6-Bromo-[1,2,4]triazolo[4,3-b]pyridazine: Handling & Use Protocol
6-Bromo-[1,2,4]triazolo[4,3-b]pyridazine: Handling & Use Protocol
6-Bromo-[1,2,4]triazolo[4,3-b]pyridazine is a fused bicyclic heteroaromatic building block bearing a reactive C-6 bromine substituent, widely employed in medicinal chemistry as a versatile scaffold for the synthesis of kinase inhibitors and other bioactive small molecules.
- CAS Registry Number
- Not specified in source material — see product datasheet
- Molecular Formula
- C₅H₃BrN₄
- Molecular Weight
- Approximately 199.01 g/mol (calculated from C₅H₃BrN₄)
- Key Reactive Handle
- C-6 aryl bromide — amenable to Pd-catalyzed cross-coupling (Suzuki, Buchwald-Hartwig) and nucleophilic aromatic substitution
- Recommended Storage
- Cool, dry, dark conditions; store under inert atmosphere after opening
- Primary Application
- Medicinal chemistry scaffold synthesis, drug discovery, heterocyclic coupling reactions
Safety and Pre-Handling Considerations
Before working with 6-Bromo-[1,2,4]triazolo[4,3-b]pyridazine (Aladdin SKU B189818), consult the current Safety Data Sheet (SDS) available from Aladdin Scientific. As with most nitrogen-rich brominated heterocycles, treat this compound with standard laboratory precautions:
- Personal Protective Equipment (PPE): Wear nitrile gloves, a laboratory coat, and safety glasses. Work in a well-ventilated fume hood.
- Inhalation and Contact: Avoid generating dust. Brominated heterocycles may cause skin, eye, and respiratory irritation. In case of skin or eye contact, flush with copious water and seek medical advice.
- Waste Disposal: Dispose of all waste in accordance with local institutional and government regulations for halogenated organic compounds.
- Storage: Store in a tightly sealed container under an inert gas (nitrogen or argon) in a cool, dry, dark location. Protect from moisture, which may promote degradation of the reactive aryl bromide bond.
Review flag: Confirm GHS hazard classifications from the official Aladdin SDS before use.
Solubility and Solution Preparation
Proper dissolution of 6-Bromo-[1,2,4]triazolo[4,3-b]pyridazine is essential for reproducible results in coupling reactions and biological assays.
Recommended Solvents
- Dimethyl sulfoxide (DMSO): Generally suitable for dissolving polar heteroaromatic solids; prepare stock solutions at 10–100 mM.
- N,N-Dimethylformamide (DMF): Suitable for synthetic applications requiring an aprotic polar medium.
- Dichloromethane (DCM) or Tetrahydrofuran (THF): May be used for reaction setups where protic solvents are incompatible.
- Water: Solubility in water is expected to be limited due to the lipophilic fused ring system; avoid aqueous stock solutions unless solubility is confirmed.
Preparation Steps
- Allow the sealed vial to equilibrate to room temperature before opening to minimize condensation of atmospheric moisture onto the solid.
- Weigh the required amount rapidly on a calibrated analytical balance inside the fume hood.
- Add the appropriate dry solvent in increments and vortex or sonicate gently until complete dissolution is achieved.
- Prepare fresh solutions where possible, or store DMSO stocks at –20 °C in small aliquots to minimize freeze-thaw degradation.
Review flag: Exact solubility values (mg/mL) in common solvents are not available in the source material and should be verified experimentally or from the Aladdin product datasheet.
Synthetic Applications and Reaction Protocols
The principal synthetic utility of 6-Bromo-[1,2,4]triazolo[4,3-b]pyridazine derives from the electrophilic C-6 position activated by the bromine leaving group and the electron-deficient ring system. The following reaction classes are most commonly employed:
1. Suzuki–Miyaura Cross-Coupling
The aryl bromide can be coupled with aryl- or heteroarylboronic acids or boronate esters under palladium catalysis to introduce diverse aryl/heteroaryl substituents at C-6.
- Typical conditions: Pd(PPh₃)₄ or Pd(dppf)Cl₂ catalyst (2–5 mol%), base (K₂CO₃ or Cs₂CO₃), solvent mixture (DMF/H₂O or dioxane/H₂O), 80–100 °C, inert atmosphere (N₂ or Ar).
- Procedure: Combine aryl bromide substrate, boronic acid (1.1–1.5 equiv.), catalyst, and base in degassed solvent. Heat under reflux or in a sealed vial. Monitor by TLC or LCMS. Work up by aqueous extraction and purify by column chromatography.
2. Buchwald–Hartwig Amination
C-N bond formation at C-6 using primary or secondary amines under palladium catalysis enables access to aminotriazolopyridazine analogues relevant to kinase inhibitor programs.
- Typical conditions: Pd₂(dba)₃ or Pd(OAc)₂ with a bidentate phosphine ligand (e.g., BINAP, XantPhos), base (Cs₂CO₃ or NaOtBu), toluene or dioxane, 90–110 °C, inert atmosphere.
3. Nucleophilic Aromatic Substitution (SNAr)
The electron-deficient triazolopyridazine core may facilitate direct displacement of the C-6 bromide by heteroatom nucleophiles (amines, alkoxides, thiolates) without transition-metal catalysis under forcing conditions.
- Typical conditions: Nucleophile (2–5 equiv.), base (Et₃N or DIPEA), polar aprotic solvent (DMF or NMP), 100–150 °C or microwave irradiation.
Review flag: Specific yields, exact catalyst loadings, and literature precedents for this exact substrate are not available in source material. All conditions listed are textbook-level guidance for analogous aryl bromides and must be optimized experimentally.
Quality Control and Analytical Characterization
Confirming compound identity and purity before use is critical, especially for structure-activity relationship (SAR) studies and biological screening. Recommended analytical methods for 6-Bromo-[1,2,4]triazolo[4,3-b]pyridazine include:
- ¹H NMR Spectroscopy: Verify proton environments consistent with the fused triazolopyridazine ring system. Expect signals in the aromatic region (δ 7–9 ppm) corresponding to ring protons, plus the triazole C-H. Compare against the certificate of analysis (CoA).
- ¹³C NMR Spectroscopy: Confirm the carbon skeleton and the presence of C-Br carbon (characteristically low-field shift relative to unsubstituted analogue).
- LC-MS: Confirm molecular ion [M+H]⁺ and check purity (≥95% by UV at 254 nm is recommended for SAR studies). The characteristic isotope pattern of bromine (⁷⁹Br/⁸¹Br, ~1:1) confirms the brominated species.
- HPLC: Quantitative purity assessment by reverse-phase HPLC (C18 column, acetonitrile/water gradient).
- Melting Point: Compare measured value with certificate of analysis data.
Always request and retain the Aladdin CoA for batch traceability.
Review flag: Specific NMR chemical shift values and melting point are not provided in the source material; obtain from the product CoA (SKU B189818).
Troubleshooting and Best Practices
The following guidance addresses common challenges encountered when working with 6-Bromo-[1,2,4]triazolo[4,3-b]pyridazine:
| Problem | Likely Cause | Recommended Action |
|---|---|---|
| Low coupling yield | Catalyst poisoning by ring nitrogen; moisture in reaction | Use nitrogen-tolerant catalyst ligands (e.g., XPhos, SPhos); rigorously dry solvents and degas thoroughly |
| Partial dissolution in DMSO | Insufficient mixing or low temperature | Warm gently to 37–40 °C and sonicate; confirm solubility limit is not exceeded |
| Compound degradation over time | Moisture ingress, light exposure, or thermal stress | Store under argon in amber vial at –20 °C; use fresh aliquots |
| Multiple spots on TLC | Proto-debromination or hydrolysis side products | Ensure anhydrous conditions; minimize reaction time; monitor progress closely by LCMS |
| Inconsistent biological results | Purity issues or DMSO vehicle effects | Verify purity ≥95% by HPLC; limit DMSO concentration to ≤0.1% v/v in biological assays |
Review flag: Troubleshooting recommendations are based on general best practices for analogous electron-deficient bromoheterocycles. Compound-specific data are not available in the source material.
Frequently asked questions
What is the recommended solvent for preparing stock solutions of 6-Bromo-[1,2,4]triazolo[4,3-b]pyridazine?
DMSO is the most widely recommended solvent for preparing stock solutions of this compound, offering good solvating power for polar heteroaromatic solids. DMF is an alternative for synthetic applications. Aqueous solubility is expected to be limited and should be confirmed experimentally before use in biochemical assays.
How should 6-Bromo-[1,2,4]triazolo[4,3-b]pyridazine be stored to maintain stability?
The compound should be stored in a tightly sealed container under an inert atmosphere (nitrogen or argon) in a cool, dry, and dark environment. For long-term storage, –20 °C is advisable. Moisture exposure should be strictly avoided, as it can promote degradation of the reactive aryl bromide functional group. Aliquoting prior to storage minimizes repeated freeze-thaw cycles.
What transition-metal-catalyzed reactions are suitable for functionalizing the C-6 bromide of this compound?
The C-6 aryl bromide is well-suited for palladium-catalyzed Suzuki–Miyaura cross-coupling with boronic acids and Buchwald–Hartwig C-N bond-forming reactions with amines, enabling rapid diversification of the triazolopyridazine scaffold. Nickel-catalyzed alternatives may also be explored. Nitrogen-tolerant ligands such as XPhos or SPhos are recommended to mitigate catalyst deactivation by the ring nitrogen atoms.
How can I confirm the identity and purity of 6-Bromo-[1,2,4]triazolo[4,3-b]pyridazine upon receipt?
Upon receipt, compare the lot-specific Certificate of Analysis (CoA) provided by Aladdin Scientific against analytical data obtained in-house. LC-MS analysis is recommended to confirm the molecular ion and the characteristic bromine isotope pattern (⁷⁹Br/⁸¹Br ≈ 1:1). Reverse-phase HPLC provides quantitative purity assessment. ¹H NMR can be used to verify the aromatic proton pattern consistent with the triazolopyridazine ring system.
References
- Joule, J. A.; Mills, K. Heterocyclic Chemistry, 5th ed.; Wiley-Blackwell: Oxford, 2010. (General reference for fused azine and triazole chemistry.)
- Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chem. Rev. 1995, 95, 2457–2483. doi:10.1021/cr00039a007
- Hartwig, J. F. Palladium-Catalyzed Amination of Aryl Halides: Mechanism and Rational Catalyst Design. Synlett 1997, 329–340.
- Aladdin Scientific. Product Datasheet and Certificate of Analysis: 6-Bromo-[1,2,4]triazolo[4,3-b]pyridazine, SKU B189818. (Consult current lot CoA for physical data.)
Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.
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