Tertiary-Amine-Initiated Synthesis of Acyl Fluorides from Carboxylic Acids and CF3SO2OCF3

A convenient method for deoxyfluorination of aromatic and aliphatic carboxylic acids with CF₃SO₂OCF₃ in the presence of a suitable base at room temperature has been developed. The reaction allows a straightforward access to a variety of acyl fluorides and proves that CF₃SO₂OCF₃ is an effective deoxyfluorination reagent for carboxylic acids. The method features simplicity, expeditiousness, high efficiency, ease of handling, good functional group tolerance, a wide range of substrates, excellent yields of products, compatibility of many amine initiators, use of environmentally friendly reagents, and effortless removal of byproducts. This reaction represents the first utilization of trifluoromethyl trifluoromethanesulfonate as a fluorination reagent.     

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.     

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).     

Kinetics and products of chlorine atom initiated oxidation of HCF2OCF2OCF2CF2OCF2H and HCF2O(CF2O)n‐(CF2CF2O)mCF2H

Smog chamber/FTIR techniques were used to measure k(Cl + HCF₂OCF₂OCF₂‐CF₂OCF₂H) = k(Cl + HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H) = (5.0 ± 1.4) × 10^?17 cm³ molecule^?1 s^?1 in 700 Torr of N₂/O₂ diluent at 296 ± 1 K. The Cl‐initiated atmospheric oxidation of HCF₂OCF₂OCF₂CF₂OCF₂H and the sample of HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H used in this work gave COF₂ in molar yields of (476 ± 36)% and (859 ± 63)%, respectively, with no other observable carbon containing products (i.e., essentially complete conversion of both hydrofluoropolyethers into COF₂). The results are discussed with respect to the atmospheric chemistry and environmental impact of hydrofluoropolyethers of the general formula HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 819–825, 2008     

New perfluorovinylethers through the bis(fluoroxy)difluoromethane (BDM) chemistry

In the present work we give an overview of the CF₂(OF)₂ radical reactivity and report the synthesis of new perfluorovinylethers. CF₂CFOCF₂OCF₂CF₃ and CF₂CFOCF₂OCF₂CF₂OCF₃ are prepared in a semi-continuous methodology starting from CF₂(OF)₂. These highly reactive vinylethers are characterized by the OCF₂O group directly bonded to the insaturation. For this reason they are excellent candidates for the preparation of very low T_g perfluororubbers.     

Perfluoro and polyfluoroalkanesulfonic acid: XVII. Difluoromethyl perfluoroalkanesulfonates and their reactions

In contrast to R_FSO₃CH₂R(1)(R=hydrogen, alkyl and perfluoroalkyl) and R_FSO₃CF₂R_F′ (2), the reactions of difluoromethyl perfluoroalkanesulfonates RFSO₃CF₂H (3) With nucleophiles are more complicated. Halide inos, X^? (X = F, Cl, I) and ethanol only attack the alkoxyl carbon atom, cleaving the C? O bond to give HCF₂X (4) and HCF₂OEt (5) respectively. Other reagents such as RCO₂^? (R=CH₃, CF₃), C₆H₅S^? etc. can either attack the carbon or sulfur atom of 3 to give the corresponding products of C? O and S? O bond cleavages. More basic nucleophiles RO^? (R = C₆H₅, Et) mainly abstract the proton of the HCF₂ moiety to produce difluorocarbene. Ether and benzene, which can be alkylated by methyl perfluoroalkanesulfonate, do not react with 3 under similar conditions. The reaction rate of 3 with KF is much slower than that of 1 (R = H). All these data seem to indicate that the shielding effect caused by the two fluorine atoms on the methyl carbon in 3 prevents to some extent the nucleophilic attack on this carbon, but not so completely as in 2 due to the presence of a hydrogen atom.     

Superelectrophilic activation of N-aryl amides of 3-arylpropynoic acids: synthesis of quinolin-2(1H)-one derivatives

The superelectrophilic activation of N-aryl amides of 3-arylpropynoic acids by Bronsted superacids (CF₃SO₃H, HSO₃F) or strong Lewis acids AlX₃ (X=Cl, Br) results in the formation of 4-aryl quinolin-2(1H)-ones in quantitative yields. The vinyl triflates or vinyl chlorides may be formed as additional reaction products. The investigated amides in reactions with benzene give 4,4-diaryl 3,4-dihydroquinolin-2-(1H)-ones under the superelectrophilic activation. 4-Aryl quinolin-2(1H)-ones in POCl₃ are converted into 4-aryl 2-chloroquinolines. 4-Fluorophenyl-4-phenyl 3,4-dihydroquinolin-2-(1H)-one give N-formylation products in a yield of 79% under the Vilsmeier–Haack reaction conditions.     

Copper induced single electron transfer trifluoromethylation of organic halides with 3-oxo-ω-fluorosulfonylperfluoropentyl iodide

Treatment of ICF₂CF₂OCF₂CF₂SO₂F (1) with organic halides in the presence of copper powder in a co-solvent DMF/HMPA(V/V= 1:1) gave the corresponding trifluoromethylated compounds in good to excellent yields. A copper induced single electron transfer reaction mechanism is proposed.     

Syntheses of novel delocalized cations and fluorinated anions,new fluorinated solvents and additives for lithium ion batteries

To improve the properties of rechargeable lithium ion batteries, like conductivity, SEI-formation, thermal and electrochemical stability, low and high temperature performance and safety new electrolyte salts, novel solvents (co-solvents) and additives have been synthesized. All new anions, solvents and additives contain fluorine proving the importance of this element for the electrolyte system. Tetrafluoroborates having bulky delocalized nitrogen-, phosphorus and sulfur-centered counter-cations containing tetramethylguanidyl substituents, like [(Me₂N)₂CNC(NMe₂)₂]⁺, have been prepared to improve the conductivity in polymer electrolytes. The hitherto unknown lithium sulfonate, MeOCF₂CF₂SO₃Li, has been successfully synthesized along with further analogs, and also MeOCF₂CF(CF₃)SO₃Li was obtained, both from precursors, FO₂SCF₂C(O)F or FO₂SCF(CF₃)C(O)F accessible by ring opening reactions from the respective sultones. For the lithium salt CF₃OCF(CF₃)SO₃Li, a new simple synthetic pathway was found where CF₃OCFCF₂ and SO₂F₂ were used as precursors. Novel possible redox shuttles, namely (CF₃)₅C₆OLi and fluorinated pyridine-N-oxides have been prepared. A neutral cyclic carben-PF₅ adduct turned out to be a very effective overcharge protection additive. The family of cyclic and acyclic carbonates playing a key-role as electrolyte solvents in lithium ion batteries could be extended by derivatives of 1,1,1,4,4,4-hexafluorobutandiol. Reaction products from perfluoropropene oxide and alcohols, ROC(F)CF₃C(O)OR (R = CH₂CF₃, CH₂CH₂, CH(CF₃)₂) were obtained according to new optimized methods. New cyclic sulfonamides synthesized from FO₂SCF₂C(O)F and FO₂SCF(CF₃)C(O)F could be successfully identified as versatile electrolyte additives.     

Synthesis of the first difunctional N-fluoro perfluoroalkylsulfonylimides, CF3SO2NFSO2(CF2)nSO2NFSO2CF3

Synthesis of difunctional N,N′-difluoro perfluoroalkylsulfonamides, CF₃SO₂NFSO₂(CF₂)_nSO₂NFSO₂CF₃, where n=4, 6 is reported. A related compound with an oxygen linkage CF₃SO₂NFSO₂(CF₂)₂O(CF₂)₂SO₂NFSO₂CF₃ has also been prepared. These reagents showed good activity for electrophilic fluorination.     

Synthesis and Properties of CF3(OCF3)CH‐Substituted Arenes and Alkenes†

A silver‐mediated oxidative trifluoromethylation of easily accessible α‐trifluoromethyl alcohols with TMSCF₃ was developed to access novel CF₃(OCF₃)CH‐containing compounds. Deprotonation of CF₃(OCF₃)CH‐substituted arenes afforded synthetically useful CF₃O‐substituted gem‐difluoroalkenes. Furthermore, evaluation of the lipophilicities (log P) indicated that CH(OCF₃)CF₃ is more lipophilic than the common fluorinated motifs such as CF₃, OCF₃, and SCF₃, thus rendering the CH(OCF₃)CF₃ motif appealing in drug discovery.     

Spectroscopic studies on the carboxylic acids of some carbonyl fluoride telomers

The NMR and infrared spectra of a series of carboxylic acids of carbonyl fluoride telomers, CF₃O(CF₂O)_nCF₂COOH (with n = 1 through 7) are described and tentative assignments for the main vibrational modes proposed.     

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.     

Bis(trifluoromethyl)dicarbonate, CF3OC(O)OC(O)OCF3

The synthesis of the new compound, bis(trifluoromethyl)dicarbonate, CF₃OC(O)OC(O)OCF₃, is carried out by reduction of bis(trifluoromethyl)trioxidicarbonate with excess of CO at 0 °C. The product is characterized by IR, Raman, ¹³C and ¹⁹F NMR spectroscopy and its properties are compared with those of the other members of the series CF₃OC(O)O_xC(O)OCF₃, x = 0-3. Single crystals are grown at −25 °C and the X-ray diffraction analysis shows the packing of syn-syn rotamers exhibiting C₂ symmetry. DFT calculations predict this rotamer as the most stable one and also structural and vibrational data are predicted reasonably well.     

Synthesis of Tri‐ and Difluoromethoxylated Compounds by Visible‐Light Photoredox Catalysis

Trifluoromethoxy (OCF₃) and difluoromethoxy (OCF₂H) groups are fluorinated structural motifs that exhibit unique physicochemical characteristics. Incorporation of these substituents into organic molecules is a highly desirable approach used in medicinal chemistry and drug discovery processes to alter the properties of a parent compound. Recently, tri‐ and difluoromethyl ethers have received increasing attention and several innovative strategies to access these valuable functional groups have been developed. The focus of this Minireview is the use of visible‐light photoredox catalysis in the synthesis of tri‐ and difluoromethyl ethers. Recent photocatalytic strategies for the formation of O?CF₃, C?OCF_3, O?CF₂H, and C?OCF₂H bonds as well as other transformations leading to the construction of OR_F groups are discussed herein.     

Selective fluorination of m-tyrosine by OF2

Fluorine-18 labeled aromatic amino acids are routinely used as tracers in positron emission tomography (PET) to study in vivo metabolic processes. The most versatile method for the production of such radiotracers is electrophilic fluorination of the aromatic amino acid with [¹⁸F]F₂, which is most commonly produced by the gas-phase nuclear reaction ¹⁸O(p, n)¹⁸F. Although [¹⁸F]F₂ is the major product, considerable amounts of [¹⁸F]OF₂ (up to 20%) are also produced. Electrophilic fluorination reactions of l-phenylalanine, 3-nitro-l-tyrosine, 4-nitro-dl-phenylalanine, 3,4-dihydroxyphenyl-l-alanine (l-DOPA), 3-O-methyl-l-DOPA, 3,4-dimethoxy-l-phenylalanine, p-tyrosine and o-tyrosine in H₂O and of m-tyrosine in anhydrous HF (aHF), CF₃SO₃H, CF₃COOH, CH₃COOH, HCOOH and H₂O using OF₂ were investigated. Although F₂ is an efficient fluorinating agent in aHF, electrophilic fluorination reactions using OF₂ were shown to be most efficient in less acidic media such as H₂O. In addition, and contrary to reports that OF₂ and F₂ have similar reactivities, m-tyrosine was the only aromatic system studied that was fluorinated by OF₂ and this was optimum in H₂O for the fluorinated m-tyrosine isomers (total yield, 4.35 ± 0.04%). The presence of [¹⁸F]OF₂ byproduct has no significant impact on the fluorination of aromatic amino acids investigated in this study and the subsequent production of their corresponding ¹⁸F-labeled radiotracers for patient use.     

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.     

Perfluoro- ω -iodo-3-oxaalkanesulfonyl fluorides as intermediates for surfactants and vinyl compounds

The well known fluorosulfonyldifluoroacetyl fluoride (I), FOCCF₂SO₂F (I) quantitatively formed from sulfur trioxide and TFE through the tetrafluoroethanesultone has been converted into the octafluoro- -5-iodo-3-oxapentanesulfonyl fluoride (II) ICF₂CF₂OCF₂CF₂SO₂F (II) by the well known reaction (1) involving MF, iodine, TFE in aprotic solvents.The iodo compound (II) allowed us to obtain TFE telomers having both fluorosulfonyl and iodo as terminal groups.The said telomers have been easily converted into surfactants (III) through fluorination and vinyl derivatives (IV) by dehalogenation.CF₃CF₂(CF₂CF₂)_nOCF₂CF₂SO₃M (III)CF₂CF(CF₂CF₂)_nOCF₂CF₂SO₂F (IV)     

Die elektrofluorierung von chlormethylsulfochlorid

The electrochemical fluorination of ClCH₂SO₂Cl was studied. The main products were CF₄, CF₃Cl, SO₂F₂, SF₆, CF₃SO₂F and ClCF₂SO₂F. Also minor amounts of CF₃H and CF₂HCl were formed as well as traces of CFH₂Cl and CF₂H₂ under certain conditions. The yield of ClCF₂SO₂F increased with descending temperature, concentration and current density.     

Conformational analysis of fluorinated copolymers of tetrafluoroethylene

Conformational analysis of fluorinated copolymers of tetrafluoroethylene (TFE) is performed by taking into account only intramolecular effects (isolated-chain model). In particular, variations of the chain conformation, which are induced by incorporating different side groups, such as –Cl, –CF₃, –OCF₃, –OCF₂CF₃, and –OCF(CF₃)₂, are investigated and discussed with respect to qualitative correlations between conformation, crystal structure, and supramolecular morphology.