A one-pot telescopic synthesis of benzo[b]carbazoles and exploration of their liquid crystalline properties

We describe a diversity-oriented one-pot telescopic synthesis of various benzo[b]carbazoles with the naphthannulation of indoles as the key step, enabled by an intramolecular furan-olefin Diels-Alder reaction. This strategy is general and efficient across a wide range of substrates. We applied this method to synthesize and characterize the first benzo[b]carbazole-based liquid crystalline materials, where the unique molecular design led to the formation of a rare nematic phase at room temperature.

Acid-Promoted Domino Access to Substituted Benzo[b]carbazoles

Herein, a straightforward Bro̷nsted acids-promoted domino pathway to build substituted benzo[b]carbazoles has been described from easily accessible ortho-formyl (or ortho-acyl) cinnamate esters and indoles. Noticeably, the protocol was amenable to protecting group-free indoles. Notably, this methodology is based on a single-pot regioselective construction of two new C-C bonds and aromatization sequences under mild and metal-free reaction conditions. The mechanistic studies suggested the initial formation of bis-indole substituted intermediate via a dual aromatic substitution with two indole molecules at the carbonyl carbon of ortho-formyl (or ortho-acyl) cinnamate ester followed by intramolecular cyclization and aromatization with exclusion of a second indole molecule. Besides, the efficacy of this approach was also illustrated by scale-up and derivatization reactions, including the photophysical properties study.

Recent synthetic strategies for the construction of functionalized carbazoles and their heterocyclic motifs enabled by Lewis acids

This article demonstrates recent innovative cascade annulation methods for preparing functionalized carbazoles and their related polyaromatic heterocyclic compounds enabled by Lewis acid catalysts. Highly substituted carbazole scaffolds were synthesized via Lewis acid mediated Friedel-Crafts arylation, electrocyclization, intramolecular cyclization, cycloaddition, C-N bond-formations, aromatization and cascade domino reactions, metal-catalyzed, iodine catalyzed reactions and multi-component reactions. This review article mainly focuses on Lewis acid-mediated recent synthetic methods to access a variety of electron-rich and electron-poor functional groups substituted carbazole frameworks in one-pot reactions. Polyaromatic carbazole and their related nitrogen-based heterocyclic compounds were found in several synthetic applications in pharma industries, energy devices, and materials sciences. Moreover, the review paper briefly summarised new synthetic strategies of carbazole preparation approaches will assist academic and pharma industries in identifying innovative protocols for producing poly-functionalized carbazoles and related highly complex heterocyclic compounds and discovering active pharmaceutical drugs or carbazole-based alkaloids and natural products.

Iodine-Catalyzed Annulation Reaction of Ortho-Formylarylketones with Indoles: A General Strategy for the Synthesis of Indolylbenzo[b]carbazoles

The iodine-catalyzed cascade reaction of ortho-formylarylketones with indoles for the synthesis of indolylbenzo[b]carbazoles is reported. The reaction is initiated in the presence of iodine by two successive nucleophilic additions of indoles with an aldehyde group of ortho-formylarylketones, and the ketone does not undergo a nucleophilic addition and only involves in the Friedel-Crafts-type cyclization. A variety of substrates are tested, and the efficiency of this reaction is demonstrated with gram-scale reactions.

Benzannulation strategies for the synthesis of carbazoles, indolocarbazoles, benzocarbazoles, and carbolines

This review presents a critical and authoritative analysis of several exciting benzannulation approaches developed in the past decade for the construction of carbazoles, indolocarbazoles, benzocarbazoles, and carbolines.

Direct access to substituted benzo[b]carbazoles through cascade annulation of 2-vinylbenzaldehydes with indoles

A highly efficient palladium-catalyzed cascade annulation of 2-vinylbenzaldehydes with indoles has been achieved to afford 6-(3-indolyl)benzo[b]carbazoles under mild conditions in good yield and with excellent regioselectivity.