Overview and Chemical Properties

4-Ethynylpyridin-2-amine (CAS not confirmed in source material; SKU E729946, Aladdin Scientific) is a low-molecular-weight heterocyclic compound with the molecular formula C₇H₆N₂ (MW ≈ 118.14 g/mol). Its structure consists of a pyridine ring substituted at the 2-position with an amino group (–NH₂) and at the 4-position with a terminal alkyne (–C≡CH).

The co-presence of these two reactive handles makes 4-Ethynylpyridin-2-amine particularly attractive as a bifunctional building block. The terminal alkyne participates readily in copper-catalyzed azide–alkyne cycloaddition (CuAAC) click reactions and Sonogashira palladium-catalyzed cross-coupling, while the aromatic amine enables acylation, sulfonylation, reductive amination, and condensation reactions. The pyridine nitrogen further expands utility as a ligand or hydrogen-bond acceptor in drug design.

Appearance: Typically a solid (exact color should be confirmed against Certificate of Analysis).

Purity: Confirm lot-specific purity on the Certificate of Analysis (CoA) supplied with each order.

Storage and Stability

Proper storage is essential to maintain the integrity of 4-Ethynylpyridin-2-amine over time. Follow these guidelines:

• Temperature: Store at 2–8 °C (refrigerator) or at room temperature as specified on the product label and CoA. Always confirm with the supplier specification sheet.
• Container: Keep the container tightly sealed under an inert atmosphere (nitrogen or argon) after first opening to minimise exposure to atmospheric moisture and oxygen, which can degrade terminal alkynes over time.
• Light: Protect from direct light exposure; store in amber vials or wrapped in aluminium foil if required.
• Humidity: Store away from moisture. Terminal alkynes and free amines can be sensitive to hydrolytic or oxidative conditions.
• Shelf Life: Refer to the expiry date on the product label. If the compound shows discoloration or changes in physical appearance, do not use and contact Aladdin Scientific.

Note: Specific stability data for this compound are not provided in current source material and should be confirmed with the manufacturer's technical documentation.

Stock Solution Preparation Protocol

The following is a general protocol for preparing a stock solution of 4-Ethynylpyridin-2-amine. Adjust volumes and concentrations to meet your specific experimental requirements.

Materials Required

• 4-Ethynylpyridin-2-amine (SKU E729946)
• Analytical balance (0.1 mg readability)
• Suitable solvent (see Solubility note below)
• Volumetric flask or calibrated microcentrifuge tubes
• Inert gas line (N₂ or Ar) — recommended
• Vortex mixer or sonicator

Solubility Note

4-Ethynylpyridin-2-amine is expected to be soluble in common polar organic solvents such as DMSO, DMF, methanol, and ethanol based on its structural features. Aqueous solubility may be limited; the free base form may show pH-dependent solubility due to the pyridine nitrogen (pKa not confirmed in source material). Always verify solubility empirically for your specific solvent system.

Procedure

1. Allow the sealed vial to equilibrate to room temperature before opening (approximately 15–30 minutes) to prevent condensation of moisture onto the compound.
2. Accurately weigh the required mass of 4-Ethynylpyridin-2-amine using an analytical balance. Record the exact mass.
3. Transfer the compound to a clean, dry vessel.
4. Add the appropriate volume of solvent to achieve the desired stock concentration (e.g., 10 mM or 100 mM). For example, to prepare 1 mL of a 10 mM solution: dissolve 1.18 mg in 1 mL DMSO.
5. Mix thoroughly using a vortex mixer or sonicator until fully dissolved. If the compound does not dissolve, gently warm the solution (do not exceed 37 °C) or try an alternative solvent.
6. Visually inspect for complete dissolution (clear solution).
7. Aliquot the stock solution into single-use volumes to avoid repeated freeze–thaw cycles.
8. Store aliquots at –20 °C (for DMSO solutions) or as appropriate for your solvent system. Label with compound name, concentration, solvent, date, and operator.

Disclaimer: The specific solubility values and recommended solvents have not been confirmed in the provided source material. The above guidance is based on general physicochemical principles for structurally similar compounds. Verify with the CoA and technical datasheet.

Applications in Research

4-Ethynylpyridin-2-amine serves as a versatile bifunctional building block across multiple research domains:

1. Click Chemistry (CuAAC)

The terminal alkyne group undergoes highly efficient copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) with organic azides to form 1,2,3-triazole linkages. This bioorthogonal ligation strategy is widely used in bioconjugation, activity-based protein profiling (ABPP), and the synthesis of triazole-containing drug candidates. The aminopyridine moiety further differentiates the resulting triazole products.

2. Sonogashira Cross-Coupling

Under palladium/copper catalysis, the terminal alkyne reacts with aryl or vinyl halides in Sonogashira cross-coupling reactions, enabling the construction of extended π-conjugated systems and complex heterocyclic architectures. This is valuable in the synthesis of fluorescent probes, materials chemistry, and medicinal chemistry lead optimization.

3. Medicinal Chemistry and Drug Discovery

The 2-aminopyridine scaffold is a privileged structure in medicinal chemistry, present in numerous kinase inhibitors and antiviral agents. The additional alkyne handle allows for rapid diversification via click chemistry or cross-coupling, enabling structure–activity relationship (SAR) exploration.

4. Coordination Chemistry and Ligand Design

Both the pyridine nitrogen and the amine group can coordinate to metal centers, making 4-Ethynylpyridin-2-amine useful in the design of metal–organic frameworks (MOFs), catalytic complexes, and luminescent metal complexes.

Note: Specific published applications of 4-Ethynylpyridin-2-amine were not identified in the provided source material. The applications described above are based on established reactivity of terminal alkynes and 2-aminopyridine scaffolds in the literature and should be verified with primary references.

Safety and Handling Precautions

As with all laboratory reagents, appropriate safety measures must be observed when handling 4-Ethynylpyridin-2-amine. Refer to the Safety Data Sheet (SDS) available from Aladdin Scientific for complete hazard information.

• Personal Protective Equipment (PPE): Wear appropriate gloves (nitrile recommended), laboratory coat, and safety glasses. Use a fume hood when weighing or handling the compound in powder form to avoid inhalation of dust.
• Skin and Eye Contact: Avoid skin and eye contact. In case of contact, wash immediately with copious water and seek medical advice if irritation persists.
• Inhalation: Avoid breathing dust or vapours. Work in a well-ventilated area or fume hood.
• Ingestion: Do not ingest. Wash hands thoroughly after handling.
• Disposal: Dispose of waste in accordance with local environmental regulations and institutional guidelines for chemical waste. Do not dispose of down the drain.
• First Aid: Consult the SDS for specific first-aid measures. In case of significant exposure, seek immediate medical attention.

Note: Specific toxicological and hazard classification data for 4-Ethynylpyridin-2-amine were not available in the provided source material. Always consult the current SDS before use.