Synthesis of Cyclo[<i>b</i>]fused Carbazoles via SnCl₄‑Mediated Domino Reaction of 2‑Indolylmethylpivalates with Arenes and Heteroarenes

A straightforward synthesis of aryl and heteroaryl-annulated cyclo­[b]­carbazoles has been developed via SnCl4-mediated one-pot arylation, cyclization and aromatization reaction sequence from 3-acetyl/aroyl-2-pivaloyloxymethylindoles. The starting material is easily accessible from commercially available 2-methylindole via Friedel–Crafts acylation, bromination and pivaloylation. Remarkably, electron withdrawing/donating aroyl units including heterocyclic systems are well tolerated in the present domino reaction protocol. Furthermore, this methodology could be extended to the synthesis of dibenzofurocarbazole via bis-annulation of 2,5-bis­(2-pivaloyloxymethyl)­pyrrole.