Novel synthesis of 5-methyl-5,10-dihydroindolo[3,2-b]indoles by Pd-catalyzed C-C and two-fold C-N coupling reactions.

A series of 5,10-dihydroindolo[3,2-b]indoles was successfully prepared by an efficient two-step strategy based on site-selective Pd-catalyzed cross-coupling reaction with N-methyl-2,3-dibromoindole and subsequent cyclization by two-fold Pd-catalyzed C-N coupling with amines. The products show a strong fluorescence.