Dialkyl quinone-2,3-dicarboxylates in the Nenitzescu reaction

Diethyl naphthoquinone-2,3-dicarboxylate reacts with different enamines to give 5-oxo-1,5-dihydro-benzo[g]indole-3,4,9b-tricarboxylate derivatives by migration of one ethoxycarbonyl group. These new products aromatize to planar indoles by elimination of one ethoxycarbonylgroup. With an N,N-dimethyl-enamine cyclization yields a 5-oxo-4,5-dihydro-cyclopenta[a]naphthalene-3,3a,4-tricarboxylate as well as a naphthyl-malonic acid derivative by migration of an ethoxycarbonylgroup.