Tetrabutylammonium hydrogen sulfate phase-transfer agent

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... 

Another synthetic method involves treating the parent aromatic hydrocarbon with sodium hypochlorite in water-chloroform, using phase transfer agents like tetrabutylammonium hydrogen sulfate or benzyltrimethylam-monium chloride.15 The epoxides are formed in high yields. The rate is pH dependent, and epoxide formation is most facile at pH 8-9. Many K-region arene oxides like 1,165, acenaphthylene 1,2-oxide (19), 1-azaphenanthrene 5,6-oxide (20), 4-azaphenanthrene 5,6-oxide (21), 1,10-phenanthroIine 5,6-oxide... 

A related system for the bromination of alkenes and alkynes using NaOCl, sodium bromide and a phase transfer agent such as tetra-butylammonium hydrogen sulfate has been reported [28]. In this reaction a third, red coloured phase formed between the aqueous and organic layers, which consisted mainly of tetrabutylammonium tribromide. This brominating system converted cyclohexene to 1,2-dibromocyclohexane (40%) and l-bromo-2-chlorocyclohexane (46%), 1-octyne to 1-bromo-l-octene (88%) and diphenylmethane to benzophenone (65%). 

FIG. 10 Reaction profiles for decyl nitrile and decyl azide formation in micro-emulsion and in a two-phase system with added tetrabutylammonium hydrogen sulfate (Q salt) as phase transfer agent. 

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