Olefin catalyst efficiency

Begue and coworkers recently achieved an improvement in this method by performing the epoxidation reaction in hexafluoro-2-propanol [120]. They found that the activity of hydrogen peroxide was significantly increased in this fluorous alcohol, in relation to trifluoroethanol, which allowed for the use of 30% aqueous H202. Interestingly, the nature of the substrate and the choice of additive turned out to have important consequences for the lifetime of the catalyst. Cyclic dis-ubstituted olefins were efficiently epoxidized with 0.1 mol% of MTO and 10 mol%... 

For a review of asymmetric Mo-catalyzed metathesis, see Catalytic Asymmetric Olefin Metathesis, A. H. Hoveyda, R. R. ScHROCK, Chem. Eur. J. 2001, 7, 945-950 for reports on chiral Ru-based complexes, see (b) Enantioselective Ruthenium-Catalyzed Ring-Qosing Metathesis, T.J. Sei-DERS, D.W. Ward, R.H. Grubbs, Org. Lett. 2001, 3, 3225-3228 (c) A Recyclable Chiral Ru Catalyst for Enantioselective Olefin Metathesis. Efficient Catalytic Asymmetric Ring-Opening/Cross Metathesis In Air, J. J. Van Veldhuizen, S. B. 

If complexation between TiCl4 and the olefin (and with arcxnatic dimers and polymers) does take place to such a degree that the catalyst complexed is not available for initiation, as suggested by Sauvet et al. for 1,1-diphenylethylene, then obviously the inverse catalyst efficiency, expressed as the number of its molecules consumed to prepare one active species, will be higher tiian three, although again the stoicheiometiy of the initiation step remains simply one to one. 

In summary, this pioneering work clearly demonstrated the possibility of aqueous catalytic insertion polymerization of acyclic and cyclic olefins, as well as aqueous ROMP. On the other hand, metal salts without any additional ligands to control the properties of the metal centers were utilized, and activation to the active species was probably also relatively ineffective in most cases. Consequently, catalyst efficiencies were moderate at best. Most of the polymerizations also afforded low molecular weight materials, or employed rather special monomers. The possibility of polymer latex synthesis appears not to have received much attention, although free-radical emulsion polymerization of styrene and butadiene was already a large-scale process at the time. 

The addition of HOOH to 2 1 pyridine/acetic acid solutions that contain FeIRPA)2 (PA = picolinate ion) and cyclohexane (C-C6H12) results in the catalyzed transformation of C-C6H12 to cyclohexanone [c-CgHioCO)]. Table 4-5 summarizes the conversion efficiencies and product yields for the oxygenation by the HOOH/Fe(PA)2 combination of several organic substrates (hydrocarbons with methylenic carbons, acetylenes, and aryl olefins). Catalyst turnovers (moles of product per mole of catalyst) are also tabulated. The relative reaction efficiencies for cyclohexane, n-hexane, cyclohexene, and 1,4-cyclohexadiene are roughly... 

Besides various iron and ruthenium complexes [43, 44], nickel-based catalysts have recently been shown to be highly reactive in this respect as well [45]. Thus, a nickel catalyst prepared in situ from equimolar amounts of NiCl2(dppe) (dppe, l,2-bis(diphenylphosphino)ethane) and LiBHEtj (5 mol% each), which presumably resulted in the formation of NiHCl(dppe) as the active catalyst, efficiently catalyzed the isomerization/aldol event of allyl alcohols 82 and aldehydes 83 in combination with the Lewis acid MgBr2 (5 mol%) to furnish aldol products 84 in typically excellent yields and variable isomeric ratios (Table 8.11). Allyl alcohols with a terminal alkene reacted much faster than those with an internal olefin, and the aldol reaction occurred exclusively on the side of the former allyl alcohol. 

In the hydroamination of unsaturated carbon-carbon bonds, gold catalysts play an important role. Intermolecular hydroamination of alkenes [177], 1,3-dienes [204], terminal and internal alkynes [205], and allenes [206] are known to proceed smoothly in the presence of PhsP AufI) or AuCls catalyst. In addition, amino olefins also efficiently undergo intramolecular hydroamination using similar gold catalysts. He and coworkers have developed the catalytic cycloaddition of tosylated amino olefins [207], A representative example is shown in Scheme 18.35. When N-tosylated y-amino olefin (97) is exposed to a mixture of PhsP AuCl and AgOTf (5 mol% each) in toluene at 85 °C, pyrrolidine (98) is obtained in 96% yield. The gold(I)-catalyzed intramolecular hydroamination is applicable to N-alkenyl carbamates [208], N-alkenyl carboxamides [209], and N-alkenyl ureas [210], The use of microwave irradiation results in completing the hydroamination in a much shorter time than that required under thermal reaction conditions [211], The... 

Y.-X. Chen, T. J. Marks, Constrained geometry dialkyl catalysts. Efficient syntheses, C-H bond activation chemistry, monomer-dimer equilibration, and a-olefin polymerization catalysis. OrganometalUcs 16, 1997 3649. 

Dror and Manassen hydrogenated a- and cyclic olefins such as 1-octene, 1 -dodecene and cyclohexene in micellar systems using rhodium catalysts modified with water-insoluble carboxylated tenside phosphines 45 (Table 3 n=3,5,7,9,l 1) in the presence of conventional tensides such as sodium dodecylsulfate (SDS) or cetyltrimethylammonium bromide (CTAB) and cosolvents e.g. dimethyl sulfoxide. Linear olefins were more reactive than cyclic olefins. Maximum efficiency was observed in the presence of the anionic surfactant SDS when 45 contained a chain of 5-7 carbon atoms. In contrast, using the cationic tenside CTAB the ligand 45 with 5 C atoms was almost inactive but became active again with dodecyl trimethylammonium bromide. 

G-5 Aliphatic Petroleum Resins. Carbocationic polymerization of C-5 feedstreams has been accomptished with various Friedel-Crafts catalyst systems. Table 3 compares the efficiencies of selected Lewis acids ia the polymerization of a typical C-5 stream containing 43 wt % C-5—C-6 diolefias and 47 wt % C-5—C-6 olefins (20). Based on weight percent yield of resia at equimolar coaceatratioas of catalyst (5.62 mmol/100 g), efficieacy follows AICI3 AlBr3 > BF3etherate-H20 > TiCfy > SnCl. The most commonly used catalyst in petroleum resin synthesis is AlCl. ... 

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