Salts triflate

Other THF polymerization processes that have been disclosed in papers and patents, but which do not appear to be in commercial use in the 1990s, include catalysis by boron trifluoride complexes in combination with other cocatalysts (241—245), modified montmorrillonite clay (246—248) or modified metal oxide composites (249), rare-earth catalysts (250), triflate salts (164), and sulfuric acid or Aiming sulfuric acid with cocatalysts (237,251—255). 

Cyclic dication ether triflate salts can be prepared by the reaction of diamides with tnflic anhydnde [91] (equation 43). 

Similarly, the temperature dependence of the conductivity of (triflate salts)o 25/MEEP complexes (the cations being Sr, Na, Li, Ag) has been studied. It was shown that the conductivity increases in the order Sr[Pg.204]

Outer-sphere electron transfer reactions involving the [Co(NH3)6]3+/2+ couple have been thoroughly studied. A corrected [Co(NH3)6]3+/2+ self-exchange electron transfer rate (8 x 10-6M-1s-1 for the triflate salt) has also been reported,588 which is considerably faster than an earlier report. A variety of [Co(NH3)g]3+/2+ electron transfer cross reactions with simple coordination compounds,589 organic radicals,590,591 metalloproteins,592 and positronium particles (electron/ positron pairs)593 as redox partners have been reported. 

The silver(I) complexes with the tetrakis(methylthio)tetrathiafulvalene ligand have been reported, the nitrate salt presents a 3D structure with an unprecedented 4.16-net porous inorganic layer of silver nitrate,1160 the triflate salt presents a two interwoven polymeric chain structure.1161 The latter behaves as a semiconductor when doped with iodine. With a similar ligand, 2,5-bis-(5,5,-bis(methylthio)-l,3,-dithiol-2 -ylidene)-l,3,4,6-tetrathiapentalene, a 3D supramolecular network is constructed via coordination bonds and S"-S contacts. The iodine-doped compound is highly conductive.1162 (Methylthio)methyl-substituted calix[4]arenes have been used as silver-selective chemically modified field effect transistors and as potential extractants for Ag1.1163,1164... 

A violent explosion occurred dining vacuum evaporation of an aqueous mixture of excess dimethylamine and perchloric acid [1], and a similar incident occurred when the moist solid from a like preparation was moved [2], Use of this explosive salt as an intermediate for the preparation of 3-dimethylamino-2-propenylidenedimethylimmonium perchlorate should be avoided, the methylsulfate or triflate salts being preferred [3],... 

Detailed investigations of the chemical reactivity of the diketiminato-stabilized phosphenium cations like 28 (Scheme 17) are to date rare and include only two reports dealing with the substitution and reduction of P-halogen-derivatives. Thus, reaction of 28 (X=Br) with sodium hydroxide in toluene was reported to proceed with displacement of the halide substituent at phosphorus and conservation of the heterocyclic ring to give a mixture of bromide and triflate salts containing a P-hydroxy-substituted cation, both of which were isolated in small yields [89], The products are remarkable as they represent one of very few examples of a stable phosphinous acid which does not rearrange to the tautomeric secondary phosphine oxide. Potassium reduction of the P-chloro-substituted derivative 34 produced the... 

Similar observations were made with bis[alkoxy(alkylamino)carbene]gold complexes, which are prepared by ring opening of trinuclear precursors with trifluoromethanesulfonic (triflic) acid. Through anion metathesis, several crystalline forms were obtained, the structures of which were determined. The triflate salt has a chain of cations in the crystal, while the chloroform solvate of a />-benzoquinolate contains only monomeric cations. In the solvent-free crystals, dimers are present (Scheme 59).251... 

A priori, derivatives of triflic acid (silyl triflates, salts of triflic acid, etc.) correspond to the above conditions. After a series of experiments, Zn(OTf)2 was chosen as the most efficient LA for the rearrangement BENA—>(504) (Scheme 3.261) (534). (It should be noted that the rearrangement BENA—>(504) under the action of silyl LA has been observed earlier (188, 465, 466), but the yields of derivatives (504) have been disappointing.)... 

Martin et al. have developed a unique series of capped tris(l,2-di-aminoethane) cages which can encapsulate divalent transition metal ions in a near octahedral geometry (28). The iron(II) complex with the ligand (NH2)2sar turns out to be a crossover system in solution [34], but the solid triflate salt is low-spin [43]. This is the only Fe(II) crossover system having 6 identical aliphatic nitrogen donors. 

Complex [RuCl(=C=C=CPh2)( 7 -p-cymene)(PCy3)][PF6] (or its triflate salt) was also effective in the RCM of enynes. Thus, as shown in Scheme 38, the straightforward synthesis of 3-vinyl-2,5-dihydrofurans 104 from enynes 103... 

Katritsky and co-workers ° reacted primary amines with the triflate salt of 5,6,8,9-tetrahydro-7-phenyl-dibenzo[c, /tjacridine to generate the corresponding A -substituted acri-dinium triflate salts, which on refluxing in dioxane in the presence of benzyltrimethylammo-nium nitrate, yield the corresponding nitrate esters. 

The undefined mechanism of the aldol-type Mukaiyama and Sakurai allylation reactions arose the discussion and interest in mechanistic studies [143-145]. The proposed mechanism was proved to proceed through the catalytic activation of the aldehyde and its interaction with the silyl ketene acetal or allylsilane producing the intermediate. From that point the investigation is complicated with two possible pathways that lead either to the release of TMS triflate salt and its electrophihc attack on the trityl group in the intermediate or to the intramolecular transfer of the TMS group to the aldolate position resulting in the evolution of the trityl catalyst and the formation of the product (Scheme 51). On this divergence, series of experimental and spectroscopic studies were conducted. 

Earlier work on directed hydrogenation used tetrafluoroborate salts. Triflate salts seem superior in keeping properties, and their preparation is easy and convenient. 

Dodd and co-workers (5) reported the first known synthesis of 11//-indolizino[8,7-h]indoles by the cycloaddition reaction of a nonstabilized ylide 21 and diethylacetylene dicarboxylate (DEAD). The azomethine ylide, formed by the alkylation of the 3,4-dihydro-p-carboline (22) with trimethylsilyl methyl triflate to the triflate salt, followed by in situ desilyation with cesium fluoride, underwent cycloaddition with DEAD at low temperature. The expected major cycloadduct 23 was isolated, along with quantities of a minor product 24, presumed to have been formed by initial reaction of the ylide with 1 equiv of DEAD and the intermediate undergoing reaction with a further equivalent of DEAD before cyclization. Dodd offers no explanation for the unexpected position of the double bond in the newly generated five-membered ring, although it is most likely due to post-reaction isomerization to the thermodynamically more stable p-amino acrylate system (Scheme 3.5). 

Novel [4+2] cycloadditions of 1-phenyl-1-benzothiophenium triflate salt 89 with dienophiles (cyclopentadiene and 1,3-diphenylbenzofuran) have been reported <990L257>. Heating 89 and cyclopentadiene in CHjClj gave a single product, endo cycloadduct 90. The stereochemistry of 90 was confirmed by single-crystal X-ray analysis. The cycloaddition of 3-methyl-l-phenyl-benzothiophenium triflate salt with cyclopentadiene proceeded only in low yield and required much more rigorous reaction conditions (CHjCN, sealed tube. A). 

H NMR titration data in aqueous solution involving the triflate salt of 51 with a variety of anions is often complex and must be modeled in terms of a number of... 

Triflates of boron, aluminum, and gallium were found to be efficient catalysts in Friedel-Crafts acylations.46 However, these are water-sensitive materials and were required to be used in equimolar quantities to be effective. More recently various water-tolerant and recyclable triflate salts, which were also tested in alkylation, were found to exhibit similar good characteristics in Friedel-Crafts acylations. Although benzene cannot be acylated, Sc triflate,47 48 lanthanum triflates,48-51 and Hf triflate52 usually give high yields of aryl ketones in acylation with acid anhydrides. In many cases, Li perchlorate was found to accelerate the reactions.48 52... 

Triflate salts, mainly scandium triflate273 and lanthanide(III) triflates,274,275 have found increasing use in various aromatic substitutions. They have some unusual properties specifically, they may be used in catalytic quantity and active even in the presence of water. They are also easily recyclable via aqueous workup. 

The rates, selectivities, and stabilities of transition-metal-substituted poly-oxometalates in olefin epoxidation are compared with those of metallopor-phyrins, Schiff base complexes, and triflate salts, as follows (320b) ... 

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