Activated difluoride

Table 11 describes the thermal properties of polyether sulfone based on DCDPS and heteroarylenediol. The TgS range from 230 to 315°C and the decomposition temperature is higher than 450°C. Their thermal stability depends on the bisphenol and activated difluoride used in the polymer synthesis (Tables 10 and 11). 

Phenolphthalein reacts with hydroxylamine to give 4-aminophenol and 2(4-hydroxybenzoyl)benzoic acid in high yield. 2-(4-Hydroxybenzoyl)benzoic acid reacts with hydrazine to yield phtlialazinone.194 This monomer behaves like a bisphenol and reacts with activated difluorides (Scheme 6.25).195 The resulting poly(arylene ether)s have high glass transition temperatures (over 265°C). 

Bismuth pentafluoride is an active fluorinating agent. It reacts explosively with water to form ozone, oxygen difluoride, and a voluminous chocolate-brown precipitate, possibly a hydrated bismuth(V) oxyfluoride. A similar brown precipitate is observed when the white soHd compound bismuth oxytrifluoride [66172-91 -6] BiOF, is hydrolyzed. Upon standing, the chocolate-brown precipitate slowly undergoes reduction to yield a white bismuth(Ill) compound. At room temperature BiF reacts vigorously with iodine or sulfur above 50°C it converts paraffin oil to fluorocarbons at 150°C it fluorinates uranium tetrafluoride to uranium pentafluoride and at 180°C it converts Br2 to bromine trifluoride, BrF, and bromine pentafluoride, BrF, and chlorine to chlorine fluoride, GIF. It apparently does not react with dry oxygen. 

Xenon difluoride [4, 5, 7, 8,10] is a white crystalline material obtained through the combination of fluorine and xenon m the presence of light The reagent is commercially available and possesses a relatively long shelf-life when stored cold (freezer) Xenon difluoride is very effective for small-scale fluormation of alkenes and activated nucleophilic substrates. The reactions are usually conducted between 0 °C and room temperature in chloroform or methylene chloride solutions Hydrogen fluoride catalysis is sometimes helpful Xenon difluoride reacts in a manner that usually involves some complexation between the substrate and reagent followed by the formation of radical and radical cation intermediates... 

Xenon difluoride fluorinates adamantane in low yield [45] (equation 22) When the carbon-hydrogen bond is activated by an a-sulfur atom, fliiorination occurs readily The reactions involve intermediates that contain sulfur-fluorine bonds. At-Fluoropyridinium reagents behave similarly [99, 100, 101, 102] (equations 55-57)... 

The new fluorescent poly(aryl ethers) derived from nonfluorescent monomers have gained significant attention from polymer scientists [20]. These polymers are prepared by the polymerization of phenolphthalein and its derivatives with activated aromatic difluorides. 

Recently, the pyrazole group containing bisphenols have been synthesized from activated aromatic dihalides and 3,5-bis (4-hydroxy phenyl)-4-phenyl pyrazole or 3,5-bis(4-hydroxy phenyl)-1,4-diphenyl pyrazole. A novel synthesis of imido aryl containing bisphenols has been reported [32]. N-substituted l,4-bis(4-hydroxy phenyl)-2,3-naphthalimides were prepared from phenolphthalein and copolymerized with aromatic sulfone or ketone difluorides to obtain the poly(imidoaryl ether) sulfones/ ketones. 

Mixtures of silica gel and the liquid difluoride sealed in tubes at 334 mbar exploded above -196°C, presence of moisture rendering the mixture shock-sensitive at this temperature [1], Reaction of oxygen difluoride with silica, alumina, molecular sieve or similar surface-active solids is exothermic, and under appropriate conditions may be explosive [2], A quartz fibre can be ignited in the difluoride [3],... 

The anodes of these two graphite samples were fabricated from a slurried mixture which contains 92 wt% of active graphite powder and 8wt% polyvinylidene difluoride (PVDF) polymer binder (Kureha 9130) and using 1 -methyl-2-pyrrolidinone (NMP) (Aldrich, >99%) as the solvent. After getting the homogenous slurry, the electrode laminates were coated on Cu current collector foil using a doctor blade in the laboratory-made laminate-coater. The laminates were then dried first at 75°C in air for 3 hrs and then the final heat treatment was carried out in a vacuum oven at 75 C for 10 hrs. Finally, the laminates were calendared to about 35% porosity in a dry room. 

Alkylated (R,RHetrahydroindcnyItitanium difluoride and phenylsilane serve to asymmetrically reduce a variety of ketones, especially aryl alkyl ketones, in excellent chemical yields and >96% ee.587 The use of the easier to handle and less expensive PMHS is also highly effective in these transformations. In a related study using the (W, W)-tctrahydroindcny I titanium l,T-binaphth-2,2/-diolate precursor to the active catalyst, similarly impressive results are obtained.588... 

The enantioselective hydrosilylation of 2-pentylcyclopentenone is effected with PMHS and an active catalyst derived from (R.R)-ethylenebis(tetrahydro-indenyl)titanium difluoride and phenylsilane (EBTHI)Ti (Eq. 3 50).587 The use of diphenylsilane, a rhodium catalyst, and (W, / )-(. ,.S )-BuTRAP as the chiral ligand gives similar results.576 Other related approaches give greatly inferior enantioselectivies, 592 594... 

The thallium trinitrate-mediated ring contraction of frani-decal-2-ones has opened up a new route to the hydrindane system, and fluorinative ring contraction of cyclic alkenes to afford difluorocycloalkanes has been induced by iodotoluene difluoride and EtsN-HF. A possible mechanism is shown in Scheme 78. The double bond of the cyclohexene ring is attacked by iodotoluene difluoride activated by HF from the axial direction, followed by the addition of a fluoride ion from the trans direction. Reductive elimination of iodotoluene from the resulting adduct, ring contraction and the addition of the fluoride ion to the carbocation stabilized by fluorine then take place to give the ring-contracted difluorinated product. 

Fluorine/iodine mixtures, which can be regarded as sources of both iodonium and fluoride ion, have been used to prepare glycosyl fluorides from the corresponding thioglycosides and gem-difluorides from some diaryl-1,3-dithio-lanes (Fig. 68) [161,162]. Activation of the carbon-sulfur bond towards nucleophilic attack by fluoride ion is achieved by complexation of the thiophilic iodonium species with the sulfur atoms. 

In the area of reaction energetics. Baker, Muir, and Andzehn have compared six levels of theory for the enthalpies of forward activation and reaction for 12 organic reactions the unimolecular rearrangements vinyl alcohol -> acetaldehyde, cyclobutene -> s-trans butadiene, s-cis butadiene s-trans butadiene, and cyclopropyl radical allyl radical the unimolecular decompositions tetrazine -> 2HCN -F N2 and trifluoromethanol -> carbonyl difluoride -F HF the bimolecular condensation reactions butadiene -F ethylene -> cyclohexene (the Diels-Alder reaction), methyl radical -F ethylene -> propyl radical, and methyl radical -F formaldehyde -> ethoxyl radical and the bimolecular exchange reactions FO -F H2 FOH -F H, HO -F H2 H2O -F H, and H -F acetylene H2 -F HC2. Their results are summarized in Table 8.3 (Reaction Set 1). One feature noted by these authors is... 

The in situ preparation of the active fluorinating species lead diacctate difluoride from lead(I V) acetate (dissolved in chloroform) and hydrogen fluoride at 0 C was described in an earlier report.48 The crystalline lead diacetate difluoride could be isolated by a modified preparation.49... 

Sulfanyl groups are active substrates for perfluorodecarboxylation reactions. 2,3,5,6-Tetra-chloro-4-sulfanylpyridine reacts with xenon difluoride and perfluoroalkanecarboxylic acids in dichloromethane at room temperature to form 2,3,5,6-tetrachloro-4-perfiuoroalkylsulfanyl-pyridines in moderate to high yields.87... 

To overcome problems associated with the removal of iodobenzene and its derivatives formed upon fluorination of arylalkenes and arylalkynes with (difluoroiodo)arenes, polymer-supported (difluoroiodo)arenes were proposed.139 With these agents, the separation procedures are reduced to filtration of the iodinated polymer. For this purpose popcorn polystyrene is io-dinated and then transformed into the difluoroiodide by treatment with xenon difluoride in the presence of hydrogen fluoride in dichloromelhane at 25 C. The amount of active fluorine bonded to iodine atoms on the polymer support is estimated by iodometric titration. The reactions with phenyl-substituted alkenes result in rearranged gew-difluorides. The procedure provides the same fluorination products as with (difluoroiodo)benzenc (see Section 4.13.) but in much higher yields, e.g. PhCF2CH2Ph (96%), PhCF2CH(Me)Ph (95%). PhCH2CF2H (86%), and l,l-difluoro-2-phenylcyclopentanc (91 %). 

Highly enantioselective hydrosilylation of the imine 144 was achieved using (S,S)-(ebthi)titanium difluoride as a catalyst precursor to give the optically active benzylamine 145 with 99% ee in 95% after acidic workup [85],... 

Et2NSF3, DAST). In this reaction, an alcohol displaces a fluoride of DAST resulting in an activated intermediate, which in turn is displaced by the liberated fluoride (Scheme 3.2c).11 A gem-difluoride is formed when a kptone or aldehyde is treated with DAST. 

The reactivities of xenon difluoride and other fluoro-xenon derivatives depend strongly on the organic substrate structure AL (A being the active part of the molecule where functionalization is expected) and the reaction conditions, of which the most important are the solvent, reaction temperature and catalyst, while in some cases the concentration of reagent and substrate and the order of mixing of the organic substances may also play a crucial role (Scheme 3). 

Triphenylantimony difluoride (Ph3SbF2) catalyzes the formation of cyclic carbonates from oxiranes and C02 (Equation (33)).65 The best result is obtained when the reaction is conducted using a high pressure of C02 at 180 °C in HMPA. Under similar reaction conditions, Ph3BiF2 shows only a low catalytic activity. 

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