3+2]-Annulation of oxindolinyl-malononitriles with Morita–Baylis–Hillman acetates of nitroalkenes for the regio- and diastereoselective synthesis of spirocyclopentane-indolinones

Abstract

3-Oxindolinyl-malononitrile participates as a 1,2-binucleophile in a highly regio- and stereoselective [3 + 2] annulation with 1,3-bielectrophilic nitroallylic acetates leading to spirocyclopentane-indolinones. The reaction takes place in the presence of DABCO in THF at room temperature and affords the multi-functional spirocyclic compounds possessing three chiral centers, including a spiro-chiral center in good to excellent yields and short reaction time. The key role of the malononitrile moiety in controlling the reactivity and selectivity has also been demonstrated. An SN2′-intramolecular Michael addition pathway is proposed for the [3 + 2] annulation based on DFT calculation results.