Synthesis and reactions of 2-SF5-butadiene

A stable and storable precursor of 2-SF₅-butadiene, 3-SF₅-3-sulfolene, has been synthesized and its reactivity studied with several olefinic compounds. When SF₅Br is added to sulfolene, 3-bromo-4-SF₅-sulfolane is formed and when reacted further with silver tosylate forms 4-SF₅-2-sulfolene. The 4-SF₅-2-sulfolene undergoes rearrangement with silicic acid to give 3-SF₅-3-sulfolene and when heated forms 2-SF₅-butadiene; in the absence of a dienophile, dimerization does occur. The new 2-SF₅-butadiene is a reactive diene undergoing a Diels-Alder reaction with olefinic sytems such as maleic anhydride, p-naphthoquinone, and methyl acrylate.     

Synthesis of 5-pentafluorosulfanyl indazoles

An efficient method for the synthesis of 5-SF₅ substituted indazoles from commercially available 4-nitro-(pentafluorosulfanyl)benzene through vicarious nucleophilic substitution of hydrogen (VNS) reaction, reduction of nitro group and cyclization of resulting anilines were described. Transformations of 5-SF₅-indazoles led to a variety of SF₅-substiuted heteroarenes that can serve as a versatile building block for diversity-oriented organic synthesis.     

Palladium-Catalyzed Regioselective Synthesis of 2-SF5-Indenols and Further Derivatizations

A palladium-catalyzed synthesis of 2-SF₅-indenols has been developed by reacting commercially available boronic acid derivatives and readily accessible SF₅-alkynes. The present methodology is fully regioselective thanks to the intrinsic polarization of SF₅-alkynes. A selection of downstream functionalizations has been performed to highlight the versatility of 2-SF₅-indenols and indenones as platforms for the design of more complex SF₅-containing molecules.     

Regio- and Stereoselective Hydroelementation of SF5-Alkynes and Further Functionalizations.

Herein is described a fully regio- and stereoselective hydroelementation reaction of SF₅-alkynes with N, O and S-nucleophiles and further functionalization of the corresponding Z-(hetero)vinyl-SF₅ intermediates, a suitable platform to access α-SF₅ ketones and esters, β-SF₅ amines and alcohols under mild reaction conditions. Experimental and computational comparative studies between SF₅- and CF₃-alkynes have been performed to highlight and explain the difference of reactivity and selectivity observed between these two fluorinated motifs.     

New pentafluoro-λ-sulfanyl (SF5) perfluoroalkyl benzene derivatives

Preparation of the following new SF₅-perfluoroalkyl benzene derivatives, m-SF₅CF₂CF₂C₆H₄X (X=NO₂, NH₂, OH, I, NHCOCH₃, SO₂Cl, SO₃H, SO₃K) has been achieved. The new compounds were characterized by their respective IR, NMR and HRMS or elemental analysis.     

New acrylate systems: derivatives of β-SF5-acrylic acid

Addition of pentafluorothio bromide, SF₅Br, to ethyl propiolate results in an 1:1 adduct, SF₅CHCBrC(O)OC₂H₅, and a small amount of a 1:2 adduct. The former is converted by reduction to the corresponding β-SF₅-acrylic ester, SF₅CHCHC(O)OC₂H₅. Treatment of SF₅CH₂CBr(CH₃)C(O)OCH₃ with base produces methyl-β-SF₅-methacrylate, SF₅CHC(CH₃)C(O)OCH₃. The preparation and characterization of these new compounds are described.     

Site directed synthesis of mono and disubstituted SF5-polyfluoroalkyl benzenes

A novel method for the preparation of o-, m-, p-SF₅CF₂CFYC₆H₄X (Y = Br, F and X = m-Br, p-Br, Cl, CH₃, CF₃, NO₂, o-NO₂, F, CF₃, CH(CH₃)₂) derivatives was devised by a two-step reaction: SF₅Br-addition to o-, m-, p-CF₂CFC₆H₄X followed by reaction of AgBF₄ with the o-, m-, p-SF₅CF₂CFBrC₆H₄X adducts. Additional studies have been carried out with several derivatives and includes the preparation of SF₅CF₂C(O)C₆H₅, p-CF₃CFBrC₆H₄NO₂, SF₅CF₂CF₂C₆H₃(NO₂)₂, SF₅CF₂CF₂C₆H₃(NH₂)₂, and an SF₅CF₂CF₂-containing polyimide and dye. The complete characterization (IR, NMR, and MS) of these compounds is given.     

New aromatic pentafluoro-λ-sulfanyl (SF5) derivatives, m-SF5(CF2)2C6H4X: (X = N3, Br, OC(O)CHCH2, CHCH2)

Preparation of the following new m-SF₅CF₂CF₂C₆H₄X derivatives has been achieved: X=N₃(2), Br(3), OC(O)CHCH₂(4), CHCH₂(5). The compounds were characterized by their respective IR, NMR, mass spectra (MS) and high resolution mass spectrometry (HRMS). An improved yield of SF₅(CF₂)₂C₆H₅ (1) is also reported along with the synthesis of the polyacrylate (6) and polystyrene (7) from their respective monomers.     

Synthesis and characterisation of 3- and 4-(pentafluorosulfanyl)benzoic acid derivatives: X-ray structure of 3-SF5-C6H4-COOH

The high yield synthesis of 3- and 4-(pentafluorosulfanyl)benzoic acid derivatives is described starting from the NO₂-derivatives, which are reduced to the corresponding anilines. Then the NH₂- group is converted to bromide and subsequently to the HCO moiety. The benzaldeydes are then oxidised to the corresponding benzoic acids. The X-ray structure of 3-SF₅-C₆H₄-COOH is also reported.     

CO2 laser-induced interaction between sulfur hexafluoride and carbon disulfide

Interaction between carbon disulfide and sulfur hexafluoride is excited by cw CO₂ laser radiation and has been investigated for different ratios over a pressure range from 3.1 to 34.6 kPa. The reaction yields sulfur tetrafluoride, sulfur, carbon, thiocarbonyl fluoride, tetrafluoromethane and hexafluoroethane, the ratio of these latter products is dependent on the partial pressure of sulfur hexafluoride in the initial CS₂-SF₆ mixture. Interaction is considered to include both the SF₆-sensitized decomposition of carbon disulfide and reaction between sulfur hexafluoride and carbon disulfide.     

Resonant two-photon ionization spectroscopy of C6H6-(SF6)1,2

Vibrationally resolved electronic spectra of heteroclusters C₆H₆-SF₆ and C₆H₆-(SF₆)₂ were studied in the spectral regions near the S₀-S₁, 0 ₀ ⁰ and 6 ₀ ¹ transitions of the benzene monomer. A nonvanishing 0 ₀ ⁰ vibrational band has been observed for C₆H₆-SF₆ with a C_3v symmetry. For both clusters we have determined the ionization potentials as well as the binding energies in the electronic ground state and the ionization state. The fragmentation of larger clusters (C₆H₆)_n(SF₆)_m is restricted to the loss of SF₆ molecules while the emission of C₆H₆ molecules have not been observed.     

Total synthesis of fluvirucinine A1

An efficient and highly stereocontrolled convergent synthesis of fluvirucinine A₁ is reported herein. In fluvirucinine A₁ both C₅-C₁₃ and C₁-C₄ fragments were accessed from a common intermediate 6 derived from (S)-Roche ester in 15 and 7 steps, respectively. The key steps involve Evans asymmetric alkylation, Sharpless asymmetric epoxidation, amidation and a ring-closing metathesis reaction (RCM) for macrocyclization.     

Ring-closing iodoamination of homoallylic amines for the synthesis of polysubstituted pyrrolidines: application to the asymmetric synthesis of (−)-codonopsinine

Ring-closing iodoamination of (E)-configured, N-α-methyl-p-methoxybenzyl protected homoallylic amines upon treatment with I₂ and NaHCO₃ in MeCN occurs with concomitant loss of the N-α-methyl-p-methoxybenzyl group to give 3-iodopyrrolidines in >99:1 dr. This transformation was used as one of the key steps in the total asymmetric synthesis of (?)-codonopsinine, which was achieved in seven steps (from commercially available tert-butyl crotonate) in 5% overall yield and >99:1 dr.     

A novel asymmetric synthesis of oseltamivir phosphate (Tamiflu) from (−)-shikimic acid

Oseltamivir phosphate 1 was synthesized starting from a readily available acetonide, that is, ethyl (3R,4S,5R)-3,4-O-isopropylidene shikimate 2, through a new route via 11 steps and in 44% overall yield. The synthesis described in this article is characterized by two particular steps: the highly regioselective and stereoselective facile nucleophilic replacement of an OMs by an N₃ group at the C-3 position of ethyl (3R,4S,5R)-3,4-O-bismethanesulfonyl-5-O-benzoyl shikimate 5, and the mild ring-opening of an aziridine with 3-pentanol at the C-1 position of ethyl (1S,5R,6S)-7-acetyl-5-benzoyloxy-7-azabicyclo[4,1,0]hept-2-ene-3-carboxylate 8.     

Oxidative cyclization of N-alkyl-o-methyl-arenesulfonamides to biologically important saccharin derivatives

Various biologically important saccharin skeletons and their N-alkyl derivatives have been efficiently prepared by chromium(VI) oxide catalyzed H₅IO₆ oxidation of N-alkyl-o-methyl-arenesulfonamides in acetonitrile. N-tert-Butyl saccharin skeletons were easily prepared by H₅IO₆-CrO₃ oxidation of N-tert-butyl-o-methyl arenesulfonamides in the presence of acetic anhydride. The method that furnished the novel fluoro and trifluoromethyl substituted saccharin skeletons is characterized by two steps, a simple work-up procedure, a single purification and good overall yields from substituted toluene derivatives.     

The thioacetate approach to vitamin D analogues. Part 2: Synthesis of (25S)-23-thia-1α,25,26-trihydroxyvitamin D3

(25S)-23-Thia-1α,25,26-trihydroxyvitamin D₃ (4) was prepared from alcohol 5 in 56% overall yield (five steps) using our previously developed methodology. Alcohol 5 was synthesized from commercially available vitamin D₂.     

Synthesis of a new precursor to the nicotinic receptor tracer 5-IA-85380 precursor using trimethylsilyl iodide as deblocking agent

We describe the synthesis of a new precursor of 5-IA-85380, specific radiotracer for α₄β₂ nicotinic acetylcholine receptors. (S)-5-Trimethylstannyl-3-(2-azetidinylmethoxy)pyridine (4) was prepared in six steps and 62% overall yield starting from (S)-2-azetidinecarboxylic acid. The key step of this synthesis is selective release of the amine function without removing the stannyl moiety using trimethylsilyl iodine.     

Synthesis of cis,cis,cis-1-alkylidene-2,3,4,5-tetrakis(diphenylphosphinomethyl)cyclopentanes

A new strategy to prepare tetradentate or pentadentate diphenylphosphine ligands has been explored from Diels-Alder adducts of fulvenes and maleic anhydride. A tetradentate phosphine ligand, bearing a side chain allowing the formation of a bond with polystyrene resin, has been prepared in seven steps from cyclopentadiene. The cis,cis,cis-1-cyclohexylidene-2,3,4,5-tetrakis(diphenylphosphinomethyl)cyclopentane (Cyclo-Tedicyp) in combination with [PdCl(C₃H₅)]₂ led to an efficient catalyst for the Heck, Suzuki and Sonogashira coupling reactions.     

Polarographie de quelques halogénures organostanniques dans le diméthylformamide

The polarographic behavior of compounds R_nSnX_4?n with R=CH₃, C₂H₅, C₆H₅; X=Cl,Br and n=0–3, on a dropping Hg electrode, in dimethylformamide, has been examined and for all cases, reduction pathways have been proposed; the most important features being: the disappearance of the second one-electron step for chlorotrimethyl(ethyl)tin, the observation of two one-electron steps for R₂SnBr₂ dibromides, the easy complexation of R₂SnCl₂ and RSnCl₃ compounds by chloride ions, and the discrete steps involving 2 and 1 electrons for tribromo(ethyl)tin.     

Radical mediated stereoselective synthesis of (4R,8R)-4,8-dimethyldecanal, an aggregation pheromone of Tribolium flour beetles

(4R,8R)-4,8-Dimethyldecanal, a common aggregation pheromone of Tribolium flour beetles, has been synthesized from (R)-2,3-O-isopropylideneglyceraldehyde in 11 steps and 7% overall yield. The key step in the synthesis is the highly diastereoselective chelation-controlled radical reaction of ethyl (4S,5R)-4-benzyloxy-5,6-(isopropylidenedioxy)-2-methylenehexanoate with ethyl (R)-5-iodo-3-methylpentanoate performed in the presence of 7 equiv of MgBr₂·OEt₂.