Synthesis of benzimidazole[2.1-b][1,3]oxazine spirooxindoles via three-component reaction of N-benzylbenzimidazole, acetylenedicarboxylates, and N-alkylisatins.

The three-component reaction of N-benzylbenzimidazole, dialkyl acetylenedicarboxylate, and N-alkylisatins in tetrahydrofuran at room temperature afforded the novel functionalized benzimidazole[2.1-b][1,3]oxazine spirooxindoles in good yields. (1)H NMR spectra indicated that two diastereoisomers with a ratio of 1:3-1:6 exist in the obtained spirooxindole derivatives.