Green Synthesis of Functional γ‐Lactams via Metal‐Free Promoted Selective Reductive Amination/Cyclization

Developing a “green” synthetic method to functional γ‐lactam is essential due to their significant importance to numerous fields. In this work, we developed an efficient and highly chemoselective reductive amination/cyclization to access isoindolinones and pyrrolidones from 2‐formylbenzoic and levulinic acid with anilines by a metal‐free and HBpin reaction system under mild conditions with tolerated functional rings and unsaturated groups. In addition, various oxazino isoindolinones were easily synthesized from substituted 3‐aminopropanols via HBpin‐promoted reductive amination/cyclization under mild conditions. Moreover, HBpin demonstrates the dual roles of promoter and reducing reagent. Density functional theory calculations were performed to verify the mechanism of HBpin‐promoted reductive amination/cyclization.