Highly regioselective and diastereoselective synthesis of novel pyrazinoindolones via a base-mediated Ugi- N -alkylation sequence.

An efficient base-mediated/metal-free approach has been developed for the synthesis of 1-oxo-1,2,3,4-tetrahydropyrazino[1,2- a ]indole-3-carboxamide derivatives via intramolecular indole N-H alkylation of novel bis-amide Ugi-adducts. In this protocol the Ugi reaction of ( E )-cinnamaldehyde derivatives, 2-chloroaniline, indole-2-carboxylic acid and different isocyanides was designed for the preparation of bis-amides. The main highlight of this study is the practical and highly regioselective preparation of new polycyclic functionalized pyrazino derivatives. This system is facilitated by Na 2 CO 3 mediation in DMSO and 100 °C conditions.