Carbonium ions derivs., review

Although no mechanistic studies of this hydrolysis have been reported, the data available suggest that the mechanism is similar to that proposed for the hydrolysis of a-D-glucopyranosyl phosphate in weakly acidic media,332 namely protonation of the glycosyl pyrophosphate derivative and slow heterolysis of the resulting monoanion (79) to produce a cyclic carbonium ion (80), a species considered to be an intermediate in the hydrolysis of glycosides (for a review, see Ref. 333). 

The basic data related to the structure and properties of various carbocationic derivatives can be found in a treatise Olah, G. Schleyer, P. von R. Carbonium Ions, Wiley, New York, 1968-1976, vols. 1-5 for a consise review, see Bethell, G. Reactive Intermediates, Wiley, New York, 1978, vol. I. 

Cycloheptatriene and derivatives thereof donate hydride readily to a variety of carbonium ion acceptors. The position of the end equilibrium depends on the thermodynamics of the exchange. " These reactions are prototypes of a broad area of carbonium ion chemistry wherein carbonium ions equilibrate via intra- and inter-molecular hydride shifts between a donor C—H bond, usually jp hybridized, and a carbonium ion acceptor. This chemistry is often achieved with heterogeneous catalysts and is of great industrial significance it lies outside the emphasis of this review, however. Excellent treatises are available, and a review has appeared on the use of carriers like adamantane to promote hydride transfer in hydrocarbons under strongly acidic conditions. ... 

A review of the relationship between electronic structure and n.m.r. data has been published, which includes considerations of five- and six-membered rings and derived carbonium ions. 

A convenient way to summarize the reactions of coenzyme A thioesters is by reviewing the )3-oxidation pathway for fatty adds". Fatty acid activation occurs by acylation of the coenzyme A thiol by way of an acyl adenylate. This is then dehydrogenated to an o,/3-enoyl acyl coenzyme A derivative by a flavin-dependent dehydrogenase. The ability of the adjacent carbonyl to provide resonance stabilization of the product appears to be an important aspect of this reaction. Such flavin-dependent dehydro- nations occur in other reaction sequences, but only where carbonyl resonance stabilization is possible. Water adds to the a,j8-enoyl thioester to generate a j8-hydroxy fatty acid derivative, a reaction facilitated by j8-carbonium ion stabilization in enoyl thioesters. The j3-hydroxyl is next... 

The electrophilic attack of carbonium ions on carbon-hydrogen bonds has been reviewed. The use of two new leaving groups from nonafluoro-butanesulphonates and 2,4-dinitrophenyl ethers has been studied. The latter derivatives of tertiary alcohols can be prepared and so solvolytic comparisons may be made with picrates, which cannot be prepared for most tertiary alcohols. Nonafluorobutanesulphonates solvolyse even more readily than trifluoromethanesulphonates. 

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