Tosylhydrazine-promoted self-conjugate reduction-Michael/aldol reaction of 3-phenacylideneoxindoles towards dispirocyclopentanebisoxindole derivatives.

An efficient tosylhydrazine-mediated conjugate reduction of 3-phenacylideneoxindole and sequential Michael/intramolecular aldol reaction is reported under base-catalyzed conditions towards the formation of densely substituted dispirocyclopentanebisoxindole derivatives. The reaction proceeded in a diastereoselective manner to afford four chiral stereocenters. The method also has advantages of wide substrate scope, readily available starting materials and operational simplicity through one pot reaction.