Benzannulation of Functionally Enhanced Indole-3-carbaldehydes with Ynones and Alkynoates: A Domino Approach to Bioactive Carbazoles─Synthesis of Clauolenzole A, Calothrixin A & B, Methyl Carbazole-3-carboxylate, and Quinocarbazole

A flexible, regioselective, benzannulation strategy toward multifunctional carbazoles from 2-(2-oxo-2-arylethyl)indole-3-carbaldehydes, employing either ynones or alkynoates as reaction partners, has been envisaged and implemented. This enabling access to variegated carbazoles in one-flask operation leads to strategic substituent diversification via reaction partner variation. The efficacy and applications of this methodology are demonstrated through 23 examples and concise syntheses of bioactive clauolenzole A, calothrixin A & B, methyl carbazole-3-carboxylate, and pharmacophoric quinocarbazole.