Phosphine-Catalyzed [4 + 3] Annulation of β′-Acetoxy Allenoates with 1C,3N-Dinucleophiles: Access to Functionalized Azepine Derivatives

A novel method for the synthesis of functionalized azepine derivatives has been developed through a phosphine-catalyzed [4 + 3] annulation of β′-acetoxy allenoates with benzimidazole-derived 1C,3N-dinucleophiles. This approach demonstrates high efficiency and yields ranging from moderate to excellent. The reaction exhibits a wide substrate scope under the optimized conditions. Furthermore, an initial exploration of the asymmetric variant of this reaction has been conducted, utilizing phosphine (R)-SITCP as the catalyst.