Rhodium catalysis allylic

Hydroformylation - [CARBON MONOXIDE] (Vol 5) - [OXO PROCESS] (Vol 17) -of allyl alcohol [ALLYL ALCOHOL AND MONOALLYL DERIVATIVES] (Vol 2) -catalysts for [CATALYSIS] (Vol 5) -C-19 dicarboxylic acids from [DICARBOXYLIC ACIDS] (Vol 8) -of ethylene [ETHYLENE] (Vol 9) -of ethylene [PROPYL ALCOHOLS - N-PROPYLALCOLHOL] (Vol 20) -of maleate and fumarate esters [MALEIC ANHYDRIDE, MALEIC ACID AND FUMARIC ACID] (Vol 15) -phosphine catalyst [PHOSPHORUS COMPOUNDS] (Vol 18) -platinum-group metal catalysts for [PLATINUM-GROUP METALS] (Vol 19) -rhodium catalysis [PLATINUM-GROUP METALS, COMPOUNDS] (Vol 19) -ruthenium cmpds or catalyst [PLATINUM-GROUP METALS, COMPOUNDS] (Vol 19) -use of coordination compounds [COORDINATION COMPOUNDS] (Vol 7)... 

Allylamines cyclize readily with a dicobalt octacarbonyl catalyst (equation 55).1,2 Rhodium catalysis generally allows the carbonylative cyclization to be carried out under milder conditions.86 Application of this reaction to unsaturated amides yields the corresponding imides, the best yields arising when R1 = H and R2 = allyl (equation 56).I>2... 

Rhodium catalysis for effecting allylic oxidation has been developed and has led to considerable controversy over the operative mechanistic pathway. ... 

The fust example of rhodium catalysis for this purpose utilized chlorotiis(triphenylphosphine)rho-diumG) to catalyze the allylic oxidation of a range of alkenes. 47oxidize cyclic allylsilanes " to afford -silyl-2-cycloalkoiones in very good yields and with exclusive fearrangemrat (equation 43). 

Allyl methyl ether (ethyl diazoacetate, rhodium catalysis) and allyl terf-butyl ether (dimethyl diazomalonate, copper catalysis) yield cyclopropanes exclusively. With y-substituted allyl methyl ethers, C-0 insertion is generally strongly favored over cyclopropanation, even with tetraacetatodirhodium as catalyst.In view of these findings, the cyclopropanation of ( )- ,4-dibenzyloxybut-2-ene in moderate yield, only, to give (la,2a,3j5)-31 is notable. 

A modification called tandem [2,3] sigmatropic rearrangement of sulfonium ylide—bromine allylic rearrangement has been reported (88JOC5149). Thus, reaction of the C5 brominated 2-pyrone 224 with ethyl diazoacetate under rhodium catalysis results not only in transfer of the ester moiety to C5, as described earlier, but also in the transfer of the bromine atom from C5 to the side chain at C6 in such a way that the functional group remaining at that side chain, as in 225, can be further elaborated (89JHC1205). 

The interpretation of the formation of the Ci3-lactone requires a sequence of mechanistical pathways which are unknown so far in rhodium-catalysis. Two proposals for the mechanism were given in Equation 12. The mechanism of path B is similar to that shown for palladium catalysis. A rhodium Cg-carboxylate complex is formed which under further incorporation of butadiene could yield the lactone. In the mechanism of path A three molecules of butadiene react with the starting rhodium compound forming a C- 2 Chain, which is bound to the rhodium by two n -ally1 systems and one olefinic double bond. Carbon dioxide inserts into one of the rhodium allyl bonds thus forming a C- 3-carboxyl ate complex, which yields the new C-13-lactone. 

That Rh-allyl complexes can also act as nucleophiles in addition to aldehydes has been demonstrated by Oshima et al. in 2006 [198]. Retro-aUylation of the homoallyl alcohol 191 under rhodium catalysis generates a nucleophilic aUylrhodium species that reacts with aldehydes 190 to give the corresponding secondary alcohols 192 in situ (Scheme 12.94). Subsequent isomerization of these alcohols proceeds under the reaction conditions to furnish the corresponding saturated ketones 193 in modest to good yields. 

Evans and coworkers developed a rhodium-catalyzed allylic substitution of chiral acyclic tertiary allylic carbonates with acyl anion equivalents. This substitution pathway provides a route to undergo a stereo- and regioselective substitution to provide the quaternary carbon 73. The enantioenriched product is isolated in greater than 95 5 selectivity and 87% yield. This pathway provides a product that could be obtained through enolate chemistry, only lacking the same atom economy obtained with rhodium-catalysis. 

Recently, hydrosilanes are also employed for the silylation of aryl halides in the presence of a palladium,platinum, or rhodium catalyst. In view of atom efficiency, this procedure has an advantage. Palladium-catalyzed reactions are suitable for the silylation of electron-rich aryl halides, whereas rhodium-catalysis works well with a wide range of aryl halides (Scheme 3-17). Silylation of allyl halides with trichlorosilane proceeds in the presence of a copper catalyst. ... 

I 7 Well-Defined Surface Rhodium Siloxide Complexes and Their Application to Catalysis Table 7.5 Hydrosilylation of 1-hexadecene and allyl ethers by polyhydrosiloxane (7.1) . 

Abstract The purpose of this chapter is to present a survey of the organometallic chemistry and catalysis of rhodium and iridium related to the oxidation of organic substrates that has been developed over the last 5 years, placing special emphasis on reactions or processes involving environmentally friendly oxidants. Iridium-based catalysts appear to be promising candidates for the oxidation of alcohols to aldehydes/ketones as products or as intermediates for heterocyclic compounds or domino reactions. Rhodium complexes seem to be more appropriate for the oxygenation of alkenes. In addition to catalytic allylic and benzylic oxidation of alkenes, recent advances in vinylic oxygenations have been focused on stoichiometric reactions. This review offers an overview of these reactions... 

The formation of a branched chiral product from the alkylation of monosubstituted substrates is not limited to the catalysis of metals described thus far. Allylic alkylation reactions catalyzed with rhodium [211] and iridium [212] complexes have been shown to occur at the more... 

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