NIS Mediated Cross-Coupling of C(sp2)-H and N-H Bonds: A Transition-Metal-Free Approach toward Indolo[1,2-a]quinazolinones.

A metal- and base-free protocol for intramolecular cross-coupling of C(sp2)-H and N-H bonds using N-iodosuccinimide (NIS) has been demonstrated. This environmentally benign approach furnishes a series of substituted indolo[1,2-a]quinazolinones from the suitably fabricated indoles via C-N bond forming cyclization in 28-82% yield. A plausible mechanism is proposed for this cyclization based on the results of a control experiment. This methodology requires no additional metal catalyst, oxidant, or base. Furthermore, the synthetic utility of the protocol is demonstrated by performing a gram scale reaction.