Synthesis of pyrazino[1,2-a]indoles and indolo-[1,2-a]quinoxalines (microreview)

The review is dedicated to the methods of synthesis of pyrazino[1,2-a]indoles and indolo[1,2-a]-quinoxalines. The primary approach to the synthesis of these heterocyclic systems is the annulation of a pyrazine ring to a functionalized indole ring by means of condensation of carbonyl compounds, radical reactions catalyzed by transition metals, as well as hypervalent iodine compounds.