Alkyl halides reductive elimination from

In-depth study of Pd(IV) alkyl halide reductive elimination showed competitive reactions in operation (Scheme 11). Several intriguing, albeit unsupported, mechanisms were considered for the elimination of ethane from (45). In contrast to the palladium complex, the iridium species, (46), did not undergo reductive elimination when R, R = Neither did elimination occur when 1 was... 

Our examples will first center on the complexes Ir(CO)(R)(R0L2X (R and R = H, alkyl, or aUcoxy L = PPhs or P(/ -tolyl)3 X = halide or H), which reductively eliminate a number of different products. The reactions are summarized in Table 11. The reactions described in Table 11 show that reductive elimination from Ir results in formation of different types of bonds. These reductive elimination reactions occur under very similar conditions, indicating that the nature of R and R does not significantly affect the rate. However, the coupling of two sp carbon centers does not occur. Theoretical studies have suggested that the directionality of the sp hybrid inhibits bond formation. ... 

The stereochemistry of oxidative addition to the palladium(II) palladacycle was studied by Lautens using an enantioenriched secondary alkyl halide (Scheme 9) [32], From alkyl halide 23, product 24 was obtained, showing a net inversion of stereochemistry [33-35], Previous work by Stille showed that reductive elimination from palladium(IV) occurs with retention of stereochemistry [36], suggesting that oxidative addition occurs with an inversion of stereochemistry. This corresponds with the generally accepted SN2 mechanism for the reaction of palladium(O) with alkyl halides [37, 38],... 

The elimination reaction, given in Equation 7e, is accompanied by a formal reduction in the oxidation state of the rhodium from (III) to (I). The stereochemistry of this reaction has also attracted substantial interest. If /8-hydrogens are absent, the alkyl halide is eliminated with retention of configuration at the carbon. If /8-hydrogens are present, /8-hydride elimination occurs as shown in Equation 7f, giving an alkene and hydrogen halide. Investigations into the /8-hydride elimination have shown... 

When 1,3-diene is the radical acceptor, a three-component coupling reaction of alkyl halide, 1,3-diene, and trimethylsilylmethyl-magnesium chloride takes place to afford homoallylsilane The final step of the three-component coupling is reductive elimination from allyl(trimethylsilylmethyl)cobalt that predominates over conceivable /3-hydride elimination. 

Reaction between alkyl halides and cyanide ion Elimination of water from N-alkylformamides Reduction of isocyanates... 

Secondary bromides and tosylates react with inversion of stereochemistry, as in the classical SN2 substitution reaction.24 Alkyl iodides, however, lead to racemized product. Aryl and alkenyl halides are reactive, even though the direct displacement mechanism is not feasible. For these halides, the overall mechanism probably consists of two steps an oxidative addition to the metal, after which the oxidation state of the copper is +3, followed by combination of two of the groups from the copper. This process, which is very common for transition metal intermediates, is called reductive elimination. The [R 2Cu] species is linear and the oxidative addition takes place perpendicular to this moiety, generating a T-shaped structure. The reductive elimination occurs between adjacent R and R groups, accounting for the absence of R — R coupling product. 

A clean twofold Heck coupling of unsubstituted butadiene 46 (R = H) in the 1- and 4-positions has not been reported. However, the initial carbopalladation product from 46 (R = H) and an in situ formed arylpalladium halide, the cr-allylpalladium halide 47 equilibrating with the corresponding 7r-allylpalladium halide, can efficiently be trapped with the anion formed by arylation of malononitrile or cyanoacetate to give 48, a product of reductive 1,4-arylation-alkylation of 1,3-butadiene 46 (R = H)." /3-Hydride elimination from the intermediate 47 (R H) can be accomplished when the reaction is carried out in the presence of silver acetate or thallium acetate, leading to the... 

Alkenes are obtained by the transformation of various functional groups, e.g. dehydration of alcohols (see Section 5.4.3), dehalogenation of alkyl halides (see Section 5.4.5) and dehalogenation or reduction of alkyl dihalides (see Section 5.4.5). These reactions are known as elimination reactions. An elimination reaction results when a proton and a leaving group are removed from adjacent carbon atoms, giving rise to a tt bond between the two carbon atoms. 

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