Phase transfer catalysts sulfate

Pyrrohdinone can be alkylated by reaction with an alkyl haUde or sulfate and an alkaline acid acceptor (63,64). This reaction can be advantageously carried out with a phase-transfer catalyst (65). Alkylation can also be accompHshed with alcohols and either copper chromite or heterogenous acid catalysts... 

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). 

V-Alkylation of 3-hydroxypyridine results from direct treatment with an alkyl halide or dimethyl sulfate and alkali (59JA5140,57RTC58). Regioselectivity depends, however, on other substituents present as well as conditions. For example, 3-hydroxy-2-nitropyridine is exclusively O-alkylated with dimethyl sulfate and potassium carbonate (81MI20600) and 2-amino-3-hydroxypyridines are exclusively O-benzylated with benzyl chloride and alkali in a two phase system and phase transfer catalyst (Scheme 96) (81S971). 

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. 

Benzophenone hydrazone (5.88 g, 20 mM) was dissolved in methylene chloride (20 ml) and over-layered with 1 M sodium hydroxide (40 ml) containing, as phase transfer catalyst, tetrabutylammonium sulfate (0.68 g) and sodium iodide (300 mg). The cathode half cell contained 1 M sodium hydroxide (60ml). The whole cell was cooled to 0°C, the anode compartment stirred and electrolysed at a current of 50 mA. Formation of DDM was followed using the DDM absorption peak at 525 nm. The chart obtained was as shown in Figure 2. 

An attempt was also made to accelerate the same reaction performed in a microemulsion based on water, nonionic surfactant and hydrocarbon oil [9]. The reaction was performed in a Winsor III system and the same Q salt, tetra-butyl ammonium 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 [52]. The addition of a Q salt gave no effect for a system based on cationic surfactant, a marginal increase in rate for a system based on nonionic surfactant and a substantial effect when an anionic... 

N-Alkylation of 1,2,3-triazoles and benzotriazoles is readily achieved using (1) alkyl halides, dialkyl sulfates, diazoalkanes, and jS-tosylates or (2) the Mannich reaction. When alkyl halides are used, sodium alkoxide, sodium hydride, or sodium hydroxide is usually employed as the base. The N-alkylation of benzotriazole with alkyl halides proceeds efficiently using powdered NaOH as the base in DMF. The highest yields (80100%) of the alkylated benzotriazoles are obtained when a fourfold excess of NaOFl is employed. A-Alkylbenzotriazoles have been prepared from benzotriazole and alkyl halides using phase-transfer catalysts, e.g., KOFI, benzene, tetrabutyl-ammonium salts or KOH, benzene, polyethylene glycol. 

A detailed study of the N-methylation of 2,3,3-trimethylindolenine with methyl sulfate using triethylbenzylammonium chloride as a phase-transfer catalyst has appeared. The reported yields of high-purity (96-99%) Fischer s base were 90-92%.19 N-alkylation is the most practical method for preparing a Fischer s base with alkyl groups having, for example, thienyl,20 hydroxy, carboxy, or sulfonate substituents. 

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. 

Coupling of a benzoic acid derivative under basic conditions is achieved with alkyl iodides," alkyl chlorides,dimethyl sulfate, or (l,1-dihydroperfluoroalkyl)phenyliodonium triflates. Common bases used arc potassium carbonate or sodium hydroxide (with phase-transfer catalyst). " Again, employing acid chlorides " - or anhydrides, " is the method of choice. The reaction can be performed without further activation, " " but in most cases the transformation takes place in the presence of the usual bases, triethylamine - " or pyridine " " " " " [in some cases 4-(dimethylamino)pyridine is added " ]. In a similar manner carbamates. thiocarbamates, " or thiocarbonates are synthesized. Perfluoropropcn-2-ol... 

Dehydrohalogenation. Aryl vinyl ethers are prepared conveniently by dehy-drohalogenation of aryl 2-haloethyl ethers with aqueous sodium hydroxide with tetra-n-butylammonium hydrogen sulfate as phase-transfer catalyst (equation I). 

Solid-liquid phase-transfer catalysts. Diphenylphosphinic hydrazide (1) is not alkylated efficiently under usual phase-transfer conditions, but is alkylated by use of solid Na0H-K2C03 with benzene as solvent. The reaction is strongly accelerated by tetra-n-butylammonium hydrogen sulfate. The role of K2CO3 is not clear. The products are hydrolyzed by 15% HCl to pure monoalkylhydrazines. 

An oxidative addition with concomitant carbonylation also occurs when (butadiene)Fe(CO)j is protonated under CO by HBF4 or CF3COOH [( -crotyl)Fe(CO)4] is formed . Phase-transfer catalysis can be used to prepare metal carbonyl anions. For example it has been applied to the preparation of [NR4][Ni(CO)3CN] from NiCNj and CO in a 4-methyl-2-pentanone mixture, tetrabu-tylammonium hydrogen sulfate being the phase-transfer catalyst . ... 

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. 

Tetra-n-butylammonium hydrogen sulfate [32503-27-8] M crystallises from acetone. It has been used as a phase transfer catalyst. 

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