Epoxides multifunctional catalysts

Olefin isomerization can be catalyzed by a number of catalysts such as molybdenum hexacarbonyl [13939-06-5] Mo(CO)g. This compound has also been found to catalyze the photopolymerization of vinyl monomers, the cyclization of olefins, the epoxidation of alkenes and peroxo species, the conversion of isocyanates to carbodiimides, etc. Rhodium carbonylhydrotris(triphenylphosphine) [17185-29-4] RhH(CO)(P(CgH )2)3, is a multifunctional catalyst which accelerates the isomerization and hydroformylation of alkenes. 

Enantiomerically pure 3-amino alcohols which are important intermediates for many bioactive compounds can be directly synthesized by the ARO reaction of readily accessible racemic and meso epoxides with appropriate amines. Indeed, some simple and multifunctional p-amino alcohols have been obtained using this strategy by the promotion of chiral BINOL [30-32,88,89], salen [35,52], bipyridine [33,40,90-94] and proline-A,JV-dioxide based metal complexes [95]. However, none of these systems demonstrated the recyclability of the precious chiral catalyst. 

Conceptually new multifunctional asymmetric two-center catalysts, such as the Ln-BINOL derivative, LnMB, AMB, and GaMB have been developed. These catalysts function both as Brpnsted bases and as Lewis acids, making possible various catalytic, asymmetric reactions in a manner analogous to enzyme catalysis. Several such catalytic asymmetric reactions are now being investigated for potential industrial applications. Recently, the catalytic enantioselective opening of meso epoxides with thiols in the presence of a heterobimetallic complex has... 

If the epoxide rearrangement (see chapter 15.2.1) of styrene oxide is carried out in the presence of hydrogen and by use of a bifunctional boron-pentasil zeolite catalyst having a hydrogenation component such as Cu, then 2-phenylethanol is obtained in one step. This hydro-isomerization renders high yields (> 85%) at 250 °C under the gas phase conditions. It is an example for multifunctional catalysis in a one pot-reaction, that means simultaneous rearrangement and hydrogenation. 

Table 12.1 gives typical values of the diffusion constant for a series of thermosetting matrices where the effect of polarity of the resin on the equilibrium on moisture concentration is illustrated. Epoxy resins are the network product of the reaction of a multifunctional epoxide monomer with a hardener. One of the important aspects of composite materials which needs to be recognised is that the material is synthesised at the same time as the component is manufactured. The precise chemistry of the final network can be uncertain but is a function of the chemical stmctures of the epoxide and hardener and/or catalyst, which determine the mechanism of cure. In this way, the cured resins can have differing polarities. 

All the independent variables significantly influence the gel content (yi2), which is a sensitive indicator of the quality of the polymer network created from reactive multifunctional components. Its dependence on the molar ratio COOH/epoxy and the filler content is shown in Fig, 14. The gel content has a linear growth with the increase of epoxide concentration and decreasing content of filler. In the absence of catalyst, the dependence on the epoxide concentration is steeper, because in these conditions the homoaddition reactions of epoxide are preferred. In the presence of a sufficient quantity of... 

Similarly, photolatent base, 9, can be used to catalyze the addition of thiols, amines, and carboxylic acids to epoxide monomers. Oftentimes, the irradiation is followed by a brief thermal treatment as well to complete the polymerization reaction. The conjugate addition of thiols to electron-deficient acrylate double bonds has been successfully conducted under UV irradiation conditions through the use of a photolatent base such as 9 as a catalyst. " An unusual type of Michael polymerization reaction explored by Dietliker and co-workers is depicted in eqn [15]. Photogenerated DBN is a sufficiently strong base to remove a proton from the multifunctional malonate monomer, 10, and the corresponding malonate carbanion adds to the acrylate monomer, 11. 

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