Sulfur Tetrafluoride Research Articles

ChemInform Abstract: The First Synthesis of Chiral Dialkylamines with α,α‐Difluoroethers Fragments

Abstractstarting from N‐trimethylsilyl derivatives of α‐aminoacid esters using sulfur tetrafluoride as fluorine source

The first synthesis of chiral dialkylamines with α,α-difluoroethers fragments

The reaction of N-trimethylsilyl derivatives of α-aminoacids esters with sulfur tetrafluoride provides convenient synthetic route to chiral dialkylamines possessing difluoroether fragments.

ChemInform Abstract: A New Synthetic Route to Rhenium and Iodine Oxide Fluoride Anions: The Reaction Between Oxoanions and Sulfur Tetrafluoride.

AbstractOne‐step preparation of [Ag(MeCN)x][ReVIIO2F4] (x = 0, 2, 4) is achieved by addition of excess SF4 to a frozen MeCN solution of Ag[ReO4] at ‐196 °C followed by warming up to room temp.

An approach to (4-fluoroalkyl-1-alkyl-1H-pyrazol-3-yl)methylamines

An approach to the synthesis (4-di- and -trifluoroalkyl-1-alkyl-1H-pyrazol-3-yl)methylamines – promising building blocks for drug discovery and medicinal chemistry is described. The key step of the reaction sequence is fluorination of the corresponding non-symmetric trisubstituted pyrazole derivatives bearing phtalimide moiety with diethylaminosulfur trifluoride or sulfur tetrafluoride. The title compounds are obtained in 5–6 steps from the commonly available materials and 35–36% overall yields.

Lewis acid behavior of SF4 : synthesis, characterization, and computational study of adducts of SF4 with pyridine and pyridine derivatives.

Sulfur tetrafluoride was shown to act as a Lewis acid towards organic nitrogen bases, such as pyridine, 2,6-dimethylpyridine, 4-methylpyridine, and 4-dimethylaminopyridine. The SF4 ⋅NC5 H5 , SF4 ⋅2,6-NC5 H3 (CH3 )2 , SF4 ⋅4-NC5 H4 (CH3 ), and SF4 ⋅4-NC5 H4 N(CH3 )2 adducts can be isolated as solids that are stable below -45 °C. The Lewis acid-base adducts were characterized by low-temperature Raman spectroscopy and the vibrational bands were fully assigned with the aid of density functional theory (DFT) calculations. The electronic structures obtained from the DFT calculations were analyzed by the quantum theory of atoms in molecules (QTAIM). The crystal structures of SF4 ⋅NC5 H5 , SF4 ⋅4-NC5 H4 (CH3 ), and SF4 ⋅4-NC5 H4 N(CH3 )2 revealed weak SN dative bonds with nitrogen coordinating in the equatorial position of SF4 . Based on the QTAIM analysis, the non-bonded valence shell charge concentration on sulfur, which represents the lone pair, is only slightly distorted by the weak dative SN bond. No evidence for adducts between quinoline or isoquinoline with SF4 was found by low-temperature Raman spectroscopy.

A new synthetic route to rhenium and iodine oxide fluoride anions: The reaction between oxoanions and sulfur tetrafluoride

Sulfur tetrafluoride is a reagent for the one-step syntheses of [ReVIIO2F4]−, [IVOF4]−, and [IVIIO2F4]− salts. Pure Ag[ReO2F4] as well as its CH3CN coordination compounds were obtained from CH3CN solvent. The Ag[ReO2F4], [Ag(CH3CN)2][ReO2F4], and [Ag(CH3CN)4][ReO2F4] salts were characterized by Raman spectroscopy. The [Ag(CH3CN)4][ReO2F4]·2CH3CN coordination compound was characterized by single-crystal X-ray diffraction. The reaction of SF4 with KIO4 in anhydrous HF gave the known K[IO2F4] salt. The reaction of [N(CH3)4]IO3 with SF4 in CH3CN yielded the new [N(CH3)4][IOF4] salt, which was characterized by Raman spectroscopy.

Derivatization Technique to Increase the Spectral Selectivity of Two-Dimensional Fourier Transform Infrared Focal Plane Array Imaging: Analysis of Binder Composition in Aged Oil and Tempera Paint

The interpretation of standard Fourier transform infrared spectra (FT-IR) on oil-based paint samples often suffers from interfering bands of the different compounds, namely, binder, oxidative aging products, carboxylates formed during aging, and several pigments and fillers. The distinction of the aging products such as ketone and carboxylic acid functional groups pose the next problem, as these interfere with the triglyceride esters of the oil. A sample preparation and derivatization technique using gaseous sulfur tetrafluoride (SF4), was thus developed with the aim to discriminate overlapping signals and achieve a signal enhancement on superposed compounds. Of particular interest in this context is the signal elimination of the broad carboxylate bands of the typical reaction products developing during the aging processes in oil-based paints, as well as signal interference originating from several typical pigments in this spectral range. Furthermore, it is possible to distinguish the different carbonyl-containing functional groups upon selective alteration. The derivatization treatment can be applied to both microsamples and polished cross sections. It increases the selectivity of the infrared spectroscopy technique in a fundamental manner and permits the identification and two-dimensional (2D) localization of binder components in aged paint samples at the micrometer scale. The combination of SF4 derivatization with high-resolution 2D FT-IR focal plane array (FPA) imaging delivers considerable advances to the study of micro-morphological processes involving organic compounds.

Theoretical study of the hydrolysis of sulfur tetrafluoride

The reaction between sulfur tetrafluorine (SF4) and H2O was computationally investigated using the G4//MP2/6-311G(d, p) theoretical model. Among four reactive channels in the initial attack process, the primary path, which occurred via a SN2 displacement reaction to produce SF3OH, is the rate-determining step in the complete hydrolysis of SF4, resulting in the formation of SO2 (H2SO3). The energy barrier (i.e., 22.48kcalmol−1) in the gas phase will be substantially reduced when catalyzed by H2O and/or HF, and the Berry pseudorotation reaction (BPR) process of SF3OH becomes the rate-controlling step. The hydrolysis mechanism of SF4 in aqueous solution and the activation energy of the rate-determining step using the PCM model do not substantially change compared to the gas phase results. The hydrolysis of SF4 in an aqueous solution has a higher enthalpy. For secondary reactions in aqueous solution, the intermediates are prone to dehydrofluorination instead of hydrolysis. Although the activation energy of SOF2 hydrolysis is higher than that of SF4, the relative energy of the former is lower than that of the latter in aqueous solution. Therefore, SOF2 might be an important intermediate for the formation of SO2.

SF4·N(C2H5)3: the first conclusively characterized SF4 adduct with an organic base

Sulfur tetrafluoride and triethylamine react at low temperatures to form a 1:1 adduct. The unambiguous characterization of the SF(4)·N(C(2)H(5))(3), which is only stable at low temperature, proves the Lewis acid property of SF(4) towards organic Lewis bases. The S-N bond has a length of 2.384(2) Å and is an archetypical example of a dative S(IV) ← N bonding modality.

“Reported, but Still Unknown.” A Closer Look into 3,4-Bis- and 3,4,5-Tris(trifluoromethyl)pyrazoles

Straightforward practical synthetic approaches to 3,4-bis- and 3,4,5-tris(trifluoromethyl)pyrazoles have been developed. The key step of the both syntheses is a transformation of the carboxylic group in a pyrazole core into the trifluoromethyl group by sulfur tetrafluoride. The elaborated synthetic protocols allow gram-scale preparation of the target products. The obtained compounds are comprehensively characterized by means of crystallographic analysis, determination of pK(a) values and fluorescence measurements.

(5S)‐5‐(Trifluoromethyl)pyrrolidin‐2‐one as a Promising Building Block for Fluoroorganic Chemistry

AbstractPyroglutamic acid smoothly reacts with sulfur tetrafluoride at room temperature to afford enantiomerically pure (5S)‐5‐(trifluoromethyl)pyrrolidin‐2‐one (92 % yield, >99 % ee). Representative one‐step transformations of 1 provided both γ‐(S)‐trifluoromethyl GABA and (2S)‐2‐(trifluoromethyl)pyrrolidine on a multigram scale.

Multigram Synthesis of trans-2-(Trifluoromethyl)cyclopropanamine

2-(Trifluoromethyl)cyclopropanamine was synthesized. The key step of the synthesis is a transformation of the carboxy group into the trifluoromethyl group by using sulfur tetrafluoride. Twenty gram of the target product was conveniently prepared in a single batch.

ChemInform Abstract: Fluorinated γ-Alumina. Catalytic Fluorination of 1,1,1- Trichloroethane at Ambient Temperature.

γ-Alumina, fluorinated with sulphur tetrafluoride followed by treatment with 1,1,1-trichloroethane, behaves as a catalyst for the room temperature fluorination of CH3CCl3 with anhydrous HF, giving a mixture of chlorofluorohydrocarbons.

ChemInform Abstract: Alkali Metal Fluorides Supported on Fluorinated γ-Alumina, Lewis Base, and Catalytic Properties.

Abstract Caesium and potassium fluorides supported on fluorinated γ-aluminaare active catalysts for the room temperaturechlorofluorination of sulphur tetrafluoride by chlorinemonofluoride. Maximum catalytic activity is observed at thecomposition 5.5 mmol g -1 in agreement with their behaviourtowards volatile Lewis acids.

A simplified and efficient bromine-facilitated SF 4-preparation method

A novel, simple method for SF 4-preparation has escaped discovery over the last 50 years of sulfur–fluorine chemistry and is described in the present study. Sulfur tetrafluoride is readily produced according to the equation: S + (2 + x)Br 2 + 4KF → SF 4↑ + xBr 2 + 4KBr The reaction is carried out either under autogeneous pressure at ambient or slightly raised temperature in a bomb tube, or in an open system at atmospheric pressure with mild heating and concomitant condensation of the product in a −78 °C cold-trap. Runs from the 5- to the 21-g-scale gave similarly good yields. The new SF 4-producing method may be useful for laboratory preparation, and may also represent a new cost-effective alternative for industrial-scale production of this important fluorination reagent.

Determination of C1–C4 hydrocarbons and sulfur hexafluoride in high-purity germanium tetrafluoride of natural and isotopically enriched composition using gas chromatography

The procedure for gas-chromatographic determination of hydrocarbons and sulfur tetrafluoride in germanium tetrafluoride of natural and isotopically enriched composition was characterized. For improving the efficiency of the chromatographic determination of impurities, it was proposed that the major compound be removed from the test sample with the subsequent cryofocusing of impurity hydrocarbons. The detection limits of C1–C4 and sulfur hexafluoride content were achieved with a plasma ionization detector and electron-capture detector, respectively. They amounted to (2–6) × 106 vol % and 8 × 106 vol %, respectively. The sensitivity of the electron-capture detector is no less than 5 × 105 times higher toward SF6 than that toward hydrocarbons, while the plasma ionization detector is 104 times more sensitive toward hydrocarbons than toward SF6.

Sulfur tetrafluoride methylimide, CH 3N [dbnd]SF 4: Vibrational spectra and quantum chemical calculations

Infrared (gas) and Raman (liquid) spectra of sulfur tetrafluoride methylimide, CH 3N SF 4, were recorded and interpreted. Structural, vibrational and configurational properties were derived from quantum chemical calculations [HF, MP2 and B3LYP methods with 6-311+G(2df,p) basis sets]. The assignment of the normal modes of vibrations was carried out by comparison with analogous molecules and with calculated frequencies and intensities. All theoretical approaches predict the existence of a unique form in the fluid phases which possesses C S symmetry, in good agreement with experimental results.

Electron scattering by sulfur tetrafluoride (SF4) molecules

Absolute total cross section (TCS) for electron scattering from sulfur tetrafluoride (SF4) molecules was measured in a linear transmission experiment at energies ranging from low (0.1 eV) to intermediate (370 eV). Below 1.6 eV the TCS function increases steeply towards lower energies and shows small resonant-like maximum near 0.4 eV. Two other distinct enhancements are located at higher energies: a narrow one is peaked at 12 eV, and a very broad hump is centred near 40 eV. Our experimental TCS results are compared with the previous TCS measurements at low impact energies and at intermediate energies—with our total cross section estimations based on calculations of elastic and ionization cross sections. The TCS for SF4 is also compared with SFn (n = 1, 2, 6) total cross sections.

Clifford V. Heer

Clifford V. Heer

Gas-Phase Fluorination of Films and Coatings Based on Polyvinyl Acetate Dispersions with Sulphur Tetrafluoride

Gas-Phase Fluorination of Films and Coatings Based on Polyvinyl Acetate Dispersions with Sulphur Tetrafluoride