Tetra-n-butylammonium

Table 1. Anion Extraction Constants Eq, of Tetra-n-Butylammonium Ion Pairs Between Water and Chloroform...

Tetra-n-butylammonium chloride [1112-67-0] M 277.9, m 15.7". Crystd from acetone by addition of diethyl ether. Very hygroscopic and forms crystals with 34H2O. 

Tetra-n-butylammonium fluoroborate [429-42-5] ammonium fluoroborate on p. 480 in Chapter 5. 

Tetra-n-butylammonium hexafluorophosphate [3109-63-5] M 387.5, m 239-241 . Recrystd from satd EtOH/water and dried for lOh in vac at 70°. It was also recrystd three times from abs EtOH and dried for 2 days in a drying pistol under vac at boiling toluene temperature [Bedard and Dahl J Am Chem Soc 108 5933 1986],... 

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 nitrate [ 1941-27-1 ] M 304.5, m 119". Crystd from benzene (7mL/g) or EtOH, dried in a vacuum over P2O5 at 60° for 2 days. 

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... 

A/ HE, 0.1 M NaF, pH 5. THE, 25°, 2 days, 77% yield. In this substrate, a mixture of products resulted from the attempted cleavage of the t-butyl-dimethylsilyl ether with tetra-n-butylammonium fluoride, the reagent generally used. ... 

AcCl, NaOH, dioxane, Bu4N HS04 , 25°, 30 min, 90% yield. Phase-transfer catalysis with tetra-n-butylammonium hydrogen sulfate effects acylation of sterically hindered phenols and selective acylation of a phenol in the presence of an aliphatic secondary alcohol. 

In addition, NaOMe, and NaNH2, have also been employed. Applieation of phase-transfer conditions with tetra-n-butylammonium iodide showed marked improvement for the epoxide formation. Furthermore, many complex substituted sulfur ylides have been synthesized and utilized. For instance, stabilized ylide 20 was prepared and treated with a-D-a/lo-pyranoside 19 to furnish a-D-cyclopropanyl-pyranoside 21. Other examples of substituted sulfur ylides include 22-25, among which aminosulfoxonium ylide 25, sometimes known as Johnson s ylide, belongs to another category. The aminosulfoxonium ylides possess the configurational stability and thermal stability not enjoyed by the sulfonium and sulfoxonium ylides, thereby are more suitable for asymmetric synthesis. 

The highest yields in the Ciamician-Dennstedt reaction have been achieved using phase transfer catalysts (Table 8.3.1). In the reaction, the pyrrole or indole and a phase transfer catalyst (PTC, in this case benzyltriethylammonium chloride) are dissolved in chloroform and aqueous sodium hydroxide is added. Yields are typically in the 40s to 60s (rather than in the 20s for a typical Ciamician-Dennstedt reaction). More recently, yields as high as 80% have been reported using tetra-n-butylammonium hydrogen sulphate as the phase transfer catalyst. ... 

To a stirred solution of 2,3-dimethyl indole (6, 1.45 g, 10 mmol, 1.0 equiv) and tetra-n-butylammonium sulfate (3.40g, 10 mmol, 1.0 equiv) in chloroform (150 mL) was added potassium hydroxide (50% aqueous solution, 20 mL) over 30 minutes. The stirring was continued for six hours, at which time the mixture was extracted with chloroform, the chloroform-water mixture was washed with water, and the organic layer concentrated. Silica gel chromatography provided 2,4-dimethyl-3-chloroquinoline (7, 1.52 g, 79% yield). 

The use of tetra-n-butylammonium fluoride (54) in an aprotic solvent such as acetonitrile may be more advantageous. Foster and colleagues (19, 37) have effected an SN2 type of reaction using this reagent in the conversion of l,2 5,6-di-0-isopropylidene-3-0-p-tolylsulfonyl-D-allofura-nose into the C-3 epimeric fluorodeoxy derivative. Note that whereas potassium fluoride is ineffective in displacing secondary sulfonate esters in sugars, tetra-n-butylammonium fluoride is capable of effecting a displacement with Walden inversion even in a furanose drivative. 

Tetra n-butylammonium fluoride. .. 162 2-Thiobarbituric acid-malonaldehyde... 

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 %. 

DME ethylene glycol dimethyl ether TBAI tetra-n-butylammonium iodide... 

Water samples showing contamination by phenols are best examined by extracting the phenol into an organic solvent tri-n-butyl phosphate is very suitable for this purpose. Photometric measurements can be carried out on the extract, and the requisite alkaline conditions are achieved by the addition of tetra-n-butylammonium hydroxide. 

Tetra-n-butylammonium hydroxide (0.1 M solution in methanol). Prepare an anion exchange column using an anion exchange resin such as Duolite A113 or Amberlite IRA-400, convert to the hydroxide form and after washing with water, pass 300-400 mL of methanol through the column to remove water (see Section 7.2). 

Dissolve 20 g of tetra-n-butylammonium iodide in 100 mL of dry methanol and pass this solution through the column at a rate of about 5 mL min - L the effluent must be collected in a vessel fitted with a Carbosorb guard tube to protect it from atmospheric carbon dioxide. Then pass 200 mL of dry methanol through the column. Standardise the methanolic solution by carrying out a potentiometric titration of an accurately weighed portion (about 0.3 g) of benzoic acid. Calculate the molarity of the solution and add sufficient dry methanol to make it approximately 0.1M. 

Prepare an alkaline solution of the phenol concentrate by placing 4.0 mL of a tri-n-butyl phosphate layer in a 5 mL graduated flask and then adding 1.0 mL of the tetra-n-butylammonium hydroxide do this for each of the four solutions. The reference solution consists of 4 mL of the organic layer (in which the phenol is undissociated) plus 1 mL of methanol. Measure the absorbance of each of the extracts from the four test solutions and plot a calibration curve. 

Determination of organic compounds. The application of photometric titrimetry to organic compounds may be exemplified by the titration of phenols. This can be carried out by working at the /max value (in the ultraviolet) for the phenol being determined (see Section 17.50). It has been shown that by titrating with tetra-n-butylammonium hydroxide and using propan-2-ol as solvent, it is possible to differentiate between substituted phenols.24... 

It would appear that when fluoride ion is to be used in stoichiometric amounts, benzyltrimethylammonium fluoride is the preferred source on the other hand, tetra-n-butylammonium fluoride, commercially available as its trihydrate, is more convenient in catalytic situations. However, there are difficulties. (19) in successfully dehydrating the latter source without inducing Hofmann elimination. 

Sulfones with a trimethylsilyl or trialkylstannyl group at the -position or at the -position are readily converted to olefins upon treatment with tetra-n-butylammonium fluoride in THF (equations 39-41). The method is compatible with the presence of a variety of functionalities. 

Although the catalyst with a longer chain length benefits the reaction rate, it is not easy to be recovered. Tetra-n-butylammonium bromide is the best choice. 

Jones, P.G. (1993) Crystal structure of tetra-n-butylammonium trans-dichlorobis(pentafluorophenyl)aurate (III), (C4H9)4N(Cl2Au(C6F5)2). Zcitschrift jur KristaUographie, 208(2), 362-365. 

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