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Shlomo Rozen - One of the best experts on this subject based on the ideXlab platform.
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Activation of a CH bond in polypyridine systems by acetyl Hypofluorite made from F2.
Organic & Biomolecular Chemistry, 2012Co-Authors: Julia Gatenyo, Youlia Hagooly, Inna Vints, Shlomo RozenAbstract:Activation of the relatively inactive polypyridine backbone with strong electrophilic fluorine, originating from acetyl Hypofluorite (AcOF) enables attack of the acetoxy moiety at the α position to the heteroatom. Derivatives of bipyridine, phenanthroline and terpyridine systems have been acetoxylated or oxygenated within a few minutes usually in very good yields.
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Patai's Chemistry of Functional Groups - The Formation of the CF Bond: The Last Twelve Years
PATAI'S Chemistry of Functional Groups, 2009Co-Authors: Shlomo RozenAbstract:1 Introduction 2 Nucleophilic Fluorinating Reagents 3 Electrophilic Fluorinating Reagents 4 Synthesis of Compounds Containing The 18F Isotope For Use In Positron-Emitting Tomography 5 Recent Reviews on Selective Fluorination Methods Keywords: nucleophilic fluorinating reagents; hydrogen fluoride and its complexes; potassium fluoride; tetrabutyl ammonium fluoride; electrophilic fluorinating reagents; acetyl Hypofluorite and higher homologs; elemental fluorine reactions; recent selective fluorination methods
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Widening the alkyl Hypofluorite family. On the existence of ethyl Hypofluorite
Journal of Fluorine Chemistry, 1995Co-Authors: Shlomo Rozen, Arie Bar-haimAbstract:Abstract Unlike methanol and t-butanol, most other alcohols do not form alkyl Hypofluorites when reacting with fluorine, since immediate HF elimination takes place even at low temperatures. Notable exceptions to this trend are the two deuterated ethanols CD 3 CD 2 OD and CH 3 CD 2 OH, which do produce the corresponding Hypofluorites. Their identification and some of the reasons for this exclusive behavior are outlined.
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The Chemistry of Methyl Hypofluorite: Its Reactions with Various Unsaturated Centers
The Journal of Organic Chemistry, 1994Co-Authors: Shlomo Rozen, Eyal Mishani, Moshe Kol, Iris Ben-davidAbstract:Methyl Hypofluorite was until recently grouped as a hypothetical member of those smallest organic molecules which had not been synthesized. Passing F 2 through a solution of methanol in MeCN or PrCN resulted in its successful preparation. MeOF is an unique reagent, since it generates the novel electrophilic methoxylium moiety in contrast to the much more common methoxide group. This Hypofluorite was reacted with several types of olefins including benzylic, cyclic, bicyclic, straight chain, and steroidal ones. In most cases the regioselectivity is very good, reflecting the unique polarization of the reagent: MeO δ+ F δ- . The stereoselectivity tends to be less emphasized, but usually anti addition is dominant
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Synthesis, characterization, and reaction chemistry of tert-butyl Hypofluorite
Journal of the American Chemical Society, 1993Co-Authors: Evan H. Appelman, Eyal Mishani, David French, Shlomo RozenAbstract:tert-Butyl Hypofluorite ((CH[sub 3])[sub 3]COF) can be synthesized by the low-temperature reaction of elemental fluorine with tert-butyl alcohol dissolved in propionitrile or acetonitrile. The isolated compound, which melts around -94[degrees]C and has an extrapolated boiling point of about +40[degrees]C, has been characterized by mass, NMR, and IR spectrometry. The [sup 19]F NMR shift of +67 ppm lies between the corresponding shifts of HOF and CH[sub 3]OF and implies a rather high O-F bond energy. Although sterically crowded, tert-butyl Hypofluorite adds to olefins to form [beta]-fluoro-tert-butoxy compounds. Addition is mainly in an anti mode, and the regioselectivity corresponds to the action of a hitherto unknown tert-butoxylium electrophile. Also formed are adducts containing F and CH[sub 2]CN, the latter deriving from the acetonitrile solvent. 19 refs., 1 tab.
Walter Navarrini - One of the best experts on this subject based on the ideXlab platform.
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Catalytic microreactor with electrodeposited hierarchically nanostructured nickel coatings for gas-phase fluorination reactions
Journal of Fluorine Chemistry, 2018Co-Authors: Maurizio Sansotera, Alberto Baggioli, Simona Ieffa, Mariella Tedesco, Benedetta Sacchi, Claudia L. Bianchi, Michele Navarrini, Massimo Migliori, Luca Magagnin, Walter NavarriniAbstract:Abstract The fabrication of a catalytic microreactor for the reaction of undiluted carbonyl difluoride and elemental fluorine to synthesize trifluoromethyl Hypofluorite, CF 3 OF, on CsF catalyst supported on F 2 -passivated nanosctructured Ni coating was studied. The nanosctructured Ni support for catalyst immobilization was electrodeposited by a two-step procedure, consisting of a low current density step followed by a brief high current density one, for a hierarchical differentiation of structural features. An aqueous solution of NiCl 2 with diethanolamine, as crystal modifier, and sodium lauryl sulphate, as anti-pitting agent, was used as electrolyte. Constant-pH Ni electrocrystallization was performed on H 2 SO 4 -etched Cu substrates in a range of pH from 1 to 4 via a HCl/H 3 BO 3 based buffer. Passivation was carried out under up to 300 mbar of undiluted F 2 . XRD, XPS, SEM, AFM, and static contact angle measurements were performed. Ni coatings obtained from pH 3 electrolytes were selected for microreactor fabrication on the basis of characterization data, due to the reproducibility and homogeneity of the structured Ni layers. The catalytic microreactor allowed the quantitative production of CF 3 OF from pure reactants, on demand, and removing any criticality relative to thermal and safety control of the synthesis. The CF 3 O-group selective transfer ability of the synthetized Hypofluorite has raised interest in pharmaceutical and agrochemical industries in recent years.
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Recent developments in the chemistry of organic perfluoro Hypofluorites
Journal of Fluorine Chemistry, 2013Co-Authors: Venturini Francesco, Maurizio Sansotera, Walter NavarriniAbstract:Abstract Recent findings in the synthesis of perfluoro-Hypofluorites, their reactivity and their use in the preparation of important perfluoro monomers are herein summarized and analyzed. The experimental conditions to induce free radical or electrophilic reactivity as well as their use as initiation system in the oxidation and oxypolimerization of fluorinated olefins are also presented. Particular emphasis is dedicated to safety issues since organic Hypofluorites have the tendency to self-decompose forming gaseous compounds.The Hypofluorites considered in this review are: CF 3 OF, CF 2 (OF) 2 , CF 3 CF 2 OCF 2 OF, CF 3 OCF 2 CF 2 OCF 2 OF, CF 3 O(CF 2 O) n CF 2 OF, CF 3 OCF 2 CF 2 OF, (CF 3 ) 2 CFOF (CF 3 ) 3 COF, FS(O) 2 CF 2 CF 2 OF, CF 3 OCF 2 CF 2 CF 2 OF, cyclo-(CF 2 OCF 2 OCF)-CF 2 OF, (CF 3 ) 2 N-CF 2 OF.
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RADICAL INDUCED REACTiON BETWEEN CF3OF AND AROMATICS
2012Co-Authors: Francesco Venturini, Vito Tortelli, Antonino Famulari, Andrea Adamo, Walter NavarriniAbstract:The reactivity of CF3OF has been widely studied especially in halogenated olefinic systems [1] and its use in pharmaceutical synthesis as a mild radical and electrophilic fluorinating agent is also well documented. On the other hand, the chemical behavior of the perfluoro-methyl-Hypofluorite with aromatic substrates is much less studied. Up to now few and scattered data regarding its use as electrophilic fluorinating agent of variously substituted aromatic compounds are found in the literature. The reactivity of CF3OF with simple electron rich and electron poor aromatics (α,α,α-trifluoro-toluene, toluene, benzene, chloro-benzene, methoxybenzene) has been investigated. The possibility of selectively bind the trifluoro-methoxy group by varying the reaction conditions has been explored. The perfluoro-Hypofluorite was obtained via direct fluorination of carbon monoxide. This reaction is recognized as a gas phase, radical and thus fast exothermic reaction. In the absence of proper temperature control the reaction is also prone to thermal run-away. To obtain a clean stream of CF3OF the direct fluorination of carbon monoxide has been studied and optimized in a newly designed stainless steel microreactor [2]. Its performances, in terms of operability and selectivity, have been compared with a standard reactor assembly. This research resulted in the development of a one-step synthesis of aromatic-trifluoro-ethers via radical addition [3]
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Direct trifluoro-methoxylation of aromatics with perfluoro-methyl-Hypofluorite
Journal of Fluorine Chemistry, 2012Co-Authors: Francesco Venturini, Walter Navarrini, Maurizio Sansotera, Patrizia Dardani, Antonino Famulari, Vito TortelliAbstract:Abstract The reactivity of CF 3 OF (FTM) has been widely studied especially in halogenated olefinic systems and its use in pharmaceutical synthesis as a mild radical and electrophilic fluorinating agent is well documented. On the other hand, the chemical behavior of the perfluoro-methyl-Hypofluorite with aromatic substrates is much less studied. Up to now few and scattered data regarding its use as electrophilic fluorinating agent of variously substituted aromatic compounds are found in the literature. In this work the reactivity of CF 3 OF with simple electron rich and electron poor aromatics (α,α,α-trifluoro-toluene, toluene, benzene, chloro-benzene, methoxybenzene) has been investigated. The possibility of selectively bind the trifluoro-methoxy group (via radical mechanism) or the fluorine atom (via electrophilic addition) by varying the reaction conditions has been explored. In particular we have observed that the trifluoro-methoxy free radical substitution can be the main synthetic pathway if the reaction is promoted by an independent and steady source of CF3O radical.
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The use of perfluoroalkyl Hypofluorites for an efficient synthesis of perfluorinated ethers characterized by low Ostwald coefficient
Journal of Fluorine Chemistry, 2008Co-Authors: Walter Navarrini, Francesco Venturini, Maurizio Sansotera, Maurizio Ursini, Pierangelo Metrangolo, Giuseppe Resnati, Marco Galimberti, Emma Barchiesi, Patrizia DardaniAbstract:Abstract In the reaction between perfluoroolefins and perfluoroalkylHypofluorites the existence of two different free radical reaction mechanisms is demonstrated by the presence of characteristic byproducts. These kinetic schemes can be experimentally controlled by tuning the Hypofluorite concentration in the reaction media. In particular, in the reactions between trifluoromethyl Hypofluorite and highly reactive perfluoroolefins like CF 2 CFOCF 3 and CF 2 CF 2 , the free radical oligomerization and dimerization products can be suppressed by utilizing the opportune experimental conditions. The pure perfluorinated ethers obtained, having low Ostwald coefficient, can be utilized as contrast agents for diagnostic ultrasound imaging injectable microbubbles composition.
Sebastian Riedel - One of the best experts on this subject based on the ideXlab platform.
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Perfluoro Alkyl Hypofluorites and Peroxides Revisited.
Chemistry – A European Journal, 2019Co-Authors: Jan H. Nissen, Thomas Drews, Benjamin Schröder, Helmut Beckers, Simon Steinhauer, Sebastian RiedelAbstract:A more convenient synthesis of the perfluoro alkyl Hypofluorite (F3 C)3 COF as well as the hitherto unknown (C2 F5 )(F3 C)2 COF compound is reported. Both Hypofluorites can be prepared by use of the corresponding tertiary alcohols RF OH and elemental fluorine in the presence of CsF. An appropriate access to these highly reactive Hypofluorites is crucial. The Hypofluorites are then transferred into their corresponding perfluoro bisalkyl peroxides RF OORF [RF =(F3 C)3 C, (C2 F5 )(F3 C)2 C] by treatment with partially fluorinated silver wool. NMR, gas-phase infrared, and solid-state Raman spectra of the perfluoro bisalkyl peroxides are presented and their chemical properties are discussed.
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Oxygen radical character in group 11 oxygen fluorides
Nature Communications, 2018Co-Authors: Tony Stüker, Helmut Beckers, Stefanie Kieninger, Dirk Andrae, Tobias Schlöder, Yu Gong, Lester Andrews, Sebastian RiedelAbstract:While transition metal complexes bearing terminal oxido ligands are common, those of group 11 elements have yet to be experimentally observed. Here, Riedel and colleagues synthesise molecular oxygen fluorides of copper, silver and gold, and show that the oxo ligands possess radical character. Transition metal complexes bearing terminal oxido ligands are quite common, yet group 11 terminal oxo complexes remain elusive. Here we show that excited coinage metal atoms M (M = Au, Ag, Cu) react with OF_2 to form Hypofluorites FOMF and group 11 oxygen metal fluorides OMF_2, OAuF and OAgF. These compounds have been characterized by IR matrix-isolation spectroscopy in conjunction with state-of-the-art quantum-chemical calculations. The oxygen fluorides are formed by photolysis of the initially prepared Hypofluorites. The linear molecules OAgF and OAuF have a ^3 Σ ^− ground state with a biradical character. Two unpaired electrons are located mainly at the oxygen ligand in antibonding O−M π* orbitals. For the ^2 B _2 ground state of the OM^IIIF_2 compounds only an O−M single bond arises and a significant spin-density contribution was found at the oxygen atom as well.
Vito Tortelli - One of the best experts on this subject based on the ideXlab platform.
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RADICAL INDUCED REACTiON BETWEEN CF3OF AND AROMATICS
2012Co-Authors: Francesco Venturini, Vito Tortelli, Antonino Famulari, Andrea Adamo, Walter NavarriniAbstract:The reactivity of CF3OF has been widely studied especially in halogenated olefinic systems [1] and its use in pharmaceutical synthesis as a mild radical and electrophilic fluorinating agent is also well documented. On the other hand, the chemical behavior of the perfluoro-methyl-Hypofluorite with aromatic substrates is much less studied. Up to now few and scattered data regarding its use as electrophilic fluorinating agent of variously substituted aromatic compounds are found in the literature. The reactivity of CF3OF with simple electron rich and electron poor aromatics (α,α,α-trifluoro-toluene, toluene, benzene, chloro-benzene, methoxybenzene) has been investigated. The possibility of selectively bind the trifluoro-methoxy group by varying the reaction conditions has been explored. The perfluoro-Hypofluorite was obtained via direct fluorination of carbon monoxide. This reaction is recognized as a gas phase, radical and thus fast exothermic reaction. In the absence of proper temperature control the reaction is also prone to thermal run-away. To obtain a clean stream of CF3OF the direct fluorination of carbon monoxide has been studied and optimized in a newly designed stainless steel microreactor [2]. Its performances, in terms of operability and selectivity, have been compared with a standard reactor assembly. This research resulted in the development of a one-step synthesis of aromatic-trifluoro-ethers via radical addition [3]
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Direct trifluoro-methoxylation of aromatics with perfluoro-methyl-Hypofluorite
Journal of Fluorine Chemistry, 2012Co-Authors: Francesco Venturini, Walter Navarrini, Maurizio Sansotera, Patrizia Dardani, Antonino Famulari, Vito TortelliAbstract:Abstract The reactivity of CF 3 OF (FTM) has been widely studied especially in halogenated olefinic systems and its use in pharmaceutical synthesis as a mild radical and electrophilic fluorinating agent is well documented. On the other hand, the chemical behavior of the perfluoro-methyl-Hypofluorite with aromatic substrates is much less studied. Up to now few and scattered data regarding its use as electrophilic fluorinating agent of variously substituted aromatic compounds are found in the literature. In this work the reactivity of CF 3 OF with simple electron rich and electron poor aromatics (α,α,α-trifluoro-toluene, toluene, benzene, chloro-benzene, methoxybenzene) has been investigated. The possibility of selectively bind the trifluoro-methoxy group (via radical mechanism) or the fluorine atom (via electrophilic addition) by varying the reaction conditions has been explored. In particular we have observed that the trifluoro-methoxy free radical substitution can be the main synthetic pathway if the reaction is promoted by an independent and steady source of CF3O radical.
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Organic Hypofluorites and their new role in industrial fluorine chemistry
Journal of Fluorine Chemistry, 1999Co-Authors: Walter Navarrini, Vito Tortelli, Antonio Russo, Sandra CortiAbstract:Abstract In this work a historical background of the synthesis and chemistry of fluorinated organic Hypofluorites is given and some of the known applications of this class of compounds are reviewed. Recently, new industrial processes based on Hypofluorite chemistry have been developed for the production of a variety of fluoromonomers. These processes are all based on the addition of Hypofluorites having different structures to fluorinated olefins. Some mechanistic features of this key reaction are discussed, in terms of reactivity and stability of the intermediate primary radicals deriving from homolytic cleavage of the Hypofluorite bond. Various aspects of these new processes are described and, in the light of these recent achievements, it is shown how Hypofluorite chemistry has acquired great importance as a powerful and versatile methodology for the production of fluoromonomers of prominent industrial interest.
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EPR and ENDOR of perfluoroalkyl radical intermediates in the reaction between perfluoroHypofluorites and perfluoroalkenes
Journal of the Chemical Society Faraday Transactions, 1995Co-Authors: Fosca Conti, Walter Navarrini, Carlo Corvaja, Francesca Cremonese, Vito TortelliAbstract:EPR and ENDOR spectra of the reaction products of sterically hindered perfluoroalkenes with perfluoromethyl Hypofluorite and with the perfluoroether Hypofluorite X(CF2O)n(CF2CF2O)mCF2OF, where X is either OCF3 or a second Hypofluorite group OCF2-OF, have been recorded. Tertiary and secondary free radicals are produced by the addition to the alkene double bond of a fluorine atom or of the partner radical formed by the homolysis of the Hypofluorite O—F bond. Analysis of the spectra reveals that hyperfine splitting by 19F nuclei in the γ and δ positions, and even further from the radical centre, contribute spectra. The α- and β-19F hyperfine splitting are discussed in relation to the radical structure and conformation. The β-19F splittings are accounted for by the well known equation aβF=B cos2(θ); different values of the constant B have to be used according to the number of β-fluorine substituents bonded to the same α-carbon.
Evan H. Appelman - One of the best experts on this subject based on the ideXlab platform.
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Synthesis, characterization, and reaction chemistry of tert-butyl Hypofluorite
Journal of the American Chemical Society, 1993Co-Authors: Evan H. Appelman, Eyal Mishani, David French, Shlomo RozenAbstract:tert-Butyl Hypofluorite ((CH[sub 3])[sub 3]COF) can be synthesized by the low-temperature reaction of elemental fluorine with tert-butyl alcohol dissolved in propionitrile or acetonitrile. The isolated compound, which melts around -94[degrees]C and has an extrapolated boiling point of about +40[degrees]C, has been characterized by mass, NMR, and IR spectrometry. The [sup 19]F NMR shift of +67 ppm lies between the corresponding shifts of HOF and CH[sub 3]OF and implies a rather high O-F bond energy. Although sterically crowded, tert-butyl Hypofluorite adds to olefins to form [beta]-fluoro-tert-butoxy compounds. Addition is mainly in an anti mode, and the regioselectivity corresponds to the action of a hitherto unknown tert-butoxylium electrophile. Also formed are adducts containing F and CH[sub 2]CN, the latter deriving from the acetonitrile solvent. 19 refs., 1 tab.
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Trifluoromethanesulfonyl Hypofluorite, a hitherto unknown fluoroxy compound
Journal of the American Chemical Society, 1993Co-Authors: Evan H. Appelman, Albert W. JacheAbstract:Trifluoromethanesulfonyl Hypofluorite (CF[sub 3]SO[sub 2]OF) has been synthesized by the reaction of fluorosulfuryl Hypofluorite (FSO[sub 2]OF) with cesium trifluoromethanesulfonate. It is the first compound in which a sulfur atom is bonded both to carbon and to an O-F moiety. The compound has a melting point of -87 [plus minus] 2[degrees]C and an extrapolated boiling point of 0 [plus minus] 1[degrees]C. The [sup 19]F NMR spectrum of the compound in CFCl[sub 3] at -80[degrees]C shows a CF[sub 3] doublet at -71 ppm and a broad OF singlet at +238 ppm. From the latter can be deduced an O-F bond energy of about 145 kJ/mol, comparable to that of FSO[sub 2]OF. The compound hydrolyses in base to give a mixture of O[sub 2] and CF[sub 4], along with (presumably) sulfate and trifluoromethanesulfonate. It decomposes thermally in the presence of CsF to yield principally CF[sub 3]SO[sub 2]F and OF[sub 2] along with (presumably) cesium trifluoromethanesulfonate. 14 refs., 1 tab.
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Some recent developments in the chemistry of Hypofluorites
Journal of Fluorine Chemistry, 1991Co-Authors: Evan H. Appelman, Moshe Kol, Branko Ruscic, Joseph Berkowitz, S. Rosen, Oliver Dunkelberg, Alois HaasAbstract:Abstract In this paper we shall discuss a new and convenient method for the preparation of hypofluorous acid, HOF, and we shall describe the synthesis and characterization of the hitherto unknown methyl Hypofluorite, CH 3 OF. The archetypal Hypofluorite HOF is known to have remarkable oxygenating properties. Its investigation and application have been inhibited, however, by the difficulty of its synthesis, which has heretofore involved passage of elemental fluorine over ice in a complex recirculating system, and by the fact that the neat material can be explosively unstable. It has recently been found that passage of fluorine through acetonitrile containing 5–20% water generates strongly oxidizing solutions, and we have subsequently shown that these solutions contain HOF. Characterization of the solutions by NMR and molecular spectrometry indicates that a 1:1 hydrogen-bonded complex between the HOF and acetonitrile is present. The complex appears to be significantly more stable than neat HOF, and this interaction therefore serves as a means of “taming” hypofluorous acid and making the compound more accessible to researchers interested in working with it. Methyl Hypofluorite has widely been assumed to be unmakeable because of the ease with which it could decompose to HF and formaldehyde. In fact, the compound can be readily prepared by fluorination of a cooled solution of methanol in acetonitrile or propionitrile, and even by fluorination of neat methanol at Dry Ice temperature. The extremely volatile compound (m.p. −142 °C, b.p. −33 °C) can be distilled from the reaction mixture, and it has been isolated and characterized by mass, NMR, and infrared spectrometry. Photoionization mass spectrometric measurements of fragment thresholds yield values of ca. −94 and 196 kJ/mol respectively for the enthalpy of formation of CH 3 OF and the dissociation energy of its oxygen-fluorine bond. This makes the oxygen-fluorine bond in CH 3 OF very slightly weaker than that in HOF, but stronger than that in any other known Hypofluorite. Neat liquid CH 3 OF can decompose explosively, but the compound is well-behaved and relatively long-lived in the gas phase and as a solution in acetonitrile or propionitrile. It adds the elements of CH 3 O and F to olefins; with unsymmetrical olefins the addition takes place in the direction of electrophilic methoxylation rather than electrophilic fluorination.
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Isolation and characterization of methyl Hypofluorite (CH3OF)
Journal of the American Chemical Society, 1991Co-Authors: Moshe Kol, Shlomo Rozen, Evan H. AppelmanAbstract:Methyl Hypofluorite (CH 3 OF) has been prepared by the reaction of elemental fluorine with methanol in acetonitrile or propionitrile at low temperature. It was removed from the reaction mixture in a stream of nitrogen and purified by fractional distillation. The compound is moderately long-lived, although the liquid has exploded upon rapid warming. The liquid compound has a freezing point of about −142°C, and vapor pressure measurements indicate a normal boiling point of −32.6±0.9°C and an enthalpy of vaporization of 23.37±0.26 kJ/mol. The infrared spectrum of the vapor is consistent with the molecule being isostructural with CH 3 OH and CF 3 OF. The compound has also been characterized by mass spectrometry and by 1 H, 19 F, and 13 C NMR spectrometries. This novel reagent adds across various double bonds to form the corresponding fluoro methoxy adducts, which are not easily accessible by other methods
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Laser flash photolysis and pulse radiolysis of aqueous solutions of the fluoroxysulfate ion, SO4F-
Inorganic Chemistry, 1991Co-Authors: Ulrik K. Kläning, Knud Sehested, Evan H. AppelmanAbstract:The fluoroxysulfate ion, SO{sub 4}F{sup {minus}}, is the only known ionic Hypofluorite. It is a very strong oxidant capable of oxidizing water, but the rate of its reaction with water is sufficiently low to allow studies of its chemistry in aqueous solution. Aqueous fluoroxysulfate appears to react primarily as a 1-electron oxidant, and an F atom transfer mechanism has been proposed to account for many of its reactions. The present work is a study of the laser flash photolysis and pulse radiolysis of aqueous solutions of SO{sub 4}F{sup {minus}}.