Imidazolium-dithiocarboxylate zwitterions catalyzed synthesis of fully substituted spiro-glutarimides via [3+3] annulation of cyclopropenones

Abstract

An organocatalytic [3+3] annulation reaction of cyclopropenones and cyclic β-ketoamides has been reported for the synthesis of fully substituted spiro-glutarimides. Under the catalysis of imidazolium-dithiocarboxylate zwitterions (NHC•CS2), cyclopropenones react with cyclic ketoamides through a tandem ring opening/intermolecular nucleophilic substitution/intramolecular nucleophilic addition/tautomerization process to afford a diverse of spirocyclic glutarimide derivatives that containing one all-carbon quaternary spirocenter in high yields and excellent diastereoselectivity. The reaction can be scaled-up easily and the stable NHC•CS2 zwitterion catalyst can be recovered and reused at least four times.