Taming elemental fluorine: Indirect use of fluorine for the synthesis of α-fluoroketones[1]

Fluorine and sodium trifluoroacetate react at ?75° to produce a variety of fluoroxy-compounds. Although it is possible to direct the reaction towards the formation of CF₃COOF or CF₃CF₂OF, mixtures may be used when only the electrophilic fluorine has to be attached to the molecule of interest. Such is the case of the reaction of enol-acetates with the mixture of the fluoroxy reagents. A wide variety of compounds, including steroids and containing various functional groups, were tested. In most cases the desired α-fluoroketones were obtained in good to very good yields. The new fluorine containing compounds are the compounds numbered $\text{2, 9, 11, 13, 15, 16}$ and $\text{20}$.     

Studies on the syntheses of azole derivatives—V: The mass spectra of 1,2,4-triazoles and oxadiazoles (studies on the syntheses of heterocyclic compounds—CCCLXXIV)

The electron-impact induced fragmentation of twenty 3-alkyl-1-phenyl-Δ²-1,2,4-triazolin-5-ones, three 1-phenyl-1,2,4-triazolin-3,5-diones and ten 2-alkyl-4-phenyloxadiazolin-5-ones has been studied by conventional mass spectrometry. The major cleavages take place in the 1-phenyl-Δ²-1,2,4-triazolin-5-one nucleus, producing three major fragment ions. 4-Phenyloxadiazolin-5-ones exhibit a similar fragmentation pattern to 1-phenyl-Δ²-1,2,4-triazolin-5-ones. Furthermore, several additional fragmentation processes are observed in the case of specific 1,2,4-triasolines.     

Heterocyclic and acyclic derivatives of F-N-isopropylacetimidoyl chloride

$\text{F}$-N-Isopropylacetimidoyl chloride, CF₃CClNCF(CF₃)₂, has been used as a precursor for a variety of heterocyclic and acyclic compounds. Reaction with azide ion yields a mixture of the imidoyl azide, CF₃(N₃)CNCF(CF₃)₂, and the 1,5-tetrazole, CF₃$\text{CNNN}$CF(CF₃)₂. Hexafluoropropylideniminolithium produces as a minor product the conjugated diimine, (CF₃)₂CNC(CF₃)NCF(CF₃)₂, from nucleophilic attack at the imidoyl chlorine and as a major product the triimine, (CF₃)₂CNC(CF₃)NC(CF₃)₂NC(CF₃)₂, from further attack at the isopropyl fluorine. A thio-amide, CF₃C(S)NHCH(CF₃)₂, and a Δ³-1,2,4-dithiazoline, $\text{SSC(CF}{}_3\text{)NC}$(CF₃)₂, are produced upon reaction of hyrogen sulfide with the imidoyl chloride. Pathways are proposed for each of the reactions.     

Selective activation of organic molecules by elemental fluorine

Reactions on tertiary hydrogen atoms, attached to unactivated saturated carbons, are very rare and usually inefficient. The electron density however, of a carbon-tertiary hydrogen bond is relatively high and therefore there is a chance it will react with a strong electrophile. One of the strongest electrophiles existing is, of course, the electrophilic fluorine. Two main sources for such an unusual species exist. One source is the various fluoroxy compounds like CF₃OF or CF₃COOF ant the other is the elemental fluorine itself.Indeed, when fluorine is allowed to react, at low temperatures, with various alkylcyclohexanol esters, a highly regio- and an absolutely stereospecific electrophilic substitution on the tertiary unactivated hydrogen takes place as for example:

The radical pathway possibility of these reactions is excluded and it is believed that they are of ionic nature. By dehydrofluorination, a double bond is introduced in sites that no other reagent is known to do, thus activating the molecule towards further chemical transformations. The influence of the electron-withdrawing group on the reaction center will also be discussed.The described reaction is not restricted only to cyclic compounds as aliphatic chains also react as expected, i.e.

The scope of these unusual reactions in both alicyclic and aliphatic fields will be evaluated.     

Enantiomeric N-(tert-Butylsulfinyl) Polyfluoroalkyl Aldimines in aza-Henry Reaction: Effective Route to Chiral Polyfluoroalkyl Nitroamines and Diamines

A highly diastereoselective addition of nitromethane to the C=N bond of enantiomeric fluorine containing Ellman's aldimines, R_FCH=NS(O)tert-Bu (R_F=CF₃, CF₂Br, C₂F₅, HC₂F₄), has been successfully developed. The synthetic potential of the resulting β-nitrosulfinylamides was demonstrated through their conversion into optically active α-fluoroalkylated 1,3-nitroamines, 1,3-diamines, and 4-fluoroalkylated imidazolidin-2-ones.     

Studies on the syntheses of azole derivatives. Part VII. Syntheses of 1 -phenyl-Δ2-1,2,4-triazolin-5-one derivatives [studies on the syntheses of heteroeyclic compounds. CD XI]

Bromination of 3-methyl-1-phenyl-Δ²-1,2,3-lriazolin-5-one (II) and its 4-phenyl derivative III afforded the corresponding I-(p-Bromophenyl) derivatives IV and V, respectively. (Chlorination of the 4-phenyl derivative III gave I-(P-chlorophenyl) derivative VI. In addition, 3-N-subsuituted-carhamoyl-1,2,4-triazolin-5-ones(XII, XIII, and XIV) were synthesized by the Schotten-Baumann reaction of 3-carboxy-1-phenyl-Δ²-1,2,4-triazolin-5-one (XI) with various amines.     

Kinetics and mechanism of the thermal gas‐phase oxidation of perfluorobutene‐2 in presence of trifluoromethyl hypofluorite

The oxidation of perfluorobutene‐2 (C₄F₈) initiated by trifluoromethyl hypofluorite (CF₃OF) in presence of O₂ has been studied at 323.1, 332.6, 342.5, and 352.0 K, using a conventional static system. The initial pressure of CF₃OF was varied between 4.8 and 23.6 Torr, that of C₄F₈ between 48.7 and 302.4 Torr, and that of O₂ between 51.5 and 270.4 Torr. Several runs were made in presence of 325.5–451.2 Torr of N₂. The main products were COF₂, CF₃C(O)F, and CF₃OC(O)F. Small amounts of compound containing ? CF(CF₃)? O? C(O)CF₃ group were also formed, as detected by ¹³C NMR spectroscopy. The oxidation is a homogeneous short‐chain reaction, attaining, at the pressure of O₂ used, the pseudo‐zero‐order condition with respect to O₂ as reactant. The reaction is independent of the total pressure. Its basic steps are as follows: the thermal generation of CF₃O^? radicals by the abstraction of fluorine atom of CF₃OF by C₄F₈, the addition of CF₃O^? to the alkene, the formation of perfluoroalkoxy radicals RO^? in presence of O₂, and the decomposition of these radicals via the C? C bond scission, giving products containing ? C(O)F end group and reforming RO^? and CF₃O^? radicals. The mechanism consistent with experimental results is postulated. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 532–541, 2003     

Kinetics and mechanism of the thermal gas-phase reaction between trifluoromethylhypofluorite,CF3OF,and tetrachloroethene

The thermal gas-phase reaction of CF₃OF with CCl₂CCl₂ has been studied between 313.8 and 343.8 K. The initial pressure of CF₃OF was varied between 10.8 and 77.5 torr and that of CCl₂CCl₂ between 3.7 and 26.8 torr. CF₃OF was always present in excess, varying the initial ratio of CF₃OF to that of CCl₂CCl₂ from 1.3 to 10. Three products were formed: CF₃OCCl₂CCl₂F, CCl₂FCCl₂F, and CF₃O(CCl₂CCl₂) ₂OCF₃. The yields of CF₃OCCl₂CCl₂F were 98–99.5%, based on the sum of the products. The reaction was a homogeneous chain reaction not affected by the total pressure. In presence of O₂ the oxidation of CCl₂CCl₂ to CCl₃C(O)Cl and COCl₂ occurred. The proposed basic reaction steps are: generation of the radicals CF₃O˙ and CCl₂FCCl₂˙ (κ₁) in a biomolecular process between CF₃OF and CCl₂CCl₂, formation of the radical CF₃OCCl₂CCl₂˙ by addition of CF₃O˙ to CCl₂CCl₂, chain generation of CF₃O˙ by abstraction of fluorine atom from CF₃OF by CF₃OCCl₂CCl₂˙ (κ₄), and chain termination by recombination of the radicals CF₃OCCl₂CCl₂˙. The expressions obtained for the constants κ₁ and κ₄ are κ₁ = 3.16 ± 0.6 × 10⁷ exp(−15.2 ± 1.7 Kcal mol⁻¹/RT) dm³ mol⁻¹ s⁻¹, κ₄ = 3.7 ± 0.5 × 10⁹ exp(−6.0 ± 1.1 Kcal mol⁻¹/RT) dm³ mol⁻¹ s⁻¹. © 1996 John Wiley & Sons, Inc.     

Chiral substituierte Schwefelfluoride

Chirally Substituted Sulfur Fluorides The compounds CF₃? CFCl? SF₃, (CF₃? CFCl)₂SF₂, and CF₃? CFCl? SOF were prepared and their ¹⁹F-nmr spectra fully analysed. In CF₃? CFCl? SF₃ the chiral carbon atom leads to a splitting of the two axial fluorine atoms on sulfur. (CF₃? CFCl)₂SF₂ exists in a dl-form with equivalent (sulfur)-F atoms and a meso form with non-equivalent (sulfur)-F atoms. CF₃? CFCl? SOF exists in two diastereomeric forms.     

Perfluoro-4-methyl-1,3-dioxole: a new monomer for high-Tg amorphous fluoropolymers

A 4-Chloro-5-trifluoromethyl-2,2,4-trifluoro-1,3-dioxolane (1) was synthesised by reaction of CF₂(OF)₂ with CF₃CHCFCl; the elimination of HCl from (1) in basic conditions led to the formation of dioxole perfluoro-4-methyl-1,3-dioxole (2). Both these synthetic steps gave the corresponding product in high yield.A new synthetic route for the preparation of CF₃CHCFCl, starting from CF₂ClBr and CH₂CF₂, together with some examples of polymerisation products obtained by reaction of dioxole (2) with fluoroolefins are also reported.     

The addition of fluorine to perhalogenated compounds containing carbon-nitrogen double bonds

The reaction of elementary fluorine with ten perhalogenated compounds containing carbon-nitrogen double bonds is reported. The reactions were carried out without added catalysts in a static system. With CF₃N=CF₂, (CF₃)₂NCF=NCF₃, SF₅N=CF₂, CF₂=NCl, CF₃CF=NCl and CF₂=NF a simple addition of fluorine to the carbon-nitrogen double bond was observed forming the respective N-fluoroamines in high yield. Two imines, CF₃CF=NF and (CF=NF)₂, were unreactive under the same conditions and reactions of CF₃CF₂CF=NF and (CF₃)₂C=NF were explosive.     

Synthesis,Reactivity and Structural Properties of Trifluoromethylphosphoranides

Phosphoranides are interesting hypervalent species which serve as model compounds for intermediates or transition states in nucleophilic substitution reactions at trivalent phosphorus substrates. Herein, the syntheses and properties of stable trifluoromethylphosphoranide salts are reported. [K(18-crown-6)][P(CF₃)₄], [K(18-crown-6)][P(CF₃)₃F], and [NMe₄][P(CF₃)₂F₂] were obtained by treatment of trivalent precursors with sources of CF₃⁻ or F⁻ units. These [P(CF₃)_4-nF_n]⁻ (n=0–2) salts exhibit fluorinating (n=1–2) or trifluoromethylating (n=0) properties, which is disclosed by studying their reactivity towards selected electrophiles. The solid-state structures of [K(18-crown-6)][P(CF₃)₄] and [K(18-crown-6)][P(CF₃)₃F] are ascertained by single crystal X-ray crystallography. The dynamics of these compounds are investigated by variable temperature NMR spectroscopy.     

Synthesis of certain 1,2,4-triazole nucleoside derivatives

The syntheses of 3-amino-4-methyl-1-(β-D-ribofuranosyl)-1,2,4-triazolin-5-one ( 8a ) and its 2′-deoxy analog 8b as well as 5-amino-2-methyl-1-(β-D-ribofuranosyl)-1,2,4-triazolin-3-one ( 12 ) have been accomplished. Compounds 8a and 8b were synthesized via glycosylation of 3-bromo-5-nitro-1,2,4-triazole which was followed by replacement in three steps of the 3-bromo function to yield 3-nitro-1-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)-1,2,4-triazolin-5-one ( 4a ) and its 2′-deoxy analog 4b . Compounds 4a and 4b were methylated at N², hydrogenated and deblocked to give 3-amino-4-methyl-1-(β-D-ribofuranosyl)-1,2,4-triazolin-5-one ( 8a ) and the 2′-deoxy analog 8b . Compound 12 was synthesized by glycosylation of 3-amino-1-methyl-1,2,4-triazolin-5(2H)-one ( 10 ). The structures of 8b and 12 were confirmed by single crystal X-ray diffraction analysis.     

The infrared spectra of gaseous 1,1,3,3-tetrachlorotetrafluoro-4-(trifluoromethyldioxy)butyl trifluoromethyl ether and 1,1,3,3-tetrachlorotetrafluoro-1,4-bis(trifluoromethoxy)butane

1,1,3,3-Tetrachlorotetrafluoro-4-(trifluoromethyldioxy)butyl trifluoromethyl ether, CF₃O(CF₂CCl₂)₂O₂CF₃, was formed as one of the products in the reaction of CF₃O₃CF₃ with CF₂CCl₂ at 322.6 - 342.5 K. It was isolated by fractional condensation between 213 and 243 K and characterized by molecular weight determination and ¹⁹F NMR spectrum. 1,1,3,3-Tetrachlorotetrafluoro-1,4-bis(trifluoromethoxy)butane, CF₃O(CF₂CCl₂)₂OCF₃, was condensed as residue at 193 K from the reaction of CF₃OF with CF₂CCl₂ at 266 - 302.7 K, when [CF₂CCl₂]/[CF₃OF] ≦ 0.5. It was characterized by gas chromatography and molecular weight determination. The infrared spectra of both compounds are given, providing additional support for their characterization.     

Improved Access to Organo‐Soluble Di‐ and Tetrafluoridochlorate(I)/(III) Salts

A facile one‐pot gram‐scale synthesis of tetraalkylammonium tetrafluoridochlorate(III) [cat][ClF₄] ([cat]=[NEt₃Me]⁺, [NEt₄]⁺) is described. An acetonitrile solution of the corresponding alkylammonium chloride salt is fluorinated with diluted fluorine at low temperatures. The reaction proceeds via the [ClF₂]^? anion which is structurally characterized for the first time. The potential application of [ClF₄]^? salts as fluorinating agents is evaluated by the reaction with diphenyl disulfide, Ph₂S₂, to pentafluorosulfanyl benzene, PhSF₅. The CN moieties in acetonitrile and [B(CN)₄]^? are transferred in CF₃ groups. Exposure of carbon monoxide, CO, leads to the formation of carbonyl fluoride, COF₂, and elemental gold is dissolved under the formation of tetrafluoridoaurate [AuF₄]^?.     

Formation of bromodifluoroacetyl fluoride, CF2BrC(O)F, in the thermal gas-phase oxidation of bromotrifluoroethene, CF2CFBr, initiated by trifluoromethylhypofluorite, CF3OF

The oxidation of CF₂CFBr by molecular O₂, initiated by CF₃OF, has been studied at 273, 253.5, 239 and 218 K. The initial pressure of CF₃OF was varied between 0.9 and 2.4 Torr, that of CF₂CFBr between 11.5 and 30.7 Torr and that of O₂ between 42.5 and 100.7 Torr. The main product was CF₂BrC(O)F (yields 81-95% based on the CF₂CFBr consumed). Minor amounts of C(O)F₂ and C(O)FBr and traces of bromotrifluoroethene epoxide were also formed. The reaction is a chain reaction with bromine atoms as chain carriers. Its basic steps are: the thermal generation of CF₃O radical by abstraction of fluorine atom from CF₃OF, chain initiation by addition of CF₃O to the double bond of alkene, leading, in presence of O₂, to the formation of bromine atom and chain propagation by the reaction of bromine atom with CF₂CFBr, originating CF₂BrCFBrO radical. The predominant fate of the latter is the bromine atom extrusion with CC bond scission playing the minor role. The full mechanism is postulated.     

Reaction of ethylene oxide with n-phenylated isomers of 1,2,4-triazoline-3-thione and 1-phenyltetrazoline-5-thione

It is demonstrated that ethylene oxide forms N--hydroxyethyl derivatives of the corresponding triazolin-3-ones in the reaction with 1-phenyl- and 4-phenyl-1,2,4-triazolin-3-thiones and with 3--hydroxyethylthio derivatives of 1-phenyl- and 4-phenyl-1,2,4-triazole in acetic acid. 1-Phenyltetrazolin-5-thione reacts similarly with ethylene oxide. Under the influence of ethylene oxide, 2-methyl-4-phenyl-1,2,4-triazolin-3-thione is converted to 2-methyl-4-phenyl-1,2,4-triazolin-3-one.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 700–703, May, 1971.     

Synthese von (5,10)-(7,8)-Bisepoxiden aus α- und β-4-Phenyl-1,2,4-triazolin-3,5-dion-Addukten von Vitamin D3 und Röntgenstrukturanalyse eines der Benzoylderivate

Oxidation of the α- and β-4-phenyl-1,2,4-triazolin-3,5-dione adducts of vitamin D₃ (2 and1) withMCPBA yields two diastereomeric mixtures of the (5,10)-(7,8)-dioxiranes3 a,3 b,3 c and4 a,4 b respectively. The corresponding benzoates5 a,5 b,6 a and6 b were prepared and the X-ray crystal structure of5 b was determined. This analysis proved5 b to be the (5R, 1 OS)-(7R, 8R)-dioxirane of the β-resp. (6S)-4-phenyl-1,2,4-triazolin-3,5-dione adduct1 of vitamin D₃.     

Reaktionen des fluorcyans,FCN

By reaction of cyanogen fluoride with fluorine compounds like COF₂, SF₄, SOF₄ and HF in the presence of nucleophilic catalysts the addition products CF₃NCO, CF₃NSF₂, CF₃NSOF₂ and CF₃NH₂ could be obtained together with polymer and copolymer products of FCN. By rearrangement and further reaction of intermediates also CF₃OCOF, (CF₃)₂NCOF and the hitherto unknown compounds CF₃N(CN)₂ and F₂CNCF₂NSOF₂ are formed.     

Cu/Pd Synergistic Dual Catalysis: Asymmetric α‐Allylation of an α‐CF3 Amide

Despite the burgeoning demand for fluorine‐containing chemical entities, the construction of CF₃‐containing stereogenic centers has remained elusive. Herein, we report the strategic merger of Cu^I/base‐catalyzed enolization of an α‐CF₃ amide and Pd⁰‐catalyzed allylic alkylation in an enantioselective manner to deliver chiral building blocks bearing a stereogenic carbon center connected to a CF₃, an amide carbonyl, and a manipulable allylic group. The phosphine complexes of Cu^I and Pd⁰ engage in distinct catalytic roles without ligand scrambling to render the dual catalysis operative to achieve asymmetric α‐allylation of the amide. The stereoselective cyclization of the obtained α‐CF₃‐γ,δ‐unsaturated amides to give tetrahydropyran and γ‐lactone‐fused cyclopropane skeletons highlights the synthetic utility of the present catalytic method as a new entry to non‐racemic CF₃‐containing compounds.