What Is 5-Bromo-1H,2H,3H-pyrrolo[2,3-b]pyridine Hydrochloride?

5-Bromo-1H,2H,3H-pyrrolo[2,3-b]pyridine hydrochloride is a bicyclic nitrogen-containing heterocycle belonging to the pyrrolopyridine family. The parent ring system, pyrrolo[2,3-b]pyridine, is also known as the 7-azaindole scaffold. In this compound, the pyrroline ring is partially saturated (positions 1, 2, and 3 carry the hydrogen atoms indicated in the IUPAC name), giving an azaindoline-type structure rather than a fully aromatic azaindole.

A bromine atom is installed at position 5 of the pyridine ring. This electrophilic handle makes the compound an ideal precursor for transition-metal-catalyzed cross-coupling reactions, including Suzuki–Miyaura, Negishi, and Buchwald–Hartwig amination reactions, enabling efficient construction of more complex, drug-like molecules.

The compound is supplied as the hydrochloride salt (HCl salt), which improves crystallinity, stability, and ease of handling compared with the free base. Researchers should account for the molecular weight contribution of the HCl moiety when preparing stock solutions and calculating molar equivalents.

Chemical Properties and Structural Considerations

Partial saturation: Unlike the aromatic 7-azaindole, the 1,2,3-trihydro (azaindoline) form of the ring system alters the basicity, conformational flexibility, and hydrogen-bond donor/acceptor profile of the molecule. The saturated nitrogen (N-1) is a secondary amine and a stronger base than an aromatic pyrrole nitrogen, which influences salt formation and solubility.

Bromine reactivity: The C–Br bond at position 5 is well-suited for palladium- or nickel-catalyzed cross-coupling. Because position 5 is on the pyridine ring adjacent to the ring nitrogen, the local electronic environment can be tuned by the choice of metal catalyst and ligand system.

Solubility: As a hydrochloride salt, the compound typically shows improved aqueous solubility relative to the free base. For organic synthesis, polar aprotic solvents such as DMF, DMSO, or acetonitrile are commonly employed. Specific solubility data should be confirmed from the product CoA or by in-house testing.

Stability: Hydrochloride salts of secondary amines are generally air-stable solids. Nevertheless, prolonged exposure to moisture, light, or elevated temperatures should be avoided. Store sealed under inert atmosphere if long-term storage is required.

Synthetic and Research Applications

The pyrrolopyridine/azaindoline scaffold is a privileged structure in medicinal chemistry because it combines the hydrogen-bond acceptor capacity of the pyridine nitrogen, the amine donor of the saturated nitrogen, and a flat aromatic surface suitable for stacking interactions within enzyme active sites.

Cross-coupling reactions: The C-5 bromide is readily converted to biaryl, vinyl, alkynyl, or amino products via standard palladium-catalyzed protocols. This makes B175164 a key intermediate for building kinase inhibitor candidates, antiviral agents, and CNS-active molecules where the azaindoline motif is a recurring pharmacophore.

N-functionalization: The secondary amine at N-1 can be acylated, sulfonylated, or alkylated to modulate physicochemical and pharmacological properties, providing orthogonal diversification points in parallel synthesis or library campaigns.

Fragment-based drug discovery (FBDD): The compact, rigid scaffold with multiple interaction vectors is well-suited as a fragment hit or fragment lead for FBDD programs targeting protein kinases, bromodomains, and other druggable targets.

Handling, Safety, and Storage Guidelines

Personal protective equipment (PPE): Handle in a well-ventilated fume hood. Wear appropriate gloves (nitrile recommended), safety glasses, and a lab coat. Avoid inhalation of dust or aerosols.

Hazard considerations: The compound contains an organobromine moiety and an HCl salt. As with all fine chemicals of unknown complete toxicological profile, treat as potentially harmful. Consult the Safety Data Sheet (SDS) provided by Aladdin Scientific before use. Specific GHS hazard classifications should be confirmed from the current SDS.

Storage: Store in a tightly closed container in a cool (typically 2–8 °C or room temperature as specified on the label), dry, dark location. Keep away from incompatible materials such as strong oxidizers and strong bases. Confirm recommended storage temperature from the product label or CoA, as requirements may vary by lot.

Disposal: Dispose of waste material in accordance with local, regional, and national regulations. Do not pour down the drain. Contact your institution's environmental health and safety office for guidance.

Ordering, Specification, and Quality Information

SKU and availability: 5-Bromo-1H,2H,3H-pyrrolo[2,3-b]pyridine hydrochloride is listed under SKU B175164 at Aladdin Scientific. Contact your local Aladdin representative or visit the Aladdin Scientific website for current stock levels, pack sizes, and pricing.

Purity and specifications: Purity grade and analytical data (HPLC purity, NMR, MS confirmation) are reported on the Certificate of Analysis (CoA) supplied with each lot. Request the CoA from Aladdin Scientific customer service or download it from the product page using your lot number.

Custom quantities and bulk orders: For quantities beyond standard pack sizes, contact Aladdin Scientific's custom synthesis or bulk procurement team. Lead times and pricing will vary depending on quantity and current production schedules.

Quality assurance: Aladdin Scientific applies rigorous quality control processes. Each lot is tested against internal specifications before release. If you observe any discrepancy between the product received and the CoA, contact customer service immediately to initiate a quality complaint.