfluoroacyl nitroxides Bu^sN(O) COR_f (R_f=CF₃, 9; n-C₃F₇, 10) have been employed as ESR probes of solvation in different common organic solvents. In aprotic solvents, the measured a_N values for each of the nitroxyl probes show a linear correlation with the cybotactic polar solvent parameters E_T (Dimroth) and Z (Kosowar), i.e. a_N=bE_T+c, and a_N=b′Z+c′. The physical significance for the slope (b or b′), the slope×E_T or slope×Z, the extrapolated intercept on a_N axis, c or c′, are linked, respectively, to the sensitivity of a specific nitroxide toward solvation, the magnitude of the overall solvation effect on the a_N value, and the intrinsic a_N value of each nitroxide in the ideal gaseous state. The intercept on the a_N axis may also serve as a new measure of electronegativity for perfluoroalkyl groups, CF₃, C₂F₅, n-C₃F₇, and perfluoroacyl groups, CF₃CO, n-C₃F₇CO. In protic solvents, i.e. alcohols and carboxylic acids, however, a_N values of all the probes, kept almost no change with the increase in E_T and Z. Furthermore, the plots of a_N versus non-cybotactic solvent constants, such as dipolar moment (μ) and dielectric constant (ε), all show random variations.     

A new method of one-pot synthesis of dicarboxylic acid derivatives and diketones containing quaternary carbon atom and remote functional groups from linear acyl halides

The one-pot, regioselective synthesis of branched diacid derivatives – diesters, dithioesters, diamides [YC(O)O(CH₂)_mC(Me)₂OC(O)Y] and diketones of aromatic and heteroaromatic series, [ArCO(CH₂)_mC(Me)₂C(O)Ar,) from available linear acyl halides, C_nH_2 n+1COCl (n = 7–9), CO (1 at) and various nucleophiles (YH = EtOH, CF₃CH₂OH, H(CF₂)₂CH₂OH, thiophene, anisole, Et₂NH, aniline, and morpholine) in the presence of the superelectrophilic complex, CBr₄·2AlBr₃ has been performed for the first time. This method provides access to new and promising groups of dicarboxylic acid derivatives and diketones containing quaternary carbon atom and remote functional groups.     

Organocatalytic chemoselective monoacylation of 1,n-linear disulfonamides

Predominant monoacylation of 1,n-linear disulfonamides took place in the presence of pyrrolidinopyridine-type organocatalysts when the chain length of the linear disulfonamides was n = 3, 4, or 5 (monoacylate/diacylate = up to 44). The chemoselectivity of the competitive acylation between N,N′-ditosyl-1,5-pentanediamine (n = 5) and N,N′-ditosyl-1,3-propanediamine (n = 3) was found to be 36, favoring the former substrate. Different chain length by only one carbon atom was discriminated in the competitive acylation between N,N′-ditosyl-1,5-pentanediamine (n = 5) and of N,N′-ditosyl-1,4-butanediamine (n = 4) with the relative acylation rate of 16 in the presence of the organocatalyst.     

S6 Isomer of C60(CF3)12: Synthesis,properties and thermodynamic functions

A crystalline form of S₆-С₆₀(CF₃)₁₂ was synthesized in an amount sufficient for reliable experimental investigation. We determined the enthalpy of combustion of S₆-С₆₀(CF₃)₁₂ in oxygen and its heat capacity, which made possible to derive the thermodynamic functions of S₆-С₆₀(CF₃)₁₂, namely the enthalpy of formation, the entropy and the Gibbs energy at T = 298.15 K. These experimental thermochemical data enabled estimation of the formation energy for a broad range of other trifluoromethylated compounds C₆₀(CF₃)_n, with n = (2–18; 24), on the basis of their DFT calculated relative energies.     

Stereocontrolled self-assembly of luminescent lanthanide helicates and their enantiodifferentiation using Δ-TRISPHAT as the NMR resolving agent

Self-assembled supramolecular lanthanide constructs have great potential in luminescent bioprobes/sensors. Stereoselectivity on the lanthanide assemblies is needed to facilitate chiroptical probes and sensors. Herein we report the stereocontrolled synthesis of M₂L₃-type (M = metal ion, L = organic ligand) lanthanide triple-helicates using a chiral-induction strategy, where the periphery point-chirality [(R,R) or (S,S)] of the organic ligands was transferred into the metal centered chirality (ΔΔ or ΛΛ), thus leading to the formation of topological chiral (P or M) helicates. Moreover, commercially available Δ-TRISPHAT proved to be an effective NMR chiral resolving agent to differentiate between the two enantiomers of the helicate.