Synthesis and characterization of tri-block fluorinated-n-alkanes

A series of triblock semifluorinated n-alkanes of general formula F(CF₂)_n(CH₂)_m(CF₂)_nF (n = 6, 8 and m = 4, 6, 8) have been synthesized and characterized. The synthesis of triblock compounds was performed in two different ways according to the length of the hydrogenated moiety. Coupling of two molecules of β-(perfluoro-n-alkyl)ethyl iodides leads to the triblock materials F(CF₂)₆(CH₂)₄(CF₂)₆F and F(CF₂)₈(CH₂)₄(CF₂)₈F. The synthesis of compounds with larger hydrogenated part is accomplished in two steps by the addition of perfluoro-n-alkyl iodide F(CF₂)_nI to 1,5-hexadiene and 1,7-octadiene, respectively to give the diiodo-adducts which are subsequently deiodinated to the final triblock products F(CF₂)₆(CH₂)₆(CF₂)₆F, F(CF₂)₆(CH₂)₈(CF₂)₆F, F(CF₂)₈(CH₂)₆(CF₂)₈F and F(CF₂)₈(CH₂)₈(CF₂)₈F. The obtained triblock semifluorinated n-alkanes are characterized by low surface free energies with good lubricant properties usable as additives in ski-wax formulations.     

Studies on fluoroalkylation and fluoroalkoxylation: 2. Perfluoroalkylation of aromatics with perfluoroalkyl iodides in the presence of copper

Perfluoroalkyl iodide R_fI [R_f = (CF₂)_nO(CF₂)₂SO₂F, n = 2, (a); n = 4, (b); (CF₂)₄Cl, (c)] reacted with substituted benzene C₆H₅Y (Y = alkyl, OCH₃, CF₃, F, Cl, Br, I) in the presence of copper in acetic anhydride to give the corresponding mixture of isomeric disubstituted benzene (R_fC₆H₄Y). The conversion and yield depend on both the amount of copper used and nature of substituent. The likely explanation is that the reaction may involve a free radical process. The perfluoroalkyl radical can be trapped by cyclohexene, isopropylbenzene and styrene. Using DMSO in place of acetic anhydride as a solvent the reaction takes a different course, it is believed that the reaction in DMSO proceeds through a perfluoroalkylcopper intermediate.     

Hetero-Diels–Alder reactions of perfluoroalkyl thioamides with electron-rich 1,3-dienes: synthesis of new 2-aminosubstituted-3,6-dihydro-2H-thiopyrans and related compounds

Hetero-Diels–Alder reactions of perfluoroalkyl thioamides with electron-rich 1,3-dienes such as 2,3-dimethylbutadiene, isoprene or penta-1,3-diene gave a simple and efficient access to new 2-aminosubstituted-3,6-dihydro-2H-thiopyrans. Three different procedures were used depending on the nature of the polyfluoroalkyl chains (R_F=CF₃, (CF₂)_nCF₃, (CF₂)₄H) and on the nitrogen substituents of the thioamides (R¹, R²=H, p-Tol, morpholino, Ac). Moreover, cycloadditions of silyloxydienes (1- or 2-trimethylsilyloxy-1,3-butadiene and Danishefsky's diene) with N-acyl,N-tolyl trifluoromethylthioamides afforded in almost all cases the corresponding 3,6-dihydro-2H-thiopyrans or 3-oxo-tetrahydrothiopyrans. For non-symmetrical 1,3-dienes, the regio- and stereochemistry of the reactions were studied (especially using X-ray diffraction analysis) indicating a strong similarity with those reported for fluorinated thiocarboxyl derivatives. Finally, two silylated 3,6-dihydro-2H-thiopyrans underwent an unexpected base-induced ring contraction to give new 1,3-thiazolidin-4-ones.     

The first series of ferroelectric steroidal fluorinated liquid crystals

A series of cholesteryl p-perfluoroalkylphenyl carbonate (CPC) [C₂₇H₄₅OCO₂C₆H₄(CF₂)_nF, n=1,4,6,8] liquid crystals was synthesized and their phase transition behaviours were studied. The results show that the compounds containing a not too long perfluoroalkyl chain (n=6,8) have monotropic chiral smectic C phases.     

Hybrid Calixarene/Inorganic Salt/Diiodoperfluorocarbon Supramolecular Assemblies

1,3-Bis(α-picolyloxy)-p-tert-butylcalix[4]crown-5 in the cone conformation (2), 1,8-diiodoperfluorooctane or 1,6-diiodoperfluorohexane, and potassium iodide ternary mixtures undergo in solution self-sorting and afford crystalline “supramolecular salts”. These hybrid materials consist of supercation [K⁺ ? 2] and superanion [I–(CF₂) _n –I…I^? …I–(CF₂) _n –I…I^? …] (n = 6,8) components. In the supercations the potassium ion is embedded in the ionophoric pocket created by the heteroatoms present at the lower rim. In the superanions the iodide ions form infinite fluorous polyanionic chains as a result of a self-assembly process which relies on halogen bonding. Both cation encapsulation and anion-perfluorocarbon halogen bonding were detected in solution by ¹H and ¹⁹F NMR, and in the gas phase by ESI MS.     

Studies on sulfinatodehalogenation: III. The sulfinatodeiodination of primary perfluoroalkyl iodides and α,ω-perfluoroalkylene diiodides by sodium dithionite

Using P. T. C. or cosolvents, both perfluoroalkyl iodides such as Cl(CF₂),_nI (n=2, 4, 6, 1a-1c), H(CF₂)₈I (1d), CF₃(CF₂)_nI (n=3, 5, 7, 1e-1g), and α. ω-perfluoroalkylene diiodides such as (ICF₂CF₂)₂O (4a), I (CF₂)_nI (n=6, 8, 10, 4b-4d) reacted smoothly with sodium dithionite in aqueous solution under mild conditions to give the corresponding perfluoroalkanesulfinates Cl(CF₂)_nSO₂Na (n=2, 4, 6, 2a-2c), H(CF₂)₈SO₂Na (2d), CF₃(CF₂)nSO₂Na (n=3, 5, 7, 2e-2g), α, ω-perfluoroalky-lenedisulfinates O (CF₂CF₂SO₂K)₂ (5a), and KO₂S(CF₂)_nSO₃K (n=6, 8, 10, 6b-6d) in moderate to high yields. These sulfinates were converted to the corresponding sulfonyl chlorides by reacting with chlorine in the usual way. Thus the discovery of the new reagent renders sulfinatodeiodination a practical method for the synthesis of perfluorosulfinic and perfluorosulfonic acids and their derivatives from the corresponding perfluoroalkyl iodides.     

The reactions of perfluoro- and α,α-dichloropolyfluoroalkanesulfinates

Sodium perfluoroalkanesulfinate, R_FSO₂Na [R_F?Cl(CF₂)₄, 1a; CF₃(CF₂)₅, 1b; Cl(CF₃)₆, 1c] reacted with bromine in aqueous solution to give the corresponding sulfonyl bromide R_FSO₂Br (2a-2c) and in acetonitrile or acetic acid, to form perfluoroalkyl bromide R_FBr (3a-3c). Heating in acetonitrile at 80°C, 2a-2c were converted smoothly into 3a-3c. However, reaction of sodium α,α-dichloropolyfluoroalkanesulfinate RCCl₂SO₂Na (R?CF₃, Cl(CF₂)n, n=2, 4, 6, 5a-5d) with bromine in aqueous solution gave directly the corresponding bromoalkanes 1-bromo-1,1-dichloropolyfluoroalkane RCCl₂Br (6a-6d). In aqueous potassium iodide solution, 1a-1c, 5a and 5b also reacted with iodine to form the corresponding iodo-polyfluoroalkane 4a-4c, 7a and 7b directly. 6a and 7a underwent free radical addition to alkene readily in the presence of free radical initiator and reacted with Na₂S₂O₄ in the usual way to form α,α-dichloropolyfluoroethane sulfinate (5a). 5a was stable in strong acid, but reacted with strong base to yield 10. 5a was oxidised by hydrogen peroxide to the sulfonate 11 and reduced by zinc in dilute acid to from the α-chloro sulfinate 12.     

Studies on sulfinatodehalogenation: IX. Synthesis and reaction of secondary perfluoroalkyl iodides

Several derivatives of secondary perfluoroalkyl iodides such as CF₃CFI(CF₂)₂O(CF₂)₃SO₂F (3), CF₃CFI(CF₂),O(CF₂)₂SO₃Na (4), CF₃CFI(CF₃)_n Cl (n=2, 7a; n=4, 7b) and CF₃(CF2)₂-OCFICF₃ (8) were synthesized using known methods, their reaction with sodium dithionite was studied and various olefins were added into the reaction system as radical traps to yield the 1:1 radical adducts.     

Synthesis and characterization of partially fluorinated ethers

A series of partially fluorinated ethers PFE-m,n with general formula F(CF₂)_mCH₂CH₂O(CH₂)_nH (m = 4, 6, 8 and n = 2, 3, 5, 8, 14, 18, 21) has been synthesized and characterized. The present work aimed to investigate the synthesis of PFE-m,n and evaluate some of their fundamental physico-chemical properties such as: specific gravity, refractive index, viscosity, solid-solid transitions, solubility and amphiphile surface activity in a variety of solvents. Further, a comparison between PFE-m,n and the well known semifluorinated n-alkanes F(CF₂)_m-(CH₂)nH (FHm, n) with the same value of the m/n ratio have been reported.     

Studies on fluoroalkylation and fluoroalkoxylation: 8. Palladium(0)-catalyzed addition reaction of fluoroalkyl iodides with alkynes

Fluoroalkyl iodide R_fI [R_F=(CF₂)_nCl, n=2, 4, 6; CF₃(CF₂)_n, n=1, 3; H(CF₂)₄] reacted with alkyne (CH≡CC₄H₉; CH≡CSiMe₃; CH≡CC₆H₅) in the presence of catalytic amounts of tetrakis (triphenylphosphine) palladium (0) to give a mixture of E and Z-fluoroalkylated adduct. The reaction could not be catalyzed by dichloro-bis(triphenylphosphine)palladium (II) and fluoroalkyl complex of palladium (II). 2-Nitro-2-nitrosopropane partly suppressed the reaction. It is believed that the reaction proceeds through a free radical intermediate rather than fluoroalkyl complex of palladium (II).     

Synthesis and properties of gemini-type hydrocarbon-fluorocarbon hybrid surfactants

Gemini-type hybrid surfactants with two fluorocarbon chains connected through a hydrocarbon spacer, F(CF₂)_m(CH₂)₂CH(OSO₃Na)(CH₂)_nCH(OSO₃Na)(CH₂)₂(CF₂)_mF [Fm(Hn)FmOS, m = 4, 6; n = 5, 6, 7, 8)], were synthesized and their surface chemical properties were examined with the aim to have highly functional and highly water-soluble fluorinated surfactants when compared with the conventional fluorinated surfactants. Comparisons of the surface chemical properties of the synthesized gemini-type hybrid surfactants with those of monounit-type hybrid surfactants, F(CF₂)_m(CH₂)₂CH(OSO₃Na)(CH₂)_nH [FmEHnOS, m = 4, 6; n = 3, 5)], revealed that gemination causes a remarkable lowering (about 1/100) in cmc value while it produces little changes in Krafft point (below 0 °C) and surface tension at cmc (γ_cmc).     

Studies on sulfinatodehalogenation: XVII. The sulfinatodehalogenation of primary perfluoroalkyl iodides and bromides by Rongalite

Using acetonitrile or DMF as cosolvent, both perfluoroalkyl iodides such as Cl(CF₂)_nI (n = 4,6,8, la—lc ), CF₃ (CF₂)_n I (n = 5,6,7, ld—lf ), I (CF₂)_n O (CF₂) SO₃ Na(n = 2,4,6, lg—li ) and perfluoroalkyl bromides such as Cl (CF₂)_n Br (n = 4,6, 3a—3b ) and C₇F₁₅ Br (3e) reacted with Rongalite in aqueous solution to give the corresponding sulfinates Cl (CF₂)_n SO₂ Na (n = 4,6,8, 2a—2c ), CF₃-(CF₂)_nSO₂Na (n = 5,6,7, 2d—2f ) and NaO₂S(CF₂)_nO(CF₂)₂SO₃Na (n = 2,4,6, 2g—2i ) in moderate yields. 1 H-perfluoroalkanes were formed as the main products when other solvents such as ethanol. iso-propanol, 1,4-dioxane and morpholine were used.     

Synthesis,properties, and reactions of enantiomerically pure,chiral fluorous phosphines of the formula (menthyl)P(CH2CH2(CF2)n−1CF3)2 (n=6, 8)

Reactions of (menthyl)PH₂ and H₂CCHR_f6 (menthyl=1R,3R,4S; R_fn=(CF₂)_n−1CF₃) or H₂CCHR_f8 (AIBN, refluxing THF) give (menthyl)PH(CH₂CH₂R_fn) and then (menthyl)P(CH₂CH₂R_fn)₂ (n=6, 7; n=8, 8), but with purification or other difficulties at each stage. Reactions of (menthyl)PCl₂ with IMgCH₂CH₂R_fn give, under careful conditions, analytically pure 7 or 8 in 28–32% yields after distillation. Some R_fn(CH₂)₄R_fn also form. These represent the first chiral (and non-racemic) fluorous phosphines. Reactions of 7 or 8 with [Ir(COD)Cl]₂ and CO give trans-[(menthyl)P(CH₂CH₂R_fn)₂]₂Ir(Cl)(CO) (n=6, 71%; 8, 51%) as analytically pure yellow oils. Their IR ν_CO values show the donor/acceptor properties of 7 and 8 to be intermediate between those of P((CH₂)₃R_f8)₃ and P((CH₂)₄R_f8)₃. The CF₃C₆F₁₁:toluene partition coefficients of 7 and 8 (27°C, 78.4:21.6 and 93.7:6.3) are distinctly lower than those of P((CH₂)₂R_fn)₃ (n=6, 98.8:1.2; n=8, >99.7:<0.3), reflecting the replacement of a linear C₈–C₁₀ group that is ca. 75–80% fluorinated by a cyclic C₁₀ terpenyl group. Reactions of 7 or 8 with [Rh(COD)Cl]₂ give [(menthyl)P(CH₂CH₂R_fn)₂]Rh(Cl)(COD) (n=6, 69%; 8, 70%) as orange crystallizable oils.     

Novel perfluoroalkylated oligo(oxyethylene) methyl ethers with high hemocompatibility and excellent co-emulsifying properties for potential biomedical uses

Two series of novel perfluoroalkylated amphiphilic compounds were synthesized from monomethyl ethers of mono-, di- and tri-(oxyethylene) glycols. The first series CH₃(OCH₂CH₂)_nOCH₂CH(OH)CH₂-CF₂(CF₂CF₂)_nCF₃ (n = 1-3) bearing the hydroxy group at the spacer between hydrophilic and hydrophobic parts was prepared by the reactions of the monomethyl ethers with 2-(perfluoroalkylmethyl)oxiranes in 76-97% yields. The second series CH₃(OCH₂CH₂)_nOCH₂CH₂CH₂-CF₂(CF₂CF₂)_nCF₃ (n = 1-3) possessing the non-hydroxylated spacer was synthesized from allyl methyl ethers of oligo(oxyethylene) glycols using radical additions of perfluoroalkyl iodides and subsequent selective reductions of the C-I bond in the adducts in overall yields of 23-69%. Some of the novel amphiphilic compounds displayed very low hemolytic activity to erythrocytes and excellent co-emulsifying properties on testing on perfluorodecalin/Pluronic F-68 microemulsions. 1-O-(2-Hydroxy-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorononyl)-d-xylitol was prepared by a novelized synthesis and employed as a standard compound in the testing.     

Practice of fluorous biphase chemistry: convenient synthesis of novel fluorophilic ethers via a Mitsunobu reaction

The evolution of the term fluorous is addressed first, then a concise terminology is proposed, including fluorous partition coefficient, specific fluorophilicity and fluorousness. Some examples are shown for the design of higher generation fluorophilic molecules, involving Class I to Class III ponytails. Fluorophilic ethers of the structure of ArC(CF₃)₂O(CH₂)_m(CF₂)_nF (m=1, n=1, 7; m=3, n=8) are obtained in high yields, when 2-aryl-1,1,1,3,3,3-hexafluoro-propanols are reacted either with trifluoroethyl- and 1H,1H-perfluorooctyl triflates (NaH/DMF, Williamson ether synthesis) or with 3-perfluorooctyl-propanol (Ph₃P/EtO₂CNNCO₂Et/PhCF₃, Mitsunobu reaction), respectively. Fluorophilic phenol- and perfluoro-tert-butyl ethers can also be prepared effectively by the latter method. In case of higher homologues (n=7, 8) product isolation can be facilitated using fluorous extraction (C₆F₁₄/CH₃OH). Specific fluorophilicity values of target molecules are estimated using a 2D method and compared with experimentally determined ones.     

Polar addition of perfluoro-tert-hexyl iodide to alkenes and alkynes

The effective charges on the atoms in molecules of perfluoroalkyl halides of general formula (CF₃)_nCF_3–nX (X=Cl, Br, I) have been calculated by the AM1 semiempirical method. In polar solvents perfluoro-tert-hexyl iodide is reduced under the action of alkenes and aromatic hydrocarbons to form 2-hydroperfluoro-2-methyl-pentane and perfluoro-2-methyl-2-pentene. In ethyl acetate the regio- and stereo-specific addition of perfluoro-tert-hexyl iodide to alkenes, butadiene, and alkynes takes place, which is associated with the realization of a polar ion-radical mechanism for the reaction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2057–2061, September, 1989.     

Polymorphism of Acrylic and Methacrylic Acid Esters Containing Long Fluorocarbon Chains and Their Polymerizability

The molecular aggregation of acrylic and methacrylic acid esters containing long-fluorocarbon chains: 2-(perfluoroalkyl)ethyl acrylate (FF_nEA) and 2-(perfluoroalkyl)ethyl methacrylate (FF_nEMA) (F(CF₂)_nCH₂CH₂OCOC(X)=CH₂, where X=H, CH₃ and n=6, 8, 10) was investigated by differential scanning calorimetry (DSC) and temperature controlled X-ray powder diffraction measurement. These compounds exhibited some characteristic polymorphic behaviors depending on the length of fluorocarbon chain and the -position methyl group. The solid-state polymerization by -ray irradiation was studied for these compounds in the various crystal forms. In the solid-state polymerization, highest polymerizability was observed in the crystal form that exists in the highest temperature region for each compound.This revised version was published online in November 2005 with corrections to the Cover Date.     

Synthesis and repellent properties of vinylidene fluoride-containing polyacrylates

Fluorinated polyacrylats with side group containing vinylidene fluoride (VDF) units (CF₃(CF₂)_n (CH₂CF₂)_m, n = 3, 5; m = 1, 2) were successfully synthesized. The water and oil repellency properties of these polymers are similar to those of fluorinated polyacrylate with side group containing long perfluorooctyl group (CF₃(CF₂)₇). The thermal telomerization of CF₃(CF₂)₅I and CF₃(CF₂)₃I with vinylidene fluoride (VDF) provided CF₃(CF₂)₅CH₂CF₂I (1b) and CF₃(CF₂)₃CH₂CF₂CH₂CF₂I (1c), respectively. The addition of 1b with ethylene followed by hydrolysis gave CF₃(CF₂)₅CH₂CF₂CH₂CH₂OH (2b). Treatment of 1c with ethyl vinyl ether in the presence of Na₂S₂O₄ followed by reduction produced CF₃(CF₂)₃CH₂CF₂CH₂CF₂CH₂CH₂OH (2c). Fluoroacrylates 3b-d were prepared by acrylation of the corresponding fluoroalcohols 2b-d. The semi-continuous process emulsion co-polymerization of 3a-d with octadecyl acrylate and 2-hydroxylethyl acrylate initiated by (NH₄)₂S₂O₈ in the presence of a mixture emulsifiers of polyoxyethylene(10)nonyl phenyl ether (TX-10) and sodium lauryl sulfate provided stable latexes 4a-d, respectively. The water and oil repellency properties of 4b (R_f: CF₃(CF₂)₅CH₂CF₂) and 4c (R_f: CF₃(CF₂)₃CH₂CF₂CH₂CF₂) containing vinylidene fluoride (VDF) units were similar to those of 4a (R_f: CF₃(CF₂)₇) containing long perfluoroalkyl group and much better than those of polymer 4d (R_f: CF₃(CF₂)₃) with short perfluoroalkyl chain. Thus, polyacrylates containing vinylidene fluoride units showed promising aspects as the alternatives to the currently used water and oil repellent agents with long perfluoroalkyl chains.     

Studies on sulfinatodehalogenation: IV. The sulfinatodebromination of primary perfluoroalkyl bromides and perfluoroalkylene α, ω-dibromides

Using PTC or cosolvent, both perfluoroalkyl bromides such as Br (CF₂)₂O(CF₂)₂SO₂Na ( 1 ), Br(CF₂)₂OCF₂CO₂H ( 2 ), Cl(CF₂)₄Br ( 3 ), Cl(CF₂Br ( 4 ), n-C₆F₁₃Br ( 5 ), n-C₈F₁₇Br ( 6 ), H(CF₂)₈Br ( 7 ), α, ω-dibromides O(CF₂CF₂Br)₂ ( 8 ), Br(CF₂)₆Br ( 9 ) and Br(CF₂)₈Br ( 10 ) reacted readily with Na₂S₂O₄ in the presence of NaHCO₃ in aqueous solution to form the corresponding perfluoroalkane sulfinates NaO₂S(CF₂)₂O(CF₂)₂SO₂Na ( 11 ), NaO₂S(CF₂)₂OCF₂CO₂Na ( 12 ), Cl(CF₂)₄SO₂Na ( 13 ), Cl(CF₂)₂SO₂Na ( 14 ), n-C₃F₁₃SO₂Na ( 15 ), n-C₈F₁₇SO₂Na ( 16 ), H(CF₂)₈SO₂Na ( 17 ), α, ω-disulfinates O(CF₂CF₂SO₂Na)₂ ( 18 ), NaO₂S(CF₂)₄SO₂Na ( 19 ) and NaO₂S(CF₂)₈SO₂Na ( 20 ) in 66—97% yields. To this new and general reaction of perfluoroalkyl bromides, the name sulfinatodebromination is proposed.     

Bi-functional fluoroalkylation reagents: an introduction to halo-substituted 3-oxa-perfluoroalkanesulfonyl fluorides

X(CF₂CF₂)_nOCF₂CF₂SO₂F (X=I, Br, Cl; n=1, 2, 3, 4) are widely used fluoroalkylation reagents, which can incorporate ‘heavy’ fluorous tags into organic compounds. X(CF₂CF₂)_nOCF₂CF₂SO₂F have both sulfonyl and halo groups. They behave as bi-functional fluoroalkylation reagents. The cleavage of the C–I bonds of I(CF₂CF₂)_nOCF₂CF₂SO₂F by reductants (such as Na₂S₂O₄, Zn), single electron transfer reagents and radical initiator systems (like Bz₂O₂, AIBN, and (t-BuO)₂, or under UV and heat) gives, respectively, the sulfinatodehalogenated products, the hydrodehalogenated products, the homo-coupling products and the perfluoroalkylated products (if alkenes, alkynes or arenes were added). The functionalization of the sulfonyl groups (SO₂F) of X(CF₂CF₂)_nOCF₂CF₂SO₂F by esterification, amidation, and fluorination affords the corresponding perfluoroalkanesulfonates, fluoroalkanesulfonamide, and perfluoroalkanes. In many cases, both the halo and sulfonyl groups of X(CF₂CF₂)_nOCF₂CF₂SO₂F are transformed. These transformations finally lead to hundreds of useful highly fluorinated materials, such as supper acids, catalysts, surfactants, ion-exchange resins, electrolytes, polymers, and dense ionic liquids. Furthermore, X(CF₂CF₂)_nOCF₂CF₂SO₂F have commendable advantages, such as the easy preparation, the wide range of substrate tolerance, the mild reaction condition, and the high yields of desired products, which make them very promising. This review briefly summarizes the synthesis, reactivity, and applications of these intriguing reagents.