Synthesis of Fused Spiropyrrolidine Oxindoles Through 1,3‐Dipolar Cycloaddition of Azomethine Ylides Prepared from Isatins and α‐Amino Acids with Heterobicyclic Alkenes

The synthesis of various fused spiropyrrolidine oxindoles from isatins, amino acids, and heterobicyclic alkenes through a 1,3‐dipolar cycloaddition is described. For the first time, we used heterobicyclic alkenes as a dipolarophile in 1,3‐dipolar cycloaddition of the azomethine ylide generated by decarboxylation. Triflic acid mediated aromatization of cycloaddition products has been demonstrated. A possible mechanism is proposed that the formation of iminium carboxylate intermediate (I), azomethine ylide intermediate (II) via decarboxylation, subsequent 1,3‐dipolar cycloaddition with oxabenzonorbornadiene to give cycloaddition product.