Catalyst-Free Construction\nof 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\nAnnulative Functionalizations

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