Chemical Identity and Structural Features

3-Bromo-5-chloro-[1,2,4]triazolo[4,3-a]pyridine (Aladdin SKU B194500) belongs to the triazolopyridine class of fused bicyclic heterocycles. The compound integrates a 1,2,4-triazole ring fused at the [4,3-a] positions of a pyridine ring, generating a planar, electron-deficient aromatic system that is highly attractive in drug discovery programs.

Two distinct halogen substituents are present on the scaffold: a bromine atom at the C-3 position of the triazole ring and a chlorine atom at the C-5 position of the pyridine ring. This dual-halogenation pattern endows the molecule with orthogonal reactivity. The C-3 bromo group is particularly amenable to palladium-catalyzed cross-coupling reactions (e.g., Suzuki-Miyaura, Negishi, Buchwald-Hartwig), while the C-5 chloro group serves as a handle for selective nucleophilic aromatic substitution (SNAr) reactions due to the electron-deficient nature of the ring system.

The molecular formula is C₆H₃BrClN₃ with an approximate molecular weight of 232.47 g/mol. All exact physicochemical constants should be confirmed against the official Aladdin product datasheet and Safety Data Sheet (SDS).

Recommended Handling and Storage Protocols

Personal Protective Equipment (PPE): When handling this compound, wear appropriate PPE including nitrile gloves, a laboratory coat, and safety glasses. Operations generating dust or aerosols should be performed in a chemical fume hood. Consult the product SDS for full hazard classification before use.

Storage Conditions: Store the compound in a tightly sealed container under cool, dry, and dark conditions. Halogenated heterocycles of this type are generally sensitive to prolonged exposure to moisture and light, which may promote slow degradation. Long-term storage at 2–8 °C or lower (as specified in the SDS) is recommended to preserve purity and stability.

Solubility and Solvent Selection: The compound is expected to dissolve in common polar aprotic solvents such as DMSO, DMF, and acetonitrile. Confirm solubility data against the official datasheet prior to preparing stock solutions. For cross-coupling reactions, THF and 1,4-dioxane are commonly used solvents.

Waste Disposal: Dispose of all waste in accordance with local institutional and governmental regulations for halogenated organic compounds. Never dispose of chemical waste down the drain without prior approval from your institutional environmental health and safety office.

Applications in Synthetic and Medicinal Chemistry

Cross-Coupling Chemistry: The C-3 bromo substituent makes this compound an excellent electrophilic partner in palladium- or nickel-catalyzed cross-coupling reactions. Suzuki-Miyaura coupling with aryl or heteroaryl boronic acids, Negishi coupling with organozinc reagents, and Sonogashira coupling with terminal alkynes can all be employed to introduce diverse substituents at C-3, enabling rapid diversification of the triazolopyridine scaffold.

Nucleophilic Aromatic Substitution (SNAr): The C-5 chlorine, activated by the flanking electron-withdrawing triazole nitrogen atoms, can participate in SNAr reactions with amines, alkoxides, and thiolates. This provides a complementary strategy for scaffold diversification independent of metal catalysis.

Drug Discovery and Fragment-Based Design: Triazolopyridine scaffolds are recognized pharmacophores found in kinase inhibitors, CNS-active agents, and anti-infective leads. The dual-halogenation of this building block allows sequential or selective functionalization, making it particularly valuable in fragment-based drug discovery (FBDD) and lead optimization campaigns where stepwise elaboration of the core scaffold is required.

Material Science: Nitrogen-rich fused heterocycles such as triazolopyridines are also explored as ligands in coordination chemistry and as components of functional organic materials, expanding the utility of this building block beyond pharmaceutical synthesis.

Quality, Purity, and Analytical Verification

Aladdin Scientific supplies 3-Bromo-5-chloro-[1,2,4]triazolo[4,3-a]pyridine (SKU B194500) at research-reagent grade. Users should consult the Certificate of Analysis (CoA) supplied with each lot for purity data, typically assessed by HPLC and/or NMR spectroscopy.

Identity Confirmation: Upon receipt, identity can be confirmed by ¹H NMR spectroscopy, which should show two aromatic proton signals consistent with the substituted triazolopyridine ring system. High-resolution mass spectrometry (HRMS) can confirm the molecular ion with the expected bromine and chlorine isotope pattern (M, M+2, M+4).

Purity Assessment: Reverse-phase HPLC (C18 column, UV detection at 254 nm) is a standard method for purity assessment. Users performing sensitive catalytic reactions should consider additional purification (e.g., column chromatography or recrystallization) if the required purity exceeds the lot specification.

Moisture Sensitivity Check: If the compound has been stored for an extended period, re-analysis before use in critical experiments is recommended. Any changes in appearance (e.g., discoloration, caking) should be noted and the compound re-tested for purity prior to use.

Ordering and Procurement Information

3-Bromo-5-chloro-[1,2,4]triazolo[4,3-a]pyridine is available from Aladdin Scientific under SKU B194500. Researchers and procurement personnel can place orders directly through the Aladdin Scientific website or by contacting the local sales representative.

Quantity and Packaging: Available pack sizes should be confirmed on the Aladdin product page. For large-scale or custom quantity requirements, please contact Aladdin Scientific's sales team directly to discuss bulk pricing and availability.

Lead Time and Shipping: Standard reagents are typically dispatched promptly from stock. Shipping conditions (temperature-controlled if required) should be confirmed at the time of ordering. All shipments comply with applicable regulations for the transport of chemical reagents.

Returns and Quality Concerns: If a product does not meet the specifications stated on the CoA, customers should contact Aladdin Scientific customer service with the lot number and a description of the issue. Aladdin Scientific's returns and refunds policy will apply as per standard terms and conditions.