Alkenes styrene

The first was from a CA article [81]. Various alkenes, styrene and cycloalkenes were tried. But a more followable method is the following [82]. The supported salt of NaNs-AljOs was made by mixing the NaNs with the alumina in water then evaporating the mixture under vacuum in a water bath until dry ... 

In comparison with the platinum catalysts, rhodium catalysts are much more reactive to effect addition of bis(catecholato)diboron even to non-strained internal alkenes under mild reaction conditions (Equation (5)).53-55 This higher reactivity prompted trials on the asymmetric diboration of alkenes. Diastereoselective addition of optically active diboron derived from (li ,2i )-diphenylethanediol for />-methoxystyrene gives 60% de (Equation (6)).50 Furthermore, enantioselective diboration of alkenes with bis(catecolato)diboron has been achieved by using Rh(nbd)(acac)/(A)-QUINAP catalyst (Equation (7)).55,56 The reaction of internal (A)-alkenes with / //-butylethylene derivatives gives high enantioselectivities (up to 98% ee), whereas lower ee s are obtained in the reaction of internal (Z)-alkenes, styrene, and a-methylstyrene. 

A wide range of olefins can be cyclopropanated with acceptor-substituted carbene complexes. These include acyclic or cyclic alkenes, styrenes [1015], 1,3-dienes [1002], vinyl iodides [1347,1348], arenes [1349], fullerenes [1350], heteroare-nes, enol ethers or esters [1351-1354], ketene acetals, and A-alkoxycarbonyl-[1355,1356] or A-silyl enamines [1357], Electron-rich alkenes are usually cyclopropanated faster than electron-poor alkenes [626,1015],... 

High yields are obtained with terminal alkenes (styrene and a-methylstyrene) and with the strained acenaphthylene, whereas stilbene and -methylstyrene are barely reduced. 

Ru(0)(biqn)(tmtacn)](C10 )2 and [Ru(0)(diopy)(tmtacn)](C10 )2 (biqn=C2 symmetric 1,T-biisoquinoline, diopy=(R,R)-3,3 -(l,2-dimethylethylenedioxy)-2,2 -bipyridine) aremadefrom [RuCl(L)(tmtacn)] + (L=biqn, diopy) and(NH )2[Ce(N03)J with Li(ClO ). Electronic and IR spectra were measured (v(Ru=(0) bands lie at 760 and 795 cm" respectively). The (diopy) complex is paramagnetic with 2.88 B.M. As stoich. [Ru(0)(biqn)(tmtacn)] + and [Ru(0)(diopy)(tmtacn)] VCH3CN they oxidised alkenes (styrene, cis and fran.y-P-methylstyrenes, fran -stilbene, nor-bomene, cyclohexene) to mixtures of aldehydes and epoxides. Conttary to expectation the (diopy) complex did not effect enantioselective epoxidations except with fran -stilbene, for which a moderate e.e. of 33% was observed [623]. 

As for additions of allylic Grignard reagents, the relative reactivity order of the olefins appears to be 1-alkenes < styrene < 1,3-butadiene < ethylene and a,oi-or a,/3-disubstituted alkenes do not react94. However, strained alkenes such as cyclopropenes constitute an exception. Indeed, dicrotylzinc smoothly reacted with 3,3-dimethylcyclopropene and afforded the dicyclopropylzinc reagent 130 resulting from a syn addition process (equation 62)93. 

Alkenylation of thiophenes with substituted alkenes (styrene, acrylic ester, acrylonitrile) in the presence of equimolar amounts of palladium(II) acetate results in mono- and... 

A large number of accurate rate constants are known for addition of simple alkyl radicals to alkenes.33-33 Table 2 summarizes some substituent effects in the addition of the cyclohexyl radical to a series of monosubstituted alkenes.36 The resonance stabilization of the adduct radical is relatively unimportant (because of the early transition state) and the rate constants for additions roughly parallel the LUMO energy of the alkene. Styrene is selected as a convenient reference because it is experimentally difficult to conduct additions of nucleophilic radicals to alkenes that are much poorer acceptors than styrene. Thus, high yield additions of alkyl radicals to acceptors, such as vinyl chloride and vinyl acetate, are difficult to accomplish and it is not possible to add alkyl radicals to simple alkyl-substituted alkenes. Alkynes are slightly poorer acceptors than similarly activated alkenes but are still useful.37... 

The necessary alkene, styrene, is available by dehydrohalogenation of the given starting material, 1-phenylethyl bromide. 

Cleavage with an ensuing Heck reaction was developed by using the T1 triazene linker [51] (Scheme 6.1.20). On cleavage with trifluoroacetic acid a diazonium ion is first formed this can couple to an added alkene under the action of palladium catalysis. The coupling proceeds well with simple terminal alkenes, styrenes, and di- and even trisubstituted alkenes. The advantage of this process is clearly the possibility of using volatile alkenes (and alkynes) without contamination by any salt or other less volatile by-product, particularly with the use of palladium on charcoal as the catalyst. 

The catalytic performance of the fluoropolymer ligands 1 and 2 was first tested in the fluorous biphase hydroformylation of 1-alkenes, styrene and n-butyl acrylate. The reaction was conducted in a batch reactor in a 40/20/40 vol% hexane/toluene/perfluoromethylcyclohexane solvent mixture (10 mL). The catalyst was formed in situ by adding [Rh(CO)2(acac)] (5 rmol, P/Rh = 6) to the polymer-containing solvent mixture followed by introduction of syngas (30 bar, CO/H2 = 1/1). Table 2 summarises the results obtained. The salient features of the results are Firstly, the activity of the fluorous soluble polymer catalysts are significantly higher than that reported for solid polymer- and aqueous soluble polymer-supported rhodium catalysts.18-22 For example, the average turnover frequency (TOF) for the fluorous biphase hydroformylation of 1-decene is 136 mole aldehyde h-1 per mol of rhodium catalyst with an aldehyde selectivity of 99%. In comparison, a rhodium catalyst supported on the... 

Early studies of the supported metal complexes utilized as hydrosilylation catalysts focused on the immobilization of H2PtCl6 on ion exchangers. Chloroplatinic acid and other Pt complexes have been used as efficient precursors of the catalysts anchored to silica or organic materials for the hydrosilylation of 1-alkenes, styrene, allyl derivatives, and acetylene [2, 84-87]. 

Functionalization of alkenes. Styrenes are converted to v(c-bisthioisocyanates using the combination of NH SCN and CAN. lodohydrins are formed by reaction of alkenes with I -CAN in aqueous MeCN. Note that halohydrins are also obtained by... 

Alkylation and silylation of alkenes. Styrenes are alkylated by two alkyl halides, ... 

In addition to propene and ethene many other alkenes (higher alkenes, styrenes, cyclic alkenes) have been polymerized with these new catalysts and a great variety of new polymers and oligomers have been synthesized, including plastic materials with melting points as high as 500°C, novel rubber materials etc. Several new polymers can now be made by catalyst design. Basically, the con-... 

A series of polymer-anchored epoxidation catalysts was obtained by modifying Merrifield resin with imidazole [61], diphosphines [62], or piperazine [63] followed by treatment with UV-activated Mo(CO)6. High activities in the epoxidation of cyclic (cyclooctene, cyclohexene, indene, and a-pinene) as well as linear alkenes (styrene, a-methylstyrene, 1-heptene, 1-dodecene, cis- and frans-stilbene) were observed using TBHP as oxidant. The catalysts were recovered and reused up to 10 times in the epoxidation of cyclooctene without loss of activity. 

Key Words Density functional theory, DFT calculations. Porphyrin, Alkene, Styrene, Epoxidation, Reaction pathway. 2008 Elsevier B.v. 

The results of asymmetric hydroformylation are described here for individual substrate types such as normal open chain and cyclic alkenes, styrene and other alkenylaromatics, dienes, functionalized alkenes and alkynes. Earlier extensive compilations of results concerning this subject are found in several monographs and reviews31 45,54,104,105, l21,177,178,180,, 81. 

Reaction of 1,3-diones with propargylic alcohols leads to 3-acylfurans. Using other Lewis acids such as FeCU the reaction stops short of cyclization. Alkylation by alkenes (styrene, norbornene, cyclopentadiene, dihydropyran,. ..) affords moderate yields of the adducts.Again, InCU appears to show a special catalytic activity, as AICI3, TiCU, MnCl2, Bids are ineffective. 

Friedel—Crafts alkylation. Alkenes (styrenes and trisuhstituted alkenes) alkylate indoles at the 3-position in CH2CI2 containing 5 mol% of TfOH (or an Au(III) species). Benzyl trifluoromethyl carhinols are obtained from reaction of arenes with trifluoro-methyl epoxides. The direction of epoxide ring opening is determined by the electron-withdrawing trifluoromethyl group. ... 

The discussion of cis-trans photoisomerization of alkenes, styrene, stilbene, and dienes has served to introduce some important ideas about the interpretation of photochemical reactions. We see that thermal barriers are usually low, so that reactions are very fast. Because excited states are open-shell species, they present new kinds of structures, such as the twisted and pyramidalized CIs that are associated with both isomerization and rearrangement of alkenes. However, we will also see familiar structural units as we continue our discussion of photochemical reactions. Thus the triplet diradical involved in photosensitized isomerization of dienes is not an unanticipated species, given what we have learned about the stabilization of allylic radicals. 

The reversal in the regioselectivity of the hydroboration of styrenes using a cationic rhodium complex (see Scheme 5.14), to provide the secondary (rather than primary) organoborane, allows the study of the asymmetric hydroboration of mono-Caryl) substituted alkenes (styrenes). A variety of chiral phosphine ligands can be used to good effect, a popular choice being (7 )-2,2 -bis(diphenylphosphino)-l, T-binaphthyl (BINAP). Just 0.02 molar equivalents of the rhodium catalyst and... 

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