Catalyst-Free Construction of Imidazole-Pyrrolo[1,2-<i>a</i>]pyrazine Hybrid, 2,6-Disubstituted Imidazo[1,2-<i>a</i>]pyrrolo[2,1-<i>c</i>]pyrazine via Regioselective Annulative Functionalizations

Highly efficient catalyst-free annulative functionalization approaches to a novel imidazole-pyrrolo[1,2-<i>a</i>]pyrazine hybrid structure were devised from the reaction of β-enaminone with propargylamine where regioselective conjugate substitution of β-enaminone with propargylamine followed by cycloisomerization proceeded smoothly in a domino fashion to construct two heterocyclic moieties (pyrazine and imidazole) via successive formation of three C-N bonds, leading to the target tricyclic skeleton.