Tsuji-Trost reaction stereochemistry

In the carbohydrate chemistry arena, the Tsuji-Trost reaction has been applied to construct N-glycosidic bonds [53]. In the presence of Pd2(dba>3, the reaction of 2,3-unsaturated hexopyranoside 68 and imidazole afforded N-glycopyranoside 69 regiospecifically at the anomeric center with retention of configuration. In terms of the stereochemistry, the oxidative addition of allylic substrate 68 to Pd(0) formed the jc-allyl complex with inversion of configuration, then nucleophilic attack by imidazole proceeded with another inversion of the configuration. Therefore, the overall stereochemical outcome is retention of configuration. 

Another important aspect of the Tsuji-Trost reaction is the stereochemistry. The representation of the r -allylpalladium complex of formula 4 is an oversimplification. In reality, i73-allylpalladium complexes are square-planar, as indicated by formulas 10 and 11 in Scheme 4, the two auxiliary ligands L being placed approximately near the two vertical parallel planes... 

Catalytic Cycles Showing the Stereochemistry Associated with the Tsuji-Trost Reaction... 

The Tsuji-Trost reaction is the Pd-catalyzed allylation of nucleophiles [105] with allylic halides, acetates, carbonates, etc. This transformation proceeds via intermediate allylpalladium complexes (e.g. 110), and typically proceeds with overall retention of stereochemistry. In addition, the trapping of the intermediate allylpalladium complex usually occurs at the least hindered carbon. A representative example of this transformation is shown below in an application to the formation of an 7V-glycosidic bond. Treatment of 2,3-unsaturated hexopyranoside 109 with imidazole in the presence of a Pd(0) catalyst... 

The stereochemistry at the allylic C pB center is also a very intricate issue. In the 1970s it was demonstrated that Pd-catalyzed dlylation of doubly stabilized enolates, that is, the Tsuji-Trost reaction, proceeded with retention at that C pS center, resulting from double... 

The inclusion of the allyl moiety in an appropriate ring system led to the formation of a new, chiral quaternary carbon center (3.13.), By the use of optically active starting material, Mori and co-workers were able to control the stereochemistry of the new chiral centre (N.B. the chirality of the first centre was also set by a palladium catalysed reaction, the Tsuji-Trost allylation).17... 

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