Product Subclass 4: Pyrazino[1,2-a]indoles and Related Benzo-Fused Ring Systems

The synthesis of pyrazino[1,2-a]indoles and related indolo[1,2-a]quinoxalines and pyrido[2',1':3,4]pyrazino[1,2-a]indol-5-ium salts are reviewed in this chapter. The most common routes to pyrazino[1,2-a]indoles involve cyclization of indole derivatives containing a formyl, keto, ester, or nitrile function at the 2-position. Indolo[1,2-a]quinoxalines are most readily accessed via cyclization of 1-(aryl)-1H-indoles, where the aryl group is substituted at the 2-position by either amino, iodo, or nitro functionality.