Tetrabutylammonium hydrogen sulfate phase transfer catalyst

The mesogenic units with methylenic spacers were prepared by reacting the sodium salt of either 4-methoxy-4 -hydroxybiphenyl or 4-phenylphenol with a bromoester in DMF at 82° C for at least 4 hours in the presence of tetrabutylammonium hydrogen sulfate (TBAH) as phase transfer catalyst. In this way, ethyl 4-(4-oxybi-phenyl)butyrate, ethyl 4-(4-methoxy-4 -oxybiphenyl)butyrate, ethyl 4-(4-oxybiphenyl)valerate, ethyl 4-(4-methoxy-4 -oxybiphenyl)-valerate, n-propyl 4-(4-oxybiphenyl)undecanoate and n-propyl 4-(4-methoxy-4 -oxybiphenyl)undecanoate were obtained. These esters were hydrolyzed with base and acidified to obtain the carboxylic acids. The corresponding potassium carboxylates were obtained by reaction with approximately stoichiometric amounts of potassium hydroxide. Experimental details of these syntheses were described elsewhere (27). 

The dimer of chloro(l,5-hexadiene)rhodium is an excellent catalyst for the room temperature hydrogenation of aromatic hydrocarbons at atmospheric pressure. The reaction is selective for the arene ring in the presence of ester, amide, ether and ketone functionalities (except acetophenone). The most useful phase transfer agents are tetrabutylammonium hydrogen sulfate and cetyltrimethylammonium bromide. The aqueous phase is a buffer of pH 7.6 (the constituents of the buffer are not critical). In all but one case the reaction is stereospecific giving cis products... 

The solubility of the components in the solvent must be sufficient. To improve the solubility, cosolvents can be used. Another possibility is the application of a two-phase system or an emulsion in the presence of phase-transfer catalysts. A two-phase system also has advantages in product isolation and continuous electrolysis procedures. A typical example is the synthesis of p-methoxy benzonitrile by anodic substitution of one methoxy group in 1,4-dimethoxybenzene by the cyanide ion (Eq. 22.21). The homogeneous cyanation system (acetonitrile, tetraethylammonium cyanide) [24] can be efficiently replaced by a phase-transfer system (dichloro-methane, water, sodium cyanide, tetrabutylammonium hydrogen sulfate) [71]. 

Alkynes.10 Alkynes can be prepared by double dehydrobromination of pic-dibromides in petroleum ether by use of powdered KOH and catalytic amounts of a phase-transfer catalyst. Tetraoctylammonium bromide, 18-crown-6, or even Aliquat 336 are much more effective than more hydrophilic quarternary ammonium salts, such as tetrabutylammonium hydrogen sulfate, previously used (7, 354-355)." Isolated yields are 80-98%. Yields are generally lower when mc-dichlorides are used as the starting material. 

Hydrogenation of arenes Hydrogenation >f benzene rings occurs selectively and stereospecifically at 25° and atmospheric pressure in the presence of this rhodium catalyst under phase-transfer conditions (tetrabutylammonium hydrogen sulfate, buffered aqueous hexane, pH 7.4-7.6). 

Gomberg-Bachmann biphenyl synthesis. Reaction of stable arenediazonium tet-rafluoroborates or hexafluorophosphates in an aromatic solvent with potassium acetate (2 equiv.) and a phase-transfer catalyst results in biar Is in high yield. Crown ethers, Aliquat 336, and tetrabutylammonium hydrogen sulfate arc all effective catalysts. The reaction is useful for synthesis of unsymmetrical biaryls. The ortho-isomer predominates in reactions with a monosubstituted benzene. The most selective method is to couple a substituted arenediazonium salt with a symmetrical arene. 

The complex [ RhCl(l,5-COD) 2] and a phase transfer catalyst (cetyltrimethylammonium bromide or tetrabutylammonium hydrogen sulfate) also reduce aromatic hydrocarbons under hydrogen. ... 

Biphenol (0.93 g, 5 mmol) and monomer 10 (0.83 g, 5 mmol) are dissolved in the CO2/O2-free sodium hydroxide solution prepared in step 2 above. The solution is then placed into a household blender to form the aqueous phase of the interfacial polymerization. Then, tetrabutylammonium hydrogen sulfate (0.18 g, 0.05 mmol) is added as phase transfer catalyst. 

Singh et al. have developed an efficient protocol for the selective N-1 alkylation of DHPMs 8 using tetrabutylammonium hydrogen sulfate and 50% aqueous NaOH as the phase transfer catalyst and base, respectively, under mild solvent-free conditions (Scheme 13). This protocol of N-1 alkylation not only preserves the simplicity of the synthetic operation but also furnished remarkable selectivity (over N-3), giving 18 in moder-ate-to-high yields (09MI10). 

For a similar catalytic oxidation, Giannis group utilized a water-ethyl acetate biphasic solvent system in the presence of 10 mol% of 2-iodobenzoic acid and tetrabutylammonium hydrogen sulfate as a phase-transfer catalyst. Under these conditions, primary benzylic alcohols were oxidized to the corresponding aldehydes, which, in contrast to the Vinod s procedure, did not undergo further oxidation (Scheme 4.45) [5]. 

Chloroform added dropwise at room temp, to a stirred mixture of N-methyl-aniline, aq. 50%-NaOH, benzyltriethylammonium chloride, and, optionally, methylene chloride, and stirring continued 1-2 hrs. -> N-formyl-N-methylaniline. Y 76%. F. e. s. J. Grafe, I. Frohlidi, and M. Muhlstadt, Z. Chem. 14, 434 (1974) s. a. M. Makosza and A. Kacprowicz, Rocz. Chem. 49, 1627 (1975) (Eng) C. A. 84, 43265 N-alkylation with alkyl halides, ibid. 49, 1203 (Eng) C. A. 84, 30793 cf. R. Brehme, Synthesis 1976, 113 with tetrabutylammonium hydrogen sulfate as phase transfer catalyst, indole derivs., cf. A. Barco et al., Synthesis 1976, 124. 

Conventional liquid-liquid two-phase (organic solvent-50% NaOH aqueous solution) phase transfer catalyzed polyetherification reaction conditions were used for the preparation of both the polyfonnal and polyethers reported in Table 1. The polymerizations were carried out at 70 C in o-dichloro-benzene- 50% NaOH water solution (10 times mole excess NaOH vs phenol groups), in the presence of tetrabutylammonium hydrogen sulfate (TBAH) as phase transfer catalyst. A typical example is presented below. HMS,... 

Ahmed-Omer et ol. [31] have shown that phase-transfer catalyzed segmented flow in a capillary microreactor can even be accelerated by sonication. The hydrolysis of p-nitrophenyl acetate in toluene with 0.5 M aqueous sodium hydroxide at different temperatures was used as a test reaction for this system (Scheme 8.5). Sonication and tetrabutylammonium hydrogen sulfate as phase-transfer catalyst were used to increase the rate of reaction showing an increase in the yields. It was also shown in a comparison of flow forms that segmented flow had an advantage over parallel flow because of the increased surface to volume ratio. The reaction in flow was also shown to be superior to batch conditions. A more in-depth investigation of the effect of sonication on the hydrolysis of p-nitrophenyl acetate has been performed by Janisch and Hiibner et al. [32]. They showed that sonication of the reaction was indeed beneficial showing increased yields compared to silent conditions. 

Freedman and Dubois [ 1 ] have found that a variety of ethers can be prepared by the reaction of either primary or secondary alcohols with inexpensive primary alkyl chlorides in the presence of excess concentrated aqueous sodium hydroxide solution and tetrabutylammonium hydrogen sulfate as catalyst. The formation of -butyl n-hexyl ether is shown in equation 5.1. Typically, the 8 2 displacement reaction was not successful with secondary alkyl halides even under phase transfer conditions. 

A soln. of p-methylbenzyl alcohol in ethyl acetate stirred 0.5 hr. at room temp, with excess aq. 10%-NaCl (commercial bleach) in the presence of ca. 5% tetrabutylammonium hydrogen sulfate as phase transfer catalyst p-tolualdehyde. Y ca. 100%. - Similarly Cyclohexylamine, after hydrolysis of the intermediate N-chlorimine with dil. mineral acid -> cyclohexanone. Y 98%. F. e., also nitriles from prim, amines, and limitations, s. G. A. Lee and H. H. Freedman, Tetrah. Let. 1976, 1641. 

Many catalysts can be used tetrabutylammonium halides, tetrabutylammonium hydroxide, tetrabutylammonium hydrogen sulfate, tetrabutylphosphonium bromide, 18-crown-6 ether, and cryptand[2.2.2]. There have been few studies on the influence of the catalyst on the reactions. However, Nishibuko et al carried out an excellent study on the influence of experimental conditions on phase transfer catalyzed polymer modification they showed that the nature of the catalyst and the type of phase transfer reaction (solid-liquid, liquid-liquid), as well as the polarity of the solvent are very important parameters. The purity of the system must be carefully controlled thus, the presence of traces of water may have a great influence on the conversion and the occurrence of side reactions. 

To synthesize alcohol with the reversed configuration at C-2, we started with the reduction of levoglucosenone to form the well-known alcohol (4) (Scheme 11.8). It was reacted with mesyl chloride to produce mesylate (28). The nucleophilic substitution was performed in refluxing toluene (or xylene) using sodium benzoate as a nucleophile and a nonnucleophilic phase transfer catalyst (tetrabutylammonium hydrogen sulfate) to give a very good yield of the expected benzoate (29). The hydrolysis of the... 

The reaction rates of the nucleophilic substitution reaction were compared with the rates obtained by phase transfer catalysis using either a quaternary ammonium salt (tetrabutylammonium hydrogen sulfate) or a crown ether (18-crown-6) as catalyst [28]. The microemulsions were based on the non-... 

An attempt was also made to accelerate the same reaction performed in a microemulsion based on water, nonionic surfactant, and hydrocarbon oil [23]. The reaction was performed in a Winsor HI system and the same Q salt, tetrabutylammonium hydrogen sulfate, was added to the formulation. In this case the addition of the phase transfer catalyst gave only a marginal increase in reaction rate. Similar results have been reported for an alkylation reaction performed in different types of micellar media [30]. The addition... 

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