Isomerisation reaction catalysis

Larcher, A. V., Alexander, R., Rowland, S. J. and Kagi, R. I. (1986) Acid catalysis of alkyl hydrogen exchange and configurational isomerisation reactions acyclic isoprenoid acids. Organic Geochemistry 10, 1015. 

While the use of achiral ACTCs in catalytic hydrogenation and isomerisation reactions is well-studied [14], planar chiral derivatives for asymmetric catalysis have so far received relatively scant attention. 

Scheme 7.62 Tandem Michael-q clisation-isomerisation reaction catatysed by chiral amine catalysis and gold catalysis.

Scheme 7.64 Tandem nitro-Mannich-hydroamination-isomerisation reaction catalysed by chiral urea catalysis and gold catalysis.

The surface (catalysis) Addo-basic Acid catalysis Basic catalysis Activation of alkanes and alcenes Breaking of C-C bonds in aUphatics Formation of C-C bonds in ahphatics Rearrangements of C-C bonds Reactions of isomerisation Reactions of nucleophUic substitution and addition CycUzation reactions Reactions of electrophilic substitution on aromatic rings Dehydrogenation of alcohols Isomerization of the double bonds of olefins... 

A wide variety of new approaches to the problem of product separation in homogeneous catalysis has been discussed in the preceding chapters. Few of the new approaches has so far been commercialised, with the exceptions of a the use of aqueous biphasic systems for propene hydroformylation (Chapter 5) and the use of a phosphonium based ionic liquid for the Lewis acid catalysed isomerisation of butadiene monoxide to dihydrofuran (see Equation 9.1). This process has been operated by Eastman for the last 8 years without any loss or replenishment of ionic liquid [1], It has the advantage that the product is sufficiently volatile to be distilled from the reactor at the reaction temperature so the process can be run continuously with built in product catalyst separation. Production of lower volatility products by such a process would be more problematic. A side reaction leads to the conversion of butadiene oxide to high molecular weight oligomers. The ionic liquid has been designed to facilitate their separation from the catalyst (see Section 9.7)... 

In this paper the author presents some of his contributions to the theory and practice of the cationic polymerisation (CP) of alkenes since 1944. The first phase of his work at the University of Manchester comprises the discovery of co-catalysis by water with TiCl4, the invention of the pseudo-Dewar reaction vessel, the use of trichloroacetic acid as co-catalyst, and the disproof of the alleged cationic isomerisation of cis-stilbene. 

In heterogeneous metal catalysis alkanes, alkenes, and aromatics adsorbed on the metal surface rapidly exchange hydrogen and deuterium. The multiple adsorption of reactants and intermediates lowers the barriers for such exchange processes. Hydrogenation of unsaturated aliphatics and isomerisation can be accomplished under mild conditions. Catalytic dehydrogenation of alkanes to alkenes requires temperatures >200 °C, but this is because of the thermodynamics of this reaction. 

The first class includes non-redox reactions like isomerisation, dimerisation or oligomerisation of unsaturated compounds, in which the role of the catalyst lies in governing the kinetic and the selectivity of thermodynamically feasible processes. Electrochemistry associated to transition metal catalysis has been first used for that purpose, as a convenient alternative to the usual methods to generate in situ low-valent species which are not easily prepared and/or handled [3]. These reactions are not, however, typical electrochemical syntheses since they are not faradaic they will not be discussed in this review. 

Supercritical fluids, another class of alternative reaction medium, have been used as solvents in catalysis for many years. Ipatiev reported the isomerisation of cyclohexane to methylcyclopentane under supercritical conditions using A1203 as the catalyst1151 and shortly afterwards communicated the oligomerisation of supercritical ethylene catalysed by AICI3.1161 However, it took another 60 years before supercritical fluids were used as solvents for... 

Although the hemilabile behaviour of the imino functional group together with an apparent isomerisation process on palladium may make it difficult to achieve high chiral resolution (ee) in asymmetric catalysis. Bonnet and Douthwaite developed an imino functionalised carbene ligand system based on the diamino cyclohexane framework that has achieved ees of up to 92% in palladium catalysed allylic alkylatiou reactions using ( )-l,3-diphenylprop-... 

Heterogeneous catalysis is especially important in industry. Some of the major industrial processes that use solid catalysts include the synthesis of inorganic chemicals such as NH3, SO3 and NO, the various reactions used in the refining of crude petroleum such as cracking, isomerisation and reforming, and many of the major reactions of the petrochemical industry, such as the synthesis of methanol, the hydrogenation of aromatics and various controlled oxidations. Some of the major industrial processes to be catalysed by inorganic solids are shown in Table 1.3. 

One of the unique features of zeolites in alkylation reactions is their shape selectivity. In many zeolite-catalysed reactions, however, shape-selective catalysis occurring on the inside of the zeolite can be affected by non-selective catalysis on the external surfaces. Paparatto et al. have reported that during aromatic alkylation, the para isomer is formed selectively within the zeolite, whereas isomerisation occurred only on the external surfaces, decreasing para product selectivity.17... 

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