Asymmetric Michael Addition of Aldimino Esters with Chalcones Catalyzed by Silver/Xing-Phos: Mechanism-Oriented Divergent Synthesis of Chiral Pyrrolines.

The mechanism-oriented reaction design for the divergent synthesis of chiral molecules from simple starting materials is highly desirable. In this work, aromatic amide-derived nonbiarylatropisomer/silver (silver/Xing-Phos) complex was used to catalyze the Michael addition of glycine aldimino esters to chalcones and successfully applied to the subsequent cyclocondensation to afford substituted cis-Δ(1)-pyrroline derivatives with up to 98 % ee. Besides the inherent performance of the chiral Ag/Xing-Phos catalyst system, it was found that the workup of such reactions played an important role for the stereoselective construction of stereodivergent Δ(1)-pyrrolines, in which an epimerization of the cis-Δ(1)-pyrrolines to the trans-isomers during was revealed.