Tetrabutylammonium hydrogen sulfate groups

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]. 

Acetylation of phenols and anilines. These substrates can be acetylated rapidly and in generally high yield by reaction with acetyl chloride using powdered NaOH and tetrabutylammonium hydrogen sulfate in an organic solvent (CH2CI2, dioxane, THE). Even 2,6-di-f-butyI-p-cresol can be acetylated in this way in 72% yield. Selective acylation of the phenolic hydroxyl group of estradiol is possible. ... 

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]. 

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,... 

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