Lithium tetrafluoroborate

In contrast to liPFg, which is very moisture sensitive and thermally unstable, UBF4 is thermally stable and hydrolyzes slowly (see Section 17.2.5), but its low conductivity has inhibited further research. So far it at least occupies a niche, because its low-temperature performance equals that of other salts [90-92] with the merits mentioned above and forms a better passivation film at the aluminum conductor, which allows higher potentials [90]. 

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Lithium tetrafluoroborate yields only poorly conducting solutions with all solvents. It is unstable [61] and also leads to polymerization with cyclic ethers initiated by the corresponding Lewis base BFj. 

Lithium fefrafc/s-(3,5-ditrifluoromethyl)borate, which provides an unsolvated lithium cation in noncoordinating solvents, exhibits a several thousandfold catalysis of the reaction of cyclopentadiene and methyl vinyl ketone.37 Lithium tetrafluoroborate is also an effective catalyst and in some instances has worked when LiC104 has failed, such as in the intramolecular reaction shown below.38... 

Recently, Shimizu reported a novel polar cycloaddition of a 1,2-thiazinylium salt <99TL95>. Compound 175 was generated in situ from the reaction of compound 165 with trifluoroacetic anhydride and lithium tetrafluoroborate. It can undergo a cyclization reaction... 

Lithium sulfuryl chloride batteries, 23 654 Lithium SVO cells, speciality for military and medical use, 3 430t Lithium t-butoxide, 15 148 Lithium tetraborate, 15 137 Lithium tetrafluoroborate, in lithium cells, 3 459... 

Lipshutz BH, Harvey DF (1982) Hydrolysis of acetals and ketals using lithium tetrafluoroborate. Synth Commun 12 267-277... 

A, Dimethyl (s)-2-hexenedioate. A 100-roL, one-necked, round-bottomed flask is capped by a septum, swept with dry nitrogen and flame-dried. The flask is charged with methyl acrylate (50 ml, 0.55 mol. Note 1), then anhydrous lithium tetrafluoroborate (9 g, 0.096 mol, Note 2), and finally tetrakis(acetonitrile)palladium tetrafluoroborate (1.33 g, 0.003 mmol. Note 3). The mixture is stirred briefly until homogeneous. It is warmed under nitrogen in a 40°C-o11 bath for 72 hr (Note 4) and then allowed to cool to room temperature. The mixture is added to saturated aqueous sodium bicarbonate (100 mt) and extracted with ether (3 x 50 mt). The combined ether extracts are dried over anhydrous magnesium sulfate, filtered and concentrated to an oil with a rotary evaporator. The residue is distilled through a lO-cm... 

The greyish precipitate which begins to appear after ca. 40 hr is the 1 1 adduct of the product with lithium tetrafluoroborate. 

Anhydrous 98% pure lithium tetrafluoroborate (L1BF4) from Alfa Products, Morton/Thiokol, Inc. was used as received. 

Several catalyst systems have been described for the tail-to-tail dimerization of methyl acrylate.7 -7 Advantages of the dimerization procedure described here are its mild conditions, efficient use of the catalyst, and high selectivity for the b isomer. Tetrakis(aceto-nitnle)palladium tetrafluoroborate, Pd (NCMe)4(BF )2, also efficiently catalyzes dimerization of ethyl acrylate and methyl methacrylate. The presence of lithium tetrafluoroborate in the reaction mixture increases the rate of the reaction and prolongs catalyst life. Dimerization of methyl acrylate can be effected without lithium tetrafluoroborate if the reaction is performed in mtromethane. 

Lithium tetrafluoroborate [14283-07-9] M 93.7. Dissolve in THF just below its solubility, filter from insol material and evap to dryness in a vacuum below 50°. Wash the residue with dry Et2O, and pass dry N2 gas over the solid and finally heat in an oven at 80-90°. Solubility in Et2O 1.9 (1.3)g in 100ml at 25°, in THF 7Ig in 100ml at 25°. It is hygroscopic and is an irritant. [JACS 74 5211 1952, 75 1753 1953]. 

Potassium, sodium and lithium tetrafluoroborate as well as sodium hexafluorophosphate and hexafluoroantimonate can be used to fluorinate organosilicon chlorides.64 65 An overview is reported in Table 10.65... 

Lithium tetrafluoroborate efficiently catalyzes the cyclization of n-hydroxybenzaldimines 469 with 3,4-dihydro-277-pyran 455 at ambient temperature to afford a class of pyrano derivatives representated by 470 in excellent yields with high diastereoselectivity (Equation 34) <2001TL6381>. The use of catalytic indium trichloride and phospho-nium perchlorate has been found to efficiently effect the same transformation <2002T10301>. 

Preparation of gem-Dinitroalkanes. A methanolic solution of alkali metal hydroxide (Li, Na, or K) was treated with 10% excess nitroalkane and stirred for 30 minutes. The solution was evaporated to dryness in vacuo, and the alkali metal alkyl nitronate was aned over phosphorus pentoxide at reduced pressure (0.1 mm.) for 24 hours. (Caution nitronate salts may be shock sensitive and have been known to explode after prolonged storage.) A slurry of 3.3 grams (0.02 mole) of lithium 1-nitro-cyclohexane in 50 ml. of acetonitrile was cooled to —40°C., and 2.7 grams (0.02 mole) of nitronium tetrafluoroborate were slowly added. The reaction was not exothermic, and the reaction mixture turned brilliant blue upon adding nitronium tetrafluoroborate. The reaction mixture was stirred for 2 hours at —30° to —40°C., then filtered to give a quantitative yield of lithium tetrafluoroborate. The filtrate was quenched into 100... 

Lithium tetrafluoroborate, (LiBF4), lithium hexafluorophosphate, (LiPF6), lithium hexafluoroarsenate, (LiAsF ), lithium trifluoromethane sulfonate, (LiSOjCFj), are the electrolyte salts of the 21st Century. The performance of lithium ion cells, primary and secondary lithium cells depends on the purity of these compounds. Several hundred tons of these materials have been produced and many more tons — and perhaps thousands of tons — will be required in the near future. One of the largest automotive producers predicts that there may be a market for 10-15 million pounds of these salts. The demand for Lithium ion primary cells is also very huge in electronics, computers, communication systems and military applications. 

Lithium tetrafluoroborate, LiBF4, is prepared by dissolving LiF in AHF and then BF3 gas is passed until precipitation is complete. After the reaction is over, excess HF is decanted and LiBF4 is dried under nitrogen until HF and H20 contents are reduced below 100 ppm level. Reaction is carried out in Teflon , polyethylene or polypropylene lined reactors to avoid metallic contamination. 

Fluoride-induced -elimination of p-(trimethylsily )ethyl ethers, which is the cornerstone of the 2-(trtmethylsilyl)ethoxymethyl (SEM) protecting group for hydroxyl functions (see section 4.4.5), has been modified for use in deprotecting cyclic acetals. For example, 4-(trimethylsilyl)methyM,3-dioxolanes46 and 5-tri-methylsilyl-13-dioxanes47 cleave on heating with lithium tetrafluoroborate [Scheme 2.16], The method works well for unhindered aldehydes and ketones. 

During a synthesis of the Chlorothricolide, Roush and Sciotti encountered unexpected problems with the hydrolysis of the dimethyl acetal 54.1 [Scheme 2.54].112 Use of some of the standard hydrolysis conditions (oxalic acid, PPTS, PTSA, HO Ac, or trifluoroacetic acid — all in acetone) resulted in recovery of 54.1 or decomposition. Success was achieved by exploiting the mild Lewis acidic properties of the lithium cation under conditions first reported by Lipshutz and Harvey.113 Thus treatment of the dimethyl acetal 54,1 with lithium tetrafluoroborate in acetonitrile containing 2% water returned the desired aldehyde 54J in 97% yield after 2 h at room temperature. The reaction was also applied to the deprotection of a cyclic ketal in a synthesis of Pumi-liotoxin.114 115... 

In the dosing stages of a synthesis of Mitomycin derivative FR-900482, a densely functionalised intermediate had to be shorn of its robust MOM protector [Scheme 4.250].46S The task was accomplished with trityl tetrafluoroborate under conditions devised some years ago by Kishi and co-workers.466 Lithium tetrafluoroborate in refluxing aqueous acetonitrile has been successfully deployed in the deprotection of a MOM ether in the presence of a benzyl ether [Scheme 4 2511 467... 

The selective deprotection of acetal to a carbonyl group can be achieved with lithium tetrafluoroborate LiBp4 in THE... 

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