Chalcogen-Containing Oxazolines in the Palladium-Catalyzed Asymmetric Allylic Alkylation

The search for new ligands in asymmetric catalysis is a field of continuing interest. To facilitate practical applications, new ligands should be easy to prepare from simple and easily available starting materials. In this context, the use of chiral nitrogen compounds bearing an organochalcogen moiety and their metal complexes have gained increased importance in the field of asymmetric catalysis due to their novel and unprecedented properties. For example, they have been reported to be efficient chiral catalysts in several different enantioselective reactions, such as the asymmetric hydrosilylation and hydrogenation of ketones, enantioselective diethylzinc ’ 5 and alkynylzinc addition to aldehydes, and conjugate addition of organocopper reagents to to enones. Among the transition metal-catalyzed reactions known to form carbon-carbon and carbon-heteroatom bonds, the palladium-catalyzed allylic substitution stands out as one of the most valuable synthetic tools available. Many sulfur-containing ligands have been described to catalyze this transformation in an asymmetric fashion. On the other hand, the parent selenium-containing ligands for asymmetric allylations have been largely overlooked. Furthermore, to the best of our knowledge, telluriumcontaining analogues have never been tested in such transformation. In this paper we report about the examination on the behavior of a series of sulfurseleniumand telluriumcontaining oxazolines as chiral catalysts for the asymmetric alkylation of racemic 1,3-diphenyl-2-propenyl acetate with dimethylmalonate, catalyzed by palladium.