Palladium catalysis enantioselective allylic alkylation

With 1-alkoxyallenes as proelectrophiles, the palladium-catalysed asymmetric allylic alkylation proceeds with 1,3-dicarbonyl compounds as pronucleophiles with excellent regioselectivity good enantioselectivity (82-99% ee) was obtained with the Trost lig- and. The pH of the medium proved crucial for the reactivity and selectivity. By using the more acidic Meldrum s acids, the reactions required a co-catalytic amount of a Brpnsted acid, such as CF3CO2H. On the other hand, the less acidic 1,3-diketones failed to react under these conditions but the reaction proved to occur in the presence of the weaker benzoic acid, suggesting the need for general base catalysis. Indeed, a mixture of Et3N and PhCOiH proved to be optimal (93-99% ee). A mechanistic model to rationalize these results has been developed.88... 

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