Reactions of tetrafluorophthalic and difluoropyromellitic acids with sulphur tetrafluoride

Fluorination of tetrafluorophthalic acid (1) with an SF₄/HF mixture at 190–300°C afforded,beside the expected perfluoro-o-xylene (2) and perfluoro-o-toluyl fluoride (4), considerableamounts of octafluoro-1,3-dihydroisobenzofuran (3). The reaction with difluoropyromelliticacid (5) at 190°C gave a mixture of perfluoro-2,4,5-trimethylbenzoyl fluoride (9),perfluoro-2,5-dimethylterephthaloyl difluoride (10a), perfluoro-2,4-dimethylisophthaloyl difluoride(10b) and perfluoro-5-methyl-6-fluoroformyl-1,3-dihydroisobenzofuran (11), but at 300°C perfluorodurene (6), perfluoro-5,6-dimethyl-1,3-dihydroisobenzofuran (7) and perfluoro-2,4,5-trimethylbenzoyl fluoride (9) were obtained in a 3:1:0.8 ratio.     

The [F]2-Fluoro-1,3-thiazolyl Moiety - an Easily-Accessible Structural Motif for Prospective Molecular Imaging Radiotracers

2-Fluoro-1,3-thiazoles were rapidly and efficiently labeled with no-carrier-added fluorine-18 (t_1/2 = 109.7 min) by treatment of readily prepared 2-halo precursors with cyclotron-produced [¹⁸F]fluoride ion. The [¹⁸F]2-fluoro-1,3-thiazolyl moiety constitutes a new and easily-labeled structural motif for prospective molecular imaging radiotracers.     

An Improved Synthesis of 2,2-Dialkyl-1,3-Indanediones

2,2-Dialkyl-1,3-indanediones are useful synthetic intermediates (^1,2) and are know to possess an anticonvulsive activity (³). These compounds are usually prepared by alkylation of 1,3-indanedione under drastic conditions and thus are obtained with low yields (20% to 40%). We describe here a convenient and high yield procedure for the synthesis of symmetrical and unsymmetrical 2,2-dialkyl-1,3-in-danediones based on alkylation of 1,3-indanediones in the presence of celite coated with potassium fluoride (KF-celite). This new reagent has been very recently used to carry out various alkylation reactions (³). We found that KF-celite promotes excellent C-dialkylation (⁴) of 1,3-indanedione la, giving rise to symmetrical 2,2-dialkylated compounds 2a. In the same way, unsymmetrical 2,2-dialkyl-1,3 indanediones 2b can be easily prepared from 2-methyl-1,3-indanedione Ib (⁵).     

Chemistry of organo halogenic molecules,LXXV. Polymer-supported hydrogen fluoride

Polymer-supported hydrogen fluoride prepared by reaction of hydrogen fluoride with crosslinked poly(styrene-$\text{co}$-4-vinyl- pyridine) containing 40–45 mol % of 4-vinylpyridine did not react with $\text{trans}$-stilbene, 1,2-diphenylacetylene, and cyclohexanol under various conditions, whereas 1-phenyl-1-hydroxy- 4-tert-butylcyclohexane was converted to 1-phenyl-4-tert-butylcyclohexene. Bromofluorination of various phenyl-substituted olefins with N-bromosuccinimide in the presence of polymer supported hydrogen fluoride in methylene chloride proceeds with Markovnikov type regioselectivity. Fluorination and halofluorination of norbornene with xenon difluoride or N-bromosuccinimide or N-chlorosuccinimide in the presence of polymer- supported hydrogen fluoride resulted in up to five products, with a large increase in halonortricyclane formation, compared to reactions in the presence of hydrogen fluoride-pyridine. Polymer-supported hydrogen fluoride, in comparison to hydrogen fluoride-pyridine, enhanced the $\text{endo}$ attack of the electrophile on norbornadiene by fluorination or halofluorination.     

Synthesis of [F]xenon difluoride as a radiolabeling reagent from [F]fluoride ion in a micro-reactor and at production scale

[¹⁸F]Xenon difluoride ([¹⁸F]XeF₂), was produced by treating xenon difluoride with cyclotron-produced [¹⁸F]fluoride ion to provide a potentially useful agent for labeling novel radiotracers with fluorine-18 (t_1/2 = 109.7 min) for imaging applications with positron emission tomography. Firstly, the effects of various reaction parameters, for example, vessel material, solvent, cation and base on this process were studied at room temperature. Glass vials facilitated the reaction more readily than polypropylene vials. The reaction was less efficient in acetonitrile than in dichloromethane. Cs⁺ or K⁺ with or without the cryptand, K 2.2.2, was acceptable as counter cation. The production of [¹⁸F]XeF₂ was retarded by K₂CO₃, suggesting that generation of hydrogen fluoride in the reaction milieu promoted the incorporation of fluorine-18 into xenon difluoride. Secondly, the effect of temperature was studied using a microfluidic platform in which [¹⁸F]XeF₂ was produced in acetonitrile at elevated temperature (≥85 °C) over 94 s. These results enabled us to develop a method for obtaining [¹⁸F]XeF₂ on a production scale (up to 25 mCi) through reaction of [¹⁸F]fluoride ion with xenon difluoride in acetonitrile at 90 °C for 10 min. [¹⁸F]XeF₂ was separated from the reaction mixture by distillation at 110 °C. Furthermore, [¹⁸F]XeF₂ was shown to be reactive towards substrates, such as 1-((trimethylsilyl)oxy)cyclohexene and fluorene.     

NMR Study of the Reactions of Tin(II) Difluoride and Antimony(III) Trifluoride with Niobium Pentachloride

The reactions of SnF₂and SbF₃with NbCl₅in acetonitrile or dimethyl sulfoxide were studied by ¹⁹F, ⁹³Nb, and ¹¹⁹Sn NMR spectroscopy. The products of reaction in acetonitrile are anionic, while those in di-methyl sulfoxide are neutral octahedral niobium chlorofluoride complexes. Tin(II) difluoride and antimony(III) trifluoride are powerful sources of fluoride ions in the preparation of metal chlorofluoride and fluoro complexes.     

Synthesis and properties of sulfur cyanide trifluoride,SF3CN,sulfur dicyanide difluoride,SF2(CN)2, and sulfinyl cyanide fluoride,FS(O)CN

Sulfur cyanide trifluoride, SF₃CN, and sulfur dicyanide difluoride, SF₂(CN)₂, have been prepared by metathesis between sulfur tetrafluoride, SF₄, and trimethyl silyl cyanide, (CH₃)₃SiCN, at – 30°C. Treatment of SF₃CN with freshly sublimed selenium dioxide, SeO₂, lead to sulfinyl cyanide fluoride, FS(O)CN. IR, Raman, ¹⁹F-NMR, uv and mass spectra of the novel compounds are presented as well as some physical and chemical properties.     

[11C]Carbonyl Difluoride—a New and Highly Efficient [11C]Carbonyl Group Transfer Agent

Herein, the synthesis and use of [¹¹C]carbonyl difluoride for labeling heterocycles with [¹¹C]carbonyl groups in high molar activity is described. A very mild single-pass gas-phase conversion of [¹¹C]carbon monoxide into [¹¹C]carbonyl difluoride over silver(II) fluoride provides easy access to this new synthon in robust quantitative yield for labeling a broad range of cyclic substrates, for example, imidazolidin-2-ones, thiazolidin-2-ones, and oxazolidin-2-ones. Labeling reactions may utilize close-to-stoichiometric precursor quantities and short reaction times at room temperature in a wide range of solvents while also showing high water tolerability. The overall radiosynthesis protocol is both simple and reproducible. The required apparatus can be constructed from widely available parts and is therefore well suited to be automated for PET radiotracer production. We foresee that this straightforward method will gain wide acceptance for PET radiotracer syntheses across the radiochemistry community.     

Low temperature synthesis of chlorine pentafluoride using dioxygen difluoride

Chlorine pentafluoride has been prepared successfully in high purity by the fluorination of ClF₃ at ?78°C with dioxygen difluoride. The yield of ClF₅ by this method is quantitative. The procedure illustrates the general utility of O₂F₂ in high valent fluoride synthesis.     

[11C]Carbonyl Difluoride—a New and Highly Efficient [11C]Carbonyl Group Transfer Agent

Herein, the synthesis and use of [¹¹C]carbonyl difluoride for labeling heterocycles with [¹¹C]carbonyl groups in high molar activity is described. A very mild single‐pass gas‐phase conversion of [¹¹C]carbon monoxide into [¹¹C]carbonyl difluoride over silver(II) fluoride provides easy access to this new synthon in robust quantitative yield for labeling a broad range of cyclic substrates, for example, imidazolidin‐2‐ones, thiazolidin‐2‐ones, and oxazolidin‐2‐ones. Labeling reactions may utilize close‐to‐stoichiometric precursor quantities and short reaction times at room temperature in a wide range of solvents while also showing high water tolerability. The overall radiosynthesis protocol is both simple and reproducible. The required apparatus can be constructed from widely available parts and is therefore well suited to be automated for PET radiotracer production. We foresee that this straightforward method will gain wide acceptance for PET radiotracer syntheses across the radiochemistry community.     

Carbon−Fluorine Bond Formation via a Five-Coordinate Fluoro Complex of Ruthenium(II), Preliminary Communication

The 16-electron, five-coordinate fluoro complex [RuF(dppp)₂]PF₆ ( 1a ; dppp=propane-1,3-diylbis[diphenylphosphine] smoothly reacts with 1,3-diphenylallyl bromide (=1,1′-(3-bromoprop-1-ene-1,3-diyl)bis[benzene]) in dry CDCl₃ to give 1,3-diphenylallyl fluoride and [RuBr(dppp)₂]⁺ in nearly quantitative yield. Under similar conditions, bromide (or chloride)/fluoride exchange also occurs with chlorotriphenylmethane, bromodiphenylmethane, and tert-butyl bromide. The crystal structure of 1a is reported.     

Perfluorotetramethylenesulfur difluoride and its derivatives. Perfluoro-1,3-dithietane octafluoride and perfluoro-1,4-dithiane octafluoride

The fluorination of perfluorotetramethylene sulfide with chlorine monofluoride under controlled conditions results in the formation of both sulfur(IV) and sulfur(VI) compounds as main products. While perfluorotetramethylenesulfur tetrafluoride is very stable to thermolysis and to chemical attack, the hydrolysis of the novel perfluorotetramethylenesulfur difluoride affords perfluorotetramethylene sulfoxide, and its pyrolysis gives perfluro(di-n-butyl)disulfide. Chlorine monofluoride converts perfluorotetramethylene sulfoxide to perfluorotetramethyl-enesulfur oxyfluoride, and perfluorotetramethylene sulfone is obtained quantitatively as a decomposition product in contact with Pyrex glass. Perfluoro-1,3-dithietane octafluoride and perfluoro-1,4-dithiane octafluoride are also formed by the reaction of corresponding perfluorocyclic sulfides with CIF at ambient temperature. Infrared, mass and ¹⁹F NMR spectroscopic as well as thermodynamic data are reported.     

Studies in fluorinated 1,3-diketones and related compounds Part XII. Synthesis and spectroscopic studies of some new polyfluorinated 1,3-diketones,and their copper 1,3-diketonates

New polyfluorinated 1,3-diketones have been prepared from polyfluorinated acetophenones and appropriate esters in the presence of sodamide. The corresponding copper 1,3-diketonates have been obtained by treating a methanolic solution of polyfluorinated 1,3-diketone with methanolic solution of copper acetate. The polyfluorinated 1,3-diketones have been characterized by elemental as well as by spectral studies, viz: I.R., ¹H N.M.R. and ¹⁹F N.M.R. In I.R., characteristic absorptions observed are: CF stretching bands (1300 ? 1000) cm^?1, CF deformation modes (900 ? 700 cm^?1) and intramolecular hydrogen bonding (3000 ? 2500 cm^?1). In ¹H N.M.R. methine ( = C$\text{H}$) signal is observed at δ 6.2 ? 6.8 ppm and enolic proton resonance signal at δ 13 ? 15 ppm indicating the presence of strong hydrogen bonding in such polyfluorinated 1,3-diketones.     

Preferred Binding of Carboxylates by Chiral Urea Derivatives Containing α‐Phenylethyl Group

An efficient, simple protocol for the synthesis of a new family of chiral ureas 1 – 4 is described. The binding properties of 1 – 4 toward different anion (acetate, benzoate, fluoride, and chloride) have been studied by ¹H‐NMR titration and have been observed in the case of 4 is a selective receptor for acetate. The theoretical calculation M06/6‐311+G(d,p) helped us explain the binding properties observed. The most interesting observation is that this calculated structure is consistent with expected, based on the concept of allylic 1,3‐strain (A^1,3 strain). When chiral caboxylates were studied, urea 1 was the best in discriminating between enantiomers.     

F-Induced ‘turn-on’ fluorescent chemosensor based on 1,3-alt thiacalix[4]arene

A new thiacalix[4]arene based fluorescent sensor 1 bearing two naphthyl groups has been synthesized in 1,3-alternate conformation. In the absence of fluoride ion, the receptor 1 is in ‘off-state’ showing no fluorescence emission. The presence of fluoride ion triggered the fluorescence emission to ‘on-state’. The receptor shows pronounced selectivity for fluoride ions. In THF, the presence of F⁻ ions induces the formation of a 1:1 (G:H) complex.     

Some reactions of potassium perfluoro-t-butoxide with strong oxidizing agents

Several reactions of potassium perfluoro-t-butoxide with strong oxidizing agents have been studied. The new compounds (CF₃)₃COOSO₂F and (CF₃)₃CONO₂ have been prepared by reactions with peroxydisulfuryl difluoride and nitryl fluoride, and their properties are reported. Evidence is also presented for the formation of the novel peroxy salt KOOCF₃ in the reaction with bis(fluoroxy)difluoromethane. A mechanism for the reaction of —OF compounds with KOC(CF₃)₃ is proposed.     

Preparation of 1,3-dienyl organotrifluoroborates and their Diels-Alder/cross-coupling reactions

2-BF₃-substituted 1,3-butadienes with potassium and tetrabutyl ammonium counterions have been prepared in gram quantities from chloroprene via a simple synthetic procedure. The potassium salt of this new main group element substituted diene has been characterized by ¹H, ¹³C, ¹¹B, and ¹⁹F NMR and the tetra n-butyl ammonium salt was also characterized by X-ray crystallography. Diels-Alder reactions of these dienes with dienophiles such as ethyl acrylate, methyl vinyl ketone, and N-phenylmaleimide are reported as well as subsequent Pd-catalyzed cross-coupling reactions of those Diels-Alder adducts. 4-Phenyl-2-BF₃-substituted 1,3-diene was prepared by magnesium-halogen exchange from the corresponding 2-bromo and iodo dienes. The 4-phenyl-2-bromo-1,3-butadiene was also characterized by X-ray crystallography. 4-Phenyl-2-BF₃-1,3-butadiene was used in Diels-Alder/cross-coupling reactions and the product of a Diels-Alder reaction with N-phenylmaleimide followed by cross-coupling with 4-bromo-benzonitrile was also characterized by X-ray crystallography.     

Synthesis of isoxazolidines by 1,3-dipolar cycloaddition and their bioactivity

A series of new isoxazolidines was prepared by 1,3-dipolar cycloaddition of different mono-substituted styrenes with 1,3-dipolar compounds that were prepared by the reaction of N-methylhydroxylamine sulfate with aromatic carbonyl substances. This synthetic pathway for the preparation of isoxazolidines was an ideal process of green chemistry. The synthetic products were 5-substituted isoxazolidines and their structures were characterized by mass and NMR (¹H-, ¹³C-, COSY, HSQC, and DEPT) spectrometry, and their bioactivity was investigated indicating that some new compounds inhibited Botrytis cinerea effectively. __________ Translated from Chinese Journal of Organic Chemistry, 2005, 25(11) (in Chinese)     

Synthesis and Structure of Triphenylbismuth Difluoride

The reaction of triphenylbismuth dichloride with sodium fluoride in acetone leads to formation of triphenylbismuth difluoride in 73% yield. The X-ray diffraction data show that the bismuth atom in the two symmetrically independent molecules of bismuth difluoride has a trigonal-bipyramidal coordination with equatorial fluorine atoms. The Bi-F and Bi-C distances are 2.53(1)-2.59(1) and 2.10(3)-2.22(2) Å, respectively, and the FBiF angle is 175.1(5)°.     

1,3-Adamantanyl dimethylsiloxane copolymers. Preparation and properties

1,3-bis(Dimethylhydroxysilyl)adamantane(I) has been prepared. Thermal condensation polymerization of this monomer yields poly-1,3-adamantyl-1,1,3,3-tetramethyldisiloxane. Condensation of I with bis(dimethylamino)dimethylsilane or 1,3-bis(dimethylamino)-1,1,3,3-tetramethyldisiloxane gave the expected 1,3-adamantyl dimethylsiloxane copolymers (II and III) respectively. These polymers have been characterized by ¹H,¹³C, and ²⁹SiNMR as well as GPC and TGA. They have unusually high thermal stability.