Carbazole Ring System Research Articles

Meso carbazole linked Bis-BODIPYs: Design, synthesis, structures and properties

In the present study, BODIPY 4 bearing carbazole ring system at meso position was successfully synthesized as a key building block by the acid-catalyzed condensation reaction of 6-bromo-9-ethyl-9H-carbazole-3-carbaldehyde 3 with 2,4-dimethylpyrrole in one step. The Suzuki and Stille coupling synthetic strategies were subsequently applied to the compound 4 for the construction of a new class of bis-BODIPYs 5 and 6 with extended π-conjugation by introducing phenyl and bithiophene as linkers between two N-ethylcarbazole units. The structures of novel compounds 4–6 were identified by mass, 1H and 13C NMR spectroscopy along with single crystal X-ray diffraction techniques. The photo-physical features of the targeted BODIPYs were investigated via absorption and fluorescence spectroscopies in solvents with different polarity. Photophysical studies reveal important transitions between carbazole and BODIPYs in solution state, which could be controlled by solvent polarity. Crystal geometry of the molecules and the optical band gaps were supported by DFT calculations. Electrochemical and in situ spectroelectrochemical properties of the synthesized compounds were also investigated to reveal electropolymerizable properties and electrochromic potentials of the targeted materials. The results suggested that the compounds 5 and 6 can be potentially used as useful materials in a range of electrochemical research areas.

Crystal structures of two new carbazole derivatives: ethyl 9-(benzenesulfonyl)-2-(4-fluoro-2-nitrophenyl)-6-methoxy-9H-carbazole-3-carboxylate and 12-(benzenesulfonyl)-12H-quinolino[4,3-b]carbazole

The title compounds, C28H21FN2O7S (I) and C25H16N2O2S (II), are carbazole derivatives with a benzenesulfonyl group attached to the carbazole moiety at the N atom on both molecules. A fluoro-substituted nitrophenyl ring system in I and a fused isoquinoline ring in II are attached to the respective carbazole moieties. In both compounds, the carbazole ring systems are essentially planar, with maximum deviations of 0.028 (2) and 0.026 (2) Å for carbon atoms in compounds I and II, respectively. The carbazole ring system is almost orthogonal to the benzene ring attached to sulfonyl group, with dihedral angles of 79.7 (2) in I and 88.2 (2)° in II, respectively. The mean planes of the carbazole ring systems make dihedral angles of 66.1 (2) and 1.3 (2)°, respectively, with the nitrophenyl ring in I and the planar isoquinoline moiety [maximum deviation of 0.009 (3) Å for a carbon atom in II, indicating that the ring system in II is essentially planar]. The benzenesulfonyl ring is almost normal to the isoquinoline ring, with a dihedral angle of 87.9 (2)° in II and the nitrophenyl ring forms a dihedral angle of 17.8 (2)° in I. In both compounds, intramolecular C—H...O hydrogen bonds generate S(6) ring motifs with the sulfone group O atoms. In crystals of compound I, the molecules are linked by C—H...O intermolecular weak hydrogen bonds, which generate C(7) and C(10) chains running parallel to [010] and [100], respectively.

Synthesis and crystal structure of anti-10-butyl-10,11,22,23-tetra-hydro-9H,21H-5,8:15,12-bis(metheno)[1,5,11]tri-aza-cyclo-hexa-decino[1,16-a:5,6-a']di-indole.

The title compound, C33H33N3, is a carbazolophane, which is a cyclo-phane composed of two carbazole fragments. It has a planar chirality but crystallizes as a racemate in the space group P . The mol-ecule adopts an anti-configuration, in which two carbazole fragments are partially overlapped. Both carbazole ring systems are slightly bent, with the C atoms at 3-positions showing the largest deviations from the mean planes. The dihedral angle between two carbazole fragments is 5.19 (3)°, allowing an intra-molecular slipped π-π inter-action [Cg⋯Cg = 3.2514 (8) Å]. In the crystal, the mol-ecules are linked via inter-molecular C-H⋯N hydrogen bonds and C-H⋯π inter-actions into a network sheet parallel to the ab plane. The mol-ecules of different sheets form other C-H⋯π inter-actions, thus forming a three-dimensional network.

Design, Synthesis and Evaluation of Novel Carbazole-Derived Photocages.

We report the design, synthesis and evaluation of two novel photocages, NCARB and isoNCARB, belonging to the o-nitrobenzyl chemotype and based on the carbazole ring system. The synthesis of each of these isomeric caging molecules was achieved in five steps and in 29 % overall yield, and their photochemical properties were evaluated using benzoic acid as a model for caging. In the event, upon irradiation at 400 nm for 60 min, 82 % and 42 % of benzoic acid was freed from the NCARB and isoNCARB photocages, respectively, whereas only 22 % was released from the nitrodibenzofuran (NDBF) cage. Moreover, the photochemical decaging efficiencies, ϵΦ, of the benzoates photocaged with NCARB and isoNCARB are about 150- and 20-fold better, respectively, at 400 nm than the corresponding caged benzoate derived from NDBF. The water solubility of molecules caged with nitrocarbazole analogs was improved by N-alkylation of NCARB, the better of the two new photocages, with an aminodicarboxylate group. This modified cage, NCARB-DA, was exploited in the design of a caged fluoroquinolone antibiotic, the efficacy of which was illustrated in a bacterial growth inhibition assay, and a phenol-caged tyrosine derivative.

Naturally Available Nitrogen-Containing Fused Heterocyclics as Prospective Lead Molecules in Medicinal Chemistry

Heterocyclic compounds constitute one of the largest and most versatile families of organic compounds. There are many heterocyclic compounds that are being isolated from natural sources and day by day the number is increasing rapidly due to their enormous utility. Nitrogen containing heterocyclic compounds have a prominent role in medicinal chemistry, biochemistry and other streams of science. In this review, we have covered most of the biologically active nitrogen containing heterocyclic compounds obtained from the natural sources including indole, carbazole, quinoline, isoquinoline and benzothiazole ring system. These isolated nitrogen containing heterocyclic compounds render wide spectrum of biological activities including antifungal, anti-inflammatory, antibacterial, antioxidants, anticonvulsant, anti-allergic, herbicidal and anticancer activities.

Ring closing metathesis for the construction of carbazole and indole-fused natural products.

The synthesis and functionalization of carbazole ring systems have received considerable attention in organic synthesis due to their widespread occurrence in biologically active compounds. One of the classical methods for the synthesis of carbazoles involves C-C bond formation of a biaryl amine moiety by oxidizing agents. Over the last few years, various new strategies have evolved for the synthesis of carbazole ring systems. During the past two decades, ring-closing metathesis (RCM) based approaches have been efficiently employed for the synthesis of nitrogen containing heteroaromatic systems including carbazoles. Herein, we discuss the construction of carbazole ring systems using RCM and the application of RCM based methods in the preparation of other indole-fused heterocycles. The application of these methods in the synthesis of carbazole alkaloids and bioactive indole-fused natural products has been discussed to highlight the importance of RCM in total synthesis.

Domino Relay Olefin Metathesis of Triallyl Oxindole and Indole Precursors to Access Cyclic Indoxyls and Carbazoles

AbstractWe herein disclose domino relay metathesis sequences using triallyl 3‐oxindole and indole precursors to access C2‐quaternary cyclic pseudooxindole and carbazole ring systems. Triallyl 3‐oxindoles undergo domino ring closing metathesis (RCM) and cross metathesis (CM) to provide C2‐spirocyclic 3‐oxindoles. Intriguingly, a catalyst specific relay metathesis sequence involving ring closing‐ring opening‐ring closing and cross metathesis (RC‐RO‐RC‐CM) of these trienes is established to provide fused bicyclic indoxyl dimers in high yields. Further, the CM of indoxyl dimer with methyl acrylate affords a new class of fused monomeric 3‐oxindole derivative. Moreover, a domino RCM‐CM process of triallyl indoles is demonstrated, enabling a quick access to dihydro‐carbazoles and carbazoles.

Morindolestatin, Naturally Occurring Dehydromorpholinocarbazole Alkaloid from Soil-Derived Bacterium of the Genus Streptomyces.

Novel antilipid peroxidative carbazole alkaloids, antiostatin A5 (1), antiostatin A6 (2), and (±)-morindolestatin (3), were isolated from a new soil-derived Streptomyces sp. Compound 2 possesses an unusual cyclohexene side chain. Compound 3 was a pair of enantiomers featuring an unprecedented [1,4]oxazino[2,3-c]carbazole ring system. The absolute configuration of 3 was determined by online HPLC-ECD and ECD calculation. A racemization mechanism and putative biosynthetic pathway are discussed.

Crystal structure of 4-bromo-N-[(3,6-di-tert-butyl-9H-carbazol-1-yl)methyl-idene]aniline.

In the title compound, C27H29BrN2, the carbazole ring system is essentially planar, with an r.m.s. deviation of 0.0781 (16) Å. An intra-molecular N-H⋯N hydrogen bond forms an S(6) ring motif. One of the tert-butyl substituents shows rotational disorder over two sites with occupancies of 0.592 (3) and 0.408 (3). In the crystal, two mol-ecules are associated into an inversion dimer through a pair of C-H⋯π inter-actions. The dimers are further linked by another pair of C-H⋯π inter-actions, forming a ribbon along the c-axis direction. A C-H⋯π inter-action involving the minor disordered component and the carbazole ring system links the ribbons, generating a network sheet parallel to (100).

Crystal structure determination, Hirshfeld surface analysis and energy frameworks of 6-phenyl-sulfonyl-6H-thieno[3,2-c]carbazole.

In the title compound, C20H13NO2S2, the carbazole ring system forms a dihedral angle of 89.08 (1)° with the sulfonyl-substituted phenyl ring. Intra-molecular C-H⋯O hydrogen bonds involving the sulfone O atoms and the carbazole moiety result in two S(6) rings. In the crystal, mol-ecules are linked via pairs of C-H⋯O hydrogen bonds forming inversion dimers with an R22(12) graph-set motif. Analysis of the Hirshfeld surfaces and two-dimensional fingerprint plots was used to explore the distribution of weak inter-molecular inter-actions in the crystal structure.

Tipping the Balance between Ligand and Metal Protonation due to Relativistic Effects: Unusually High Proton Affinity in Gold(I) Pincer Complexes.

Quantum theoretical studies show that the extremely high proton affinity at the metal center of the unusual T-shaped (LXL)AuI -pincer complex, consisting of a carbazole framework and two mesoionic carbenes, is caused by relativistic effects. This brings the basicity of the AuI center in line with the electron-rich nitrogen atom of the carbazole ring system, resulting in one of the highest proton affinities for a neutral molecule.

Crystal structure of 5-[2-(9H-carbazol-9-yl)eth-yl]-1,3,4-oxa-diazole-2(3H)-thione.

The title compound, C16H13N3OS, comprises an oxa-diazo-lethione ring bound to the N atom of an almost planar carbazole ring system (r.m.s. deviation = 0.0088 Å) through an ethyl-ene chain. The oxa-diazole ring is inclined to the the carbazole ring system by 40.71 (6)°. In the crystal, N-H⋯O, N-H⋯S, C-H⋯N and C-H⋯S hydrogen bonds combine with C-H⋯π(ring) and π-π contacts to stack the mol-ecules along the b-axis direction.

3-[2-(9H-Carbazol-9-yl)ethyl]-4-phenyl-1H-1,2,4-triazole-5(4H)-thione dimethyl sulfoxide monosolvate

In the title compound, C22H18N4S·C2H6OS, the central triazolethione ring is inclined to the carbazole ring system by 13.97 (18)° and to the phenyl ring by 66.4 (1)°. The lattice solvent, dimethyl sulfoxide, is strongly hydrogen bonded to the triazolethione ring. In the crystal, the main molecules form columns parallel to theaaxis, with the solvent molecules located between the columns. C—H...S hydrogen bonds and C—H...π(ring) interactions link adjacent columns. The crystal studied was refined as a two-component twin, with a fractional contribution to the minor domain of 0.0742 (14).

9H-Carbazole-9-carbaldehyde

The title carbazole derivative, C13H9NO, crystallizes with two independent molecules (AandB) in the asymmetric unit. The dihedral angle between the planar carbazole ring system and the aldehyde group (HC=O) is 3.3 (2)° inAand 7.5 (2)° inB, indicating that the molecules are both nearly planar. In the crystal, theAandBmolecules are linked by a C—H...O hydrogen bond and stack along theb-axis direction. The structure was refined as a two component twin with a refined BASF value of 0.102 (2).

3-(9H-Carbazol-9-yl)propanoic acid

The title compound, C15H13NO2, crystallizes with two molecules (AandB) in the asymmetric unit. The carbazole ring systems of both molecules are close to planar (r.m.s deviations = 0.035 and 0.053 Å). In the crystal,A+AandB+Binversion dimers linked by pairs of O—H...O hydrogen bonds generateR22(8) loops and weak C—H...π interactions link the dimers into a three-dimensional network.

Crystal structures of two new carbazole derivatives: 12-(4-nitro-phen-yl)-7-phenyl-sulfonyl-7H-benzofuro[2,3-b]carbazole and 2-methyl-4-(4-nitro-phen-yl)-9-phenyl-sulfonyl-9H-thieno[2,3-b]carbazole.

The title compounds, C30H18N2O5S, (I), and C27H18N2O4S2, (II), are carbazole derivatives with a phenyl-sulfonyl group and a nitro-phenyl group attached to the carbazole moiety in identical positions in both mol-ecules. A benzo-furan ring system in (I) and a methyl-thio-phene ring in (II) are fused with the respective carbazole moieties on the same sides. The mean plane of the carbazole ring system makes a dihedral angle of 3.17 (7)° with the benzo-furan ring system in (I) and a dihedral angle of 3.39 (11)° with the methyl-thio-phene ring in (II), implying that both fused units are essentially planar. The mean planes of the carbazole ring systems in both the compounds are almost orthogonal to the respective nitro-substituted phenyl rings, making dihedral angles of 75.64 (10) and 77.63 (12)° in compounds (I) and (II), respectively. In (I), the phenyl-sulfonyl ring system is positionally disordered with a refined occupancy ratio of 0.63 (2):0.37 (2). In both compounds, the mol-ecular structures are stabilized by intra-molecular C-H⋯O hydrogen bonds, generating S(6) ring motifs with the sulfone group O atoms. In the crystal of compound (I), mol-ecules are linked by pairs of C-H⋯O hydrogen bonds, which generate R22(18) inversion dimers, and inter-connected by C(14) chains running along the c-axis direction, whereas in compound (II), the C-H⋯O hydrogen bonds generate R43(37) ring motifs. In the crystals of both compounds, C-H⋯O hydrogen-bonded sheets are formed lying parallel to (10-1). In addition, C-H⋯π and offset π-π inter-actions [inter-centroid distance = 3.7158 (14) Å in (I) and 3.9040 (15) Å in (II)] are also present in the crystals of both compounds.

1,3,6-Tribromo-9-ethyl-9H-carbazole

In the title compound, C14H10Br3N, the carbazole ring system is almost planar, with an r.m.s. deviation of 0.023 Å from the best fit mean plane of the 13 non-H atoms of the three rings. The methyl C atom lies 1.232 (3) Å out of this plane. No hydrogen bonds are found in the crystal structure but weak C—Br...π contacts at approximately 3.721 Å may stabilize the structure.

Crystal structure of 3-(9H-carbazol-9-yl)-N'-[(E)-4-chloro-benzyl-idene]propano-hydrazide.

In the title compound, C22H18ClN3O, the carbazole ring system is essentially planar (r.m.s deviation = 0.003 Å), and makes a dihedral angle of 9.01 (8)° with the plane of the chloro­phenyl ring. In the crystal, neighbouring mol­ecules are linked into centrosymmetric R 2 2(8) dimers by pairs of N—H⋯O inter­actions and into a three-dimensional network by C—H⋯π inter­actions. The dimers are arranged into layers parallel to (010).

Crystal structure of dimethyl 9H-carbazole-2,7-dicarboxylate

In the title compound, C16H13NO4, the carbazole ring system is almost planar with non-H atoms possessing a mean deviation from planarity of 0.037 Å. The two ester groups are orientated trans to one another and tilted slightly from the mean plane of the carbazole ring system, making dihedral angles of 8.12 (6) and 8.21 (5)°. In the crystal, mol­ecules are linked by pairs of N—H⋯O hydrogen bonds forming inversion dimers. The dimers are linked by parallel slipped π–π inter­actions, forming slabs propagating along the b-axis direction [inter-centroid distance = 3.6042 (8) Å, inter-planar distance = 3.3437 (5) Å, slippage = 1.345 Å].

Crystal structure of ethyl 2-phenyl-9-phenyl-sulfonyl-9H-carbazole-3-carboxyl-ate.

In the title compound, C27H21NO4S, the dihedral angles between the carbazole ring system (r.m.s. deviation = 0.015 Å) and the sulfur-bonded and directly linked benzene rings are 79.98 (11) and 53.51 (18)°, respectively. The benzene rings subtend a dihedral angle of 48.4 (2)°. The ethyl side chain of the ester group has an extended conformation [C—O—C—C = −172.3 (3)°]. In the crystal, inversion dimers linked by pairs of weak C—H⋯O hydrogen bonds generate R 2 2(22) loops. The dimers are linked by weak C—H⋯π and π–π [centroid-to-centroid distances ranging from 3.5042 (14) to 3.888 (2) Å] inter­actions, thereby forming a three-dimensional supra­molecular network.