Enantioselective and diastereoselective Tsuji-Trost allylic alkylation of lactones: an experimental and computational study.

The Tsuji-Trost protocol has been successfully employed for the allylic alkylation of preformed lactone enolates. It has been demonstrated that this Pd-catalyzed reaction can be carried out in an enantio- and diastereoselective manner. The use of additives, such as LiCl, was found to be crucial for reaching high levels of product selectivity. For one particular pair of reactants, density functional theory was used to investigate the mechanism of the nucleophilic addition. Among the five pathways considered, the reaction between an (allyl)Pd(BINAP) complex and a LiCl-lithium enolate adduct is predicted to be the most likely route for C-C bond formation. LiCl plays a key role as the connecting link between the noble metal and the enolate in the kinetically favored transition state. The computed diastereoselectivity ratio is in good agreement with the experimentally observed value.