Synthesis of α‐Carbolines Using Palladium‐Catalyzed Intramolecular Amination of 3‐(2‐Chlorophenyl)‐2‐Aminopyridines

Novel access to α-carbolines with biological applications

In recent years, the 9H-pyrido[2,3-b]indole nuclei, also named α-carboline which is found in many organic compounds such as natural products, pharmaceuticals, and materials, have intensively stimulated the research of new synthetic pathways. After a brief report published in 2015 describing novel accesses and biological applications of α-carbolines, this update reports between 2015 and 2023 on the emergence of original syntheses to this heterocyclic nucleus. Examples representing these processes are described and the biological activities of α-carbolines are mentioned when they have been prepared for therapeutic purposes.

Synthesis of 2,3-Disubstituted 4-Ethoxycarbonyl-β-carbolin-1-ones: Application to the Synthesis of SL651498 and Its Analogue

Synthesis of 2,3-disubstituted 4-ethoxycarbonyl-β-carbolin-1-ones is developed using palladium-catalyzed intramolecular amination of 3-amino-4-(2-bromophenyl)-2-pyridones prepared by the conjugate addition reaction of diethyl 2-aminomalonate to alkynyl imines. The method was applied to the total syntheses of SL651498 exhibiting anxiolytic activity and its analogue.

Domino 1,4- and 1,6-Addition Reactions of Ketene Silyl Acetals to Dialkynyl Imines Promoted by Aluminum Chloride: Synthesis of Multifunctionalized β-Lactams

Domino 1,4- and 1,6-addition reactions of ketene silyl acetals to dialkynyl imines are disclosed. Aluminum chloride promoted domino 1,4- and 1,6-addition reactions of ketene silyl acetals to dialkynyl imines to give a variety of alkenyl iminocyclobutenones in moderate to good yields. The chemoselective reduction of alkenyl iminocyclobutenones and the subsequent thermal rearrangement of resulting alkenyl aminocyclobutenones in the presence of appropriate amines provided cis or trans multifunctionalized β-lactams in moderate to high yields with good to high diastereoselectivities.