2,3-Annulated indoles exhibit a broad spectrum of biological activities. Various annulation strategies are applied to generate these scaffolds from prefunctionalized aniline or indole derivatives. Only a few methodologies allow the direct annulation of indole itself, often associated with regioselectivity issues or restrictions on available substitution patterns. More recently, ruthenium-catalyzed cascade transformations of readily available propargyl alcohols have been applied to the selective synthesis of various cyclo[b]fused indoles directly from indole. These efficient processes provide rapid access to intricate molecular structures from simple starting materials and facilitate the preparation of drug-like molecules.
Key words
annulation - carbazoles - cascade reactions - drug discovery - heterocycles - homogeneous catalysis - indoles
