6H-Indolo[2,3-b]Quinoline: A Recent Synthetic Comprehension

Cu(OTf)2 Enhanced Intramolecular Nucleophilic N-Arylation of 2-Amino-3-arylquinolines

In the presence of Cu(OTf)₂ (5 mol %) and KO^tBu, a synergistic effect of the N-arylation process on 2-amino-3-arylquinolines is observed. Within 4 h, this method provides a wide variety of norneocryptolepine analogues with good to excellent yields. Overall, a double heteroannulation strategy for the synthesis of indoloquinoline alkaloids from nonheterocyclic precursors is demonstrated. Mechanistic investigations establish that the reaction proceeds via the S_NAr pathway. Despite moderate yields, the one-pot, two-step double heteroannulation illustrates that this procedure is highly atom-efficient. Neocryptolepine, a natural product, is also synthesized from indoloquinoline. A brief study of the photophysical properties of selected norneocryptolepine analogues is also discussed.

A Compilation of Synthetic Strategies to Access the Most Utilized Indoloquinoline Motifs

Indoloquinoline alkaloids constitute an important class of aromatic heterocycles consisting of quinoline and indole fused together in various orientations. These compounds, both natural and synthetic, often display various bioactivities which have established them to be one of the interesting medicinal targets. This class of compounds have stimulated much interest among synthetic and medicinal chemists as evidenced by growth in the number of synthetic methods to prepare and study this class of alkaloids. This review compiles the synthetic strategies and methods currently known in the literature for the construction of four important indoloquinoline skeletons.