Asymmetric allylic alkylations -1,3-diphenylprop-2-enyl acetate

Bayardon and Sinou have reported the synthesis of chiral bisoxazolines, which also proved to be active ligands in the asymmetric allylic alkylation of l,3-diphenylprop-2-enyl acetate, as well as cyclopropanation, allylic oxidations and Diels-Alder reactions. [62] The ligands do not have a fluorine content greater than 60 wt% and so are not entirely preferentially soluble in fluorous solvents, which may lead to a significant ligand loss in the reaction system and in fact, all recycling attempts were unsuccessful. However, the catalytic results achieved were comparable with those obtained with their non-fluorous analogues. 

The obtained amino functionalised imidazolium salts could be used to generate the corresponding palladium(ll) carbene complexes using the silver(l) complexes as carbene transfer agents. Application of these palladium(ll) complexes (predominantly in situ) in asymmetric allylic alkylation reactions between ( )-l,3-diphenylprop-3-enyl acetate and dimethyl malonate (a standard reaction for this catalytic process [145]) gave up to 80% ee,... 

Table 3.2 Asymmetric allylic alkylation of l,3-diphenylprop-2-enyl acetate with various carbon nucleophiles using [Pd(T 3-C3H5)Cl]2 in association with the fluorous bisoxazoline.

Phosphorous-containing amidine was prepared through several steps from L-valine and evaluated as a new ligand for asymmetric palladium (Pd) catalysed allylic alkylation of 1,3-diphenylprop-2-enyl acetate and pivalate [73]. The results with the nucleophile derived from dimethyl malonate are summarized in Table 3.5 [73a]. Excellent asymmetric inductions up to 95% ee were achieved along with an efficient conversion. 

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