Tsuji-Trost reaction elimination reactions

A wide variety of nucleophiles add to an -rf-allyl ligand. Desirable nucleophiles typically include stabilized carbanions such as CH(COOR)2 or 1° and II0 amines. Unstabilized nucleophiles such as MeMgBr or MeLi often attack the metal first and then combine with the n-allyl by reductive elimination. The Tsuji-Trost reaction, which is typified by the addition of stabilized carbanions to T 3—allyl ligands complexed to palladium followed by loss of the resulting substituted alk-ene, comprises an extremely useful method of constructing new C-C bonds, and many applications of this reaction have appeared in the literature.61 Equation 8.43 illustrates an example of a Pd-catalyzed addition of a stabilized enolate to an allyl acetate.62 The initial step in the catalytic cycle is oxidative addition of the allyl acetate to the Pd(0) complex, followed by nq1 to nq3—allyl isomerization, and then attack by the nucleophile to a terminal position of the T 3—allyl ligand. We will discuss the Tsuji-Trost reaction, especially in regard to its utility in chiral synthesis,63 more extensively in Chapter 12. 

Organometals, enolates, and metal hydrides used throughout this Handbook, especially in CTOSS-conphng and related reactions (Part HI) and the Tsuji-Trost reaction (Part V), can, in general, readily rednce Pd(ll) complexes via transmetaUation-reductive elimination, as shovra in Scheme 7. 

Although it is mechanistically different from the Tsuji-Trost allylation, indirect allyla-tions of ketones, aldehydes, and esters via their enolates are briefly summarized here. Related reactions are treated in Sect V.2.1.4. Pd-catalyzed allylation of aldehydes, ketones, and esters with aUyhc carbonates is possible via the Tr-allylpaUadium enolates of these carbonyl compounds. Tr-AUylpalladium enolates can be generated by the treatment of silyl and stannyl enol ethers of carbonyl compounds with allyl carbonates, and the allylated products are obtained by the reductive elimination of the Tr-allylpalladium enolates. 

Furthermore, following an analogous methodology, combining the Morita-Baylis-Hillman reaction and the Trost-Tsuji reaction, Krische and co-workers have obtained allyl-substituted cyclopentenones 94 [84], Reaction was initiated by Michael addition of tributyl phosphine to an enone moiety 92, generating a latent enolate 93 which reacts intramolecularly with a jr-allylPd complex as the electrophile partner. A final -elimination step of trib-utylphosphine, favored by the presence of the methoxide ion, delivered the substituted cyclopentenones 94 (Scheme 36). 

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