Ammonium tetrafluoroborate

These salts are obtained from 1,2 (or l,3)-diamines. The cyclization step is generally the condensation of the diamines on ethyl orthoformate in the presence of ammonium tetrafluoroborate (Scheme 19). By using enantiop-ure diamines, chiral salts 34 bearing stereogenic centers on the backbone, on the nitrogen substituents, or on both were prepared [1,2,4,5,26]. Several dicyclophane imidazolinium salts have been prepared by one-pot three-step procedure [27]. 

In trifluoroacetic acid [0.4 M TBABF4 (tetrabutyl ammonium tetrafluoroborate)] unbranched alkanes are oxidized in fair to good yields to the corresponding triflu-oroacetates (Table 2) [16]. As mechanism, a 2e-oxidation and deprotonation to an intermediate carbenium ion, that undergoes solvolysis is proposed. The isomer distribution points to a fairly unselective CH oxidation at the methylene groups. Branched hydrocarbons are preferentially oxidized at the tertiary CH bond [17]. 

Example 4 Wada et al. have been successful in developing a new class of activators dialkyl (cyanomethyl) ammonium tetrafluoroborates [21]. These activators have high proton-donating ability and a counteranion of low nu-cleophilicity. With this class of salts a remarkably efficient diastereocon-trolled synthesis of dinucleoside phosphorothioates has been devised. The power of this method lies in the fact that stereopure monomers can be ob-... 

Unlike glass-ionomers or compomers, composite resins are not inherently fluoride-releasing and they do not generally contain any fluoride compounds. However, they can be formulated with such compounds [281], for example NaF, YbFs or ion-leachable glass [201]. Organic fluorides can be used, too, such as methacryloyl fluoride-methyl methacrylate (MF-MMA) or tetrabutyl ammonium tetrafluoroborate. These latter substances impart the property of slow release of fluoride to the surrounding tissue without the creation of voids within the material. 

Ammonium tetrafluoroborate [13826-53-0] M 104.8. Crystd from conductivity water (Iml/g) between 100° and 0°. 

The electrochemical oxidation of tertiary phosphanes, R3P, can be carried out with a platinum electrode in acetonitrile with the addition of pentylammonium fluoride and with the electrolyte tetraethyl ammonium tetrafluoroborate.65 The observed product is the trialkyldi-fluoro-25-phosphane R3PF2. The electrolysis is carried out in a galvanostatic mode with a current density from 3.3 to 6.7 mA cm-2. The anodic oxidation may be represented by the following equation ... 

Usually, diazonium chlorides (from sodium nitrite and 37 wt % hydrochloric acid) are used as intermediates. They are treated with an alkaline tetrafluoroborate or tetrafluoroboric acid provided that its use is not prohibited by solubility problems, tetrafluoroboric acid delivers purer diazonium tetrafluoroborates than sodium or ammonium tetrafluoroborate.172 Diazonium hydrogen sulfates are also valuable auxiliary salts since they are insoluble in cold water and are obtained quantitatively and in a purer state than diazonium chlorides.118 Their warm, aqueous solutions deliver pure diazonium tetrafluoroborates when treated with tetrafluoroborate sources.137... 

Ammonium tetrafluoroborate (7 ). Both the ammonium (NH ) and tetrafiuoroborate (BF4) ions are isoelectronic with the methane molecule and we might therefore reasonably expect them to have similar structures. Indeed, all four bonds are equivalent, and since the electrons avoid each other as much as possible, the most stable arrangement is a tetrahedron (Fig. 6.1g). 

Tetrabutylammonium tetrafluoroborate (TBATFB, Bu4NBF4) is another excellent electrolyte for general use. Like other tetrafluoroborate salts, it is somewhat more soluble in both organic compounds and water than TBAHFP, and is more stable than TBAHFP in methylene chloride. House and coworkers have described procedures for the synthesis of TBATFB and other tetraalkyl-ammonium tetrafluoroborates [9]. Thus, a solution of 8.4 g (0.025 mol) of... 

Ammonium tetrafluoroborate, 2 23 by fusion reaction, 2 24 by reaction in aqueous solution, 2 23... 

In all experiments the electrolyte was the highest quality tetra-n-butyl ammonium tetrafluoroborate furnished by Eastman and J.T. Baker, the working electrode was glassy carbon (area 0.31 cm2) polished before each scan, except in film formation studies. The reference electrode was saturated calomel, and the auxiliary electrode was platinum wire. Electrodes and cells were purchased from Princeton Applied Research (PAR). The instrument was a PAR Model 170 Electrochemistry System, Serial No. 16109. 

Table 10 Limiting Reduction and Oxidation Potentials of Organic Solvents Containing 0.65 mol dm 3 Tetraethyl-ammonium Tetrafluoroborate at 25°C (glassy carbon electrodes)... 

Hydroxybenzotriazole (HOBt) and 2-(lH-benzotriazole-l-yl)-l,l,3,3-tetramethyl-ammonium tetrafluoroborate (TBTU). 

AMMONIUM TETRAFLUOROBORATE see ANHOOO AMMONIUM TETRAFLUOROBORATE(l-) see ANHOOO... 

Aminosulfenylation of alkenes can also be achieved by trapping the highly reactive (methylthio)-ammonium tetrafluoroborate, formed in situ by alkylation of /V, /V-dimethyImethanesulfenamide with trimethyloxonium tetrafluoroborate42. 

The corresponding ammonium tetrafluoroborate, like ammonium hexa-fluorophosphate, is stable to heat, and does not give the B-trifluoro-borazole. 

Current density at a Cu cathode tetrabutyl ammonium tetrafluoroborate "1 atm. 40 atm electrolysis was conducted at 20 C, and thus the mole fraction was slightly larger than 0.33. 

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