2-Chloro-5-methylpyridine-3-carbaldehyde: Handling & Use Protocol

2-Chloro-5-methylpyridine-3-carbaldehyde is a versatile heterocyclic aldehyde building block widely employed in medicinal chemistry and organic synthesis for constructing complex pyridine-containing scaffolds via condensation, reductive amination, and cross-coupling reactions.

Chemical Name

2-Chloro-5-methylpyridine-3-carbaldehyde

CAS Number

To be confirmed — see product datasheet (C188299)

Molecular Formula

C₇H₆ClNO

Molecular Weight

155.58 g/mol

Appearance

Solid (color to be confirmed per lot CoA)

Key Functional Groups

Aldehyde (–CHO), C–Cl bond, pyridine ring, methyl substituent

Primary Applications

Heterocyclic synthesis, reductive amination, Knoevenagel condensation, Suzuki cross-coupling at C2 chloro position

Storage Conditions

Cool, dry, dark conditions; store under inert atmosphere if opened; confirm exact conditions on CoA

Safety and Pre-Handling Precautions

Before working with 2-Chloro-5-methylpyridine-3-carbaldehyde (Aladdin SKU: C188299), review the Safety Data Sheet (SDS) supplied with the product. As an aldehyde-functionalized chloropyridine, this compound may be an irritant to skin, eyes, and the respiratory tract. The following personal protective equipment (PPE) is mandatory:

• Eye protection: Chemical splash goggles.
• Skin protection: Nitrile gloves (minimum); lab coat and closed-toe shoes.
• Respiratory protection: Work in a well-ventilated fume hood. If dust generation is anticipated, use an appropriate particulate respirator.

Aldehyde groups can undergo oxidation in air; the compound should be handled away from strong oxidising agents, bases, and moisture. Dispose of waste according to local chemical waste regulations. The exact hazard classification should be confirmed from the product SDS and lot Certificate of Analysis (CoA).

Storage and Stability

Proper storage of 2-Chloro-5-methylpyridine-3-carbaldehyde is critical to maintaining reagent integrity over time:

1. Temperature: Store at controlled room temperature (15–25 °C) or as specified on the product CoA. Refrigerated storage (2–8 °C) may be recommended for extended shelf life — confirm with the CoA.
2. Atmosphere: After opening, reseal the container under an inert gas (nitrogen or argon) to prevent oxidation of the aldehyde functionality and moisture uptake.
3. Light: Store in amber or opaque containers away from direct light to prevent photodegradation.
4. Moisture: Keep the container tightly closed and use a desiccant (e.g., molecular sieves or silica gel) if storing in humid environments.

Check the expiry date and lot-specific CoA for confirmed storage conditions and retest dates. If discoloration or solidification of a normally free-flowing solid is observed, assess purity by HPLC or NMR before use.

Solution Preparation and Solubility

2-Chloro-5-methylpyridine-3-carbaldehyde is expected to be soluble in common polar aprotic organic solvents based on its molecular structure. The following guidelines apply (exact solubility data should be confirmed experimentally or from the product datasheet):

• Recommended solvents: Dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dichloromethane (DCM), ethyl acetate, tetrahydrofuran (THF), acetonitrile.
• Aqueous solubility: Expected to be low; aqueous co-solvent systems (e.g., DMSO/water) may be required for biochemical assays.
• Stock solution preparation: Weigh the compound in a pre-dried, tared vessel. Dissolve in the minimum volume of solvent, then dilute to the target concentration. Vortex or sonicate gently if needed.
• Concentration verification: For critical applications, verify concentration by UV-Vis spectrophotometry or NMR.

Prepare solutions freshly where possible, as aldehyde functionality may be susceptible to slow oxidation or hydration (geminal diol formation) in aqueous environments over extended periods.

Key Synthetic Applications and Reaction Protocols

2-Chloro-5-methylpyridine-3-carbaldehyde is a bifunctional building block offering two distinct reactive handles: the electrophilic aldehyde (C3 position) and the nucleofugal chlorine at C2. This enables sequential or orthogonal synthetic transformations.

1. Reductive Amination

React the aldehyde with a primary or secondary amine in the presence of a reducing agent (e.g., sodium cyanoborohydride or sodium triacetoxyborohydride) in MeOH or DCE at room temperature or mild warming (0–40 °C). This provides N-substituted aminomethylpyridine products useful in fragment-based drug discovery.

2. Knoevenagel Condensation

Treat the aldehyde with active methylene compounds (e.g., malononitrile, ethyl cyanoacetate) in the presence of a base catalyst (e.g., piperidine or ammonium acetate) to yield conjugated alkene intermediates for further heterocycle formation.

3. Suzuki–Miyaura Cross-Coupling at C2

The C2 chloro substituent participates in palladium-catalyzed Suzuki–Miyaura coupling with aryl or heteroaryl boronic acids. Use Pd(PPh₃)₄ or Pd(dppf)Cl₂ as catalyst, K₂CO₃ or Cs₂CO₃ as base, in dioxane/water (4:1) at 80–100 °C. The aldehyde at C3 may require protection (e.g., acetal formation) or can be tolerated depending on the coupling conditions.

4. Imine (Schiff Base) Formation

Condensation with primary amines under anhydrous or azeotropic dehydration conditions yields imines that serve as ligands or intermediates for further cyclisation.

Note: All reaction conditions cited above are general textbook-level guidelines. Optimisation for specific substrates is the responsibility of the end user. Yields and selectivities are substrate-dependent and should be validated experimentally.

Quality Control and Analytical Characterisation

Before use in sensitive applications, users are encouraged to verify the identity and purity of 2-Chloro-5-methylpyridine-3-carbaldehyde using the following analytical methods:

• ¹H NMR (400 MHz, CDCl₃ or DMSO-d₆): Expect signals for the aldehyde proton (~δ 10.1–10.4 ppm), aromatic/pyridyl ring protons, and the methyl group (~δ 2.3–2.5 ppm). Exact chemical shifts should be confirmed against literature or the product CoA.
• HPLC (reverse-phase C18, UV detection at 254 nm): Purity ≥95% is typically acceptable for synthetic applications; confirm specification on CoA.
• Mass Spectrometry (ESI or EI): The molecular ion cluster should show the characteristic ³⁵Cl/³⁷Cl isotope pattern (approximately 3:1 ratio) consistent with a monochloro compound at m/z corresponding to MW 155.58.
• Melting Point: Confirm against the value stated on the product CoA; significant deviation may indicate degradation or impurity.

All lot-specific analytical data (NMR, HPLC purity, MS) are provided in the Certificate of Analysis available from Aladdin Scientific upon request or via the product page for C188299.

Frequently asked questions

What solvents are recommended for dissolving 2-Chloro-5-methylpyridine-3-carbaldehyde?

Based on its structure, this compound is expected to dissolve readily in polar aprotic solvents such as DMSO, DMF, DCM, THF, and acetonitrile. Aqueous solubility is expected to be low. Users should confirm solubility experimentally for their specific application and concentration requirements.

Can the C2 chloro group and the C3 aldehyde be reacted selectively in the same molecule?

Yes. The two functional groups offer orthogonal reactivity: the aldehyde at C3 is amenable to condensation and reductive amination under mild, metal-free conditions, while the C2 chloro group undergoes palladium-catalyzed cross-coupling under distinct conditions (elevated temperature, Pd catalyst, base). Careful selection of reaction conditions allows sequential functionalisation. Protection of the aldehyde (e.g., as a dimethyl acetal) prior to metal-catalyzed steps may be advisable in some synthetic routes.

How should I store 2-Chloro-5-methylpyridine-3-carbaldehyde to maximise shelf life?

Store the compound in a cool, dry, dark location in a tightly sealed container. After opening, purge the headspace with inert gas (nitrogen or argon) before resealing. Avoid exposure to moisture, light, and oxidising agents. Confirm exact storage temperature and shelf-life recommendations on the lot-specific Certificate of Analysis provided by Aladdin Scientific.

What is the purity specification for Aladdin Scientific C188299?

Purity specifications are provided on the lot-specific Certificate of Analysis (CoA) for C188299. Users should request or download the CoA from the Aladdin Scientific product page to confirm the exact purity value and analytical data for their specific lot before use.

Is 2-Chloro-5-methylpyridine-3-carbaldehyde suitable for use as a pharmaceutical intermediate?

This compound is supplied by Aladdin Scientific as a research reagent for laboratory use. It is widely used in medicinal chemistry research as a heterocyclic building block for synthesising drug candidates and pharmaceutical intermediates. For GMP or regulated pharmaceutical manufacturing applications, users must independently qualify the material according to their regulatory requirements, as Aladdin Scientific supplies this product for research purposes only.

References

1. March, J.; Smith, M. B. March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 7th ed.; Wiley: Hoboken, NJ, 2013. (General reference for aldehyde reactions including reductive amination and condensation.)
2. Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chem. Rev. 1995, 95, 2457–2483. (Foundational reference for Suzuki–Miyaura coupling applicable to chloropyridine substrates.) doi:10.1021/cr00039a007
3. Aladdin Scientific. Certificate of Analysis, Product C188299: 2-Chloro-5-methylpyridine-3-carbaldehyde. (Lot-specific analytical data available on request from Aladdin Scientific or via the product web page.)

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.