Synthesis of Spirocyclic Pyrrolidine Compounds via Silver-Catalyzed Asymmetric [3+2] Cycloaddition Reaction of Imino Esters with α-Alkylidene Succinimides

In this study, the AgOAc/ThioClickFerrophos (TCF) complex was used to successfully catalyze asymmetric [3 + 2] cycloaddition between glycine imino esters and CO2Me-appended alpha-alkylidene succinimides to afford spiropyrrolidines in good yields with high diastereo- and enantioselectivities (up to 95% ee). The silver/TCF afforded endo-(2,5-cis) cycloadducts in contrast to the previous exo '-(2,5-trans) selective reaction with ylidene-2,3-dioxopyrrolidine. A wide variety of imino esters bearing electron-donating and electron-withdrawing groups on the phenyl groups and heteroaryl substrates were utilized in this reaction. The scope of alpha-alkylidene succinimides was investigated, which revealed that substituents on alpha-benzylidene derivatives had negligible effect on the product yield and stereoselectivity, and alpha-alkylidene derivatives could be efficiently used as dipolarophiles.