Synthesis of Diindolocarbazoles by Ullmann Reaction: A Rapid Route to Ladder Oligo(p-aniline)s

Substituent-controlled regioselective arylation of carbazoles using dual catalysis

Regioselective arylation of carbazoles is reported using dual palladium-photoredox catalysis. Controlled monoarylation and diarylation of symmetrical and unsymmetrical carbazoles were achieved under mild reaction conditions with a broad substrate scope and functional group tolerance. Steric and electronic control the regioselectivity of the arylation of unsymmetrical carbazoles. Late-stage functionalization of a caprofen drug derivative and large-scale synthesis of mono- and di-arylated carbazoles were demonstrated to showcase the synthetic versatility of the method. Finally, we also showcased the synthesis of hyellazole analogues (a marine alkaloid) in a short route using our strategy.

Dual Palladium-Photoredox-Mediated Regioselective Acylation of Carbazoles and Indolines

We have described a dual palladium-photoredox-catalyzed highly regioselective acylation of carbazoles and indolines using molecular oxygen as the green oxidant. The reaction shows a broad substrate scope and good functional group tolerance. Late-stage functionalization of a carprofen drug derivative, further manipulation of products, and gram-scale synthesis of the acylated products were illustrated to show the versatility of the method.

High-performance five-ring-fused organic semiconductors for field-effect transistors

Organic molecular semiconductors have been paid great attention due to their advantages of low-temperature processability, low fabrication cost, good flexibility, and excellent electronic properties. As a typical example of five-ring-fused organic semiconductors, a single crystal of pentacene shows a high mobility of up to 40 cm² V^-1 s^-1, indicating its potential application in organic electronics. However, the photo- and optical instabilities of pentacene make it unsuitable for commercial applications. But, molecular engineering, for both the five-ring-fused building block and side chains, has been performed to improve the stability of materials as well as maintain high mobility. Here, several groups (thiophenes, pyrroles, furans, etc.) are introduced to design and replace one or more benzene rings of pentacene and construct novel five-ring-fused organic semiconductors. In this review article, ∼500 five-ring-fused organic prototype molecules and their derivatives are summarized to provide a general understanding of this catalogue material for application in organic field-effect transistors. The results indicate that many five-ring-fused organic semiconductors can achieve high mobilities of more than 1 cm² V^-1 s^-1, and a hole mobility of up to 18.9 cm² V^-1 s^-1 can be obtained, while an electron mobility of 27.8 cm² V^-1 s^-1 can be achieved in five-ring-fused organic semiconductors. The HOMO-LUMO levels, the synthesis process, the molecular packing, and the side-chain engineering of five-ring-fused organic semiconductors are analyzed. The current problems, conclusions, and perspectives are also provided.

Effective Synthesis of Ladder-type Oligo(p-aniline)s and Poly(p-aniline)s via Intramolecular SNAr Reaction

Symmetric ladder-type oligo(p-aniline)s and poly(p-aniline)s were successfully synthesized by an intramolecular ring closure in a highly efficient S_NAr reaction from oligo(p-phenylene)s and poly(p-phenylene)s with fluorine (F) and secondary amine (NH) groups. Unlike Cadogan ring closure, the newly designed cyclization reaction will not produce a mixture of symmetric and nonsymmetric structures. Moreover, the introduction of the F atom does not hinder Suzuki polymerization. The result indicates that preparing regular oligomers and polymers with a nitrogen bridge is possible.

Simple Route to Synthesize Fully Conjugated Ladder Isomer Copolymers with Carbazole Units

Two isomer polymers, P3 and P6, with fully conjugated ladder structures are presented by simple synthetic routes. The well-defined structures of fully conjugated ladder polymers P3 and P6 were ensured by the high yields of every reaction step. The fully rigid ladder structures were confirmed by nuclear magnetic resonance (NMR), fourier transform infrared spectroscopy (FTIR), and photophysical test. Polymers P3 and P6 with bulky alkyl side chains exhibit good solution processability and desirable thermostable properties. After the intramolecular cyclization reaction, the band gaps of polymers P3 and P6 become lower (2.86 eV and 2.66 eV, respectively) compared with polymers P1 and P4. This initial study provides insight for the rational design of fully ladder-conjugated isomeric polymers with well-defined structures.

A concise Friedländer/Buchwald–Hartwig approach to the total synthesis of quindoline, a bioactive natural indoloquinoline alkaloid, and toward the unnatural 10-methylquindoline

Friedländer and Buchwald–Hartwig reactions were used to achieve an efficient total synthesis of quindoline and a new synthesis of the unnatural 10-methylquindoline. DFT calculations were employed to explain the outcome of a failed key transformation.

Chemistry and Properties of Indolocarbazoles

The indolocarbazoles are an important class of nitrogen heterocycles which has evolved significantly in recent years, with numerous studies focusing on their diverse biological effects, or targeting new materials with potential applications in organic electronics. This review aims at providing a broad survey of the chemistry and properties of indolocarbazoles from an interdisciplinary point of view, with particular emphasis on practical synthetic aspects, as well as certain topics which have not been previously accounted for in detail, such as the occurrence, formation, biological activities, and metabolism of indolo[3,2- b]carbazoles. The literature of the past decade forms the basis of the text, which is further supplemented with older key references.

Synthesis and properties of five ring fused aromatic compounds based on S,S-dioxide benzothiophene

Asymmetrical five ring fused compounds based on S,S-dioxide benzothiophene, BTOF and BTOCz, have wide bandgaps and deep HOMO and LUMO levels.

Synthesis of dibenzo[a,c]carbazoles from 2-(2-halophenyl)-indoles and iodobenzenes via palladium-catalyzed dual C–H functionalization

We report an efficient approach to synthesize dibenzo[a,c]carbazoles via a palladium-catalyzed cross-coupling tandem reaction.

Ru-Catalyzed highly site-selective C–H bond arylation of 9-(pyrimidin-2-yl)-9H-carbazole

We describe an efficient ruthenium-catalyzed C–H bond ortho-arylation of 9-(pyrimidin-2-yl)-9H-carbazole using boronic acids. This methodology exhibits excellent and high site-selectivity, functional group tolerance and gave the desired product in moderate to good yields.

A biphenyl containing two electron-donating and two electron-accepting moieties: a rigid and small donor–acceptor–donor ladder system

A small ladder-type donor–acceptor–donor π-system, a biphenyl furnishing two phosphine oxide bridges and two amino groups, showed significantly red-shifted absorption and fluorescence.

Direct synthesis of N-H carbazoles via iridium(III)-catalyzed intramolecular C-H amination

The iridium-catalyzed dehydrogenative cyclization of 2-aminobiphenyls proceeds smoothly in the presence of a copper cocatalyst under air as a terminal oxidant through intramolecular direct C-H amination to produce N-H carbazoles. A similar iridium/copper system can also catalyze the unprecedented dimerization reaction of 2-aminobiphenyl involving 2-fold C-H/N-H couplings.

Synthesis and properties of B,N-bridged p-terphenyls

We describe the efficient synthesis and intriguing photophysical properties of a new class of ladder π-conjugated molecules, B,N-bridged p-terphenyls.

Halogen effect on structure and 13C NMR chemical shift of 3,6-disubstituted-N-alkyl carbazoles

Structures of selected 3,6-dihalogeno-N-alkyl carbazole derivatives were calculated at the B3LYP/6-311++G(3df,2pd) level of theory, and their (13) C nuclear magnetic resonance (NMR) isotropic shieldings were predicted using density functional theory (DFT). The model compounds contained 9H, N-methyl and N-ethyl derivatives. The relativistic effect of Br and I atoms on nuclear shieldings was modeled using the spin-orbit zeroth-order regular approximation (ZORA) method. Significant heavy atom shielding effects for the carbon atom directly bonded with Br and I were observed (~-10 and ~-30 ppm while the other carbon shifts were practically unaffected). The decreasing electronegativity of the halogen substituent (F, Cl, Br, and I) was reflected in both nonrelativistic and relativistic NMR results as decreased values of chemical shifts of carbon atoms attached to halogen (C3 and C6) leading to a strong sensitivity to halogen atom type at 3 and 6 positions of the carbazole ring. The predicted NMR data correctly reproduce the available experimental data for unsubstituted N-alkylcarbazoles.

Synthesis of 3-Cyano-2-(1H-Indol-3-yl)-6-(9-Butylcarbazol-3-yl)Pyridine Derivatives by a Multicomponent Reaction under Microwave Irradiation

Preparation of a series of 3-cyano-2-(1 H-indol-3-yl)-6-(9-butylcarbazol-3-yl)pyridine derivatives through the one-pot four-component coupling of aromatic aldehydes, 1-(9-butylcarbazol-3-yl)ethanone, 3-(cyanoacetyl)indole and ammonium acetate is reported. All these compounds were obtained in good yield and their structures were confirmed by 1H NMR and IR spectroscopy and by elemental analysis.

High-performance air-stable single-crystal organic nanowires based on a new indolocarbazole derivative for field-effect transistors

A new indolocabazole derivative possessing an extended aromatic core and solubilizing long aliphatic chains effectively self-assembles and crystallizes within the nanoscale channels to form single-crystal nanowires via a direct printing method from an ink solution. Single-crystal organic nanowire transistor arrays based on the π-extended indolocarbazole derivative exhibit an excellent hole mobility of 1.5 cm² V⁻¹ s⁻¹ and outstanding environmental stability.

Copper-mediated domino synthesis of pyrimido[4,5-b]carbazolones via Ullmann N-arylation and aerobic oxidative C-H amidation

New pyrimido[4,5-b]carbazolone derivatives have been synthesized through cascade Ullmann N-arylation and aerobic oxidative C-H amidation reactions catalyzed by CuBr under air and ligand-free conditions.

Experimental and theoretical study of three new benzothiazole-fused carbazole derivatives

Three new D-π-A type compounds, each containing one benzothiazole ring as an electron acceptor and one N-ethylcarbazole group as electron donor, were synthesized and characterized by elemental analysis, NMR, MS and thermogravimetric analysis. The absorption and emission spectra of three compounds were experimentally determined in several solvents and were simultaneously computed using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The calculated reorganization energy for hole and electron indicates that three compounds are in favor of hole transport than electron transport. The calculated absorption and emission wavelengths are well coincident with the measured data. The calculated lowest-lying absorption spectra can be mainly attributed to intramolecular charge transfer (ICT). And the calculated fluorescence spectra can be mainly described as originating from an excited state with intramolecular charge transfer (ICT) character. The results show that three compounds exhibited excellent thermal stability and high fluorescence quantum yields, indicating their potential applications as excellent optoelectronic material in optical field.

Experimental and theoretical study of a new carbazole derivative having terminal benzimidazole rings

A novel intramolecular donor-acceptor compound has been synthesized and characterized. This compound was a symmetrical A-pi-D-pi-A type molecule containing two benzimidazole rings as two electron acceptors (A) and an N-ethylcarbazole group as electron donors (D). The absorption and emission spectra of the compound were determined by experimental methods in solution and were computed by using the density functional theory (DFT) and the time-dependent density functional theory (TDDFT) in gas phase and in chloroform solution. The calculated absorption and emission wavelengths were in good agreement with the experimental ones. The fluorescence quantum yields and fluorescence lifetimes of the compound in several solvents have been studied by means of steady state and time resolved fluorescence. The results showed the compound had high quantum yield. The cross-section of two-photon absorption (TPA) of the compound was measured by using femtosecond laser in dichloromethane solution. The result indicated the cross-section maximum of two-photon absorption was 430 GM at 600 nm. These results made the compound of great interest as a new fluorescent probe and photoluminescence material.