5,7-Dihydro-indolo[2,3-b]carbazole
[CAS# 111296-90-3]

Identification

• Classification: Organic raw materials >> Heterocyclic compound >> Carbazoles
• Name: 5,7-Dihydro-indolo[2,3-b]carbazole
• Molecular Formula: C₁₈H₁₂N₂
• Molecular Weight: 256.30
• CAS Registry Number: 111296-90-3
• EC Number: 834-009-3
• SMILES: C1=CC=C2C(=C1)C3=CC4=C(C=C3N2)NC5=CC=CC=C54

Properties

• Solubility: Insoluble (1.6E^-5 g/L) (25 °C), Calc.^*
• Density: 1.404±0.06 g/cm³ (20 °C 760 Torr), Calc.^*
• Melting point: 348-360 °C (Expl.)
• Index of Refraction: 1.924, Calc.^*
• Boiling Point: 569.8±23.0 °C (760 mmHg), Calc.^*
• Flash Point: 269.9±13.9 °C, Calc.^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software V11.02 (©1994-2013 ACD/Labs)

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319
• Safety Statements: P264-P264+P265-P280-P302+P352-P305+P351+P338-P321-P332+P317-P337+P317-P362+P364

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315

Discovery and Applications

5,7-Dihydro-indolo[2,3-b]carbazole is a polycyclic aromatic compound composed of fused indole and carbazole rings, forming a planar heterocyclic structure. It is a member of the indolocarbazole family, which has attracted considerable attention due to its presence in natural products and its utility in synthetic organic chemistry. The compound exhibits extended conjugation and possesses a rigid framework, which contributes to its stability and distinctive chemical properties. The molecular formula of 5,7-dihydro-indolo[2,3-b]carbazole is C₁₈H₁₂N₂.

The indolocarbazole core, including the 5,7-dihydro-indolo[2,3-b]carbazole structure, has been identified in naturally occurring alkaloids isolated from actinomycetes. These structures were first reported in the context of studies on biologically active microbial metabolites, including rebeccamycin and staurosporine, which contain related ring systems and share synthetic precursors. While 5,7-dihydro-indolo[2,3-b]carbazole itself is not a natural product, it serves as a fundamental framework in the synthesis of various analogs with established biological activities.

Synthesis of 5,7-dihydro-indolo[2,3-b]carbazole can be achieved via condensation and oxidative cyclization methods. One documented approach involves the acid-catalyzed condensation of indole-3-acetaldehyde derivatives followed by intramolecular cyclization under oxidative conditions. Transition metal-catalyzed reactions, such as palladium- or copper-mediated cross-coupling strategies, have also been reported to construct the indolocarbazole skeleton efficiently. The selection of appropriate precursors and reaction conditions is essential to control the regiochemistry and ring fusion during synthesis.

Applications of 5,7-dihydro-indolo[2,3-b]carbazole and its derivatives are primarily found in materials science and medicinal chemistry. Due to the compound’s extended π-conjugation and planar aromatic structure, it has been explored as an active component in organic electronic devices. Its structural characteristics support efficient charge transport and strong intermolecular interactions, which are beneficial in the design of organic semiconductors, electroluminescent materials, and photovoltaic components. Indolocarbazole-based compounds have been incorporated into light-emitting diodes and field-effect transistors where thermal stability and photophysical properties are critical.

In medicinal chemistry, the indolocarbazole framework has served as a core structure in kinase inhibitors and DNA-intercalating agents. While 5,7-dihydro-indolo[2,3-b]carbazole itself does not have documented therapeutic uses, its close analogs have been studied for their cytotoxic, antibacterial, and antitumor properties. Structural modifications of the parent scaffold allow researchers to fine-tune biological activity and improve pharmacokinetic profiles. The core structure is particularly valued for its ability to interact with nucleic acids and protein targets through stacking interactions and hydrogen bonding.

Further functionalization of 5,7-dihydro-indolo[2,3-b]carbazole has enabled the synthesis of dyes and pigments with enhanced optical properties. Substitution at the nitrogen or carbon positions of the fused ring system can result in shifts in absorption and emission spectra, which are desirable in applications such as fluorescence imaging and sensor development. The chemical stability of the indolocarbazole system makes it suitable for use in demanding environments where durability is essential.

Safety and handling of 5,7-dihydro-indolo[2,3-b]carbazole follow standard procedures for aromatic heterocycles. The compound is typically a solid under ambient conditions and should be handled in well-ventilated areas using protective equipment. No specific toxicological or environmental hazards have been reported for this compound in the primary literature, though general caution is advised due to the potential for biological activity.

In conclusion, 5,7-dihydro-indolo[2,3-b]carbazole represents a chemically and structurally significant member of the indolocarbazole family, widely studied for its role in materials science and as a synthetic intermediate in bioactive molecule development. Its synthesis and applications are supported by established literature focused on heterocyclic chemistry and functional organic materials.

References

2023. Carbocation Catalysis in the Synthesis of Heterocyclic Compounds. Chemistry of Heterocyclic Compounds, 59(1-2), 3-14.
DOI: 10.1007/s10593-023-03157-3

2020. Facile and Mild Access to Fluorescent Ladder-Type Indolo[3,2-a]carbazoles via Cascade Annulation. Synthesis, 53(04), 811-816.
DOI: 10.1055/s-0040-1706473

2014. Indolo[2,3-b]carbazole Synthesized from a Double-Intramolecular Buchwald-Hartwig Reaction: Its Application for a Dianchor DSSC Organic Dye. Organic Letters, 16(12), 3220-3223.
DOI: 10.1021/ol500663b