Substituted Carbazole Derivatives Research Articles

Palindromic carbazole derivatives: unveiling their antiproliferative effect via topoisomerase II catalytic inhibition and apoptosis induction

Human DNA topoisomerases are essential for crucial cellular processes, including DNA replication, transcription, chromatin condensation, and maintenance of its structure. One of the significant strategies employed in cancer treatment involves the inhibition of a specific type of topoisomerase, known as topoisomerase II (Topo II). Carbazole derivatives, recognised for their varied biological activities, have recently become a significant focus in oncological research. This study assesses the efficacy of three symmetrically substituted carbazole derivatives: 2,7-Di(2-furyl)-9H-carbazole (27a), 3,6-Di(2-furyl)-9H-carbazole (36a), and 3,6-Di(2-thienyl)-9H-carbazole (36b) – as anticancer agents. Among investigated carbazole derivatives, compound 3,6-di(2-furyl)-9H-carbazole bearing two furan moieties emerged as a novel catalytic inhibitor of Topo II. Notably, 3,6-di(2-furyl)-9H-carbazole effectively selectively inhibited the relaxation and decatenation activities of Topo IIα, with minimal effects on the IIβ isoform. These findings underscore the potential of compound 3,6-Di(2-furyl)-9H-carbazole as a promising lead candidate warranting further investigation in the realm of anticancer drug development.

Catalyst- and Substrate-Controlled Regiodivergent Synthesis of Carbazoles through Gold-Catalyzed Cyclizations of Indole-Functionalized Alkynols.

A wide variety of regioselectively substituted carbazole derivatives can be synthesized by the gold-catalyzed cyclization of alkynols bearing an indol-3-yl and an additional group at the homopropargylic positions. The regioselectivity of the process can be controlled by both the oxidation state of the gold catalyst and the electronic nature of the substituents of the alkynol moiety. The 1,2-alkyl migration in the spiroindoleninium intermediate, generated after indole attack to the activated alkyne, is favored with gold(I) complexes and for electron-rich aromatic substituents at the homopropargylic position, whereas the 1,2-alkenyl shift is preferred when using gold(III) salts and for alkyl or non-electron-rich aromatic groups.

Visible‐Light‐Driven Synthesis of Phenanthridin‐6(5H)‐one and N‐Substituted Carbazole Derivatives through Intramolecular C‐H Arylation

AbstractA visible‐light‐driven approach towards phenanthridin‐6(5H)‐one and carbazole rings synthesis under transition‐metal‐free conditions is here reported. Phenanthridinones and carbazoles are synthesized through an intramolecular arylation of the corresponding N‐(2‐halobenzyl)‐N‐methylanilines or N‐substituted‐N‐phenyl anilines using KOtBu as base in dimethyl sulfoxide (DMSO) at room temperature (rt), employing blue light emitting diodes (LEDs) as the light source. The reaction proceeds through photo‐ and base‐promoted homolytic aromatic substitution via photoinduced electron transfer mechanism and it exhibits good tolerance to different functional groups, resulting in good to very good yields (up to 86 %).

HBF4‐Catalyzed 3,6‐Bis‐diarylmethylation of Carbazoles withpara‐Quinone Methides

AbstractIn this article, we demonstrate an atom economical, practical, mild and selective HBF4‐catalyzed 1,6‐conjugate addition of carbazoles topara‐Quinone Methides (p‐QMs) to access 3,6‐bis‐diarylmethyl‐ and mono‐diarylmethyl carbazoles. This metal and additive free protocol provides convenient access to the substituted carbazole derivatives in moderate to excellent yields with a good functional group tolerance. It was found that a couple of 3,6‐disubstituted carbazoles showed interesting photophysical properties and, therefore, might potentially find some applications as host materials in OLEDs.

From tryptophan to novel mitochondria-disruptive agent, synthesis and biological evaluation of 1,2,3,6-tetrasubstituted carbazoles

Mitochondrial targeting plays an important role in anticancer therapy. The Mn(III)-promoted cyclization of 5-(1H-indol-3-yl)-3-oxopentanoic acid allow to obtain novel substituted carbazole derivatives that can act as mitochondria-disruptive agents. The starting materials used for the synthesis of these new aminocarbazoles are oxopentanoate derivatives of tryptophan. The scope and limitation of this method of synthesis are determined by a series of experiments. The prepared carbazole derivatives are screened for their in vitro anticancer activity against a broad panel of human cancer cells and normal cell lines. Among the tested compounds, the most active ones are examined further against human colon cancer cells (HCT-116) and human bone osteosarcoma (U-2 OS), in complex in vitro cellular assays, including studies on cell cycle distribution, intracellular compartmentalization, antimigratory properties, mitochondrial generation of reactive oxygen species, DNA damage, and type of cellular death. The results reveal that the synthesized compounds display potent oxidative activity inducing massive accumulation of DNA double-strand breaks, which lead to a parallel change in the assembly of mitochondria causing their dysfunction. These findings provide new leads for the treatment of colon cancer and osteosarcoma.

Synthesis of Novel 3‐N‐substituted Carbazole Derivatives and Evaluation of their Abilities to Inhibit Platelet Aggregation

The carbazole moiety exhibits various biological activities, including anticancer, antiviral, anti‐inflammatory, and antimicrobial activities; some compounds containing the moiety also inhibit platelet aggregation. In the present study, we synthesized a series of 3‐N‐substituted carbazole derivatives and evaluated their abilities to inhibit in vitro platelet aggregation induced by collagen (5 μg/mL). Of the synthesized compounds, compound 5q (JSCa15), with a urea linkage within the carbazole framework, exhibited the strongest inhibitory activity (98.25% at 30 μM). Interestingly, reduction of the nitro group of compound 5q to an amine exhibited significantly decreased activity (compound 5r, 5.18% at 30 μM). Also, substitution of the urea moiety of compound 5q with a carbamate moiety resulted in a considerable loss of activity (compound 8a, 5.91% at 30 μM). These results suggest that the urea moieties and nitro groups of 3‐N‐substituted carbazole derivatives may play key roles in inhibiting in vitro platelet aggregation induced by collagen.

Novel scorpion-like carbazole derivatives: Synthesis, characterization, mechanochromism and aggregation-induced emission

A series of nitrophenyl substituted carbazole derivatives [9-(4-nitrophenyl)-9H-carbazole (1), 3,9-bis(4-nitrophenyl)-9H-carbazole (2), 9-methyl-3,6-bis(4-nitrophenyl)-9H-carbazole (3), 9-ethyl-3,6-bis(4-nitrophenyl)-9H-carbazole (4), 9-butyl-3,6-bis(4-nitrophenyl)-9H-carbazole (5), 9-hexyl-3,6-bis(4-nitrophenyl)-9H-carbazole (6)] bearing D-π-A systems were prepared and their photophysical properties were investigated comparatively and systematically. Compounds 1, 2, 5 and 6 exhibited obvious aggregation-induced emission properties in DMF/water mixtures and aggregate formation endued them bright luminescence. The elongation of the N-substituted alkyl chains leads to an obvious hypochromatic shift of solid-state fluorescence for compounds 3–6. Specifically, compound 6 showed mechanochromic property involving a reversible interconversion between crystalline form and amorphous phase by mechanical grinding and dichloromethane vapor fuming.

Synthesis and optical characterization of novel carbazole Schiff bases

In this study, newly substituted carbazole derivatives of S1; (Z)-4-((9-isobutyl-9H-carbazol-3-ylimino)methyl)phenol, S2; (Z)-9-butyl- N-(2,3,4-trimethoxybenzylidine)-9H-carbazol-3-amine, S3; (Z)-4-((9-octyl-9H-carbazol-3-ylimino)methyl)benzene-1,2-diol and S4; (Z)-3-((9-octyl-9H-carbazol-3-ylimino)methyl)benzene-1,2-diol compounds are synthesized by using condensation reaction between carbazole amines and aromatic aldehydes. All synthesized carbazole Schiff bases are purified by crystallizing from chloroform. The structural and optical characterizations of synthesized compounds are investigated by FT-IR (Fourier Transform-Infrared Spectroscopy), 1H NMR (Proton Nuclear Magnetic Resonance), 13C NMR (Carbon Nuclear Magnetic Resonance), LC-MS (Liquid Chromatography-Mass Spectrometry) and temperature dependent PL (Photoluminescence) measurements. The formations of synthesized Schiff bases were confirmed by FT-IR, NMR and microanalysis. Due to stronger π-conjugation and efficient charge transfer from host material, the broad and complex bands centered at about ∼2.16 and ∼1.76 eV are observed in PL spectra for all samples. Their relative intensities depend on functional groups associated with the carbazole. These newly synthesized Schiff bases could be considered as an active emissive layer for organic light emitting diodes.

Electrochromic Properties of Novel Selenophene and Tellurophene Derivatives Based on Carbazole and Triphenylamine Core

The 2,7- and 3,6-substituted carbazole and triphenylamine chalcogenophene (Se, Te) derivatives and their electrodeposited polymers are investigated using electrochemical and UV–vis–NIR/ESR spectroelectrochemical methods. Major differences in the case of oxidation and electropolymerization behavior between monomers and related polymers are shown. Se and Te atoms do not conjugate their lone electron pairs with the π-conjugated system and therefore only increase the contribution of the quinoid form of the chalcogenophene unit. The 2,7- substituted carbazole derivatives present stronger carbazole–chalcogenophene conjugation than 3,6-substituted derivatives. One 3,6-substituted carbazole derivative and triphenylamine derived polymers were found to have promising electrochromic properties with black electrochromism.

Synthesis, Spectroscopic Characterization and Biological Evaluation of 1-(4'-Hydroxybenzamido)-Imine-1,2,3,4-Tetrahydrocarbazole Derivatives

A facile synthetic approach towards 1-(4'-hydroxybenzamido)-imine-1,2,3,4-tetrahydrocarbazole derivatives 3a–g was reported via reaction of 1-oxo-1,2,3,4-tetrahydrocarbazoles 1a–g, with p-hydroxybenzhydrazide in ethanol in the presence of sufficient amount of acetic acid. The structure of all the compounds was confirmed by spectroscopic studies. The antioxidant properties of all the derivatives have also been checked against DPPH and OH radicals. Further, in vitro anticancer activities of all the synthesized compounds were investigated by MTT assay method. All the prepared analogues exhibited considerable anticancer properties especially, 3e and 3f which reveled the best anticancer activity among all the test compounds. Additionally, we carried out molecular docking studies using the protein kinase CK2 inhibitors. In all the biological assays, halogen substituted carbazole derivatives showed enhanced activities than the other derivatives.

Nano-cuprous oxide catalyzed one-pot synthesis of a carbazole-based STAT3 inhibitor: a facile approach via intramolecular C–N bond formation reactions

In this study, we report the one-pot synthesis of substituted carbazole derivatives using nano cuprous oxide as a catalyst and demonstrated the STAT3 inhibitory activity of new compounds.

Luminescent nanofibers fabricated from triphenylvinyl substituted carbazole derivatives via organogelation for sensing gaseous nitroaromatics

New triphenylvinyl substituted carbazole derivatives TPEICE, TPEC and TPECBr have been synthesized. They could self-assemble into nanofibers via organogelation processes in some organic solvents. Notably, the obtained xerogel-based films could emit strong fluorescence although the three compounds were non-emissive in solutions, indicating AIE in gel phases. The emission of TPEICE and TPEC in xerogel-based films could be quenched significantly upon exposed to gaseous DNT and TNT, while TPECBr could not sense nitro compounds on account of its poor electron donating ability. We also found that reversibility of the fluorescence response of TPEC was better than TPEICE because the photo-induced electron transfer would happen during the recognition of nitroaromatics for TPEICE and TPEC, except for the formation of charge–transfer complex between TPEICE and nitro compounds. Therefore, the different fluorescence response behaviors of TPEICE, TPEC and TPECBr towards nitroaromatics were resulted from their different electron donating abilities.

Structure-properties relationship of carbazole and fluorene hybrid trimers: experimental and theoretical approaches.

Synthesis and properties of fluorene and carbazole derivatives having three electrophores per molecule with different architectures are reported. The synthesized compounds possess high thermal stabilities with 5% weight loss temperatures exceeding 350 °C. They form glasses with glass transition temperatures ranging from 60 to 68 °C. Cyclovoltammetric experiments revealed the high electrochemical stability of the fluorene trimer. In contrast, 2- and 2,7-fluorenyl substituted carbazole derivatives show irreversible oxidation in the CV experiments. The electron photoemission spectra of the films of the synthesized compounds revealed ionization potentials of 5.65-5.89 eV. Hole drift mobilities in the amorphous layers of the synthesized compounds reach 10(-2) cm(2) V(-1) s(-1) at high electric fields, as established by a xerographic time-of-flight technique. DFT calculations show that HOMO and LUMO orbitals of the compounds are very similar in energy and shape. The similar hole mobilities observed for the three compounds are discussed in the frame of the Marcus theory. An important influence of the alkyl groups on the ionization potentials and on the hole mobilities was also observed and its origin is discussed.

Synthesis and characterization of heteroatom substituted carbazole derivatives: potential host materials for phosphorescent organic light-emitting diodes

A series of carbazole derivatives based on 9-ethyl-carbazole substituted at the 3-position with diphenylamine, carbazole, phenoxazine, phenothiazine, and phenothiazine-S,S-dioxide units were successfully developed, and a comparative study of their thermal and photoelectrical properties was carried out by differential scanning calorimetric measurements, thermogravimetric analysis, UV-vis absorption spectroscopy, photoluminescence spectroscopy, cyclic voltammetry, and phosphorescent spectroscopy. All the synthesized compounds were found to have high thermal decomposition temperature in the range of 304–344 °C (except for C-SO, 145 °C) and showed a remarkable improvement when compared with 9-ethyl-carbazole (180 °C). The emission properties can be effectively tuned by systematically changing the substituent units. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and triplet energy (ET) of the synthesized compounds were determined both theoretically by quantum chemical calculations and experimentally by examination. Their energy levels can also be tuned by the change of the moieties connected to the 3-position through coupling reaction. The experimental values of ionization potentials range from 5.37 to 5.46 eV. Some of these compounds exhibit high ET, and C-SO achieves the highest ET value of 2.79 eV, which exhibits a marked improvement over that of 4,4′-bis(9-carbazolyl)-biphenyl (2.6 eV). Green phosphorescent devices using tris(2-phenylpyridine)iridium as a guest and C-O as a host show excellent performances. Remarkably, a device with C-O as host exhibits the best performance with a maximum luminance of 10 270 cd m−2, a maximum current efficiency of 34.8 cd A−1, and a maximum power efficiency of 26.0 lm W−1. These results illustrate that the introduction of heteroatoms into carbazole can result in a significant change in their optoelectronic characteristics. The low LUMO, high HOMO, suitable ET and thermal stability of the carbazole derivatives endow them with the potential to be green, red, and even blue host materials for phosphorescent organic light-emitting diodes.

Efficient Synthesis of Carbazolyl- and Thienyl-Substituted β-Diketonates and Properties of Their Red- and Green-Light-Emitting Ir(III) Complexes

The efficient synthesis of novel beta-diketonates equipped with functional carbazolyl moieties and their subsequent transformations in 5-hexyl-thienyl substituted carbazole derivatives is presented by utilizing an effective Stille cross-coupling reaction. The introduced beta-diketonates served as ancillary ligands for novel heteroleptic red- and green-emitting Ir(III) complexes, when combined with 2-(naphthalen-1-yl)pyridine and 2-phenylpyridine as cyclometalating ligands. These novel Ir(III) complexes revealed color-tunability and a very good thermal stability until at least 207 degrees C. In polystyrene blends, the heteroleptic Ir(III) complexes revealed remarkable quantum yields up to 36% and suitably short phosphorescence lifetimes ranging from 1 to 4 micros. In the case of the orange-red Ir(III) emitter, equipped with 2-(naphthalen-1-yl)pyridine cyclometallating ligands, a luminous efficiency as high as 7.7 cd/A at 7.4 V was achieved. All fabricated diodes exhibited in addition favorable color stability.

An efficient synthesis of indolo[3,2-a]carbazoles via the novel acid catalyzed reaction of indoles and diaryl-1,2-diones

A mild and efficient one pot method for the synthesis of indolo[3,2-a]carbazole derivatives by the para-toluenesulfonic acid catalyzed condensation of indole with acyclic 1,2-diones is described. With cyclobutene-1,2-diones the reaction afforded indole substituted carbazole derivatives in good yield.

The host materials containing carbazole and oxadiazole fragment for red triplet emitter in organic light-emitting diodes

Abstract Three new oxadiazole substituted carbazole derivatives 9-{4-[5-(4-tert-butylphenyl)-[1,3,4] oxadiazol-2-yl]-benzyl}-9H-carbazole (t-CmOxa), 9-[4-5-phenyl-[1,3,4]oxadiazol-2-yl-benzyl]-9H-carbazole (p-CmOxa) and 9-[4-5-biphenyl-[1,3,4]oxadiazol-2-yl-benzyl]-9H-carbazole (d-CmOxa) were successfully synthesized and characterized by spectroscopy (NMR, UV–vis, mass spectrum and photoluminescence) and cyclic voltammetry measurements. Employing t-CmOxa as a host and Ir(DBQ)2(acac) (DBQ = dibenzo[f,h]quinoxaline, acac = acetylacetonate) as the dopant emitter, OLEDs with structures of ITO/NPB(30 nm)/Ir(DBQ)2(acac): t-CmOxa (30 nm, x%)/Alq3(30 nm)/Mg0.9:Ag0.1 were fabricated without using BCP as the hole blocking layer. Red emission was obtained with CIE coordinates (x = 0.66, and y = 0.34) at 5 V and a very high external electroluminescent (EL) quantum efficiency of 9.5 ± 0.1%, and an energy conversion efficiency of 9.9 ± 0.1 lm/W were achieved for the device when the doping concentration x is equal to 4%.

Synthesis and electroluminescent properties of para- and meta-tolyl carbazyl derivatives

A series of para and meta-tolyl substituted carbazole derivatives (dimer, trimer and tetramer) were synthesized to be applied as hole transporting materials (HTM) in multilayer electroluminescent devices. To evaluate electroluminescent properties, multilayer organic-emitting devices were fabricated using these materials as hole transporting layer and Alq3 as emitting layer. All of these EL devices showed a green light emission about 520 nm due to Alq3 emission. The HOMO levels of synthesized materials appear in the range of 5.07∼5.50 eV. These materials have a wide energy band gap.

A New Preparative Route to Substituted Carbazoles by Benzannulation.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A New Preparative Route to Substituted Carbazoles by Benzannulation

A new regioselective pathway to substituted carbazole derivatives is described here. According to this procedure substituted 2-alkoxycarbonyl-4-acetoxy-9-(p-toluenesulfonyl) carbazoles are obtained by treatment of substituted 6-[2-(p-toluenesulfonyl-amino)-aryl]-3-alkoxycarbonylhex-3-en-5-ynoic acids with acetic anhydride in the presence of sodium acetate. The latter acids are prepared from the easily available substituted o-iodo-anilines by Sonogashira coupling with propargylic alcohol and Wittig reaction as the key steps. The described benzannulation reaction proceeds in regiospecific fashion and a range of substituents are tolerated.