Substrate-directed divergent synthesis of fused indole polycycles through Rh(II)-catalyzed cascade reactions of bis(diazo)indolin-2-ones.

Herein, we report a substrate-directed diverse synthetic strategy toward two kinds of structurally intriguing fused indole polycycles through Rh(II)-catalyzed cascade reactions of bis(diazo)indolin-2-ones with enaminones. The subtle structural changes in enaminones lead to different reactivities. Cyclic enaminones produce indolo[2,3- b ]indoles, whereas acyclic ones afford oxazolo[3,2- a ]indoles.