Efficiency catalyst for

Polypropylene. PP is a versatile polymer, use of which continues to grow rapidly because of its excellent performance characteristics and improvements in its production economics, eg, through new high efficiency catalysts for gas-phase processes. New PP-blend formulations exhibit improved toughness, particularly at low temperatures. PP has been blended mechanically with various elastomers from a time early in its commercialisation to reduce low temperature brittleness. 

Sohd silver is more permeable by oxygen than any other metal. Oxygen moves freely within the metallic silver lattice, not leaving the surface until two oxygen atoms connect to form Og. This occurs at - 300° C. Below this temperature silver is an efficient catalyst for gaseous oxidative chemical reactions. Silver is also an extremely efficient catalyst for aqueous oxidative sanitation. 

Direct Chlorination of Ethylene. Direct chlorination of ethylene is generally conducted in Hquid EDC in a bubble column reactor. Ethylene and chlorine dissolve in the Hquid phase and combine in a homogeneous catalytic reaction to form EDC. Under typical process conditions, the reaction rate is controlled by mass transfer, with absorption of ethylene as the limiting factor (77). Ferric chloride is a highly selective and efficient catalyst for this reaction, and is widely used commercially (78). Ferric chloride and sodium chloride [7647-14-5] mixtures have also been utilized for the catalyst (79), as have tetrachloroferrate compounds, eg, ammonium tetrachloroferrate [24411-12-9] NH FeCl (80). The reaction most likely proceeds through an electrophilic addition mechanism, in which the catalyst first polarizes chlorine, as shown in equation 5. The polarized chlorine molecule then acts as an electrophilic reagent to attack the double bond of ethylene, thereby faciHtating chlorine addition (eq. 6) ... 

Certain molecules that can permit concerted proton transfers are efficient catalysts for reactions at carbonyl centers. An example is the catalytic effect that 2-pyridone has on the aminolysis of esters. Although neither a strong base (pA aH+ = 0.75) nor a strong acid (pJsfa = 11.6), 2-pyridone is an effective catalyst of the reaction of -butylamine with 4-nitrophenyl acetate. The overall rate is more than 500 times greater when 2-pyridone acts... 

An efficient catalyst for thermal isomenzations of halofluorocarbons [6, 7, 8, 9] IS prepared by treatment of alumina with dichlorodifluoromethane at 200-300 °C [9] or aluminum chloride with chlorofluorocarbons in the presence of metals [W] or palladium on alumina [II These catalysts are far more efficient than aluminum halides themselves (equations 1 and 2)... 

Stannous triflate is an efficient catalyst for aldol-type condensations [ 23, 124, 125 Under conditions of kinetic control, it provides excellent diastereo-selectivity in various cross-aldol reactions (equation 61)... 

Unusual annulated derivatives of pyrrole, 90 and 91, were found as efficient catalysts for the polymerization of propene (98JA10786). 

Gothelf presents in Chapter 6 a comprehensive review of metal-catalyzed 1,3-di-polar cycloaddition reactions, with the focus on the properties of different chiral Lewis-acid complexes. The general properties of a chiral aqua complex are presented in the next chapter by Kanamasa, who focuses on 1,3-dipolar cycloaddition reactions of nitrones, nitronates, and diazo compounds. The use of this complex as a highly efficient catalyst for carbo-Diels-Alder reactions and conjugate additions is also described. 

Chiral boron(III) Lewis acid catalysts have also been used for enantioselective cycloaddition reactions of carbonyl compounds [17]. The chiral acyloxylborane catalysts 9a-9d, which are also efficient catalysts for asymmetric Diels-Alder reactions [17, 18], can also catalyze highly enantioselective cycloaddition reactions of aldehydes with activated dienes. The arylboron catalysts 9b-9c which are air- and moisture-stable have been shown by Yamamoto et al. to induce excellent chiral induction in the cycloaddition reaction between, e.g., benzaldehyde and Danishefsky s dienes such as 2b with up to 95% yield and 97% ee of the cycloaddition product CIS-3b (Scheme 4.9) [17]. 

In benzene or similar solvents, tris(triphenylphosphine)halogenorhodium(I) complexes, RhX[P(C6H5)3]3, are extremely efficient catalysts for the homogeneous hydrogenation of nonconjugated olefins and acetylenes at ambient temperature and pressures of 1 atmosphere (6). Functional groups (keto-, nitro-, ester, and so on) are not reduced under these conditions. 

Proazaphosphao-ane, PrRNCH-,CH-j,N, is an efficient catalyst for the Henty reacdon, and arious ketones give nitro-aldols by the reacdon with nitromethane and other nitroalkanes fEq. 

Asymmetric epoxidation of olefins with ruthenium catalysts based either on chiral porphyrins or on pyridine-2,6-bisoxazoline (pybox) ligands has been reported (Scheme 6.21). Berkessel et al. reported that catalysts 27 and 28 were efficient catalysts for the enantioselective epoxidation of aryl-substituted olefins (Table 6.10) [139]. Enantioselectivities of up to 83% were obtained in the epoxidation of 1,2-dihydronaphthalene with catalyst 28 and 2,6-DCPNO. Simple olefins such as oct-l-ene reacted poorly and gave epoxides with low enantioselectivity. The use of pybox ligands in ruthenium-catalyzed asymmetric epoxidations was first reported by Nishiyama et al., who used catalyst 30 in combination with iodosyl benzene, bisacetoxyiodo benzene [PhI(OAc)2], or TBHP for the oxidation of trons-stilbene [140], In their best result, with PhI(OAc)2 as oxidant, they obtained trons-stilbene oxide in 80% yield and with 63% ee. More recently, Beller and coworkers have reexamined this catalytic system, finding that asymmetric epoxidations could be perfonned with ruthenium catalysts 29 and 30 and 30% aqueous hydrogen peroxide (Table 6.11) [141]. Development of the pybox ligand provided ruthenium complex 31, which turned out to be the most efficient catalyst for asymmetric... 

In spite of their intrinsic synthetic potential, addition reactions of metal enolates of non-stabilized esters, amides, and ketones to epoxides are not widely used in the synthesis of complex molecules. Following the seminal work of Danishefsky [64], who introduced the use of Et2AlCl as an efficient catalyst for the reaction, Taylor obtained valuable spiro lactones through the addition reaction of the lithium eno-late of tert-butyl acetate to spiro-epoxides, upon treatment of the corresponding y-... 

Some important mononuclear complexes exist such as mer-RuH(OAc)-(PPh3)3, a very efficient catalyst for the selective hydrogenation of alk-l-enes (Figure 1.36). 

Since 1,4-butanediol (BD) undergoes dehydration side reaction in the presence of acid resulting in THF formation, the hydroxy-ester interchange reaction is the preferred method for the preparation of PBT. The first stage of reaction is carried out at 150-200°C and consists of a hydroxy-ester interchange between DMT and excess butanediol with elimination of methanol. In the second stage, temperature is raised to 250°C and BD excess is eliminated under vacuum. Tetraisopropoxy-and tetrabutoxytitanium are efficient catalysts for bodi stages (Scheme 2.20). 

Mn(II) > Mg(II).270 It should be underlined that titanium and zirconium alkoxides are efficient catalysts for both stages of reaction. Lanthanide compounds such as 2,2/-bipyridyl, acetylacetonate, and o-formyl phenolate complexes of Eu(III), La(III), Sm(III), Er(III), and Tb(III) appear to be even more efficient than titanium alkoxides, Ca or Mn acetates, Sb203, and their mixtures.273 Moreover, PET produced with lanthanides has been reported to exhibit better thermal and hydrolytic stability as compared to PET synthesized with the conventional Ca acetate -Sb203 catalytic system.273... 

The synthesis of sulfones included electrophilic substitution, specifically, Frie-del-Crafts catalysis by A1C13, FeCl3, SbCl5, AlBr3 and BF3, and so on, which are efficient catalysts for the sulfonylation by arenesulfonyl halides.1 22... 

The effect of alkali addition on the adsorption of NO on metal surfaces is of great importance due to the need of development of efficient catalysts for NO reduction in stationary and automotive exhaust systems. Similar to CO, NO always behaves as an electron acceptor in presence of alkalis. 

For trialkylsilanes as substrates, evidence for the intermediacy of compounds (XXV) is available. Thus, /ra/u-(Ph3P)2lr(CO)Cl is an efficient catalyst for H/D exchange at Si (223), and adds trialkylgermanes irreversibly (114). It is probable, therefore, that for RjSiH the equilibrium is almost wholly in favor of (XXIV). The latter reacts with EtjSiH at reflux to give the silyldihydrido complex (XXVI) (51). The chlorotrialkylsilane elimination step and the interrelation of (XXIV), (XXV), and (XXVII) is similar to that suggested for the Cl/H exchange of Eq. (110) (54, 55). 

Fukuzawa et al. [99] found analogous scandium(III)triflate/ Pr-PyBOx complex as efficient catalyst for the asymmetric Diels-Alder reaction between cyclopentadiene or acyclic dienes and acyl-l,3-oxazohdin-2-ones with up to 90% ee. They latter described the same reaction in super critical CO2 in the presence of MSdA [ 100] that proceeded more rapidly than in CH2CI2 leading to the expected product with analogous selectivity. 

The combination of CsF with Si(OMe)4 58 is an efficient catalyst for Michael additions, e.g. of tetralone 130 to methacrylamide, followed hy cyclization of the addition product to the cyclic enamide 131 in 94% yield [67]. Likewise, addition of the lactone 132 to methyl cinnamate affords, after subsequent cyclization with tri-fluoroacetic acid, the lactam 133 in 58% yield [68] whereas < -valerolactam 134, with ethyl acrylate in the presence of Si(OEt)4 59/CsF, gives 135 in 98% yield [69]. Whereas 10mol% of CsF are often sufficient, equivalent amounts of Si(OEt)4 59 seem to be necessary for preparation of 135 [69] (Scheme 3.11). 

It has been reported that titanium supported vanadium catalyst is active for ammonia oxidation at temperatures above 523 K [2,3]. Also, supported vanadium oxides are known to be efficient catalyst for the catalytic reduction of nitrogen oxides (NO ) in the presence of ammonia [4]. This work investigates the nanostructured vanadia/Ti02 for low temperature catalytic remediation of ammonia in air. 

Scheme 5 FeCls as efficient catalyst for reactions of electron-rich arenes with imines or aziridines...

Bis(imino)pyridine iron complex 5 as a highly efficient catalyst for a hydrogenation reaction was synthesized by Chirik and coworkers in 2004 [27]. Complex 5 looks like a Fe(0) complex, but detailed investigations into the electronic structure of 5 by metrical data, Mossbauer parameters, infrared and NMR spectroscopy, and DFT calculations established the Fe(ll) complex described as 5 in Fig. 2 to be the higher populated species [28]. 

Carbenoid N-H insertion of amines with diazoacetates provides a useful means for the synthesis of ot-amino esters. Fe(III) porphyrins [64] and Fe(III/IV) corroles [65] are efficient catalysts for N-H carbenoid insertion of various aromatic and aliphatic amines using EDA as a carbene source (Scheme 16). The insertion reactions occur at room temperature and can be completed in short reaction times and with high product yields. It is performed in a one-pot fashion without the need for slow... 

Iron phthalocyanine is an efficient catalyst for intermolecular amination of saturated C-H bonds. With 1 mol% iron phthalocyanine and 1.5 equiv. PhlNTs, amination of benzylic, tertiary, and ally lie C-H bond have been achieved in good yields (Scheme 31). With cyclohexene as substrate, the allylic C-H bond amination product was obtained in 75% yield, and the aziridination product was found in minor amount (17% yield) [79]. 

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