Catalyst system entries

So far only two groups have reported details of the use of ionic liquids with wholecell systems (Entries 3 and 4) [31, 32]. In both cases, [BMIM][PF(3] was used in a two-phase system as substrate reservoir and/or for in situ removal of the product formed, thereby increasing the catalyst productivity. Scheme 8.3-1 shows the reduction of ketones with bakers yeast in the [BMIM][PF(3]/water system. 

Electrophilic metal complexes that have shown Markovnikov-type selectivity include catalysts based on Ru(n),383-386 Fe(m),387 Au(i) and Au(m),380,388 and Ir(m).389 Notable among these examples are Zeise s salt390 (entries 1 and 2) and the PtCl4/CO system (entry 3), the latter of which has proved to be effective for the hydration of a wide... 

A most significant advance in the alkyne hydration area during the past decade has been the development of Ru(n) catalyst systems that have enabled the anti-Markovnikov hydration of terminal alkynes (entries 6 and 7). These reactions involve the addition of water to the a-carbon of a ruthenium vinylidene complex, followed by reductive elimination of the resulting hydridoruthenium acyl intermediate (path C).392-395 While the use of GpRuGl(dppm) in aqueous dioxane (entry 6)393-396 and an indenylruthenium catalyst in an aqueous medium including surfactants has proved to be effective (entry 7),397 an Ru(n)/P,N-ligand system (entry 8) has recently been reported that displays enzyme-like rate acceleration (>2.4 x 1011) (dppm = bis(diphenylphosphino)methane).398... 

Polypropionate synthesis, 20 138 Polypropylene (PP), 20 523-548 24 272. See also Olefin fibers Propylene polymer entries Spheripol technology Spherizone technology advanced material, 2 693 asbestos substitute, 3 314t, 315 can coatings, 26 39 catalyst systems for, 20 525-528 catalyst yield for, 20 531-532 coatings, 7 40 conducting, 7 525... 

Interestingly, the dimeric Cr(salen) catalyst 64 supported on silica showed enhanced activity for ARO of 1,2-epoxyhexane and cyclohexene oxide in the presence of ionic liquids particularly with [BMIM][PF6] (64-IL) [86] (Table 6). A significant increase in the product selectivity was also observed with silica supported ionic liquid (64-SILP) for ARO of 1,2-epoxyhexane and cyclohexene oxide (ee, of 87% and 75% respectively) as eompared to silica supported catalyst minus the ionie liquid (Table 6, entries 5,6). However, after repeated recycling, the silica support material deteriorates due to the abrasive forees in the stirred reactor. As a result, silica material was non-recoverable, but the expensive dimeric Cr(salen) catalyst 64 and the ionic liquid was recovered quantitatively by Soxhlet extraction with acetone. SILP-catalyst system was also used in a eontinuous-flow reactor. 

Tab. 8.1 summarizes the various substrates that were subjected to the rhodium-catalyzed reaction using a Rh-dppb catalyst system. Only ds-alkenes were cycloisomerized under these conditions, because the trans-alkenes simply did not react. Moreover, the formation of the y-butyrolactone (Tab. 8.1, entry 8) is significant, because the corresponding palladium-, ruthenium-, and titanium-catalyzed Alder-ene versions of this reaction have not been reported. In each of the precursors shown in Tab. 8.1 (excluding entry 7), a methyl group is attached to the alkene. This leads to cycloisomerization products possessing a terminal alkene, thus avoiding any stereochemical issues. Also,... 

Table 15) highlights the stability of this system compared to the PS/MTO system (entry 6, Table 15), which shows a decrease in activity during recycling. This difference in behaviour may be due to the weaker interaction between MTO and the PS polymer, which is only accomplished by the physical envelopment of the benzene ring. The PVP/MTO combination was successfully used for other compounds of biological interest, such as ter-penes. Even highly sensitive terpenic epoxides, hke a-pinene oxide, can be obtained in excellent yields using polymer-supported MTO catalysts [73] (Scheme 20, Table 16). 

The data in Table 2 show the potential of the Na2B407 based catalyst system tested over large number of representative alcohols. The primary alcohols were oxidized to the corresponding aldehydes at complete conversion of the alcohol and at 90-93% selectivity. The only by-products observed were the corresponding acid and minor amounts of the symmetrical ester (Entry 2, 3). Benzyl alcohol was quantitatively converted to benzaldehyde. The secondary alcohols, 4-methyl cyclohexanol and 4-methylpentanol were converted to the corresponding ketones at room temperature. 

Under particularly mild conditions, a Ni-catalyst based on (] , Sc, Sc)-26 gave quantitative conversion of 11 with 84.9% selectivity for the desired product 23 and an excellent enantioselectivity of 94.8% (S) (entry 5). Moreover, the catalyst system proved extremely efficient and remarkably robust for the hydrovinylation of 11. Almost 90% conversion and perfect chemoselectivity were achieved within 4 h at -65 °C even at a substrate/nickel ratio of 4600 1 (entry 6a). Further... 

Another entry into the preparation of 3-arylpyrroles starts with the reaction of the 3-iodopyrrole derivative shown in 6.28. with hexabutyl-distannane in the presence of a palladium catalyst. The formed intermediate was reacted, in the presence of a similar catalyst system, with different aryl iodides to give the desired products in good to excellent yield38 It is worth mentioning that the presence of a formyl group in the 2-position of he pyrrole had no adverse effect on the efficiency of the couplings. 

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