Chemical Structure and Physical Properties

4-Bromoquinoline-6-carboxylic acid features a bicyclic quinoline scaffold consisting of a benzene ring fused to a pyridine ring. The molecule carries two strategically positioned substituents: a bromine atom at the 4-position and a carboxylic acid group at the 6-position. This arrangement creates an electronically and sterically differentiated platform for selective chemical modification.

The quinoline nitrogen imparts a degree of electron deficiency to the ring system, activating the C-4 position toward nucleophilic substitution and facilitating oxidative addition by palladium(0) catalysts. The C-6 carboxylic acid, positioned on the benzo ring, is electronically decoupled from the heterocyclic nitrogen, making it amenable to standard carboxylic acid transformations without interference from the ring nitrogen.

Physical characteristics include a solid appearance at ambient temperature. The compound has a molecular formula of C₁₀H₆BrNO₂ and a molecular weight of approximately 252.07 g/mol. Solubility is generally achievable in polar aprotic solvents such as DMSO and DMF, as well as dilute aqueous base.

Synthetic Applications and Reactivity

The bifunctional nature of 4-Bromoquinoline-6-carboxylic acid makes it exceptionally useful as a versatile synthetic building block in two independent reaction modes:

C–C and C–N Bond Formation via the Aryl Bromide: The C-4 aryl bromide is well-suited for palladium-catalyzed cross-coupling reactions. Suzuki-Miyaura coupling with arylboronic acids allows installation of diverse aryl and heteroaryl groups at the 4-position, enabling rapid diversification of the quinoline core. Buchwald-Hartwig amination permits introduction of amine fragments, a key transformation in building biologically active compounds. The Sonogashira reaction with terminal alkynes can be used to install alkynyl groups, valuable in click chemistry and materials science contexts.

Carboxylic Acid Transformations: The C-6 carboxylic acid can be converted to amides via standard coupling reagent-mediated reactions (e.g., using HATU, EDC, or T3P), enabling construction of pharmacologically important amide bonds. Esterification, reduction to the alcohol, or Curtius rearrangement to the amine are additional pathways that expand the accessible chemical space from this single starting material.

Sequential and Orthogonal Functionalization: Because the aryl bromide and carboxylic acid display orthogonal reactivity profiles under appropriate conditions, chemists can perform sequential transformations — for example, first coupling the boronic acid at C-4 and then forming an amide at C-6 — without protecting group manipulation. This orthogonality significantly accelerates library synthesis workflows in drug discovery settings.

Applications in Medicinal Chemistry and Drug Discovery

Quinoline-based scaffolds are among the most privileged heterocyclic frameworks in medicinal chemistry, appearing in numerous approved drugs and clinical candidates across diverse therapeutic areas including oncology, anti-infectives, and central nervous system disorders. 4-Bromoquinoline-6-carboxylic acid serves as a highly enabling intermediate in this context.

Kinase Inhibitor Programs: Quinoline cores are recurrent in kinase inhibitor pharmacophores. The C-4 position of quinoline is frequently used for hinge-binding interactions, and the C-6 carboxylic acid or its amide derivatives can project into solvent-exposed regions or form additional interactions with the ATP-binding site. This compound therefore represents a productive entry point for structure-activity relationship (SAR) exploration around kinase targets.

Fragment-Based Drug Discovery (FBDD): The compact, rigid quinoline scaffold with two orthogonal handles makes 4-Bromoquinoline-6-carboxylic acid an attractive fragment for FBDD campaigns, where elaboration at two independent vectors allows efficient exploration of binding interactions.

Antimicrobial Research: Quinoline derivatives have a well-documented history in antimicrobial and antiparasitic drug development. Functionalized quinolines continue to be investigated for activity against drug-resistant pathogens, and haloquinoline-carboxylic acid derivatives represent tractable chemical matter for such programs.

Fluorescent Probes and Materials: Quinoline compounds can serve as fluorescent scaffolds in sensing and imaging applications. Derivatization of 4-Bromoquinoline-6-carboxylic acid via cross-coupling may yield conjugated systems with tunable photophysical properties relevant to probe development.

Handling, Storage, and Laboratory Safety

As with all fine chemical research reagents, appropriate handling practices should be observed when working with 4-Bromoquinoline-6-carboxylic acid.

Storage: The compound should be stored in a cool, dry, well-ventilated location, protected from moisture, heat, and direct light. Tightly sealed containers prevent hygroscopic uptake and oxidative degradation. Refer to the product's Safety Data Sheet (SDS) for specific storage temperature recommendations.

Personal Protective Equipment (PPE): Standard laboratory PPE including nitrile gloves, safety glasses or goggles, and a laboratory coat should be worn when handling this compound. Work in a fume hood when weighing or dissolving the material to minimize inhalation exposure to dust or vapor.

Waste Disposal: Dispose of all waste in accordance with applicable local, national, and institutional regulations governing chemical waste management. Do not discharge into drainage systems or the environment.

Stability: The compound is expected to be stable under recommended storage conditions. Prolonged exposure to moisture may affect the integrity of the carboxylic acid functionality. Always verify compound quality before critical synthetic use, particularly if material has been stored for extended periods.

Consult the full SDS available from Aladdin Scientific (SKU B182858) for complete hazard classification, first-aid measures, and regulatory information.