A Two-Step Synthesis of a Novel 7,8-Dihydro-5,8-ethanoindolizine-6,9(5H)-dione

A two-step synthesis of the novel 5,8-dimethyl-7,8-dihydro-5,8-ethanoindolizine-6,9(5H)-dione from 2,3-dimethyl-1,4-benzoquinone is described. The key step of the synthesis of this unusual fused tricyclic system is the intramolecular regiospecific aza-Michael addition of a pyrrole to an activated double bond by reaction with tetrabutylammonium fluoride under mechanochemical conditions.