Cyclocondensation of F-2-methyl-2-pentene with activated methylene compounds using ‘freeze-dried’ potassium fluoride

The reactions of $\text{F}$-2-methyl-2-pentene with activated methylene compounds such as acetylacetone, ethyl acetoacetate, benzoylacetonitrile, and benzoylmethyl perfluoroalkyl ketones in the presence of potassium fluoride were carried out. Each reaction proceeded smoothly in acetonitrile at room temperature by using ‘freeze-dried’ potassium fluoride as a condensing agent. Acetylacetone and ethyl acetoacetate gave both divinyl ether and pyran compounds, whereas other activated methylene compounds afforded only pyrans in good yields.     

Synthesis of perfluorinated carboxylic acid membrane monomers by utilizing liquid-phase direct fluorination

A new synthetic procedure for the preparation of perfluorinated carboxylic acid membrane monomers from non-fluorinated compounds has been developed. A key step in the synthetic route is liquid-phase direct fluorination reaction with elemental fluorine. Direct fluorination of a partially fluorinated diester, which was prepared from a hydrocarbon diol and a perfluorinated acyl fluoride, followed by thermal elimination, gave a perfluorinated diacyl fluoride, which is a precursor of a perfluorinated carboxylic acid membrane monomer.     

Remote asymmetric trifluoromethylation induced by chiral sulfinyl group: synthesis of enantiomerically pure 1-(2-naphthyl)-2,2,2-trifluoroethanol

The reaction of 1-[(2,4,6-triisopropylphenyl)sulfinyl]-2-naphthaldehyde with (trifluoromethyl)trimethylsilane using tetramethylammonium fluoride gave trifluoromethylated compounds in high yield with high diastereoselectivity. Desilylation and subsequent recrystallization yielded the enantiomerically and diastereomerically pure trifluoroethanol, which afforded chiral 1-(2-naphthyl)-2,2,2-trifluoroethanol after removal of the sulfinyl group.     

Rhodium-catalyzed substitution reaction of aryl fluorides with disulfides: p-orientation in the polyarylthiolation of polyfluorobenzenes

In the presence of a catalytic amount of RhH(PPh3)4 and 1,2-bis(diphenylphosphino)benzene, an aromatic fluoride, an organic disulfide (0.5 equiv), and triphenylphosphine (0.5 equiv) reacted in refluxing chlorobenzene to give an aryl sulfide in high yield. Since triphenylphosphine trapped fluoride atoms forming phosphine difluoride, both organothio groups of the disulfide reacted effectively, and the fluoride substituent reacted more readily than the chloride and bromide. The reaction of hexafluorobenzene and a diaryl disulfide gave 1,4-diarylthio-2,3,5,6-tetrafluorobenzene, 1,2,4,5-tetraarylthio-3,6-difluorobenzene, and hexaarylthiobenzene in a stepwise manner; pentafluorobenzene gave 1-arylthio-2,3,5,6-tetrafluorobenzene; 1,2,3,4-tetrafluorobenzene gave 1,2-diarylthio-3,6-difluorobenzene; and 1,2,4,5-tetrafluorobenzene gave 1,4-diarylthio-2-5-difluorobenzene. The polyarylthiolation reaction of polyfluorobenzenes exhibited a strong tendency to form 1,4-difluorobenzenes.     

Treatment of dimethyl (+)-L-tartrate with sulfur tetrafluoride

Treatment of dimethyl (+)-L-tartrate (I) with sulfur tetrafluoride results in the formation of an intermediate, 2-fluoro-1,2-bis(methoxycarbonyl)ethyl fluorosulfite (II), which under the action of hydrogen fluoride, present in the reaction mixture, is converted into dimethyl (?)(2S:3S)-2-fluoro-3-hydroxysuccinate (III). The reaction of the latter with SF₄ leads to dimethyl meso-2,3-difluorosuccinate (IV). The structure and configurations of the compounds obtained were established by ¹H and ¹⁹F NMR. Treatment of dimethyl (+)-L-tartrate (I) with sulfur tetrafluoride in the presence of excessive hydrogen fluoride gave dimethyl meso-2,3-difluorosuccinate in 96% yield.     

Convenient indole synthesis from 2-iodoanilines and terminal alkynes by the sequential Sonogashira reaction and the cyclization reaction promoted by tetrabutylammonium fluoride (TBAF)

The sequential Sonogashira reaction and the cyclization reaction of various 2-iodoanilines and terminal alkynes in the presence of a palladium catalyst and tetrabutylammonium fluoride (TBAF) gave the corresponding 2-substituted indoles in good yields.     

Reactions of nitro alcohols with n,n-diethyl-1,1,2,3,3,3-hexafluoropropylamine

Fluorination of nitro alcohols with N,N-diethyl-1,1,2,3,3,3-hexafluoropropylamine (PPDA) was investigated. 3-Nitrobenzyl fluoride (II) was obtained from the reaction of PPDA and 3-nitrobenzyl alcohol (I) (yield 66%). The reaction of 2-methyl-2-nitro-1-propanol (IV) with PPDA given 2-methyl-2-nitropropyl 2,3,3,3-tetrafluoropropionate (V). reduction of 3-nitrobenzyl fluoride (II) with lithium aluminium hydride gave the corresponding amino compound, 3-aminobenzyl fluoride (VI) in poor yield.     

Anodic oxidation of p-disubstituted benzenes in the presence of fluoride ion

Electrochemical oxidation of aromatic compounds in the presence of fluoride ion gives products derived from initial oxidation of aromatic substrate and subsequent reaction with fluoride ion. The second of the one-electron transfer steps leads to benzenium ions, which give either fluoroaromatic compounds (elimination) or fluorocyclohexadienes (addition). The elimination of a t-butyl-group during anodic oxidation of p-di-t-butylbenzene yielded p-fluoro-t-butylbenzene. Further examples of the reaction involve p-fluorodiphenyl, p-fluoro-t-butylbenzene, and p-fluorophenol ethers.     

Regioselective one-pot bromination of aromatic amines

[reaction: see text] Treatment of aniline with n-butyllithium and then trimethyltin chloride gave the tin amide (PhNH-SnMe(3)) in situ. Without isolation of the tin amide, reaction with bromine and workup with aqueous fluoride ion gave p-bromoaniline in 76% yield, with no dibromoaniline or o-bromoaniline. Application of this sequence to 11 different aromatic amines gave selective bromination in 36-91% yields, without formation of dibromides. This constitutes a good general method for the regioselective bromination of aromatic amines.     

全氟和多氟烷基磺酸的研究 IX. 5-卤-3-氧杂-全氟戊磺酰氟的化学转化

5-Halo-3-oxa-perfluoropentanesulfonic acids 2,4 were obtained in high yields by treating the corresponding sulfonyl fluorides successively with KOH and concentrated H2SO4: Treatment of the acids with P2O5 gave corresponding anhydrides 3, 5. 3 reacted with various alcohols in the presence of pyridine to yield sulfonates 6. 5-Iodo-3-oxa-perfluoropentanesulfonyl fluoride (1) was converted to the acyl fluoride 9 by fuming sulfuric acid. Depending on the reaction temperature 9 can be hydrolyzed to fluorosulfonyl perfluoroalkanoic acid 10 and/or mixed dibasic acid 11. A similar phenomenon was also observed in the case of hydrolysis of fluorocarbonyl-perfluoromethanesulfonyl fluoride(13). Alcohol reacted readily with the acyl fluoride group but not with the sulfonyl group in 9 giving carboxylic esters, which can be further transformed to the corresponding sulfonates. Perfluoroalkoxide ion -O(CF2)2O(CF2)2SO2F prepared from 9 and F- reacted with active alkyl halides yielding the corresponding ethers. The interaction of 5-halo-3-oxa-perfluoroalkane-sulfonyl fluoride with AlCl3 was investigated. Friedel-crafts acylation of aromatic compounds with 9 in the presence of anhydrous AlCl3 is also reported. The yields of the desired ketones can be improved by using CCl4 as a solvent and changing the order of addition of reactants.     

Facile synthesis of aromatic unsymmetrical fluorine-containing acyloins through the reductive trifluoroacetylation of benzaldehyde and transposition of the carbonyl group

The reductive coupling reaction between benzaldehyde and ethyl trifluoroacetate in the presence of magnesium and chlorotrimethylsilane in N-methyl-2-pyrrolidinone gave the acetal of the corresponding coupling compound in good yields. The yield of the coupling product largely depended on the benzaldehyde concentration in the solution and it was essential to avoid the formation of pinacol type compounds in order to obtain the coupling product in high yields. The subsequent desilylation of the acetal using tetrabutylammonium fluoride easily yielded an acyloin compound as the sole product after the transposition of the carbonyl group through keto–enol tautomerism.     

Functional polymers and sequential copolymers by phase transfer catalysis. XXII. Vinylidene fluoride–trifluoroethylene copolymers by surface modification of polyvinylidene fluoride

Polyvinylidene fluoride films and powders have been used to synthesize vinylidene fluoride-trifluoroethylene copolymers. The synthetic procedure involves a phase transfer catalyzed heterogenous dehydrofluorination, followed by electrophilic chlorination or bromination. A phase transfer catalyzed displacement of bromine or chlorine by fluoride ion completes the synthesis. Dehydrofluorinations were up to 40% complete at room temperature and up to 100% complete at 90°C. Electrophilic chlorination of the resulting carbon–carbon double bonds were complete on both powder or films. The bromination of dehydrohalogenated polymers does not go to completion even when the reaction is carried out in solution. Displacement reactions were incomplete and resulted in further dehydrohalogenation when tetrabutylammonium hydrogen sulfate (TBAH) or 18-crown-6 and KF were used in organic solvents. Using TBAH, KHF₂, and water, high degrees of displacement were achieved only on the brominated compounds. The chlorinated products gave both displacement and elimination.     

Low-temperature reaction of magnesium with fluorobenzene

The low-temperature reaction of magnesium with fluorobenzene has been investigated. Joint condensation of magnesium and fluorobenzene vapours at low temperatures quantitatively gave phenylmagnesium fluoride in one stage.     

Chemistry of fluorinated quinones I. The Diels-Alder reactions of fluoranil

The Diels-Alder reaction of fluoranil with cyclopentadiene, 1,3-butadiene, and 1-acetoxy-1,3-butadiene gave 1,4, 5, 8-bis(methylene)-4a, 8a, 9a, 10a-tetrafluoro-1, 4, 4a, 5, 8, 8a, 9a, 10a-octahydroanthraquinone (I), 2, 3, 4a, 8a-tetrafluoro-4a, 5, 8, 8a-tetrahydro-1,4-naphthoquinone (III), and 5-acetoxy-2, 3, 4a, 8a-tetrafluoro-4a, 5, 8, 8a-tetrahydro-1,4- naphthoquinone (VI), respectively. Hydrogenation of I gave the expected saturated diketone(II). Hydrogenation of III afforded, with elimination of the two tertiary fluorines, 2,3-difluoro-5, 6, 7, 8-tetrahydro-1, 4- dihydroxynaphthalene (IV). In hydrogenation of VI, acetic acid and two moles of hydrogen fluoride were eliminated to give 2,3-difluoro-1, 4-dihydroxynaphthalene(VII). Both dihydroxy compounds IV and VII yielded on oxidation with ferric chloride the corresponding quinones, 2, 3- difluoro-5, 6, 7, 8-tetrahydro-1, 4-naphthoquinone (V) and 2, 3-difluoro-1, 4-naphthoquinone (VIII), respectively. Equivalent amounts of compounds IV and V gave a red-brown semiquinone IX, and a mixture of VI and VIII gave a dark-violet semiquinone X.     

The preparation of organomagnesium fluorides by organometallic exchange reactions

The preparation of alkyl- and aryl-magnesium fluorides by the reaction of dialkyl- and diaryl-magnesium compounds with fluorinating agents, such as BF₃ etherate, SiF₄, Bu₃SnF, Ph₃SiF and Et₂AlF in tetrahydrofuran were studied. Methyl-, ethyl-, and phenyl-magnesium fluoride were prepared in high yield by the reactions of dimethyl-, diethyl-, and diphenyl-magnesium with boron trifluoride diethyl etherate in tetrahydrofuran. Methylmagnesium fluoride was prepared in quantitative yield by the reaction of dimethylmagnesium with silicon tetrafluoride in tetrahydrofuran and butylmagnesium fluoride was prepared in quantitative yield by the reaction of tributyltin fluoride in THF with dibutylmagnesium. Other combinations of R₂Mg compounds and fluorinating agents resulted in the formation of less pure products.     

The Activation of Sulfur Hexafluoride at Highly Reduced Low‐Coordinate Nickel Dinitrogen Complexes

The greenhouse gas sulfur hexafluoride is the common standard example in the literature of a very inert inorganic small molecule that is even stable against O₂ in an electric discharge. However, a reduced β‐diketiminate nickel species proved to be capable of converting SF₆ into sulfide and fluoride compounds at ambient standard conditions. The fluoride product complex features an unprecedented [NiF]⁺ unit, where the Ni atom is only three‐coordinate, while the sulfide product exhibits a rare almost linear [Ni(μ‐S)Ni]²⁺ moiety. The reaction was monitored applying ¹H NMR, IR and EPR spectroscopic techniques resulting in the identification of an intermediate nickel complex that gave insight into the mechanism of the eight‐electron reduction of SF₆.     

5-烷氧基-4-环胺基-3-卤-2(5H)-呋喃酮的合成与表征

在氟化钾作用下,亲核试剂环状仲胺与5-烷氧基-3,4二卤-2(5H)-呋喃酮在室温下发生串联的迈克尔加成-消除反应,合成了17个新化合物.通过旋光度,UV-Vis,IR,1H NMR,13C NMR,MS,元素分析和X射线单晶衍射等表征方法,确定了目标化合物的化学结构和绝对构型.     

Synthesis of dye functionalized xerogels via nucleophilic aromatic substitution of fluoro aromatic compounds with aminosilanes

The one-pot synthesis of inorganic–organic hybrid materials via combination of sol–gel process and nucleophilic aromatic substitution reaction of various fluoro aromatic compounds and 3-aminopropyltrimethoxysilane has been studied. Both, nucleophilic aromatic substitution reaction and sol–gel process can be accomplished in the same reaction vessel due to the sol–gel precursor tetraethoxysilane acting as solvent during the first reaction step. Hydrogen fluoride, which forms as a by-product of the substitution reaction, is trapped by both silane species present and subsequently serves as catalyst during the sol–gel process. The obtained materials can be classified as type II xerogels, because of the covalent linkage between organic chromophor and inorganic silicon network. Fluoro aromatic compounds with different reactivities for nucleophilic aromatic substitution reactions containing azo, azomethine, and diphenylamine groups were used in order to (1) demonstrate the synthetic concept and (2) fine-tune the optical properties of the resulting chromophoric xerogels. The final chromophor content within the xerogels was varied by modifying the ratio of organosilicon precursor and tetraethoxysilane. All obtained organic–inorganic hybrid materials were characterized in detail using solid state NMR- and UV/vis spectroscopy. Latter one gave experimental confirmation of the partial hydrolysis of azomethine dyes in the xerogels, while no decomposition of azo or diphenylamine dyes was observed.     

Effect of fluoride salts on metal-mediated reactions. Aluminum/fluoride salt-mediated reduction and pinacol coupling of carbonyl compounds in aqueous media

[formula: see text] Metal fluoride salts were found to activate aluminum in water to react with carbonyl compounds to give the pinacol coupling products and/or the reduced alchohols. The metal ion of the fluoride salt was found to play a role in controlling the chemoselectivity and stereoselectivity of the reaction.     

Aminotroponiminatogermaacid halides with a ge(e)x moiety (e = s, se; x = f, cl)

Fluorination of aminotroponiminate (ATI) ligand-stabilized germylene monochloride [(t-Bu)(2)ATI]GeCl (1) with CsF gave the aminotroponiminatogermylene monofluoride [(t-Bu)(2)ATI]GeF (2). Oxidative addition reaction of compound 2 with elemental sulfur and selenium led to isolation of the corresponding germathioacid fluoride [(t-Bu)(2)ATI]Ge(S)F (3) and germaselenoacid fluoride [(t-Bu)(2)ATI]Ge(Se)F (4), respectively. Similarly, reaction of aminotroponiminatogermylene monochloride [(i-Bu)(2)ATI]GeCl (9) with elemental sulfur and selenium gave the aminotroponiminatogermathioacid chloride [(i-Bu)(2)ATI]Ge(S)Cl (11) and aminotroponiminatogermaselenoacid chloride [(i-Bu)(2)ATI]Ge(Se)Cl (12), respectively. Compound 9 has been prepared through a multistep synthetic route starting from 2-(tosyloxy)tropone 5. All compounds (2-4 and 6-12) were characterized through the multinuclear NMR spectroscopy, and single-crystal X-ray diffraction studies were performed on compounds 2, 4, and 8-12. The germaselenoacid halide complexes 4 and 12 showed doublet (-142.37 ppm) and singlet (-213.13 ppm) resonances in their (77)Se NMR spectra, respectively. Germylene monohalide complexes 2 and 9 have a germanium center in distorted trigonal pyramidal geometry, whereas a distorted tetrahedral geometry is seen around the germanium center in germaacid halide complexes 4, 11, and 12. The length of the Ge═E bond in germathioacid chloride (11) and germaselenoacid halide (4 and 12) complexes is 2.065(1) and 2.194(av) ?, respectively. Theoretical studies (based on the DFT methods) on complexes 4, 11, and 12 reveal the nature of the Ge═E multiple bond in these germaacid halide complexes with computed Wiberg bond indices (WBI) being 1.480, 1.508, and 1.541, respectively.