Palladium-Catalyzed Intramolecular C-H Amination in Water

Synthesis of Helical Indolophenanthridines Showing Aggregation-Induced Emission

Helical indolo[2,3-k]- and [3,2-a]phenanthridines were synthesized from amines by amide formation and Morgan-Walls cyclization. The synthetic routes offer the advantage of late-stage derivatization and do not require protecting groups, which makes the compounds directly suitable for further functionalization. The compounds exhibit remarkable acid-dependent bathochromic shifts of the luminescence, solvatochromism, and aggregation-induced emission (AIE) behavior, which make them especially interesting candidates for studies toward optoelectronic applications.

Preparation of Carbazoles Involving 6π-Electrocyclization, Photoredox-, Electrochemical-, and Thermal Cyclization Reactions: Mechanistic Insights

Carbazole is a heterocyclic motif that can be found in a diverse array of natural and unnatural products displaying a wide range of biological and physiological properties. Furthermore, this heterocycle is part of electronic materials like photoconducting polymers and organic optoelectronic materials owing to its excellent photophysical characteristics. Consequently, the development of synthetic strategies for carbazole scaffolds holds potential significance in biological and material fields. In this regard, a variety of preparation methods has been developed to exploit their efficient and distinct formation of new C-C and C-heteroatom bonds under mild conditions and enabling broad substrate diversity and functional group tolerance. Therefore, this review focuses on the synthesis of a set of carbazole derivatives describing a variety of methodologies that involve direct irradiation, photosensitization, photoredox, electrochemical and thermal cyclization reactions.

Trends in carbazole synthesis - an update (2013-2023)

The interest of scientists in the carbazole core has risen steadily over the last 30 years, particularly over the last decade given its presence in several active pharmaceutical ingredients, functional materials and a wide range of biologically active natural products. The continuous development of more efficient, more (regio-)selective and "greener" methodologies to access the carbazole core is thus imperative. This review compares and evaluates synthetic strategies towards the carbazole core that have been reported since 2013, with a focus on their applicability towards the total synthesis of carbazole-containing natural products.

A Cyclobutanol Ring-Expansion Approach to Oxygenated Carbazoles: Total Synthesis of Glycoborine, Carbazomycin A and Carbazomycin B

The transition-metal-free total syntheses of the oxygenated carbazole natural products glycoborine, carbazomycin A and carbazomycin B are reported. The key step involves an NBS-mediated cyclobutanol ring expansion to 4-tetralones for the preparation of the tricyclic carbazole core.

Synthesis of Diaza[5]helicenes by ortho,ortho′-Fusion of ortho-Terphenyls

Double ortho-fusion in suitably substituted ortho-terphenyls was used for the synthesis of diaza[5]helicenes. Bis(carboxamido)-substituted ortho-terphenyls can be condensed to 5,9- and 6,9-diaza[5]helicenes, where substituents at the 6,10- and 5,10-positions, respectively­, are introduced with the carboxamido groups. While a twofold­ coupling sequence with intermediate protection of one amino group has to be used for 5,9-diaza[5]helicenes, a more concise sequence avoiding the protection leads to 6,9-diaza[5]helicenes. The simple heating of ortho,ortho′-diazidoterphenyls furnishes 5,8-dihydroindolo[2,3-c]carbazoles, i.e., [5]helicenes with alternating benzene and pyrrole rings.

Regioselective Synthesis of Substituted Carbazoles, Bicarbazoles, and Clausine C

Substituted carbazoles are efficiently constructed from 3-triflato-2-pyrones and alkynyl anilines. Multiple substituents are tolerated on the carbazole, and complete control of regiochemistry is observed. Complicated and sterically congested substitution patterns are produced. This strategy is also used to prepare substituted bicarbazoles and related biaryls. Finally, the method was showcased in a synthesis of the carbazole natural product clausine C.

Copper-Catalyzed Electrophilic Ortho C(sp2)-H Amination of Aryl Amines: Dramatic Reactivity of Bicyclic System

A practical copper-catalyzed, 2-picolinamide-directed ortho C-H amination of anilines with benzoyl-protected hydroxylamines has been disclosed that proceeds smoothly without any external stoichiometric oxidant or additives. Remarkably, besides anilines, bicyclic naphthyl or heterocyclic amines furnished amination products with five- and six-membered cyclic and acyclic amines at the ortho position selectively. This electrophilic C-H amination also proceeds smoothly in water under slightly modified reaction conditions.

The synthesis of densely functionalised α-acyloxy enaminals and enaminones via a novel homogeneous silver(i) catalysed rearrangement

A synthesis of densely functionalised α-acyloxy enaminals and enaminones via a novel homogeneous silver(i) catalyzed rearrangement of 1-acyloxy-3-azido ketones is reported.

Cobalt-catalysed unactivated C(sp3)–H amination: two-state reactivity and multi-reference electronic character

A remarkable two-state reactivity scenario and an unusual multi-reference character have been computationally found in Co-catalysed C(sp³)–H amination. In addition, the investigation on the additive, aminating reagent, metal center, and auxiliary ligand provides implications for development of new catalytic C–H functionalization systems.