Tetraethylammonium acetate

For sufficient retention of these very polar sulfonated carboxylates on RP columns, the addition of an ion-pairing (IP) agent such as tetraethylammonium acetate (TEAA) to the LC buffer was compulsory [13]. To maintain the compatibility of the eluent with the MS interface, the use of such an involatile cationic additive entailed a cation exchanger to be placed between the column and the interface [13]. Alternatively, equimolar amounts (5 mM) of acetic acid and triethyl-amine, which form the volatile IP agent triethylammonium, were added to the mobile phase in order to improve the retardation of very polar SPC [14]. While the first approach with TEAA was effective in retaining even the very short-chain C3- and C4-SPC (Fig. 2.10.4), the weaker IP agent triethylammonium notably increased the retention of C5-SPC and higher, whereas C4-SPC elutes almost with the dead volume of the LC (Fig. 2.10.5). Addition of commonly used ammonium acetate as buffer component led to the co-elution of the short-chain SPC ([Pg.322]

Fig. 2.10.4. (—)-LC-ESI-MS chromatogram of LAS and SPC separation using water/acetonitrile containing 5 mM tetraethylammonium acetate (from Ref. [13] with permission from author).

When the secondary reaction cycle shown in Scheme 6D.3 was discovered, it became clear that an increase in the rate of hydrolysis of trioxogly colate 10 should reduce the role played by this cycle. The addition of nucleophiles such as acetate (tetraethylammonium acetate is used) to osmylations is known to facilitate hydrolysis of osmate esters. Addition of acetate ion to catalytic ADs by using NMO as cooxidant was found to improve the enantiomeric purity for some diols, presumably as a result of accelerated osmate ester hydrolysis [16]. The subsequent change to potassium ferricyanide as cooxidant appears to result in nearly complete avoidance of the secondary cycle (see Section 4.4.2.2.), but the turnover rate of the new catalytic cycle may still depend on the rate of hydrolysis of the osmate ester 9. The addition of a sulfonamide (usually methanesulfonamide) has been found to enhance the rate of hydrolysis for osmate esters derived from 1,2-disubstituted and trisubstituted olefins [29]. However, for reasons that are not yet understood, addition of a sulfon-amide to the catalytic AD of terminal olefins (i.e., monosubstituted and 1,1-disubstituted olefins) actually slows the overall rate of the reaction. Therefore, when called for, the sulfonamide is added to the reaction at the rate of one equivalent per equivalent of olefin. This enhancement in rate of osmate hydrolysis allows most sluggish dihydroxylation reactions to be mn at 0°C rather than at room temperature [29]. 

In the solution phase, cation radical oxygenations are considerably enhanced by the presence of weak nucleophiles such as acetate155. The nucleophile is believed to function as shown in Scheme 61. Use of tetraethylammonium acetate in acetonitrile for photooxygenations considerably increases the yield of benzaldehydes and reduces the yield of minor products over a range of substituted stilbenes, as shown in Table 11. 

TABLE 11. Results of photooxygenation of substituted stilbenes (PhCH=CHAr) with 9-cyanoanthracene catalyst in the presence of tetraethylammonium acetate (yields given in percent)"... 

Catalyst retention can be further optimised if a charged derivative of the (QN)2PHAL-ligand is used. Quatemisation of one of the nitrogen atoms with benzyl bromide affords the cationic ligand (QN)(QN-Benz)PHAL, and indeed recyclability was improved in the presence of this ligand, however at the cost of lower ee, as shown in Scheme 5.14.[66] The addition of one equivalent of tetraethylammonium acetate was found to improve the selectivity. 16 11... 

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. 

Preparation of Cesium and Quaternary Ammonium Actinide (VI) Acetate Salts. Tetraethylammonium uranyl acetate was prepared by evaporating to dryness a solution of uranyl acetate containing tetraethylammonium acetate in slight excess. The residue was dissolved in boiling absolute ethanol, and the product was precipitated by cooling in a dry ice bath. The product was filtered and recrystallized again from ethanol. 

A series of acetonitrile solutions was prepared which contained known concentrations of (C2H5)4NU02( 0211302)3 and tetraethylammonium acetate. The spectrum of a solution containing no tetraethylammonium acetate was taken to be that of pure 1102(0211302)3 , and the spectrum in liquid tetraethylammonium acetate [probably the monohydrate (20)] with an acetate to U ratio of about 100 was taken to be that of pure 1102(0211302)4 . The absorption spectra of the pure triacetato complex, the pure tetraacetate complex, and one mixture are compared in Figure 3. With the molar absorptivities of the pure complexes obtained in this... 

On experiencing difficulty in the preparation of the 2, 5 -diacetate of uridine-3 -phosphate (1) by usual methods, Khorana et al. found that the desired derivative could be obtained by treatment of (1) in pyridine with a tenfold excess of acetic anhydride and one equivalent of tetraethylammonium acetate as a source of acetate ions. 

Displacements Boron trifluoride etherate. N,N-Diethyl-l,2,2-trichlorovinylamine. Dimethyl sulfoxide. Hexamethylphosphoric triamide. Lead acetate. Lithium bromide. Magnesium bromide. Polyphosphoric acid. Tetraethylammonium acetate. 

Enol acetylation Perchloric acid. Sodium hydride. Epimerization Tetraethylammonium acetate. 

Cope and Nealy5 epimcrized the czs-hydroxy ester (1) by conversion to the tosyl-ate (2),. S v2 displacement by tetraethylammonium acetate (with inversion), followed by alkaline hydrolysis of the ester. 

Tetradecanal-14-ol, 252 Tetraethylammonium acetate, 277 Tetraethylammonium bromide, 140 Tetraethyl dimethylaminomethylene-diphosphonate, 277—278 Tetraethyl orthocarbonate, 285 A8-Tetrahydrocannabinol, 307 A9-Tetrahydrocannabinol, 307 1,2,3,4-Tetrahydrocarbazole, 231... 

Et4.N)[Fe(NS3)(CO)] is also formed (Figure 4) if [Fe(acac)3] is treated with H3(NS3) in presence of tetraethylammonium acetate under an atmosphere of carbon monoxide, when the excess of H3(NS3) acts as a reducing agent. If the tetraethylammonium acetate is omitted, a complex of stoichiometry Fe3(NS3)2(CO)2 and structure [Fe(Fe(NS3)(CO) 2-5, S"] (Figure 5) with a linear trinuclear Fe3S4 core is isolated. The value of v(CO) in the spectrum of this trinuclear compound is 1938 cm The following equilibrium holds in methanol, and can be demonstrated by the reversible uptake of CO. 

For the synthesis of hydroxyloganin 72, the same starting intermediate, as dimesylate 65, is treated with tetraethylammonium acetate to invert the configuration at C-7. 

Grasset, L., Guignard, C., and Ambles, A., Free and esterified aliphatic carboxylic acids in humin and humic acids from a peat sample as revealed by pyrolysis with tetramethylammonium hydroxide or tetraethylammonium acetate, Org. Geochem., 33, 181-188, 2002. 

As with permanganate oxidations, a-hydroxy ketones can be formed as side products. In some cases, structural features make the osmium complex relatively unstable, and in an aqueous medium it can react with water to give a hydroxy-hydrate, which is then converted to an a-keto alcohol. Sharpless et al. developed a procedure that used tert-butyl hydroperoxide with a catalytic amount of osmium tetroxide,367 in the presence of tetraethylammonium hydroxide (EtqN" " OH ). The procedure gave improved yields of the cis-diol and a little a-hydroxyketone, as shown in the conversion of oct-(4 )-ene to a mixture of 258 and 259 in 73% yield. This method is more reliable for oxidation of tri- and tetrasubstituted alkenes than the Upjohn procedure. The reaction was not suitable for base sensitive alkenes, but later work showed that changing the solvent to acetone allowed the use of tetraethylammonium acetate (Et4NOAc) 68 for the hydroxylation of sensitive alkenes such as ethyl crotonate. 

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