Three-Component Cascade Synthesis of Carbazoles through [1s,6s] Sigmatropic Shift under Metal-Free Conditions.

A novel method was developed for the synthesis of substituted carbazoles from commercially available starting materials under metal-free conditions. This strategy involves a [1s,6s] sigmatropic shift step and introduces an electron-withdrawing ester substituent at the C2 position of the carbazole ring. The present protocol afforded the desired carbazole derivatives with good regioselectivity and well functional group tolerance. DFT calculations were carried out to support the reaction pathway.