Heteroannulation of 3-Nitroindoles and 3-Nitrobenzo[b]thiophenes: A Multicomponent Approach toward Pyrrole-Fused Heterocycles.

A simple, efficient, and general multicomponent reaction involving an enolizable ketone, a primary amine, and an N-protected 3-nitroindole was developed for the synthesis of a range of functionalized pyrrolo[3,2-b]indoles. The methodology was efficaciously utilized for the "pyrroloindoliztion" of natural products, the pyrrolization of 3-nitrobenzo[b]thiophene, and the gram-scale synthesis of pyrroloindole. Furthermore, a "one-pot" approach for accessing indolo[3,2-b]indoles was realized.