Silylated pyrrolidones via diastereoselective Pd-catalysed intramolecular allylic alkylations

A new palladium-catalysed allylic alkylation affording silylated 3-vinyl-pyrrolidones has been developed. The method relies upon the interaction between a stabilised acetamide enolate anion and a silicon-containing nitrogen-tethered η3-allyl-palladium moiety. Two variants have been studied, involving location of the silicon atom on either olefinic carbon atom of the cyclisation precursor. In both cases 5-exo-trig ring closure was the only cyclisation process observed. These results contrast with related β-ketoester cyclisations, were competitive 7-endo-trig is observed.