Tetra-n-butylammonium acetate

Tetra-n-butylammonium acetate, 442 Tetra-n-butylammonium chromate, 443 Tetra-n-butylammonium di-f-butyl phosphate, 443... 

Tetra-n-butylammonium acetate, (C4H9)4NOCOCH3. Mol. wt. 301.50, m.p. 114-115°. The reagent is obtained by neutralization of tetrabutylammonium hydroxide in methanol with acetic acid. 

Epimerhation of hydroxyl groups. Epimerization of hydroxyl groups is often effected by S 2 displacement of the tosylates of the alcohol with tetraethylammonium acetate (1, 1136-11.37 2. 397) or with tetra-n-butylammonium acetate (3, 277). In connection with a study of configuration and biological activity in the prostaglandins, Corey and Terashima examined the reaction of the tosylatc of the model (-t)-hydroxy-laclone (1) with 5.0 eq. of tetra-n-butylammonium acetate in acetone at 25" for 2 hr. 

Isotope and solvent effects on fluxional hydrogen-bonded complexes of acetic acid and acetate have been studied by Limbach and co-workers. The spectra have been measured in the presence of tetra-n-butylammonium acetate around 110 K using liquefied Freon mixture as a solvent. Also spectra of the adduct CHs COOH SbCb have been recorded for comparison. For the first time, a two-bond coupling of the type JiCUsCOOH) between a hydrogen-bonded proton and the carboxylic carbon has been observed, Jhc = 3.0 Hz for comparison, the corresponding Jhc value in CHs COOH SbCb equals to 6.7 Hz. 

In 2013, the Scheidt group developed a highly selective NHC-catalyzed formal [4 + 2] annulation of a,p-unsaturated aldehydes and imidazolidinones with an electron-withdrawing aryl substituent at the 2-position. The use of acetic acid in conjunction with tetra-n-butylammonium acetate is essential to achieve high chemoselectivity for the formal [4 + 2] annulation product as it might increase the rate of the initial p-protonation and therefore increase the product ratio in favor of lactones. The authors proposed that this reaction processed in a favored stepwise [4 + 2] manner with a key intermediate being the NHC-bound enolate (Scheme 7.73). 

Treatment of the tosylate (404) with tetra-n-butylammonium acetate in acetone gave a mixture of acetate (405) and the elimination product (406). Using di(tetra-n-butylammonium) oxalate under the same conditions, the sole product was the olefin (406) in 82 % yield. This preference for elimination over substitution may be the result of a bidentate attack on the hydrogen to be removed, leading to a stabilized oxalate mono-acid anion (407). ... 

Tetra-n-butylammonium iodide [311-28-4] M 369.4, m 146". Crystd from toluene/pet ether (see entry for the corresponding bromide), acetone, ethyl acetate, EtOH/diethyl ether, nitromethane, aq EtOH or water. Dried at room temperature under vac. It has also been dissolved in MeOH/acetone (1 3, lOmL/g), filtered and allowed to stand at room temperature to evaporate to ca half its original volume. Distilled water (ImL/g) was then added, and the ppte was filtered off and dried. It was also dissolved in acetone, ppted by adding ether and dried in vac at 90" for 2 days. It has also been recrystallised from CH2Cl2/pet ether or hexane, or anhydrous methanol and stored in a vacuum desiccator over H2SO4. [Chau and Espenson J Am Chem Soc 108 1962... 

Tetra-n-butylammonium perchlorate [1923-70-2] M 341.9", m 210"(dec). Crystd from EtOH, ethyl acetate, from n-hexane or diethyl ether/acelone mixture, ethyl acetate or hot CH2CI2. Dried in vacuum at room temperature over P2O5 for 24h. [Anson et al. J Am Chem Soc 106 4460 1984 Ohst and Kochi J Am Chem Soc 108 2877 1986 Collman et al. J Am Chem Soc 108 2916 1986 Blau and Espenson J Am Chem Soc 108 1962 1986 Gustowski et al. J Am Chem Soc 108 1986 Ikezawa and Kutal J Org Chem 52 3299... 

The next major obstacle is the successful deprotection of the fully protected palytoxin carboxylic acid. With 42 protected functional groups and eight different protecting devices, this task is by no means trivial. After much experimentation, the following sequence and conditions proved successful in liberating palytoxin carboxylic acid 32 from its progenitor 31 (see Scheme 10) (a) treatment with excess 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) in ie/t-butanol/methylene chloride/phosphate buffer pH 7.0 (1 8 1) under sonication conditions, followed by peracetylation (for convenience of isolation) (b) exposure to perchloric acid in aqueous tetrahydrofuran for eight days (c) reaction with dilute lithium hydroxide in H20-MeOH-THF (1 2 8) (d) treatment with tetra-n-butylammonium fluoride (TBAF) in tetrahydrofuran first, and then in THF-DMF and (e) exposure to dilute acetic acid in water (1 350) at 22 °C. The overall yield for the deprotection sequence (31 —>32) is ca. 35 %. 

The catalyst anion has also been shown to have a large influence on the reaction rate. The extraction constant of tetra-n-butylammonium salts between water and chloroform decreases with different anions as follows picrate CIO4 > T > toluene sulphonate > NO.-i > Br > benzoate > Cf > acetate > OH (Esikova, 1997 Dehmlow, 1993). 

Leadbeater NE, Pillsbury SJ, Shanahan E, Williams VA (2005) An assessment of the technique of simultaneous cooling in conjunction with microwave heating for organic synthesis. Tetrahedron 61 3565-3585 Lee CKY, Holmes AB, Ley SV, McConvey IF, Al-Duri B, Leeke GA, Santos RCD, Seville JPK (2005) Efficient batch and continuous flow Suzuki crosscoupling reactions under mild conditions, catalysed by polyurea-encapsulated palladium (II) acetate and tetra-n-butylammonium salts. J Chem Soc Chem Commun 2175-2177... 

As an alternative to the Ullmann reaction, haloarenes are coupled to form the biaryls using palladium acetate in the presence of abase and tetra-n-butylammonium bromide [24], Yields are generally high (>70%) but dehalogenation of the haloarene may also occur as a side reaction. 

Sulphoximes are obtained by a facile oxidation of sulphilimines [20], The reaction, which can be conducted in ethyl acetate and/or dichloromethane, is best catalysed by tetra-n-butylammonium bromide or Adogen. Benzyltriethylammonium chloride has no significant catalytic activity. 

Tetra-n-butylammonium trisacetoxyborohydride has been prepared in situ in dichloromethane from the borohydride and acetic acid [4,5]. The effectiveness of the reagent for the reduction of aldehydes in the presence of ketones is greater than originally reported using sodium trisacetoxyborohydride [5]. In a series of competitive reductions, aldehydes were reduced to the alcohols (>90%), whereas the ketones... 

Tetra-n-butylammonium fluoroborate [429-42-5] M 329.3, m 161-163 . Recrystd from ethyl acetate/pentane in dry acetonitrile. [Hartley and Faulkner JACS 107 3436 1985. ... 

Benzyloxy-6-bromo-4-nitro-iV-(2-propenyl)aniline (5.82 g, 16 mmol), tetra-n-butylammonium bromide (5.16 g, 16 mmol) and Et,N (4.05 g, 40 mmol) were dissolved in DMF (15 ml). Palladium acetate (72 mg, 2 mol%) was added and the reaction mixture was stirred for 24 h. The reaction mixture was diluted with EtOAc, filtered through Cclite, washed with water, 5% HC1 and brine, dried and evaporated in vacuo. The residue was dissolved in CH2C12 and filtered through silica to remove colloidal palladium. Evaporation of the eluate gave the product (4.32 g) in 96% yield. 

R. Csuk, A. Fiirstner, and H. Weidmann, Branching of ketosugars by ethyl trimethylsilyl-acetate/tetra-n-butylammonium fluoride, J. Carbohydr. Chem. 5 11 (1986). 

Second-order rate coefficients for reaction (21) (X = I and OAc) were also reported by Abraham and Behbahany30 and are given in Table 20. Kinetic salt effects of added tetra-n-butylammonium perchlorate were studied for reaction (21) (X = I and OAc) both with solvent methanol and solvent tert.-butanol. Reaction (21) (X = 1) was accelerated in both solvents to about the same extent as was reaction (21) (X = Cl), and mechanism SE2(open) was therefore suggested. The reaction of tetraethyltin with mercuric acetate was subject to very large positive salt effects in methanol, perhaps due to anion exchange, but was unaffected by the electrolyte in solvent /er/.-butanol. Abraham and Behbahany30 considered that it was not possible to deduce the mechanism of the acetate reaction and that further work was necessary to decide between mechanism SE2(open) and mechanism SE2(cyclic). 

An examination of Table 2 reveals that although mercuric acetate and mercuric nitrate have often been used as electrophilic reagents, there are but few instances in which independent evidence as to their mechanism of reaction has been put forward. Positive kinetic salt effects have been observed in the substitution of sec.-butylmercuric acetate by mercuric acetate (with lithium nitrate in solvent ethanol)2, the substitution of di-sec.-butyl mercury by sec.-butylmercuric nitrate (with lithium nitrate in solvent ethanol)11, and the substitution of tetraethyltin by mercuric acetate (with tetra-n-butylammonium perchlorate in methanol)7. In the latter case, it was suggested7 that the observed very large positive kinetic salt effect was possibly due to anion exchange between mercuric acetate and the perchlorate ion. 

MICHAEL ADDITIONS Alumina. Aluminum chloride. Cesium fluoride-Silicon(lV) cthoxidc. 1,4-Diazabicyclo[2.2.2]octanc. l,8-Diazabicyclo[5.4.0]-7-undecene. Ketene r-butyldimethylsilyl methyl acetal. Lithium acetylides. (S)-( + )-2-Mcthoxymethylpyrrolidine. Methyl lithiodithioacetate. Methyl (phcnylsulfinyl)acetate. Methyl 2-trimcthylsilylacrylate. Nickel carbonyl. Organocopper reagents. 8-Phenylmcnthol. Phenyl 2-(trimethylsilyl)ethynyl sulfone. Tetra-n-butylammonium fluoride. Tiianium(IV) chloride. 3-Triisopropylsilylpropynyllithiuni. Zirconium(IV) n-propoxiilc... 

Tetra-n-butylammonium tetrafluoroborate. A solution of 8.4 g (25 mmol) of (n-Bu)4NBr in a minimum volume of water ( — 18 mL) is treated with 3.6 mL ( — 26 mmol) of aqueous 48-50% HBF4. The resulting mixture is stirred at 25 °C for 1 min and the crystalline salt is collected on a filter, washed with water until the washings are neutral, and dried. The crude salt (6.3 g or 79%, MP 155-175°C) is recrystallized three times from ethyl acetate-pentane mixtures to separate 6.0 g (75%) of (n-Bu)4NBF4 as white needles MP (after drying) 162-162.5°C. 

Tetra-n-butylammonium perchlorate. A saturated aqueous solution of 8.4 g (25 mmol) of ( -Bu)4NBr in 18 mL of water is treated with 2.1 mL ( — 26 mmol) of aqueous 70-72% HC104. After the resulting insoluble perchlorate salt has been collected, washed with cold water, and dried, the yield is 8.0 g (94%) MP 197-199°C. Two recrystallizations from an ethyl acetate-pentane mixture yield 7.6 g (90%) of pure (n-Bu)4NC104 as white needles that are dried at 100°C under reduced pressure MP 212.5-213.5°C. 

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