Highly efficient catalyst-free annulative functionalization approaches to a novel imidazole-pyrrolo[1,2-a]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.