Tetrabutylammonium purification

The method for analysing sediment involves extraction of organochlorine insecticides and polychlorobiphenyls with a mixture of acetone and hexane together with 1% aqueous ammonium chloride. The extracts are then concentrated for purification with concentrated sulphuric acid and aqueous sodium sulphite in the presence of tetrabutylammonium sulphate and finally gas chromatographic analysis is applied. 

The deprotection step and subsequent purification are equally facile. Exposure of a TiPS-ethynyl-protected dendrimer to tetrabutylammonium fluoride in THE results in a quantitative reaction within 2 h. The tetrabutylammonium salts can be removed by siHca plug filtration rendering pure product, and the obtained yields are higher than 95%. If deprotection is effected instead with ammonium fluoride and catalytic amounts of tetrabutylammonium fluoride, even silica plug filtration is unnecessary. 

A recent literature report described a green procedure for the condensation of arylacetonitriles with cyclic ketones using phase-transfer catalysis. This process was applied to the synthesis of venlafaxine, which was realized in overall 30% yield in two steps from commercially available 14. The condensation step was run in aqueous sodium hydroxide in the presence of tetrabutylammonium sulfate, to provide quantitative yield of intermediate 15. Hydrogenation in a formalin-methanol mixture provided the final product venlafaxine (1) in 30% overall yield. This protocol did not necessitate intermediate purification steps, making it attractive from the commercial standpoint. 

Parlow, J. J. Vazquez, M. L. Flynn, D. L. A Mixed Resin Bed For the Quenching and Purification of Tetrabutylammonium Fluoride Mediated Desilylating Reactions, Bioorg. Med. Chem. Lett. 1998, 8, 2391. 

Tetrabutylammonium fluoride trihydrate was purchased from Acros Chimica and used without further purification. 

Sample preparation for the determination of cyclamate by HPLC can be performed as described in Sec. I.C. (17,24,35,43). Potassium bromide can be used as an internal standard (17). In order to reduce interference, extracts can be clarified with Carrez reagents (24,35) or by solid-phase extraction. Nakazato et al. (43) added tetrabutylammonium bromide to the extract, adjusted pH to 4.0 -5.0, passed it through a Mega Bond Elut Cl 8 cartridge, and eluted cyclamate with a mixture of acetonitrile water (3 7, v/v). Lehr and Schmid (71) used an amino-anion-exchange column for the purification of cyclamate. After activation of the column with n-heptane, methanol, water, and 30% acetic acid, the sample was passed through the column and washed with water. Cyclamate was eluted with 2 M NaOH solution. 

Sodium hydride (97%), triethyl phosphite (99%), a,a dibromo-p-xylene (97%), 4-hydroxy-3-methylbenzaldehyde (97%), 3-ethoxy-4-hydroxybenzaldehyde (99%), vanillin (99%), and valeryl chloride (98%), were supplied by Aldrich Chemical Co. and were used without further purification 4-hydroxybenzaldehyde (96%, Aldrich) was resublimed prior to use. The add chlorides were supplied by Aldrich Chemical Co. and, with the exception of sebacoyl chloride (99+%), were fractionally distilled at reduced pressure through a 6-inch Vigreux column prior to use pimeloyl chloride 95-6°C at 1.1 torr, suberoyl 114-16°C at 2.2 torr, azelaoyl 104-6°C at 0.35 torr. Dibromoalkanes from Aldrich Chemical were fractionally distilled prior to use 1,7-dibromoheptane 111-114°C at 1.4 torr, 1,9-dibromononane 135-137°C at 2.7 torr, 1,11-dibromoundecane 129-131 °C at 0.85 torr. Tetrabutylammonium iodide (98%) was supplied by Aldrich. Reagent grade solvents were obtained from Fisher Scientific. 

From 2, 3 -bis-0-(tert-butyldimethylsilyl)-5 -deoxy-5-fluorocytidine and n-pentylchloroformate in dichloromethane and pyridine may be obtained 2, 3 -bis-0-(tert-butyldimethylsilyl)-5 -deoxy-5-fluoro-N4-((pentyloxy)carbonyl) cytidine.From 2, 3 -bis-0-(tert-butyldimethylsilyl)-5 -deoxy-5-fluoro-N4-((pentyloxy)carbonyl)cytidineand tetrabutylammonium fluoride in tetrahydrofuran at room temperature for 2 hours may be prepared the product which by hydrolyses may be converted to 5-deoxy-5-fluoro-N4-((pentyloxy)carbonyl)cytidine. Purification of the product may be carried out by silica gel chromatography (using dichloromethane methanol = 20 1 as an eluent). 

Iodobenzene (1.01 g, 4.9 mmol) was dissolved in dichloromethane (75 ml) and stirred vigorously with hypochlorite solution (200 ml of commercial laundry bleach adjusted to pH 8.2 and containing 200 mg of tetrabutylammonium hydrogen sulphate) at room temperature for 45 min. The reaction mixture was allowed to stand for 1 h then the precipitate was filtered to give crude iodylbenzene (0.69-0.94 g, 59-81%). Purification may be effected by crystallization from water or acetic acid. 

Treatment of the crude reaction mixture containing compounds 718, 719 and ferrocene without purification with benzoyl chloride (70 °C) followed by hydrolysis of the resulting benzoylated pyrrole 720 using tetrabutylammonium hydroperoxide (TBAH) furnished pharmaceutical agent (6 )-Ketorolac (ToradoT and Acular, 721, ee 90% determined by chiral HPLC, 25% isolated yield over three steps) along with recovered chiral auxiliary. 

As reference electrode, an Li/LiCl electrode, which in the presence of excess tetrabutylammonium chloride is an electrode of the second kind, may be used [413]. An Ag/ AgC104 reference electrode with an NaC104 salt bridge has been used [414] AgCl/Ag [415] and TlX/Tl [416] reference electrodes have also been employed. The purification of PC has been discussed [417]. 

The usual procedure to remove the protecting silyl group (tetrabutylammonium fluoride in tetrahydrofuran) has caused acetyl rearrangements rather than to give a sialic acid derivative with a free C-9 primary hydroxyl function. Compound 5c, in which the free hydroxyl appears to be the secondary one at C-7, has been obtained as the sole reaction product in a 85% jdeld, after chromatographic purification. The overall yield of 5c based on 3a has been 83% [30]. 

To a solution of the TBDPS ether (180 mg, 0.38 mmol) in THF (4 mL) was added a tetrabutylammonium fluoride solution (1.0 M in THF, 0.76 mL, 0.76 nunol). The resulting yellow solution was stirred at room temperature for 5 h and quenched by addition of a saturated aqueous solution of NH4CI. After removal of THF in vacuo, the aqueous layer was extracted with EtOAc (3x15 mL). The combined organic layers were washed with brine (10 mL), dried (MgSO4), filtered, and concentrated in vacuo. Purification of the residue by flash chromatography eluting with EtOAc/hexane (1 9) afforded the primary alcohol (73 mg, 82%) as a colorless oil. 

C-A -Methylketanserin 279, the analogue of serotonin-2 receptor antagonist, ke-tanserin 280, has been synthesized for studying these receptors in vivo using PET by alkylation of ketanserin in DMF solution in the presence of small amount of aqueous tetrabutylammonium hydroxide at 80 °C for 2 minutes followed by chromatographic purification during 22 minutes total synthesis time from EOB, with 10% radiochemical yield calculated at the end of synthesis (EOS). 

Chirality may be introduced in another part of the molecule Isobe and coworkers have performed the addition of organometallic reagents to chiral sulfones 7.78 [ 73], After sequential treatment of the adducts with tetrabutylammonium fluoride, aluminum amalgam and HgC, a-branched aldehydes were isolated with a high enantiomeric excess (Figure 7.54). Analogs formed from (5)-valinol have been used for similar purposes, but preparation of the substrates requires tedious purification [325],... 

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