Lewis acid catalyzed rapid synthesis of 5-hydroxy-benzo[g]indole scaffolds by a modified Nenitzescu reaction

A fast solvent-less synthesis of 5-hydroxy-benzog]indole scaffolds is accomplished from Lewis acid-catalyzed one-pot reaction of naphthoquinone, ω-morpholinoacetophenone, and urea under microwave irradiation. The key step in the synthesis is the Michael addition followed by in situ aza cyclization reaction using urea as an environmentally benign source of ammonia.