Versatile Base‐Catalyzed Route to Polycyclic Heteroaromatic Compounds by Intramolecular Aza‐Michael Addition

A catalytic new synthetic approach to 3,4‐dihydropyrazino[1,2‐a]indol‐1(2H)‐ones by intramolecular 1,4‐addition of readily available α,β‐unsaturated esters, is described. Here, the use of a range of organic as well as inorganic bases (5–10 mol‐%) allowed a fast (30 min) and regioselective ring‐closing reaction to be performed in high yields under simple operational conditions. Moreover, the protocol was effectively employed, as the key step, in the synthesis of the dibromopyrrolo alkaloid derivative N‐Bn‐longamide b.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)