Tsuji-trost rearrangements

To overcome the limitation of the high stability of the aluminum enolates, the oxygen atom has been transformed to silyl enol ethers, enol acetates, and allyl enol carbonates. Silyl enol ethers and enol acetates are precursors to lithium enolates. Enol acetates and allyl enol carbonates are precursors of cx-allylated adducts via the Tsuji-Trost rearrangement [75-77]. The silylation of aluminum enolates using TMSOTf is well established [78], although in some cases the isolation is difficult [33]. Silyl enol ethers allow further modification to be performed as they behave as lithium enolates (Scheme 15). A recent application can be found in the silylation of the conjugate addition adduct (/ )-((3-(but-3-en-l-yl)-3-methylcyclopent-l-en-l-yl)oxy)triethylsilane which allows aldol condensation to form an intermediate in the synthesis of Clavirolide C [79], a diterpene with a trans-bicyclo[9.3.0] tetradecane structure (Scheme 16) [80]. 

Scheme 6/1.69. Domino Tsuji-Trost reaction/rearrangement.

In one of the first papers on the subject, Billups et al. (80SC147) reported that the Pd(0)-catalyzed allylation of indole 96 with allyl acetate gave N-allyl- (97) and 3-allylindole (98) plus the diallylation product 99 (Scheme 21). They also showed that the yV-allyl isomer 97 rearranged under Pd(0) catalysis to the C-3 isomer 98, thus indicating that the formation of 98 was thermodynamically controlled (C > N). The work of Billups also includes the use of allyl alcohol instead of allyl acetate in the Tsuji-Trost reaction. 

Scheme 3. Carbon—carbon bond formation through the Carroll rearrangement and the Tsuji-Trost reaction.

Trost and Runge announced in 1981 the use of simple allyl carbonates and described even earlier the Pd(0)-catalyzed rearrangement of allyl ethers of enolic /3-ketoesters into the isomeric a-allyl-/S-ketoesters (Scheme 5). Allyl ethers of enolic /3-ketoesters are vinylogous of allyl carbonates In 1980 Tsuji and co-workers described a similar rearrangement,declaring that the palladium-catalyzed rearrangement of a similar cyclic ether has been presented in a lecture by B.M. Trost at the 1st Intern. Kyoto Conf. Org. Chem., Dec., 6,1979. ... 

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