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. © Copyright 2018 American Chemical Society.