Synthesis of fluorine containing glycolurils and oxazolines from oxides of internal perfluoroolefins

The reaction of oxides of internal perfluoroolefins 1-3 with urea gave two kinds of novel fluorine containing N-heterocyclic compounds depending on the solvent nature: 1,5-bis(perfluoroalkyl)tetraazabicyclo[3.3.0]octane-3,7-diones 4a-c and 2-amino-5-fluoro-4,5-bis(perfluoroalkyl)-4,5-dihydrooxazol-4-ols 7a-d. Use of polar dimethylsulfoxide, N,N-dimethylacetamide and acetonitrile afforded glycolurils 4a-c in moderate yields. In dioxane, unexpected cyclization occurred resulting in oxazolines 7a-d in high yields. A similar reaction of oxiranes 2, 3 with urea in aqueous dioxane gave mixtures of 4,5-dihydroxy-4,5-bis(perfluoroalkyl)imidazolidine-2-ones 9b, c, glycolurils 4b, c and oxazolines 7b-d. The molecular structure of trans-isomers of oxazoline 7b and imidazolidine 9b has been established by X-ray crystallography.     

Reactions of polyfluorinated thietanes: Selective synthesis of 4-R-2,2-bis(trifluoromethyl)thietane-1-S-oxides and 2-substituted 5-fluoro-4-(trifluoromethyl)-2,3-dihydrothiophenes

Oxidation of 4-substituted 2,2-bis(trifluoromethyl)thietanes by m-chloroperoxybenzoic acid results in selective formation of the corresponding S-oxides in 65-86% yield. Oxidation of 4-C₂H₅S-2,2-bis(trifluoromethyl)thietane under mild conditions led to selective formation of 4-C₂H₅SO₂-2,2-bis(trifluoromethyl)thietane, which under more rigorous conditions was selectively converted into trans-4-C₂H₅SO₂-2,2-bis(trifluoromethyl)thietane-1-S-oxide. Reaction of 4-substituted 2,2-bis(trifluoromethyl)thietanes with activated aluminum powder results in a highly selective ring expansion process, producing the corresponding 5-fluoro-4-(trifluoromethyl)-2,3-dihydro-2-alkoxythiophenes in 58-93% yield. These compounds were also prepared in 61-85% yield using a “one-pot” procedure, starting from sulfur, hexafluoropropene and the corresponding vinyl ether without isolation of any intermediates. Both 2-i-C₃H₇O- and 2-t-C₄H₉O- 5-fluoro-4-(trifluoromethyl)-2,3-dihydrothiophenes were converted into 2-fluoro-3-trifluormethylthiophene by reaction with P₂O₅.     

Synthesis of 2,3-bis(perfluoroalkyl)quinoxalines and 2,3-bis(perfluoroalkyl)-1,4-benzoxazines from oxides of internal perfluoroolefins

The reactions of oxides of internal trans-, cis-perfluoroolefins with o-phenylenediamine and 2-aminophenol in dioxane gave 2,3-bis(perfluoroalkyl)quinoxalines and 2,3-bis(perfluoroalkyl)-2H-1,4-benzoxazin-2-ols respectively in yields of 23-67%. When N,N-dimethylacetamide was used as a solvent an anionic isomerization of the oxides into ketones, which further yielded 2-(perfluoroalkyl)benzimidazoles in the case of o-phenylenediamine and 2-hydroxy-N-perfluoroalkanoylanilines in the case of 2-aminophenol, became the main path of these reactions. Unusual cyclization resulting in 2-pentafluoroethyl-2-pentafluoropropanoylbenzoxazolidine occurs on interaction between dodecafluoro-3,4-epoxyhexane and 2-aminophenol in N,N-dimethylacetamide.     

全氟烷基磺酰亚胺盐催化芳香化合物硝化反应的研究

利用系列全氟烷基磺酰亚胺盐[M(NPf₂)_n]作为一种新型的Lewis酸催化剂，用于催化芳香化合物与等摩尔65% (m∶m)硝酸的硝化反应. 通过考察不同的催化剂、反应时间、反应温度和反应介质效应等因素对甲苯硝化的影响，以及比较1 mol% Yb[N(C₄F₉SO₂)₂]₃催化不同结构的取代芳烃硝化反应的效果，表明全氟烷基磺酰亚胺盐不仅具有环境友好和原子经济的特点，而且是一类比常规Lewis酸更有效的、芳香化合物硝化反应的催化剂.     

Synthesen und Eigenschaften von Bis(perfluoralkyl)zink‐Verbindungen

Syntheses and Properties of Bis(perfluoroalkyl)zinc Compounds The conditions for the syntheses of bis(perfluoroalkyl)zinc compounds Zn(R_f)₂ · 2 D (R_f = C₂F₅, n‐C₃F₇, i‐C₃F₇, n‐C₄F₉, n‐C₆F₁₃, n‐C₇F₁₅, and n‐C₈F₁₇; D = CH₃CN, tetrahydrofurane, dimethylsulfoxide) are described. Mass spectra, thermal decompositions, ¹⁹F‐ and ¹³C‐NMR spectra are discussed.     

An Electrogenerated Base-Promoted Synthesis of 2-Aryl-3,3-Bis((Perfluoroalkyl) Thio)Acrylonitriles

Abstract

The preparation of 2-aryl-3,3-bis((perfluoroalkyl)thio)acrylonitriles is described. The electrogenerated cyanomethyl base/anion obtained from electroreduction of acetonitrile promotes reactions between arylacetonitrile, carbon disulfide, and perfluoroalkyl iodides. The new fluorinated acrylonitriles were obtained in good yields under mild reaction conditions.     

Regioselective nucleophilic 1,4-trifluoromethylation of 2-polyfluoroalkylchromones with (trifluoromethyl)trimethylsilane. Synthesis of fluorinated analogs of natural 2,2-dimethylchroman-4-ones and 2,2-dimethylchromenes

Reactions of 2-polyfluoroalkylchromones with (perfluoroalkyl)trimethylsilanes proceed as a 1,4-nucleophilic perfluoroalkylation to give 2,2-bis(polyfluoroalkyl)chroman-4-ones with high regioselectivity and good yields after acid hydrolysis. Oxidation of 6-methyl-2,2-bis(trifluoromethyl)chroman-4-one with a mixture of K2S2O8 and CuSO4 in aqueous acetonitrile leads to fluorinated analogues of natural lactarochromal and the corresponding acid. Reduction of substituted 2,2-bis(trifluoromethyl)chroman-4-one with sodium borohydride in methanol and subsequent dehydration of chromanols in refluxing xylene in the presence of p-toluene sulfonic acid gives 2,2-bis(trifluoromethyl)chromenes, which are fluorinated analogues of natural precocenes.     

A One‐Pot Synthesis of 1,3‐Dihydro‐1,3,3‐tris(perfluoroalkyl)isobenzofuran‐1‐olates and Their Complete NMR Spectroscopic Analysis on the Basis of 1D and 2D Experiments

A convenient synthesis of the 1,3‐dihydro‐1,3,3‐tris(perfluoroalkyl)isobenzofuran‐1‐ols 3a , b was elaborated starting from commercially available phthaloyl dichloride and trimethyl(perfluoroalkyl)silanes (Me₃SiR_f) 1a , b (R_f=CF₃, C₂F₅) in the presence of a fluoride source (Schemes 1 and 3). In a reaction analogous to alkyl Grignard reagents, double chloride substitution by two perfluoroalkyl groups and subsequent addition of one perfluoroalkyl group with concomitant ring closure led to this new class of compounds (Scheme 2). The syntheses of the alcohols and some alcoholates, as well as of the corresponding trimethylsilyl ethers are described. A combination of special 1D and 2D NMR experiments allowed the assignment of all atoms of the new compounds. The solid‐state structure of 1,3‐dihydro‐1,3,3‐tris(trifluoromethyl)isobenzofuran‐1‐ol ( 3a ) was elucidated by X‐ray diffraction methods.     

Asymmetric Synthesis of Perfluoroalkylated α-Amino Acids through Generated Radicals Using a Chiral Ni(II) Complex

Perfluoroalkylated α-amino acids (PFAAs) are a unique class of compounds for biochemistry and pharmaceutical science. In this context, we report the successful intermolecular coupling of the Belokon’s chiral dehydroalanine Ni(II) complex with a variety of perfluoroalkyl iodides. A 4-cyanopyridine/B₂Pin₂ catalytic system generates perfluoroalkyl radicals, which after trapping by the ligand sphere of a chiral Ni(II) complex provide the diastereomeric complexes with up to >20 : 1 dr (seven examples). The obtained major (S,S)-diastereomers were easily isolated by simple silica column chromatography in 33–54 % yields. The perfluoroalkylated α-AA was subsequently released from the obtained Ni(II) complex through aqueous HCl treatment. The chiral auxiliary ligand ((S)-BPB=(S)-2-(N-benzylprolyl)aminobenzophenone) can be easily recycled after the acidic complex decomposition and reused for the synthesis of the starting dehydroalanine Ni(II) complex.     

Remarkable effect of metal fluoride catalyst on reaction of hexafluoropropene, sulfur and vinyl ethers. Convenient synthesis of 2,2-bis(trifluoromethyl)-4-R-thietanes, 3,3-bis(trifluoromethyl)-5-R-1,2-dithiolanes and 2,2-bis(trifluoromethyl)-4-R-1,3-dithiolanes

It was demonstrated that the outcome of the reaction of hexafluoropropene, sulfur and vinyl ether strongly depends on the catalyst and reaction conditions. The reaction of HFP and S_x leading to the formation of 2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithietane (1) when it is catalyzed by CsF, proceeds under milder conditions and is easier to control compared to KF catalyzed process. The order of addition of reagents plays a crucial role on the outcome of the reaction. For example, the addition of vinyl ether to pregenerated solution of 1 in DMF solvent results in slow reaction, leading to the corresponding 2,2-bis(trifluoromethyl)-4-R-thietanes in 8-91% yield, and it is catalyzed by either by KF or CsF. The addition of second mole of sulfur to the solution of 2,2-bis(trifluoromethyl)-4-R-thietanes in the presence MF catalyst leads to insertion of sulfur into thietane ring with the formation of the corresponding cyclic disulfides—3,3-bis(trifluoromethyl)-5-R-1,2-dithietanes. On the other hand, the addition of second mole of sulfur to the solution of 1 in DMF in the presence of CsF catalyst, followed by addition of vinyl ether results in exothermic reaction, and it produces the corresponding 2,2-bis(trifluoromethyl)-4-alkoxy-1,3-dithiolanes in good yield.It was also demonstrated that 2,2-bis(trifluoromethyl)-4-R-thietanes can undergo disproportionation under action of fluoride anion, producing a mixture of the corresponding 1,2-dithiolane and CF₂C(CF₃)CH₂CFHOR. The nucleophilic attack of fluoride anion in this case proceeds selectively on the carbon of the thietane ring, bearing alkoxy group.The structure of 2,2-bis(trifluoromethyl)-4-R-thietanes forming as the result of 2 + 2 cycloaddition reaction between hexafluorothioacetone generated “in situ” from dimer 1 and vinyl ether was firmly supported by single crystal X-ray diffraction data, obtained for thietane bearing t-BuO-group.     

Hexafluoroacetone as protecting and activating reagent: reactions of hexafluoroacetone with α-keto acids

Hexafluoroacetone and α-keto acids react to give 5,5-bis(trifluoromethyl) substituted 2(5H)-furanones and/or 2,2-bis(trifluoromethyl)-1,3-dioxolan-4-ones depending upon the substituent pattern of the side chain of the acid. A fluoroanalogue of the natural product zymonic acid was obtained from ethyl 3,3,3-trifluoropyruvate and 2-oxosuccinic acid in one step.     

Nucleophilic trifluoromethylation of RF-containing 4-quinolones, 8-aza- and 1-thiochromones with (trifluoromethyl)trimethylsilane

Reactions of N-substituted 2-polyfluoroalkyl-4-quinolones and 8-aza-5,7-dimethyl-2-polyfluoroalkylchromones with (trifluoromethyl)trimethylsilane proceed mainly as a 1,4-nucleophilic trifluoromethylation to give N-substituted 2,2-bis(polyfluoroalkyl)-2,3-dihydroquinolin-4(1H)-ones and 5,7-dimethyl-2,2-bis(polyfluoroalkyl)-2,3-dihydro-4H-pyrano[2,3-b]pyridin-4-ones after acid hydrolysis. Similar reaction with 2-trifluoromethyl-4H-thiochromen-4-one proceeds as a 1,2-addition to give 2,4-bis(trifluoromethyl)-4H-thiochromen-4-yl trimethylsilyl ether.     

Synthesis of 2-(perfluoroalkyl)ethyl potassium sulfates based on perfluorinated Grignard reagents

The first example of nucleophilic substitution with perfluoroalkyl Grignard reagents on the sp³ carbon centre is described. Thus, a series of organometals R_F-MgBr, prepared from perfluorinated alkyl iodides R_F-I with R_F = C₄F₉, C₆F₁₃, C₈F₁₇, C₁₀F₂₁ and C₁₂F₂₅, reacted with 1,3,2-dioxathiolane-2,2-dioxide to afford the corresponding 2-(perfluoroalkyl)ethyl magnesium sulfates, which were isolated after metathesis to the corresponding potassium salts. In the model reaction, perfluorohexylmagnesium iodide was reacted with methyl triflate yielding polyfluorinated alkane. The attempts to extend the reaction to 1,3,2-dioxathiane-2,2-dioxide were unsuccessful due to its inferior reactivity and only reduced polyfluoroalkane and the product of coupling were detected in the reaction mixture. Polyfluorinated sulfates are easily hydrolyzed with hydrochloric or triflic acid to the corresponding alcohols, which is an alternative to standard transformation of perfluoroalkyl iodides to 2-(perfluoroalkyl)ethanols. Quantum-chemical calculations of the PES of the reaction with both sulfur-containing heterocycles found that the failure of the reaction with 1,3,2-dioxathiane-2,2-dioxide is caused by higher activation energy of the process.     

Factors Influencing Sulfinatodehalogenation Reactions of Perhalocarbons

The study on the factors influencing sulfinatodehalogenation of perfluorohexyl chloride plus octene-1 by using Na2S2O4/NaHCO3 discovered that among the various solvents tested (e.g. Me2SO, NMP, DMAc, CH3CN,CH3CN/H2O) at different temperatures, Me2SO was found to be the most suitable solvent and the conversion of the chloride was very dependent on the reaction temperature. When Me2SO was used in the reaction of perfluoroalkyl iodides, the reaction temperature could be decreased by 20℃ as compared with that carried out in CH3CN/H2O to reach the comparable yields.     

Pentafluoroethylsilicic Acids

Pure anhydrous hexafluorosilicic acid (H₂[SiF₆]) is a still elusive species, although its existence in aqueous solutions is well documented. Desiccation inevitably leads to decomposition to form tetrafluorosilane and hydrogen fluoride. An oxonium hexafluorosilicate turned out to not be stable at room temperature. Partial substitution of the fluorine atoms with strong electron‐withdrawing perfluoroalkyl groups results in substantial stabilization of the corresponding fluorosilicic acids. Mono‐ and bis(pentafluoroethyl)‐substituted fluorosilicic acids were prepared through conversion of the respective halosilanes (Si(C₂F₅)_nX_4?n, with X=Cl, Br) with aqueous HF, and were obtained as colorless solids. They can be stored at room temperature for several months without decomposition, and thus are the first examples of stable fluorosilicic acids.     

Synthesen und Eigenschaften von Tris(perfluoralkyl)arsen- und -antimon(III,V)-Verbindungen

Preparations and Properties of Tris(perfluoroalkyl) Arsenic and Antimony(III, V) Compounds As(R_f)₃ and Sb(R_f)₃ (R_f?C₂F₅, C₄F₉, C₆F₁₃) are prepared in good yields by the polar reactions of AsCl₃ and SbCl₃ with bis(perfluoroalkyl) cadmium compounds as colourless liquids or solids. The oxidation of As(C₂F₅)₃ and Sb(C₂F₅)₃ with XeF₂ gives the difluorides M(C₂F₅)₃F₂ (M?As, Sb). As(C₂F₅)₃Cl₂ is prepared by chlorination of As(C₂F₅)₃ in the presence of AlCl₃, while Sb(C₂F₅)₃Cl₂ is formed in the reaction of Sb(C₂F₅)₃F₂ with (CH₃)₃SiCl. During the reaction of M(C₂F₅)₃F₂ with (CH₃)₃SiBr ¹⁹F-NMR spectroscopic evidence is found for M(C₂F₅)₃ Br₂. The thermal decompositions of M(C₂F₅)₃F₂ mainly yield C₄F₁₀ and M(C₂F₅)F₂, while the thermal decompositions of M(C₂F₅)₃Cl₂ yield M(C₂F₅)₂Cl and C₂F₅Cl. The properties and spectroscopic data of the new compounds are described.     

Synthesis of new imines and amines containing organosilicon groups

The Peterson olefination reaction of terephthalaldehyde with tris(trimethylsilyl)methyl lithium, (Me₃Si)₃CLi, in THF at 0 °C gives 4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde (1) and 4,4-bis[2,2-bis(trimethylsilyl)ethenyl]benzene (2). The new aldehyde (1) reacts with variety of amines in ethanol to afford the corresponding imines (3) containing vinylbis(trimethylsilyl) group. The newly synthesized imines (3) can be completely converted into amines containing vinylbis(trimethylsilyl) group with an excess amount of NaBH₄. In the case of N-[4-(2,2-bis(trimethylsilyl)ethenyl)benzyl]-2,6-dimethylaniline LiAlH₄ was used as a reducing agent in THF.     

Synthesis, crystal structure and properties of cobalt(II) and nickel(II) coordination polymers supported by functionalized dicarboxylate ligands

Four new coordination polymers of cobalt(II) and nickel(II) with functionalized dicarboxylate ligands, namely, [Co^IIL¹(2,2′-bpy)(H₂O)] (1), [Ni^IIL¹(2,2′-bpy)(H₂O)]·H₂O (2), [Co^II₂(L²)₂(2,2′-bpy)₂(H₂O)] (3) and [Ni^II₂(L²)₂(2,2′-bpy)₂(H₂O)] (4), where H₂L¹ = 2,5-dibenzoylterephthalic acid, H₂L² = 4,6-bis(4-methylbenzoyl)isophthalic acid and 2,2′-bpy = 2,2′-bipyridine, were synthesized and characterized by elemental analysis, IR spectra and thermogravimetric analysis. Complex 1 exhibits a zigzag chain with a C–Hπ interaction between the phenyl ring proton and the phenyl ring of an adjacent chains to form a 2D supramolecular sheet. Complex 2 contains two helical chains which extend into 2D via a C–Hπ interaction between the pyridine ring proton and the pyridine ring. Complexes 3 and 4 are isomorphous with helical chains that extend in the same direction and further link to one another by supramolecular forces into a 2D structure. Moreover, magnetic and luminescence properties have been investigated for 1 and 2, respectively.     

First example of regioselective nucleophilic 1,6-addition of trimethyl(trifluoromethyl)silane to 4H-chromene derivatives

Condensation of 2-trifluoromethylchromone with diethyl malonate, ethyl cyanoacetate, and Meldrum’s acid gave the corresponding methylidene derivatives of 2-trifluoromethyl-4H-chromene. Nucleophilic 1,6-addition of an excess of Me₃SiCF₃ in the presence of Me₄NF to those obtained from the former two compounds afforded 4-substituted 2,2-bis(trifluoromethyl)-2H-chromenes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1628–1630, September, 2006.     

Perfluoroalkyl borates and boronic esters: new promising partners for Suzuki and Petasis reactions

Lithium and potassium trifluoromethyl-, pentafluoroethyl- and [(diethylphosphinyl)difluoromethyl]trialkoxyborates were synthesized by reaction of either perfluoroalkyllithium or (perfluoroalkyl)trimethylsilane/F⁻ with trialkoxyboranes. Treatment of perfluoroalkyltrialkoxyborates with methanesulfonyl chloride, methyl triflate or methyl tosylate furnished the hitherto unknown trifluoromethyl-, pentafluoroethyl- and [(diethylphosphinyl)difluoromethyl]boronic esters.