Tetra-«-butylammonium bromide

Since the amount of solvent in the anode compartment is slowly depleted as the electrolysis proceeds, it is convenient to begin the electrolysis with the level of solution in the anode compartment about 9 cm. above the level of the solution in the cathode compartment. Alternatively, additional 0.2M tetra- -butylammonium bromide in N,N-dimethylformamide may b( added to the anode compartment as the electrolysis proceeds. 

Fluoride chloride exchange of 1 -chlorooctane (3) with potassium fluoride, catalyzed by tetra-butylammonium bromide gives higher yields (72%) of 1-fluorooctane (4) in the presence of formamide than those reactions conducted in the presence of water.57 In the case of 1-bro-mooctane, benzyl chloride or phenethyl chloride, fluoride halide exchange gives only a yield of < 50%. 

Polyhalide salts are prepared in situ in the bromination of less reactive aromatic substrates. Thus, tetra- -butylammonium bromide(TBAB) functions as a catalyst in the bromination of benzene, toluene and even benzyl bromides and a-bromoethylbenzene537 (both tend to polymerize in presence of normal Friedel-Crafts catalysts). Tetra-ethylammonium chloride in CH2Cl2/methanol catalyzes the bromination of anilines538. Improved selectivity is found in the chlorination of toluene catalyzed by onium chloride salts alone or combined with SnCl4539. 

Another synthesis of vertaline (61) involves an intermolecular [3 + 2] cycloaddition of nitrone 19 as a key step (Scheme 9) (27, 22). Ullmann reaction of bromide 82 with 79 in the presence of a phase-transfer catalyst such as tetra-butylammonium bromide gave the diphenyl ether 83 in about 50% yield. The cycloadduct 84 was prepared in 99% yield by heating 83 with the nitrone 19 in refluxing toluene. Treatment of 84 with methanesulfonyl chloride afforded an in-... 

Bis(benzyl) halides react with p-toluenesulfonyl methylisocyanide (TosMIC, 94) in the two-phase system sodium hydroxide/methylene chloride and in presence of tetra- -butylammonium bromide as phase transfer catalyst to [3.3]cyclophanes which contain a carbonyl function in each bridge [72]. The furanophane 95 is accessible from 93 and 94 in 39% yield [72b]. 

Eghbali and Li have recently reported a highly efficient method for the conversion of carbon dioxide to cyclic carbonates in water (Figure 3.14). The organic base l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was used as a simple carbon dioxide activator at a level of 0.1-0.3 equivalents per mole of alkene. The reaction is catalysed by a catalytic amount of bromine provided by tetra-butylammonium bromide (TBAB) or sodium bromide. During the course of... 

A solution of 20 mL of acetic anhydride and 18 mL of 12 N HCl in 50 mL of DMF is added with stirring, and the resulting mixture is gravity filtered through a medium porosity filter paper in order to eliminate the undissolved white solid. After washing the solid with 50 mL of methanol, the clear filtrate is allowed to cool to room temperature. A solution of 15 g (47 mmol) of tetra-butylammonium bromide in 50 mL of methanol is added with rapid stirring, to give a white precipitate. This suspension is stirred for 5 min and the product... 

A solution of 4.19 g of phenylchloroformate (27 mmol) in 25 mL of dichloromethane was added over a period of an hour to an ice cooled, stirred suspension of 2 g (17.1 mmol) of indole, 2 g (50 mmol) of freshly powdered NaOH, and 0.16 g of tetra-butylammonium bromide (50 mmol) in 25 mL of dichloromethane. The mixture was stirred for a further 2 h. 50 mL of water were added and the mixture was extracted with 3 x 30 mL of dichloromethane. The combined extracts were dried with anhydrous sodium sulfate, filtered and evaporated to give pink crystals. These were recrystallized from diethyl ether to yield 3.05 g (75%) of colorless crystals, mp 94 - 95 X. 

With a catalytic system obtained from palladium(II) acetate, potassium carbonate and tetra-butylammonium bromide in dimethylformamide, the same substrates react in an even more complicated way with cis-exo addition and aryl coupling of three aryl groups2178. Under modified reaction conditions with other palladium catalysts, further changes in product selec-tivities are observed22. Several other rather complicated cis-exo dicarborations of norbornene have been described5,23-29. 

Sample preparation 1 mL Serum -i- 50 p,L 1 M HCl, add 4 mL hexane isopropanol 85 15, vortex for 30 s, centrifuge at 2000 g for 5 min, repeat extraction. Combine the organic layers and evaporate them to dryness imder a stream of nitrogen at 40°, reconstitute the residue in 300 pL MeCN 20 mM pH 3.5 phosphate buffer 40 60 containing 5 mM tetra-butylammonium bromide, inject a 200 pL aliquot onto coliunn A with mobile phase A, collect the eluate contedning ibuprofen in a sample loop and inject it onto column B with mobile phase B. Collect the eluate containing ibuprofen in a sample loop and inject it onto column C with mobile phase C, monitor the effluent from column C. 

Dichlorocarbene Dichloronorcarane can be prepared in about 75% yield from cyclohexene, chloroform, and an aqueous solution of sodium hydroxide in the presence of tri-n-butylamine or the hydrochloride as catalyst. Some other tertiary amines or quaternary ammonium salts are equally effective tetra- -butylammonium bromide, N-n-butylpiperidine, N,N-di-n-butylpiperidinium iodide. No primary or secondary amines were found to have this catalytic activity. 

Tetra- -butylammonium bromide, 601 Tetra-n-butylammonium fluoride, 78, 81 Tetra-n-butylammonium halides, 565 Tetra-n-butylammonium hydrogen sulfate,... 

The mass transfer rates of catalysts between two phases are difficultly realized due to the difficult identification of the active catalyst during the reaction [57,112-115], Mass transfer coupled rapid reactions subjected to LLPTC have been studied extensively [58,63,69,115,116], Mass transfer rates of catalysts in the reaction of 2,4,6-tribromophenol and tetra- -butylammonium bromide in a solution of KOH were determined [57,114],... 

Tetra-n-butylammoniuin bisulfate, 337 Tetra- -butylammonium bromide, 353 Tetra- -butylammonium chloride, 353 Tetra-n-butylammonium fluoride, 353-354... 

Preparative Method aqueous Hydrofluoric Acid is passed through an Amberlite IRA 410 OH column, followed by an aqueous solution of Tetrabutylammonium Bromide. After the resin is washed with water, the combined water fractions are repeatedly evaporated until no water is present. Tetrahutylammonium fluoride is collected as an oil in quantitative 3neld. TBAF-a H20 aqueous hydrofluoric acid is passed through an Amberlite IRA 410 OH column, followed by an aqueous solution of tetra- -butylammonium bromide. After the resin is washed with water, the combined water Iractions are repeatedly evaporated until no water is present. Tetrabutylanunonium fluoride is collected as an oil in quantitative yield. The hydrofluoric acid method has been described most recently by Kumar. TBAFanh under nitrogen, hexafluorobenzene is added to a cold (—50 °C) THF solution of tetra-n-butylanunonium cyanide. The highly colored solution is stirred for 4 h at —15 °C, cooled to —60 °C, and filtered. The resulting colorless solid is washed with cold THF and the residual solvent is removed in vacuo to yield anhydrous TBAF (60%). ... 

A mixture of diisopropylethylamine (Hiinig s base, 1.74 ml, 10 mmol), palladium acetate (112 mg, 0.5 mmol, 5 mol%), tetra- -butylammonium bromide (1.61 g, 5 mmol) and 4-bromoanisole (110, 1.87 g, 10 mmol) in DMF (1.25 ml) was stirred under nitrogen at 115 "C for 96 h. After cooling to room temperature, water (50 ml) and diethyl ether (50 ml) were added. The organic phase was separated, washed with water and dried (MgS04). The solvent was evaporated in vacuo. Pure 4,4 -dimethoxy biphenyl (77, 514 mg, 48%) was obtained after purification with preperative chromatography, m.p. 172-173 "C. 

An optically active PAI was prepared by the direct polyamidation of the chiral diacid with azo diamine under green condition using molten tetra- -butylammonium bromide. 

CsF added to tetra- -butylammonium bromide or Aliquat 336, the mixture stirred for 5 min, n-octyl bromide added, stirring continued for 5 min, and allowed to react for 40 h - n-octyl fluoride. Y 77%. Work-up is easy and reagents readily available yields are high from satd. chlorides and bromides (incl. benzylic), but aromatic bromides were more resistant. F.e. and with tetra-n-butylammonium fluoride, also from tosyla-tes, and comparison with other heterogeneous methods s. G. Bram et al., Synth. Commun. 18, 1661-7 (1988) review of solid-liq. phase transfer catalysis without solvent s. Bull. Soc. Chim. France 1989, 247-51. 

A soln. of diphenyl disulfide in 0.1 M tetra- -butylammonium bromide (as both mediator and electrolyte) in dichloromethane electrolysed under argon in a divided cell with platinum electrodes at a constant current of 0.02-0.03 A (current density 3 mA/cmO until 10 As of charge consumed, 0.5 eqs. 4-pentenol added, and electrolysis continued until reaction complete by g.c. or t.l.c. 2-(phenylthiomethyl)tetr hydro-furan. Y 72%. The method is inexpensive, less toxic than Se-based methodologies, and generally applicable to 5- and 6-membered O-heterocyclics reaction may also be achieved (preferably) by direct electrolysis with bis(4-methoxyphenyl) disulfide (having a much lower oxidation potential than diphenyl disulfide). F.e. and stereoselectivity, also 2-(aryIthio)lactones from ethylenecarboxylic adds, s. S. Toteberg-Kaulen, E. Steckhan, Tetrahedron 44, 4389-97 (1988). 

A soln. of benzaldehyde and tetra- -butylammonium bromide in DMF cooled to — 10° in a cell fitted with a foamy Ni cathode surrounding a sacrificial Zn rod anode, and electrolyzed at a constant current of 0.3 A with bromotrifluoromethane bubbling through the soln. for ca. 4-5 h 2,2,2-trifluoro-l-phenylethanol. Y 95%. The dissolving (sacrificial) zinc anode is essential in what is effectively an electro-assisted Barbier-type synthesis. The reaction is general with aldehydes, and reasonable yields are obtained with easily reducible ketones (preferably with added TMEDA). F.e.s. S. Si-bille et al.. Tetrahedron 45, 1423-8 (1989). 

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