Copper-Catalyzed Diazo Controlled Annulation of Naphthylamines to Benzo[g]indoles.

Herein, we report a diazo-controlled Cu(II)-catalyzed annulation of naphthylamines that provides divergent access to benzo[g]indole frameworks with excellent selectivity. Different diazocarbonyl compounds govern the reaction pathway, and malonate-derived carbenes promote ortho C-H insertion/annulation, whereas phosphonate analogues undergo N-H insertion followed by cyclization. The transformation exhibits broad substrate scope, high yields, and gram-scale practicality. Detailed control, labeling, and intermediate-isolation studies further establish the mechanistic divergence between these pathways. Several products display bright blue-to-green fluorescence with high quantum yields, underscoring the potential of this Cu-catalyzed platform for the construction of functional benzo[g]indole fluorophores.