Regioselective Synthesis of Functionalized Spiro[benzofuran‐2,3′‐Pyrrolidine]‐3,5′‐Diones via Cascade Cyclization

A highly regioselective cascade reaction was developed to construct a library of spiro[benzofuran‐2,3′‐pyrrolidine]‐3,5′‐diones (SBFPDs). This spirocyclic structure was formed by using simple enaminones and 2,2,2‐trichloro‐ N ‐methoxyacetamides as substrates through a complex cascade process. Three CCl bonds were cleaved, and CC, CO, and CN bonds were formed in a single step, leading to the production of a series of SBFPDs. The reaction mechanism encompassed aza‐Michael and oxa‐Michael addition. Notably, this process successfully achieved the polarization inversion of the α –C of enamines; the α –C serves as both an electrophilic and a nucleophilic site in the synthesis of spirocyclic structures. These strategies enable the synthesis of functionalized SBFPDs and their derivatives through one‐pot reactions, which are suitable for combinatorial and parallel syntheses.