DBU-Catalyzed Alkyne–Imidate Cyclization toward 1‑Alkoxy­pyrazino[1,2‑a]indole Synthesis

1-(Propargyl)­indol-2-carbonitriles react with alcohols to afford 1-alkoxy­pyrazino­[1,2-a]­indoles under DBU-catalyzed microwave-assisted conditions. The reaction scope includes a wide range of indoles, primary and secondary alcohols, and a thiol. The initial mechanistic study shows that the domino process presumably proceeds through an alkyne–allene rearrangement, imidate formation, and nucleophilic cyclization reaction sequence.