7t-allylpalladium species

Scheme 71).124 An intermediate 7t-allylpalladium species (60) is thought to effect this transformation and in this context it is significant that presynthesized bis[acetoxy(7,l, 2)- j-pinene)palladium(II)]12 5 reacts in a similar fashion, affording optically active 59 in comparable optical yield.124... 

Allenes represent an important class of compounds used in transition metal-catalyzed reactions, especially palladium-catalyzed cascade reactions [101], in which they are used predominantly for the formation of 7t-allylpalladium species and carbopalladations. 

Distributive addition to benzylidenemalononitrile occurs when the decomposition of allyl P-oxoalkanoates or carbonates is carried out in its presence. The counteranions of the initially formed 7t-allylpalladium salts are not stable so that the nucleophilic addends are the decarboxylated species. The reaction with vinyloxiranes generates tetrahydrofuran derivatives. ... 

Substitution reactions of allylic substrates with nucleophiles have been shown to be catalyzed by certain palladium complexes [2, 42]. The catalytic cycle of the reactions involves 7t-allylpalladium as a key intermediate (Scheme 2-22). Oxidative addition of the allylic substrate to a palladium(o) species forms a Tt-allylpal-ladium(n) complex, which undergoes attack of a nucleophile on the n-allyl moiety to give an allylic substitution product. The substitution reactions proceed in an S, or Sn manner depending on catalysts, nucleophiles, and substituents on the substrates. Studies on the stereochemistry of the allylic substitution have revealed that soft carbon nucleophiles represented by sodium dimethyl malonate attack the Ti-allyl carbon directly from the side opposite to the palladium (Scheme 2-23). 

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