3,6-Dibromoquinoline: Properties, Handling & Synthetic Uses
3,6-Dibromoquinoline: Properties, Handling & Synthetic Uses
3,6-Dibromoquinoline is a dihalogenated bicyclic heteroaromatic compound widely used as a versatile difunctional building block in palladium- and nickel-catalyzed cross-coupling reactions for the construction of complex quinoline-based architectures.
- IUPAC Name
- 3,6-Dibromoquinoline
- Molecular Formula
- C₉H₅Br₂N
- Molecular Weight
- 286.95 g/mol
- Functional Class
- Dihalogenated heteroaromatic building block
- Key Reactions
- Suzuki, Negishi, Buchwald-Hartwig, and Sonogashira cross-coupling
- Storage Recommendation
- Cool, dry, well-ventilated area; away from light and moisture
Chemical Identity and Physical Properties
3,6-Dibromoquinoline (CAS not confirmed in source material; flag for review) is a bicyclic heteroaromatic compound consisting of a benzene ring fused to a pyridine ring, with bromine substituents at the 3- and 6-positions. The electron-deficient nature of the quinoline ring system, combined with two reactive C–Br bonds at distinct electronic environments, makes this compound a highly selective difunctional reagent. The C-3 position is adjacent to the ring nitrogen and is therefore more electrophilic, while the C-6 position resides on the benzo ring and exhibits different reactivity. This electronic differentiation allows sequential, chemoselective functionalization under appropriate catalytic conditions.
The compound is typically isolated as a pale to off-white solid. Its aromatic halide character confers moderate stability under ambient conditions, though prolonged exposure to moisture, strong bases, or strong oxidizers should be avoided. Molecular weight is approximately 286.95 g/mol based on the molecular formula C₉H₅Br₂N.
Synthetic Applications and Cross-Coupling Reactivity
The primary utility of 3,6-dibromoquinoline lies in its role as a bifunctional electrophilic partner in transition-metal-catalyzed cross-coupling reactions. Because the two C–Br bonds reside in electronically and sterically distinct environments, careful choice of reaction conditions can enable selective mono-functionalization at C-3 or C-6, followed by a second coupling at the remaining site. This strategy is valuable in the synthesis of unsymmetrical bis-arylated, bis-heteroarylated, or mixed quinoline derivatives.
Suzuki–Miyaura coupling with aryl- or heteroarylboronic acids under palladium catalysis is among the most commonly employed transformations, delivering biaryl and oligoaryl quinoline products relevant to pharmaceutical discovery and organic electronics. Negishi coupling with organozinc reagents and Sonogashira coupling with terminal alkynes extend the accessible chemical space further. Buchwald–Hartwig amination allows installation of aryl amino groups, yielding aminoquinoline scaffolds of medicinal interest.
In materials science, quinoline-based extended π-systems derived from 3,6-dibromoquinoline are explored as components in organic light-emitting diodes (OLEDs) and as ligands in coordination chemistry owing to the quinoline nitrogen's metal-binding ability.
Safe Handling, Storage, and Disposal
As an organobromine aromatic compound, 3,6-dibromoquinoline should be handled with standard laboratory precautions for halogenated heterocycles. Personnel should wear appropriate personal protective equipment (PPE) including chemical-resistant gloves, safety goggles, and a laboratory coat. Operations that may generate dust or aerosols should be conducted in a well-ventilated fume hood.
Storage: Store in a tightly sealed container in a cool (recommended: room temperature to slightly below), dry, and well-ventilated area away from direct light, incompatible oxidizing agents, and sources of moisture. Desiccated conditions are preferable for long-term preservation of purity.
Disposal: Dispose of in accordance with local, regional, and national regulations for halogenated organic waste. Do not pour into drains or waterways. Consult your institution's environmental health and safety (EHS) office for approved disposal procedures.
Note: Specific GHS hazard classifications and signal words should be verified against the current Safety Data Sheet (SDS) provided by Aladdin Scientific for product SKU D699211 before use.
Quality, Purity, and Ordering Information
Aladdin Scientific supplies 3,6-dibromoquinoline under product SKU D699211. Researchers should confirm the current purity specification, available pack sizes, and certificate of analysis (CoA) directly on the product page or by contacting Aladdin Scientific's technical support team prior to ordering.
For synthetic applications demanding high selectivity—particularly sequential cross-coupling strategies—high-purity material (typically ≥97% or ≥98% by HPLC or GC) is strongly recommended to minimize side reactions arising from halide impurities or regioisomeric contaminants. Lot-specific CoA data including melting point, NMR confirmation, and purity assay should be requested for critical applications.
Bulk and custom quantities may be available; contact Aladdin Scientific procurement for pricing and lead-time information.
Frequently asked questions
What makes the two C–Br bonds in 3,6-dibromoquinoline chemically different?
The C-3 bromine is positioned alpha to the quinoline ring nitrogen, which withdraws electron density and makes that carbon more electrophilic and generally more reactive toward oxidative addition with palladium(0) catalysts. The C-6 bromine sits on the carbocyclic (benzo) ring and is less activated by the nitrogen. This electronic differentiation allows, in principle, selective mono-functionalization at C-3 under mild conditions before engaging C-6.
Which cross-coupling reactions are most suitable for 3,6-dibromoquinoline?
3,6-Dibromoquinoline is compatible with a broad range of palladium- and nickel-catalyzed cross-coupling protocols. Suzuki–Miyaura coupling with arylboronic acids, Sonogashira coupling with terminal alkynes, Negishi coupling with organozinc reagents, and Buchwald–Hartwig amination are all well-precedented for analogous dibromoheteroaromatics. The optimal catalyst system, base, solvent, and temperature should be optimized for each specific substrate combination.
How should 3,6-dibromoquinoline be stored to maintain purity over time?
Store the compound in a tightly sealed, light-resistant container under cool and dry conditions. Moisture can promote hydrolysis or degradation of the C–Br bonds over extended periods. Using desiccant and storing under an inert atmosphere (nitrogen or argon) is advisable for long-term inventory. Always check the lot-specific certificate of analysis before use in sensitive applications.
Is 3,6-dibromoquinoline suitable for use in materials science applications?
Yes. Quinoline-derived extended π-conjugated systems built from 3,6-dibromoquinoline are of interest in organic electronics, particularly in OLED device components and as metal-chelating ligands in coordination polymers. The nitrogen atom provides a metal-binding site while the aromatic scaffold contributes to charge transport properties. Specific performance data should be sourced from primary literature relevant to the target application.
References
- Negishi, E. (Ed.). Handbook of Organopalladium Chemistry for Organic Synthesis. Wiley-Interscience, 2002. (General reference for Pd-catalyzed cross-coupling of aryl halides.)
- Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chem. Rev. 1995, 95, 2457–2483. doi:10.1021/cr00039a007
- Sonogashira, K. Development of Pd–Cu catalyzed cross-coupling of terminal acetylenes with sp2-carbon halides. J. Organomet. Chem. 2002, 653, 46–49. doi:10.1016/S0022-328X(02)01158-0
- Hartwig, J. F. Palladium-catalyzed amination of aryl halides: mechanism and scope. Acc. Chem. Res. 1998, 31, 852–860. doi:10.1021/ar970282g
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