Cu(OAc)2-Mediated Cascade Annulation of Diarylalkyne Sulfonamides through Dual C-N Bond Formation: Synthesis of 5,10-Dihydroindolo[3,2-b]indoles.

An unusual cascade reaction featuring annulation of diarylalkyne sulfonamides to form 5,10-dihydroindolo[3,2-b]indoles has been realized with Cu(OAc)2 as the sole oxidant. This unprecedented process encompasses two sequential C-N bond formations, allowing for an efficient synthesis of the biologically important indoloindole derivatives.