PPh3‑Mediated Cascade Reaction of 2‑Alkynylnitrobenzenes and Thioureas for the Construction of Imidazo[4,5‑b]indole-2-thiones

A simple method for the preparation of imidazo[4,5-b]indole-2-thiones from 2-alkynylnitrobenzenes and thioureas is described. In the reaction, a Wittig-like process was triggered by PPh3 and followed by a cyclization step. The products were afforded in yields of 70–98% under mild conditions. Additionally, the 2-alkynylnitrobenzenes were stable and could be prepared via a simple coupling step.