Tetrabutylammonium bromide

Pha.se-Tra.nsfer Ca.ta.lysts, Many quaternaries have been used as phase-transfer catalysts. A phase-transfer catalyst (PTC) increases the rate of reaction between reactants in different solvent phases. Usually, water is one phase and a water-iminiscible organic solvent is the other. An extensive amount has been pubHshed on the subject of phase-transfer catalysts (233). Both the industrial appHcations in commercial manufacturing processes (243) and their synthesis (244) have been reviewed. Common quaternaries employed as phase-transfer agents include benzyltriethylammonium chloride [56-37-17, tetrabutylammonium bromide [1643-19-2] tributylmethylammonium chloride [56375-79-2] and hexadecylpyridinium chloride [123-03-5]. 

Bromine electrogeneration was carried out from tetrabutylammonium bromide in 0,1 M NaClO acetonitrile solution with 100 % current yield. 

A, tetrabutylammonium bromide B, methyltri-n-octylammonium chloride (Aliquat 336). 

Certain alkylated ammonium, phosphonium, or sulfonium compounds are effective, in relatively low concentrations, in interfering with the growth of gas hydrate crystals [972] and therefore are useful in inhibiting plugging by gas hydrates in conduits containing low-boiling hydrocarbons and water. For example, tetrabutylammonium bromide will be active. Gas hydrate or ice formation is further inhibited in lines by adding amino acids or amino alcohols [523]. 

Fig. 5.5 Chromatogram ofchlor-prothixene hydrochloride CRS which contains 2.7 % ofthe f -isomer. (Column 4 x 120 mm hypersil BDS [3 pm]. Mobile phase 6.0 g potassium dihydrogen phosphate, 2.9 g sodium lauryl sulphate, 9.0 g tetrabutylammonium bromide 550 ml water, 50 ml methanol and400 ml acetonitrile, flow rate 1.5 ml/min and detection wavelength 254 nm.)...

Tetrabutylammonium bromide (TBABr), recrystallize from ethyl acetate Ultrapure water for HPLC analysis... 

The stable complex of bromine with tetrabutylammonium bromide is safer and more easily handled than bromine itself. 

Preparation of Merrifield resin-bound nitro acetates, which is a suitable building block for the development of combinatorial solid phase synthesis, is reported.4 The anion of ethyl nitro acetate is generated in DMF by an electrochemical method using Pt cathode, magnesium rod anode, and tetrabutylammonium bromide as an electrolyte. Alkylaton of this anion with alkyl halides gives mono-alkylated products in 80% yield.5... 

The multifunctionalised thicno[2,3-7]thiophene 86 reacts with ethyl cyanoacetate, potassium carbonate, and tetrabutylammonium bromide (TBAB) in dimethylformamide (DMF) at 70 °C to give the thienothienopyridine 87. Presumably, this reaction proceeds as shown in Scheme 25, although the published structure 88 for the final cyclisation product may not represent the major tautomer <2003PS(178) 1115>. 

A related example involves the N-alkylation of azaheterocycles such as imidazole (Scheme 4.8). These reactions are typically performed using 1.5 equivalents of the alkyl halide and a catalytic amount of tetrabutylammonium bromide (TBAB). The reactants are adsorbed either on a mixture of potassium carbonate and potassium hydroxide or on potassium carbonate alone and then irradiated with microwaves (domestic oven) for 0.5 to 1 min. With benzyl chloride, a yield of 89% was achieved after 40 s [18]. 

TBAB = tetrabutylammonium bromide Scheme 6.12 Ligand-free Suzuki reactions using TBAB as an additive. 

Similarly to classical PTC reaction conditions, under solid-liquid PTC conditions with use of microwaves the role of catalyst is very important. On several occasions it has been found that in the absence of a catalyst the reaction proceeds very slowly or not at all. The need to use a phase-transfer catalyst implies also the application of at least one liquid component (i.e. the electrophilic reagent or solvent). It has been shown [9] that ion-pair exchange between the catalyst and nucleophilic anions proceeds efficiently only in the presence of a liquid phase. During investigation of the formation of tetrabutylammonium benzoate from potassium benzoate and tetrabu-tylammonium bromide, and the thermal effects related to it under the action of microwave irradiation, it was shown that potassium benzoate did not absorb micro-waves significantly (Fig. 5.1, curves a and b). Even in the presence of tetrabutylammonium bromide (TBAB) the temperature increase for solid potassium benzoate... 

Several solvent-free N-alkylation reactions have been reported which involve the use of phase transfer agent, tetrabutylammonium bromide (TBAB), under microwave irradiation conditions, an approach that is described in Chapt. 5 [34],... 

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