Catalysts multifunctionalized

To prepare multifunctionalized symmetric organosilicon compounds by the polyalkylation of benzene. (2-chloroethyi)trichlorosilane and (3-chloropropyl)tri-chlorosilane were reacted with benzene. Polyalkylations of benzene with (2-chloroethyl)silane and (3-chloropropyl)silane were carried out in the presence of aluminum chloride catalyst at a reaction temperature of 80 C. The reaction of benzene with excess (2-chloroethyI )trichlorosilanes afforded pcralkylated product, hexakis(2-(trichlorosilyl)ethyl)benzene in good yield (70%). ... 

A major reason of attention to M°/CFP catalysts appears to be their multifunctionality prospects (vide infra)... 

In conclusion, there is interest for bioethanol upgrading to fuel additives and some research is active in this direction, but much more effort is needed to demonstrate the validity and the viability of the concept of preparing oxygenated diesel fuel additives from bioethanol and glycerol. The key to success is to develop selective multifunctional solid catalysts, in which interest is more general, because similar multifunctionality is necessary in the catalytic synthesis of fine chemicals [67]. There is, thus, the possibility of cross-fertilization between the two research areas. 

Some progress has been made in explaining the splendid catalytic performance of multicomponent bismuth molybdates that are used widely for the industrial oxidations and ammoxidations of lower olefin. We have seen that the catalytic activity and selectivity are greatly enhanced by the multifunctionalization of the catalyst systems. Many functions newly introduced are... 

Reaction of Bifunctional Ketones. Competitive ligation of functionalities to the Ru atom of the catalyst tends to decrease the enantioselec-tivity in reactions with multifunctionalized ketones (92). The overall... 

In order to make use of the (potential) multifunctionality of cyclopropenes (cf. Fig. 1) in synthesis, their reactivities have to be tuned. All efforts to achieve this goal finally focussed on the use of transition metal catalysts. Before we discuss the various transition metal catalyzed reactions of cyclopropenes in detail, we will briefly summarize their stoichiometric reactions with transition metal complexes (Scheme 1). These may be regarded as equivalents of important elementary steps in a catalytic cycle. Four different types of reactions have been observed. Reactions at the double bond involve... 

Figure 2.66 Multifunctionality of solid catalysts synthesis of maleic anhydride from n-butane over a (V0)2P207 catalyst.

The ultimate aim is to favor those synergetic phenomena deriving from the interaction between different catalyst components, multifunctionality being one of the essential properties for catalytic materials in gas-phase propene epoxidation with a feed containing oxygen and a redudng component. 

This structural characterization demonstrates how the multifunctionality required for an efficient and selective catalyst is based on the multielemental distribution within such complex oxide catalysts. Neutron powder diffraction is absolutely essential to be able to refine the oxygen... 

Taking advantage of the enormous differences in molecular weight (and hydro-dynamic volume) between the catalyst (an enzyme) and the substrates or the products, it is possible to confine the catalyst in a membrane reactor while the reagents and products can be selectively extracted from the reaction mixture without modifying the catalytic active intermediate. Remarkably, the Chemzyme membrane reactor concept allows a productivity per gram of catalyst which could be higher than in the case of enzymes because the polymers can be multifunctionalized with several active centers [1]. 

Tu, Li, and coworkers also developed a new allylic functionalization without the use of metal catalysts [59-61]. Efficient annulation of enaminones 57 with arylglyoxal monohydrates 58 and the subsequent allylic functionalization with aliphatic carboxylic acids 38 as nucleophile reagents provided multifunctionalized indoles 98 with 75-89% yields (Scheme 12.38) [59]. To further explore the scope of this domino reaction, N-substituted 3-aminocyclohex-2-enones were employed. Interestingly, two molecules of arylglyoxal mono hydrate and N-substituted... 

Later it was found that to get a successful activity in alkane metathesis, catalysts need to have a multifunctionality, i.e., (i) activation of the C-H bond resulting in a metal alkyl, (ii) a-H elimination leading to a metallocarbene, (iii) p-H elimination leading to an olefin, (iv) olefin metathesis, and (v) finally successive hydrogenations of the olefins or the carbenes leading to alkanes. The selectivity of products is a consequence of the relative stabilities of metaUacyclobutanes intermediates formed during the olefin metathesis [52]. 

---