Phase transfer catalysis early examples

What will phase transfer catalysis provide polymer chemistry within the near future It is apparently still to early to predict this. We are not yet in the possession of many elemental mechanistic and kinetic understandings in order to answer questions like, for example, why not "living polyetherification "... 

An early example of a comparison between the microemulsion approach and the process of phase transfer catalysis was a study by Menger et al. on the hydrolysis of trichlorotoluene to form sodium benzoate see Fig. 6 [47]. As can be seen from Table 1, hydrolysis in the presence of the cationic surfactant... 

In the first example of the application of phase-transfer catalysis to early-transition metal organometallic chemistry, reaction of (q -cyclopentadienyOtetracarbonylvanadium with 5 N sodium hydroxide, in benzene and in the presence of tetrabutylammonium hydrogen sulphate as a phase-transfer catalyst, afforded the (q -cyclopentadienyl)tricarbonylhydridovanadate anion (Scheme 8) [75] ... 

With the probable exception of Wohler s isomerization of ammonium isocyanate to urea, most of the major advances in organic chemistry have been preceded and presaged by a number of diverse and perhaps minor advances. In some cases the early work was recognized, extended and built upon. In other cases, early examples of particular phenomena were recognized only after a general statement of principles had been offered. Phase transfer catalysis (ptc) is a major advance which is preceded by earlier examples of related phenomena but most if not all of these examples were recognized as examples of phase transfer catalysis only after the principles had coalesced in several minds across the world. 

There are undoubtedly many early examples of the phenomenon now known as phase transfer catalysis and a presentation of all of them is neither valuable nor feasible. Some of the early work does merit presentation, however, if only to provide a sense of perspective on the field. Wittig and coworkers demonstrated in 1947 the value of utilizing tetramethylammonium cations paired with trityl and fluorenide ions for alkylation in dry alcohol solution [1 ]. Jarrousse found that cyclohexanol and phenyl-acetonitrile could both be alkylated in a two phase system and the catalytic effect of quaternary ammonium salts was clearly recognized (see Eqs. 1.1 and 1.2) [2] Sarrett, in his classic cortisone synthesis, found that either Triton B or the Mannich base... 

Because of Starks early discussion of this reaction, it is one of the standard examples of phase transfer catalysis. The simple nucleophilic displacement (Sn2) of a nucleo-fuge by cyanide ion (Eq. 7.1) is well understood and the mechanism is discussed in Sect. 1.4 in general terms and in comparison with the mechanism of cyclopropana-tion in Sect. 2.2. Because of these earlier discussions, to which the reader is referred, only the salient features of the mechanism will be set forth here. 

Phase-tiansfei catalysis (PTC) is a technique by which leactions between substances located in diffeient phases aie biought about oi accelerated. Typically, one OI more of the reactants are organic Hquids or soHds dissolved in a nonpolar organic solvent and the coreactants are salts or alkah metal hydroxides in aqueous solution. Without a catalyst such reactions are often slow or do not occur at ah the phase-transfer catalyst, however, makes such conversions fast and efficient. Catalysts used most extensively are quaternary ammonium or phosphonium salts, and crown ethers and cryptates. Although isolated examples of PTC can be found in the early Hterature, it is only since the middle of the 1960s that the method has developed extensively. 

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