Regioselective Synthesis of Carbazoles via Chemodivergent Cascade Intramolecular [4 + 2] Annulation

Herein, we have reported chemodivergent Diels–Alder reaction of allene formed in situ via a base‐catalyzed alkyne‐to‐allene isomerization for the synthesis of fused carbazoles in a cascade reaction manner. The regioselectivity of the cycloaddition reaction was achieved using copper additives. The present cascade reaction involved Knoevenagel condensation, in situ allene formation, regioselective Diels–Alder reaction, followed by oxidation or aromatization.