Tetrahexylammonium bromide

Hg. Allylmercury bromide and diallylmercury are both stable in water. They can allylate aldehydes in aqueous media but, in the case of allylmercury bromide, activation with tetrahexylammonium bromide was necessary.186 The allylation reaction is chemoselective towards aldehyde on the contrary, ketone compounds are unaffected. 

The highest enantiomeric excess in the palladium(0)-assisted enantiosclcctive alkylation of racemic 3-cycloalkenyl acetate has so far been observed with the chiral ligands 2, 3a and 3b60-61 (Table 17). The addition of tetrahexylammonium bromide dramatically increases enantioselec-tivity in the case of ligand 2, as does changing the solvent from tetrahydrofuran to dichloro-methane. which is believed to enhance the formation of dimeric ionic salts of the nucleophile. In contrast, additives such as tetraalkylammonium salts or crown ethers diminish the enantiomeric excess in reactions catalyzed by the phosphinoaryl oxazoline ligands 3a and 3b. bearing a chiral phosphorus on the aryl moiety. 

Isomerizations, Under PTC conditions (presence of tetrahexylammonium bromide) 1,3-diaryIpropynes can be isomerized to diarylallenes by KOH at room temperature.A Brook rearrangement of acylsilanes occurs upon addition of cyanide ion. ... 

Sample preparation Perform all operations with the exclusion of light. Evaporate 240 jjiL derivatization solution into a vial, add 400 pL 50 mM pH 7.0 phosphate buffer, add 100 [xL plasma, add 10 (xL 46 jxg/mL undecylenic acid in MeCN, vortex for 5 s, heat at 70° for 40 min, add 500 jxL MeCN, centrifuge at 3000 g for 5 min, inject a 20 jxL aliquot. (Derivatization solution was 1.65 g Arkopal N-130 (a non-ionic surfactant, nonylphenol/13 unit chain polyoxyethylene) + 650 mg tetrahexylammonium bromide -I- 60 mg 4-bromo-methyl-7-methoxycoumarin in 20 mL acetone.)... 

Jin et al. [229] further performed the dehydrohalogenation of 2-bromo-octane with dodecane as the organic solvent and potassium hydroxide in the aqueous solution to investigate the synergistic effect of two PT catalysts in the situation of a third liquid phase using a combination of tetrahexylammonium bromide and PEG. They concluded that a molecule of tetrahexylammonium bromide surrounded by many molecules of water and some PEG 200 led to the effect of water on the catalytic activity of tetrahexylammonium bromide becoming weaker when the amount of PEG was increased. 

Tetramethylammonium bromide (or hydrogen sulfate) Tetraethylammonium bromide (or hydrogen sulfate) Tetrapropylammonlum bromide or hydrogen sulfate) Tetrabutylammonlum bromide (or phosphate, iodide) Tetrapentylammonium bromide Tetrahexylammonium bromide (or hydrogen sulfate) Tetraheptylammonlum bromide Tetraoctylammonium bromide Hexadecyltrimethyl ammonium hydroxide (or bromide, or hydrogen sulfate) Decamethylenebis (trlmethylammonium bromide)... 

Fig. 3. Schematic illustration of the electric double layer around a tetrahexylammonium bromide stabilized metal nanoparticle as an example of electrosteric (combined electrostatic and steric) stabilization.

Tetrahexylammonium phthalimide, generated in situ from potassium phthalimide and tetra-hcxylammonium bromide, aminates the racemic 3-(acyloxy)cycloalkenes 9 to imides (S)-10 with extremely high enantioselectivity in the presence of a palladium(0) complex prepared from dimeric n-allylpalladium chloride and the chiral ligand (/ ,/ )-G78. (5)-10c has been converted to a protected derivative of (S)-2-aminopimelic acid. 

The fundamental theory of phase transfer catalysis (PTC) has been reviewed extensively. Rather than attempt to find a mutual solvent for all of the reactive species, an appropriate catalyst is identified which modifies the solubility characteristics of one of the reactive species relative to the phase in which it is poorly solubilized. The literature on the use of PTC in the preparation of nitriles, halides, ether, and dihalocarbenes is extensive. Although PTC in the synthesis of C- and 0-alkylated organic compounds has been studied, the use of PTC in polymer synthesis or polymer modification is not as well studied. A general review of PTC in polymer synthesis was published by Mathias. FrecheE described the use of PTC in the modification of halogenated polymers such as poly(vinyl bromide), and Nishikubo and co-workers disclosed the reaction of poly(chloromethylstyrene) with nucleophiles under PTC conditions. Liotta and co-workers reported the 0-alkylation of bituminous coal with either 1-bromoheptane or 1-bromooctadecane. Poor 0-alkylation efficiencies were reported with alkali metal hydroxides but excellent reactivity and efficiencies were found with the use of quaternary ammonium hydroxides, especially tetrabutyl- and tetrahexylammonium hydroxides. These results are indeed noteworthy because coal is a mineral and is not thought of as a reactive and swellable polymer. Clearly if coal can be efficiently 0-alkylated under PTC conditions, then efficient 0-alkylation of cellulose ethers should also be possible. 

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