Fluoration de telomeres polyhalogenes par le fluorure de potassium (2ème partie). Synthese d'olefines perfluorees de hauts poids moleculaires

Fluorination of chlorofluorinated telomers of general formula Cl(CFClCF₂)_nCCl₃ (n ? 7) was studied using potassium fluoride in dimethylsulfoxide as fluorinating agent. The reaction leads to a mixture of perfluorinated linear olefins having 15 to 30 carbon atoms : CF₃(CF₂)_pCFCF(CF₂)_mCF₃ (p + m = 2n?3).We perfected a method to determine molecular weights of the telomers by gel permeation chromatography (G.P.C.). The olefins obtained by fluorination are analyzed both by vapor phase chromatography (V.P.C.) and by ¹⁹F nuclear magnetic resonance (N.M.R.).     

Synthese d'ethers et de thioethers allyliques fluores par catalyse par transfert de phase

Several fluorinated allylic ethers, thioethers and diethers have been prepared in excellent yields by phase transfer catalysis (CTP). The used halogenated compounds are allyl chloride and bromide, p-chloromethylstyrene. The used fluorinated alcohols are aromatic pentafluorophenol and various aliphatics: CF₃CH₂OH, CF₂HCF₂CH₂OH ClCF₂CF₂CH₂OH,C₆F₁₃C₂H₄OH, HOCH₂CF₂CFClCF₂CH₂OH and HOC₆H₄C(CF₃)₂C₆H₄OH. All these new compounds have been characterized by ¹H and ¹³C NMR. We conclude that CTP is the best method to obtain allylic and diallylic compounds.     

Synthese d'acides perfluores de hauts poids moleculaires

Perfluorinated olefins of general formula CF₃(CF₂)_pCFCF(CF₂)_mCF₃ (3 ? m + p ? 25) are oxidized by potassium permanganate or ruthenium tetroxide. The linear high molecular weight perfluorinated carboxylic acids so obtained are characterized by ¹⁹F N.M.R. spectroscopy.     

Synthese regiospecifique et identification spectrale de nouveaux amino pyrazoles F-alkyl substitues

In this paper the regiospecific synthesis of new amino-3 (-5)pyrazoles substituted, by a long perfluoroalkyl chain (C₇F₁₅) in the 5 or 3 position is reported. These compounds were obtained by condensation of a hydrazine (substituted or not) with a 2-F-alkyl propynonitrile (R_FCCCN). This reaction gives only one isomer. Each isomer (amino-3 pyrazole or amino-5 pyrazole) was identified by ¹H N.M.R. and ¹⁹F.N.M.R.     

Synthese regioselective de bases de mannich de cetones dissymetriques

Methods for the regioselective synthesis of Mannich bases starting from unsymmetrical ketones are described. The Mannich base on the more substituted carbon is obtained by reaction with (CH₃)₂N⁺CH₂,CF₃CO₂^- in CF₃CO₂H and its isomer on the less substituted carbon with (iPr)₂N⁺CH₂,ClO₄^- in CH₃CN. In the first case, the orientation corresponds to a non-selective attack of the immonium salt on a mixture of enols in which the more-substituted isomer is predominant. In the second ease, use of a bulky immonium salt induces a selectivity favoring the less-substituted enol.     

The preparation of perfluorinated carboxylic esters and perfluoro carbonates

Aliphatic perfluorinated carboxylic esters have been prepared by two methods; (i) the reaction of the potassium salt of perfluoro 3-ethyl pent-3-ol, KOC(C₂F₅)₃, with perfluoro acid chlorides R_fCOCl, to yield perfluorinated esters of composition R_fCOOC(C₂F₅)₃, and (ii) the reaction of carbonyl chloride or thionyl chloride with a mixture of the potassium salt KOC(C₂F₅)₃ and perfluoro acid salts of the general formula KOCOR_f in a polar solvent. The product ester has the composition R_fCOOC(C₂F₅)₃, and in this instance carbon dioxide or sulphur dioxide is liberated during the reaction. A qualitative study of the thermal decomposition of a perfluoro ester has been made.A tertiary perfluoro carbonate of composition [(C₂F₅)₂CF₃CO]₂CO has been prepared by the reaction of phosgene with the potassium salt KOC(C₂F₅)₂CF₃ in a polar solvent. The intermediate acid chloride (C₂F₅)₂CF₃COCOCl can be isolated.     

Synthese,structure cristalline et analyse vibrationnelle de l'hexathiohypodiphosphate de lithium Li4P2S6

The crystalline compound Li₄P₂S₆ is obtained either by devitrification of Li₄P₂S₇ glass at 450°C with sulfur formation or by crystallisation at 450°C of a Li₂S, P and S melt. The structure determination has been solved by X-ray diffraction on a monocrystal. The unit cell is hexagonal $\text{P6}{}_3\text{mcm}$ with a = 6.070(4), c = 6.577(4) Å, V = 209 ų, Z = 1. Intensities were collected at 293°K with Kα (λ = 0.71069 Å) Mo radiation on an automatic Nonius CAD-4 diffractometer. The structure was solved under the assumption of random disorder of P atoms over two sites (occupancy factor of 0.5). Anisotropic least-squares refinement with W = 1 gave R = 0.047 for 90 independent reflections and 9 variables. The structure is built according to an ABAB sequence sulfur packing. Per unit cell, four out of six octahedral sites are occupied by Li ions, and the other two are statistically filled (0.5) by PP pairs. The PP central bond (2.256(13) Å) links two staggered PS₃ groups (PS = 2.032(5) Å) to form the D_3d symmetry P₂S^4?₆ anion. Infrared and Raman spectra show features very similar to those of Na₄P₂S₆, 6H₂O and M^IIPS₃ compounds. A new assignment in terms of symmetry species is proposed for the P₂S₆ internal modes, which is confirmed by a normal coordinate calculation using a valence force field; the stretching force constants f_PP and f_PS are equal to 1.6 and 2.7 mdyne Å^?1, respectively.     

Synthese de l'acide β fluoroacrylique (fluoro-3 propenoique)

Regioselective Bayer-Villiger oxidation of 2-chloro-2-fluoroethyl-isopropyl ketone ($\text{1}$) gives isopropyl-3-chloro-3 fluoropropionate ($\text{2}$). The dehalogenation of ester ($\text{2}$) with trimethylamine gives isopropyl-3-fluoropropenoate ($\text{3}$). Ester cleavage by trimethylsilyl iodide, in the presence of cyclohexene oxide, gives $\text{trans}$-3-fluoropropenoic acid ($\text{4}$).     

Etude RMN de β-hydroxy-phosphonates-esters. Détermination du signe du couplage stéréospécifique 4J(P?C?C?O?H) dans le diastéréoisomère RS,RS

INDOR experiments indicate ⁴J(P? C? C? O? H) to be positive for the β-hydroxyphosphonate ester RS,RS dissolved in (CD₃)₂CO or (CD₃)₂SO. The higher value observed in (CD₃)₂SO than in (CD₃)₂CO shows that a W geometry makes this coupling constant more positive.     

Preparation de β-cetonitriles via l'acylation du cyanacetate de trimethylsilyle par les anhydrides mixtes.

β-ketonitriles R¹COCH₂CN and R¹COCH(R²)CN are respectively prepared from (CH₃)₃SiOCOCHLiCN or R²CHLiCN by acylation reaction with mixed anhydrides RCOOCO₂Et.     

Thermal decomposition of η5-cyclopentadienyl-η2-propenealkylnickel complexes

Thermolysis of compounds of the type CpNiR (η²-propene) (R = CH₃ (1), CD₃ (2), CH₂CH₃ (3), CH₂CH₂CH₃ (4) and CH₂SiMe₃ (5)) was studied. The methyl complex 1 gives mainly methane, ethane and (CpNi)₃CH. Toluene-d₈ has no effect on the composition of the gaseous products and does not yield gases containing deuterium. In the CD₃ complex 2 a HD exchange reaction between the complexed propene and the CD) group takes place. Decomposition of the trimethylsilylmethyl complex 5 gave tetramethylsilane. The complexes 3 and 4 containing a β-hydrogen atom, decompose via a β-elimination reaction giving the corresponding olefin. The unstable {CpNiH} formed in the reaction reacts with {CpNiR} giving the corresponding alkane and a mixture of non-isolated cyclopentadienylnickel clusters. The complexes studied undergo insertion of the coordinated olefin into the NiC σ-bond, which results in the formation of higher hydrocarbons.     

Synthese de nouveaux acides sulfoniques et de sila-sultones ethyleniques

The sulfonation of 1-sila-3-clopentenes and corresponding silabicyclohexanes by CISO₃SiMe₃ leads to novel ethylenic silasultones which are hydrolyzed to their sulfonic acids. Depending upon the degree of substitution of the double bond or cyclopropane ring, a competition may occur between the usually observed C-Si bond cleavage and the until now more rarely observed CH cleavage. An interpretation of these results is proposed.     

The scale of reagent migration in the reaction CH3 + CH3CO2− in crystalline sodium acetate trihydrate

The ESR method has been applied to studies on the reaction CH₃ + CH₃CO₂^? → CH₄ + CH₂CO₂^? in a NaAc3H₂O lattice consisting of a CH₃CO₂Na/CD₃CO₂Na mixture. It has been shown that: (i) the CH₃ radical is at a lattice point in the position occupied by a methyl group in an undamage molecule; (ii) an arbitrary point near a radical is occupied equiprobably by either an H- or D-molecule; (iii) when a transferred H atom is substituted by a D, the isotropic effect is no less than 40. The scale of reagent migration during the reaction has been estimated.     

Synthese et reactivite d'organomagnesiens perfluores. V.[1] Synthese et identification de nouveaux composes perfluoroalkyles du mercure a chaine longue.

The reaction of mercuric salts HgY₂ or organic mercuric compounds R_HHgX with long chain perfluorinated Grignard reagents R_FMgBr leads to a series of new perfluoroalkyl mercury derivatives with the general formula R_FHgZ (R_F=C₄F₉, C₆F₁₃, C₈F₁₇ ; Z=R_F,R_H,Y with Y = I,Br,Cl, NO₃,OCOCH₃,OCOCF₃).The synthesis of these organomercuric compounds is described, and their spectroscopic properties are reported.     

X-ray study of the molecular structure of α-mercury and α-platinummercury derivatives of l-menthyl phenylacetate

The molecular structures of the L-menthyl ester of S-α-bromomercuriphenyl-acetic acid, diastereomer II, [α]²⁰_D ?18°, and of the related L-menthyl ester of α-bromobis(triphenylphosphine)platinummeruriphenylacetic acid, VI, have been investigated by the X-ray method. Insertion of L₂Pt carbenoid appears to occur into the HgBr bond in II and two phosphine ligands in the product VI occupy cis positions in a planar square around the platinum atom. The HgPt distance is 2.50 Å; there is intermolecular HgBr coordination in II, the distance being 3.23 Å.     

Synthesis of pyridine N-imine complexes of methylcobaloxime and reactions of bis(dimethylglyoximato)methyl(Pyridine N-imine)cobalt with acid anyhydrides and acetylenedicarboxylic acid dimethyl ester

Pyridine N-imine complexes of methylcobaloxime, CH₃Co(Hdmg)₂(R¹— C₅H_nN⁺N^?H) (n = 4; R¹ = H, 2-CH₃, 3-CH₃, 4-CH₃: n = 3; R¹ = 2,6-CH₃), have been synthesized by the reaction of CH₃Co(Hdmg)₂S(CH₃)₂ with a pyridine N-imine which is generated from a pyridine, hydroxylamine-O-sulfonic acid and K₂CO₃. The reactions of CH₃Co(Hdmg)₂(C₅H₅N⁺N^?H) with acid anhydrides form new methylcobaloxime complexes with N-substituted pyridine N-imines, CH₃Co(Hdmg)₂(C₅H₅N⁺N^?R²) R² = COPh, COMe, COEt). With maleic anhydride, (pyridine N-acryloylimine)carboxylic acid is formed. With acetylenedicarboxylic acid dimethyl ester, 1,3-dipolar cycloaddition of the ligand gives pyrazolo[1,5-a]pyridine-2,3-dicarboxylic acid dimethyl ester.     

Ions α-cetocarbenium. Influence de la structure sur l'evolution des ions α-cetocyclohexylcarbenium

α-Ketocyclohexylcarbenium ions are formed by dehalogenation in HgSbF₆Ch₂Cl₂ of the corresponding α-bromo carbonyl compounds 6,7, 8 and 9. In this medium they lead principally to bicyclic oxonium salts, the structure of which depends on the group adjacent to the carbonyl group, and positions of ring substituents. By a suitable choice of Y, it is possible to “functionalise” an α-keto cyclohexane system in either 3 or 4 positions.     

Extension de la reaction de Wittig: Condensation “d'ylures enolates” sur les cetones aliphatiques

The enolate ylide Ph₃P⁺C^?C(Ph)O^?Li₊ obtained by the reaction of HMPT-Li with the benzoylmethylenetriphenylphosphorane Ph₃PCHCOPh reacts with aliphatic ketones, in contrast to its precursor. This condensation makes it possible to prepare β,γ-unsaturated ketones, of type RCHC(R′)CH₂COPh, instead of the α,β isomer usually obtained in a Wittig reaction.     

Nitroxydes-LXVIII : Synthese et etude cinetique de la decomposition du t-butyl isopropyl nitroxyde. Effet isotopique

Decomposition of t-butyl isopropyl nitroxide and its β²H-labelled homologue has been examined by UV and EPR. The bimolecular reaction does not show reversible formation of a dimer, but exhibits an isotope effect (k_H/k_d)_30°C?9 which shows that the rupture of the CH bond is involved in the slow step of the decomposition. The β proton coupling constant, determined by NMR, is +1.84 G.     

Vibrational spectra and normal co-ordinate analysis of CF3 compounds. Trimethyl(trifluoromethyl)silane,CF3Si(CH3)3 and CF3Si(CD3)3

The i.r. gas and Raman liquid spectra of CF₃Si(CH₃)₃ and CF₃Si(CD₃)₃ are reported and assigned for C_3vsymmetry. Force constants have been calculated by a combined analysis of both isotopomers yielding ƒ (SiCF₃) 2.63, ƒ (SiCH₃) 3.07 and ƒ (CF) 5.70 N cm⁻¹. The apparent weakness of the SiCF₃ bond confirms the results obtained on other CF₃ silanes and is discussed with respect to related molecules.