Bifunctional Brønsted base catalyzed inverse-electron-demand aza-Diels–Alder reactions of saccharin-derived 1-azadienes with azlactones

Abstract

An enantioselective inverse-electron-demand aza-Diels–Alder reaction of saccharin-derived 1-azadienes and azlactones was developed using a phenylalanine-derived bifunctional Brønsted base-squaramide catalyst, which furnished the chiral tricyclic architectures bearing a quaternary amino acid moiety in high yields with moderate to excellent selectivities. A gram-scale synthesis and further elaboration of the product were also conducted to further demonstrate the synthetic utility of the reaction.