7-Bromo-3H-imidazo[4,5-b]pyridine: Properties & Applications
7-Bromo-3H-imidazo[4,5-b]pyridine: Properties & Applications
7-bromo-3H-imidazo[4,5-b]pyridine is a brominated bicyclic heterocyclic compound that serves as a versatile and widely used synthetic building block in medicinal chemistry and drug discovery research.
- IUPAC Name
- 7-bromo-3H-imidazo[4,5-b]pyridine
- Molecular Formula
- C6H4BrN3
- Molecular Weight
- 198.02 g/mol
- Core Scaffold
- Imidazo[4,5-b]pyridine (fused imidazole-pyridine bicyclic system)
- Key Functional Handle
- C7-bromo substituent enabling cross-coupling reactions
- Primary Application
- Synthetic intermediate in medicinal chemistry and kinase inhibitor development
- SKU
- B172553
Chemical Structure and Properties
7-Bromo-3H-imidazo[4,5-b]pyridine belongs to the imidazopyridine class of fused bicyclic heterocycles. Its core structure consists of an imidazole ring fused to a pyridine ring at the [4,5-b] positions, creating a planar, aromatic bicyclic system with three nitrogen atoms. The bromine substituent is located at the 7-position of the pyridine ring component.
The compound exhibits the characteristic properties of electron-deficient nitrogen-rich heterocycles, including moderate polarity and the capacity to participate in hydrogen bonding through its NH group and pyridine-type nitrogen atoms. The aromatic, planar structure facilitates π-stacking interactions, a feature relevant to binding within enzyme active sites.
The C–Br bond at the 7-position is an electrophilically activated site due to the adjacent electron-withdrawing nitrogen atoms, making it highly reactive toward palladium-catalyzed cross-coupling reactions such as Suzuki–Miyaura, Negishi, and Buchwald–Hartwig amination.
Synthesis and Functionalization
The imidazo[4,5-b]pyridine scaffold is typically accessible through condensation reactions between appropriately substituted 2,3-diaminopyridine derivatives and one-carbon equivalents such as formic acid, triethyl orthoformate, or aldehydes under acid-catalyzed or thermal conditions. Introduction of the bromo substituent at the 7-position can be achieved either by starting from a pre-brominated diaminopyridine precursor or by direct electrophilic bromination of the parent imidazo[4,5-b]pyridine.
Once in hand, 7-bromo-3H-imidazo[4,5-b]pyridine can be efficiently converted to a wide variety of analogs. Palladium-catalyzed Suzuki–Miyaura coupling with aryl or heteroaryl boronic acids installs diverse (hetero)aryl groups at C7. Buchwald–Hartwig amination allows introduction of primary and secondary amines. Negishi coupling with organozinc reagents and Sonogashira coupling with terminal alkynes are also well suited to this substrate. The NH position can additionally be alkylated or acylated to tune physicochemical properties.
These diverse functionalization options make this compound an exceptionally productive starting point for library synthesis and structure–activity relationship (SAR) studies.
Research and Medicinal Chemistry Applications
The imidazo[4,5-b]pyridine core is a privileged scaffold in medicinal chemistry, appearing in numerous bioactive compounds and approved pharmaceutical agents. The bicyclic nitrogen-rich framework mimics purine geometry and is capable of occupying ATP-binding pockets of protein kinases, making it a recurring motif in kinase inhibitor programs.
7-Bromo-3H-imidazo[4,5-b]pyridine is employed as a key intermediate in the synthesis of compounds targeting a range of biological pathways. Researchers utilize the C7 bromo handle to rapidly diversify the scaffold and explore SAR against various therapeutic targets including oncology, inflammation, and CNS indications. The compound's NH group can also be exploited for additional diversification or to modulate solubility and permeability.
Beyond kinase inhibition, imidazopyridine derivatives have been investigated as adenosine receptor ligands, antimicrobial agents, and modulators of other enzyme classes. The availability of 7-bromo-3H-imidazo[4,5-b]pyridine as a commercial reagent therefore supports a broad spectrum of target-focused and phenotypic drug discovery programs.
Handling, Storage, and Safety Considerations
As with most brominated heterocyclic intermediates, 7-bromo-3H-imidazo[4,5-b]pyridine should be handled in accordance with standard laboratory safety protocols. Personal protective equipment including nitrile gloves, a laboratory coat, and safety eyewear should be worn at all times during handling. Operations generating dust or aerosols should be conducted in a well-ventilated fume hood.
The compound should be stored in a tightly sealed container, protected from moisture and light, at cool temperatures consistent with standard reagent storage practices. Prolonged or repeated exposure to air and humidity may affect purity; therefore, proper sealing and inert atmosphere storage (e.g., under nitrogen or argon) is recommended for long-term preservation.
Researchers should consult the product's Safety Data Sheet (SDS) provided by Aladdin Scientific for complete hazard classification, first-aid measures, and disposal guidance prior to use. Waste disposal must comply with local and institutional regulations governing halogenated organic compounds.
Frequently asked questions
What cross-coupling reactions are compatible with 7-bromo-3H-imidazo[4,5-b]pyridine?
The C7 bromo substituent is well suited for palladium-catalyzed cross-coupling reactions, including Suzuki–Miyaura coupling with boronic acids, Buchwald–Hartwig amination with amines, Negishi coupling with organozinc reagents, and Sonogashira coupling with terminal alkynes. These transformations enable rapid diversification of the imidazopyridine scaffold for SAR studies.
Why is the imidazo[4,5-b]pyridine scaffold important in drug discovery?
The imidazo[4,5-b]pyridine bicyclic core is considered a privileged scaffold in medicinal chemistry because its geometry and electronic properties closely resemble those of purines, enabling it to engage ATP-binding pockets of protein kinases and other nucleotide-binding proteins. Its nitrogen-rich framework supports multiple hydrogen-bonding interactions, and the scaffold has appeared in a range of bioactive compounds targeting oncology, inflammation, and other disease areas.
How should 7-bromo-3H-imidazo[4,5-b]pyridine be stored to maintain purity?
The compound should be stored in a tightly sealed container under cool, dry, and dark conditions. For long-term storage, an inert atmosphere such as nitrogen or argon is recommended to minimize degradation from moisture and oxygen. Always consult the Aladdin Scientific SDS and certificate of analysis for specific storage guidance.
Can the NH group of 7-bromo-3H-imidazo[4,5-b]pyridine be functionalized?
Yes, the NH group of 7-bromo-3H-imidazo[4,5-b]pyridine can be alkylated or acylated under appropriate conditions to introduce N-substituents that modulate physicochemical properties such as solubility, lipophilicity, and membrane permeability. N-functionalization can be performed independently of or in combination with C7 cross-coupling transformations to generate structurally diverse analogs.
References
- Joule, J. A.; Mills, K. Heterocyclic Chemistry, 5th ed.; Wiley-Blackwell: Oxford, 2010. General reference for imidazopyridine scaffold chemistry.
- Aladdin Scientific. Product Data Sheet: 7-Bromo-3H-imidazo[4,5-b]pyridine, SKU B172553. Aladdin Scientific, Shanghai.
- Taylor, R. D.; MacCoss, M.; Lawson, A. D. G. Rings in Drugs. J. Med. Chem. 2014, 57, 5845–5859. Discussion of privileged scaffolds including imidazopyridines in drug discovery. doi:10.1021/jm4017625
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