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Alkyl carbenes

Dehydrocyclization, 30 35-43, 31 23 see also Cyclization acyclic alkanes, 30 3 7C-adsorbed olefins, 30 35-36, 38-39 of alkylaromatics, see specific compounds alkyl-substituted benzenes, 30 65 carbene-alkyl insertion mechanism, 30 37 carbon complexes, 32 179-182 catalytic, 26 384 C—C bond formation, 30 210 Q mechanism, 29 279-283 comparison of rates, 28 300-306 dehydrogenation, 30 35-36 of hexanes over platintim films, 23 43-46 hydrogenolysis and, 23 103 -hydrogenolysis mechanism, 25 150-158 iridium supported catalyst, 30 42 mechanisms, 30 38-39, 42-43 metal-catalyzed, 28 293-319 n-hexane, 29 284, 286 palladium, 30 36 pathways, 30 40 platinum, 30 40 rate, 30 36-37, 39... [Pg.87]

Dehydrogenative Cj cyclization (25, 26). Its probable pathway is an alkene-alkyl insertion (5). A carbene-alkyl insertion mechanism may eventually also be possible. [Pg.276]

In contrast, comparable rates were determined over platinum of low dispersion suggesting that isomerization occurs without alkene formation.161 The carbene-alkyl species (21) formed with the involvement of terminal carbon atoms is a probable surface intermediate in this selective mechanism. Highly dispersed platinum catalysts are active in nonselective isomerization in which the precursor species is the 22 dicarbene allowing ring closure between methyl and methylene groups. On iridium a pure selective mechanism is operative,162 which requires a dicarbyne surface species (23). [Pg.184]

Indeed the carbene-alkyl insertion mechanism in Scheme 45 neatly explains why the rates of dehydrocyclization of 1, 2, and 3 are so similar. However, since 2-methylhexane also undergoes 1-5 dehydrocyclization, involvement of methylenic carbon atoms and not simply terminal carbon atoms must also be possible. The pathway for the C7-alkanes must be the reverse of nonselective hydrogenolysis of methylcyclopentane (Mechanism A), since it also results in isomerization to 2,4-dimethylpentane and 3-methylhexane, most likely via adsorbed 1,3-dimethylcyclopentane (scheme 46). It is... [Pg.37]

Herisson and Chanvin proposed that metathesis reactions are catalyzed by carbene (alkyl-idene) complexes that react with alkenes via the formation of a cyclic intermediate, a metallacyclobutane, as shown in Figure 14.24c. In this mechanism, a metal carbene complex first reacts with an alkene to form the metallacyclobutane. This intermediate can either revert to reactants or form new products because all steps in the process are in equilibria, an equilibrium mixture of alkenes results. This non-pairwise mechanism would enable the statistical mixture of products to form from the start by the action of catalytic amounts of the necessary carbene complexes, with both R and R groups, as shown in Figure 14.24c. [Pg.567]

The surface organometalhc complexes are thermally much more stable than their molecular counterpart. The example of [(=Si-0) WMes] on silica which is stable up to lOO C is a good example of the ability of a surface to stabilize a molecular compound which is explosive at room temperature So reactions can be performed on organometaUic compounds at very high temperature which is not possible in classical homogeneous catalysis. Such stability allows the observation of carbynes, carbenes, alkyls, amido, imido, and hydrides even at elevated temperatures. [Pg.184]

This is a group of cyclic polyethers which are used as phase transfer catalysts. These have been used for esterifications, saponifications, anhydride formation, oxidations, aromatic substitution reactions, elimination reactions, displacement reactions, generation of carbenes, alkylations etc. Some of the examples are as follows ... [Pg.51]


See other pages where Alkyl carbenes is mentioned: [Pg.106]    [Pg.106]    [Pg.110]    [Pg.275]    [Pg.2583]    [Pg.160]    [Pg.177]    [Pg.179]    [Pg.186]    [Pg.3218]    [Pg.675]    [Pg.268]    [Pg.553]    [Pg.2325]    [Pg.2583]    [Pg.2480]    [Pg.2600]    [Pg.3217]    [Pg.150]    [Pg.423]    [Pg.629]   
See also in sourсe #XX -- [ Pg.221 ]

See also in sourсe #XX -- [ Pg.221 ]

See also in sourсe #XX -- [ Pg.221 ]

See also in sourсe #XX -- [ Pg.97 , Pg.99 , Pg.221 , Pg.261 , Pg.269 ]




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Alkyl from carbene complexes

Alkyls, Carbenes, Carbynes, and Carbides

Carbene complexes alkylation

Carbene complexes alkylations

Carbene complexes, alkyl aminoalkylation

Carbene complexes, alkyl pentacarbonylalkylation

Carbene complexes, alkyl pentacarbonylalkylation anions

Carbene complexes, alkyl pentacarbonylalkylation reaction with carbonyl compounds

Carbene complexes, tetracarbonyl phosphine alkylation

Carbenes alkyl substituted, 1,2-migration

Carbenes, alkylation

Catalysts alkyl) carbene-based

Cyclic alkyl amino carbenes

Cyclic alkyl carbenes

Cyclopropanes from alkyl carbene insertion

Generation of Alkyl and Alicyclic Carbenes

Generation of Alkyl and Aryl Carbenes

Generation of Alkyl and Cycloalkyl Carbenes

Indole, alkyl-, reaction with carbenes

Reaction of alkyl, alkenyl alkynyl and carbene ligands

Reactions with alkyl pentacarbonyl carbene anions

Triflates, alkyl carbonyl phosphine carbene complexes

Tungsten complexes, alkyl carbene

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