Metal‐ and Solvent‐Free Synthesis of Maleimide Fused Carbazoles from (Indol‐3‐Yl)cyclohexanones and Maleimides

Abstract

A metal-and solvent-free strategy for the preparation of maleimide-fused carbazoles has been developed. This protocol started from 2-(indol-3-yl)cyclohexanones and maleimides, providing various maleimide-fused carbazoles in 45-90% yields. The present approach was catalyzed by trimethylsulfoxonium iodide and involved a cascade of oxidation, [4 + 2] annulation, and dehydrogenative aromatization. Moreover, these maleimide-fused carbazole products could be further transformed into other polycyclic aromatic hydrocarbons.

Brønsted‐Acid Mediated Synthesis of Symmetrical and Unsymmetrical Indolo[2,3‐a]carbazoles from Indoles and α‐Functionalized Ketones

“…Building upon this proposed mechanism, we aimed to investigate the unsymmetrical synthesis of indolo[2,3‐a]carbazoles from indolic ketone 3 a (Scheme 5). [18] 2‐(3‐Indolyl)cyclohexanone was initially chosen for screening the range of indoles. By reducing the reaction temperature to 25 °C, we were pleased to discover that a diverse range of indoles could be successfully used in this protocol, forming 7 a – f and 7 h – i with acceptable yields.…”

Brønsted Acid Promoted Facile Synthesis of Benzoacridines from Aromatic Aldehydes and N‐Phenyl Naphthylamines

“…Inspired by the Bernthsen Acridine Synthesis and our ongoing interest in the construction of nitrogen‐containing polyaromatic hydrocarbons (NPAHs), [27–36] we envision that N ‐phenyl naphthylamines can react with aldehydes to produce benzo[ a ]acridines via electrophilic annulation process. After continuous attempts, herein we describe a Brønsted acid promoted facile synthesis of benzoacridines from aromatic aldehydes and N ‐phenyl naphthylamines ( Scheme 1, e ).…”

Iodide-Dependent Selective Dehydroaromatization Affording Maleimide-Fused 9,10-Phenanthrenes and Their Analogues

“…Indeed, these classes of compounds have exhibited outstanding pharmaceutical activities, such as anticancer, antiproliferative, antitumor, angiogenesis inhibitory, and kinase inhibitory . Despite their wide applicability, the synthetic methods are mainly limited to the Diels–Alder reaction of maleimides with prefunctionalized dienes and transition-metal-catalyzed C–H bond activation of heteroarenes with maleimides under the assistance of heteroatomic directing groups . In these transformations, they generally suffer from the use of elaborate-to-access starting materials and multistep procedures and are limited for the preparation of maleimide-fused polyheterocyclic compounds …”