Ring Opening of Diketene in Superacidic Media.

The reactions of diketene were investigated in the HF/MF and DF/MF (M = As or Sb) binary superacidic systems. Depending on the stoichiometric ratio of the Lewis acids and diketene, monoprotonated acetoacetyl fluoride and diprotonated acetoacetyl fluoride were obtained. The salts were characterized by low-temperature vibrational spectroscopy, nuclear magnetic resonance spectroscopy, and single-crystal X-ray diffraction.

The crystal structures of methyl prop-2-ynoate, dimethyl fumarate and their protonated species.

Methyl prop-2-ynoate (CHO) was investigated in the binary superacidic system HF/MF (M = Sb or As) and dimethyl fumarate (CHO) in the superacidic system HF/SbF, as well as HF/BF. The starting materials methyl prop-2-ynoate and dimethyl fumarate were crystallized, the former for the first time. The protonated species of these esters, namely, (1-methoxyprop-2-yn-1-ylidene)oxidanium hexafluoroarsenate, CHO AsF, 1,4-dimethoxy-4-oxobut-2-en-1-ylidene]oxidanium tetrafluoroborate bis(hydrogen fluoride), CHO BF 2HF, and hemi{[1,4-dimethoxy-4-oxidaniumylidenebut-2-en-1-ylidene]oxidanium} undecafluorodiantimonate, 0.

Deoxyfluorination with superacids - synthesis and characterization of protonated α-fluorohydroxyacetic acid.

α-Fluoroalcohols describe a rare and unstable class of compounds, accessible mainly by fluorination of highly electrophilic carbonyl compounds. In this work, we report the syntheses of α-fluorohydroxyacetic acid (FHA) and its acyl fluoride (FHA-F) by reacting the dihydroxy species glyoxylic acid monohydrate (GAM) with SF. Surprisingly, only one of the geminal hydroxy groups is substituted when excess SF is employed.

Space Molecules in Superacidic Media─The Synthesis and Structure of Monoprotonated Cyanoacetylene and Diprotonated Dicyanoacetylene.

The molecules cyanoacetylene and dicyanoacetylene detected in the atmosphere of Saturn's largest moon Titan were investigated in superacidic media F/F ( = H, D; = As, Sb), F/GeF, and F/BF. Cyanoacetylene is obtained as a monoprotonated salt, while only the diprotonated salt of dicyanoacetylene has been isolated. The salts were characterized by vibrational spectroscopy, NMR spectroscopy, and single-crystal X-ray diffraction.

Synthesis and Stabilization of Highly Reactive Haloacetylium Ions.

The reactions of selected haloacetyl fluorides with the strong Lewis acids AsF and SbF were investigated in the aprotic solvent SOClF. Depending on the stoichiometric ratio of AsF or SbF and the haloacetyl fluorides, either -coordinated adducts or the respective haloacetylium ions were isolated as solids. The compounds were characterized by low-temperature vibrational spectroscopy and single-crystal X-ray diffraction.

The electrophilic methylating agent [SOMe] parent of two cationic species.

Methylfluoride and hydrogen fluoride react with powerful methylating agent [SOMe] in a temperature-dependent addition reaction to form methylated fluorosulfuric acid [FS(OMe)][SbF] and methylated fluorosulfuric acid methyl ester [FS(OH)(OMe)][SbF], respectively. The obtained methylated fluorosulfinic acid and methylated fluorosulfinic acid methyl ester were characterized by single X-ray structure analysis and vibrational spectroscopy.

Synthesis and Structure of Protonated Propiolic Acid.

Propiolic acid was investigated in the superacidic system F/SbF ( = H, D). The salts of the monoprotonated species of propiolic acid were characterized by vibrational and NMR spectroscopy as well as single-crystal analyses. The rotational conformers of the protonated species can be distinguished by NMR spectroscopy via the temperature-dependent rotational barrier.

Na[GeF]·2HF: the first quarternary phase in the H-Na-Ge-F system.

The structure of cis- or trans-bridged [GeF] anionic chains have been investigated [Mallouk et al. (1984). Inorg.

Accumulation, Characterization and Reactivity of Chiral Ammonium-Carboxonium Dications in Superacid.

The accumulation of chiral ammonium-oxocarbenium dications in superacid is evidenced by low-temperature NMR spectroscopy, X-ray diffraction analysis and confirmed by DFT calculations. Its potential for the diastereoselective remote hydrofunctionalization of non-activated alkene is also explored.

Synthesis and Structure of the Small Superelectrophile [C(OH)Me].

The acid-activation of 1,2-dicarbonyl compounds plays a key role in a variety of electrophilic reactions, some of which are only accessible in superacidic media when a superelectrophilic dication is formed. To obtain structural and electronic information about these elusive species, the vicinal dication [C(OH)Me] is synthesized and characterized by Raman spectroscopy and X-ray diffraction. Since this superelectrophile could not be stabilized in convenient superacids, the usage of liquid SO turned out to be crucial.

Two Roomtemperature-stable Trications - Triprotonated Triamino- and Tricyanobenzene.

Protonation of 1,3,5-tricyano- and 1,3,5-triaminobenzene was achieved in various superacidic media, resulting in the formation of the respective trinitrilium and triammonium species. Furthermore, the respective N-methyl nitrilium species was synthesized by methylation. Characterization was performed by NMR and vibrational spectroscopy, followed by single-crystal X-ray diffraction analyses of selected species.

Strengthening of the C-F Bond in Fumaryl Fluoride with Superacids.

The reaction of fumaryl fluoride with the superacidic solutions XF/MF (X=H, D; M=As, Sb) results in the formation of the monoprotonated and diprotonated species, dependent on the stoichiometric ratio of the Lewis acid to fumaryl fluoride. The salts [C H F O ] [MF ] (M=As, Sb) and [C H X F O ] ([MF ] ) (X=H, D; M=As, Sb) are the first examples with a protonated acyl fluoride moiety. They were characterized by low-temperature vibrational spectroscopy.

Ring Opening Reactions of β-Propiolactam in Superacidic Media.

The reaction of β-propiolactam in the superacidic systems HF/MF (M=Sb, As) led to the formation of monoprotonated 3-aminopropanoyl fluoride in the form of [C(O)F(CH ) NH ][SbF ] and [C(O)F(CH ) NH ][AsF ]. In the presence of traces of water, the diprotonated species β-alanine [C(OH) (CH ) NH ][AsF ] was synthesized for the first time. All salts were characterized by low-temperature infrared and Raman spectroscopy.

Protonated Ethylene Carbonate: A Highly Resonance-Stabilized Cation.

Invited for this month's cover picture is the group of Prof. Andreas J. Kornath at the LMU in Munich (Germany).

Protonated Ethylene Carbonate: A Highly Resonance-Stabilized Cation.

Salts containing the monoprotonated ethylene carbonate species of were obtained by reacting it with the superacidic systems XF/MF (X=H, D; M=Sb, As). The salts in terms of [C H O ] [SbF ] , [C H O ] [AsF ] and [C H DO ] [AsF ] were characterized by low-temperature infrared and Raman spectroscopy. In order to generate the diprotonated species of ethylene carbonate, an excess of Lewis acid was used.

Fluoromethyl-2,4,6-trinitrophenylsulfonate: A New Electrophilic Monofluoromethylating Reagent.

Fluoromethyl-2,4,6-trinitrophenylsulfonate has been prepared for the first time and qualified as a simple to use monofluoromethylating reagent. Its molecular structure in the solid state has been determined by single-crystal X-ray diffraction studies. This reagent proves to be effective for the electrophilic introduction of a CHF group into selected chalcogen and nitrogen nucleophiles.

Protonation of γ-Butyrolactone and γ-Butyrolactam.

Invited for this month's cover is the group of Andreas Kornath at the Ludwig-Maximilian University of Munich (Germany). The cover picture shows the crystal structures of protonated γ-butyrolactone ([(CH ) OCOH][AsF ]) and γ-butyrolactam ([(CH ) NHCOH][AsF ]). Both salts were synthesized by reacting the neutral compounds in the superacidic system HF/AsF at low temperature.

Protonation of γ-Butyrolactone and γ-Butyrolactam.

γ-Butyrolactone and γ-butyrolactam were reacted in the superacidic systems XF/MF (X=H, D; M=As, Sb). Salts of the monoprotonated species of γ-butyrolactone were obtained in terms of [(CH ) OCOH] [AsF ] , [(CH ) OCOH] [SbF ] and [(CH ) OCOD] [AsF ] and the analogous lactam salts in terms of [(CH ) NHCOH] [AsF ] , [(CH ) NHCOH] [SbF ] and [(CH ) NDCOD] [AsF ] . The salts were characterized by low temperature Raman and infrared spectroscopy and for both protonated hexafluoridoarsenates, [(CH ) OCOH] [AsF ] and [(CH ) NHCOH] [AsF ] , single-crystal X-ray structure analyses were conducted.

Structures and Properties of -1,3,3,3-Tetrafluoro- propene (HFO-1234ze) and 2,3,3,3-Tetrafluoropropene (HFO-1234yf) Refrigerants.

The refrigerant 1,3,3,3-tetrafluoropropene (HFO-1234ze) is used as a replacement for former cooling agents that have been phased-out due to their global warming potential or ozone depleting potential. Although it is used on a large scale, only a few vibrational data and no structural data of HFO-1234ze are known. We report structure determinations based on low-temperature single-crystal X-ray diffraction data as well as gas-phase diffraction data of HFO-1234ze and HFO-1234yf (2,3,3,3-tetrafluoropropene).

Evidence and exploitation of dicationic ammonium-nitrilium superelectrophiles: direct synthesis of unsaturated piperidinones.

Exploiting superacid activation, the reactivity of aminonitriles was enhanced through the transient formation of highly reactive ammonium-nitrilium superelectrophiles. Demonstrated by using in situ low-temperature NMR experiments and confirmed by X-ray diffraction analysis, these dications can be intramolecularly trapped by non-activated alkenes to generate unsaturated piperidinones, including enantioenriched ones, in a straightforward way.

Evidence of Phosphonium-Carbenium Dication Formation in a Superacid: Precursor to Fluorinated Phosphine Oxides.

Unambiguously confirmed by low-temperature in situ NMR experiments, X-ray diffraction and vibrational spectroscopy, phosphonium-carbenium superelectrophiles are shown to be generated in strong acidic conditions. Representing crucial intermediates, their exploitation allows for the synthesis of unprecedented fluorinated (cyclic) phosphine oxides.