Synthesis of benzo[a]carbazole derivatives from 3-ethylindoles by exploiting the dual character of benzoquinone as an oxidizing agent and dienophile

The dual character of benzoquinone is exploited for the synthesis of benzo[a]carbazole derivatives starting from 3-ethylindole derivatives. A diene is generated in situ from the 3-ethylindole derivative with the help of benzoquinone, where it acts as an oxidizing agent. Later it serves as a dienophile and participates in a Diels-Alder reaction with the diene to afford benzo[a]carbazole derivatives.