5-Chloro-3-iodo-2-methylaniline: Handling & Use Protocol

5-Chloro-3-iodo-2-methylaniline is a difunctionalized aromatic amine building block bearing an ortho-methyl group and two distinct halogen substituents, making it a versatile intermediate for palladium-catalyzed cross-coupling reactions and medicinal chemistry synthesis.

Chemical Name

5-Chloro-3-iodo-2-methylaniline

SKU

C195445

Molecular Formula

C7H7ClIN

Molecular Weight

267.49 g/mol

Key Functional Groups

Primary amine (–NH2), aryl iodide (C–I), aryl chloride (C–Cl), methyl (–CH3)

Primary Application

Palladium- and copper-catalyzed cross-coupling reactions; pharmaceutical intermediate synthesis

Storage Condition

Store in a cool, dry, well-ventilated area away from light and moisture; recommended 2–8 °C under inert atmosphere

Supplier

Aladdin Scientific

Overview and Chemical Properties

5-Chloro-3-iodo-2-methylaniline (SKU: C195445, molecular formula C₇H₇ClIN, MW ≈ 267.49 g/mol) is a polyhalogenated aromatic primary amine. Its structure features an amino group at C-1, a methyl group at C-2 (ortho to the amine), a chlorine atom at C-5, and an iodine atom at C-3. This combination of substituents confers high synthetic utility: the aryl iodide is significantly more reactive than the aryl chloride in oxidative addition steps of palladium-catalyzed coupling cycles, enabling chemoselective sequential functionalization. The free primary amine further allows diazotization, acylation, sulfonylation, and condensation reactions, broadening the scope of accessible downstream targets. The ortho-methyl group introduces steric bias that can influence regio- and stereoselectivity in subsequent transformations.

Safety and Handling Requirements

As a halogenated aromatic amine, 5-Chloro-3-iodo-2-methylaniline should be treated as a potentially toxic irritant. The following precautions must be observed:

• Personal Protective Equipment (PPE): Wear chemical-resistant gloves (nitrile or neoprene), a laboratory coat, and safety goggles at all times when handling. Use a fume hood to avoid inhalation of dust or vapors.
• Skin and Eye Contact: In case of skin contact, wash thoroughly with soap and water for at least 15 minutes. For eye contact, irrigate immediately with copious water for at least 15 minutes and seek medical attention.
• Inhalation: Move to fresh air immediately if exposure occurs. Seek medical attention if symptoms persist.
• Ingestion: Do not induce vomiting; seek immediate medical attention.
• Waste Disposal: Dispose of waste in accordance with local, regional, and national regulations for halogenated aromatic amines. Do not pour down the drain.

Consult the Safety Data Sheet (SDS) for complete hazard information before use. All handling should be performed by trained personnel.

Storage and Stability Protocol

Proper storage is critical to maintaining the integrity and purity of 5-Chloro-3-iodo-2-methylaniline:

1. Temperature: Store at 2–8 °C in a refrigerator. For long-term archiving, storage at –20 °C under an inert atmosphere (nitrogen or argon) is recommended.
2. Light: Protect from light at all times. Store in amber glass vials or ensure containers are wrapped in foil, as halogenated anilines can be sensitive to photodegradation.
3. Moisture: Keep the container tightly sealed and store in a desiccated environment. Moisture can promote hydrolysis or oxidation of the amine functionality.
4. Atmosphere: For opened containers, back-fill with dry inert gas (N₂ or Ar) before resealing to minimize oxidative degradation.
5. Compatibility: Store away from strong oxidizers, strong acids, and strong bases. Keep away from heat sources and open flames.
6. Shelf Life: When stored under recommended conditions, the reagent is expected to remain stable; verify purity by TLC or HPLC before use in critical applications.

Synthetic Application Protocol: Chemoselective Suzuki–Miyaura Coupling at the C–I Bond

The following general protocol outlines chemoselective Suzuki–Miyaura cross-coupling at the aryl iodide position of 5-Chloro-3-iodo-2-methylaniline, preserving the aryl chloride for subsequent orthogonal functionalization. This protocol is a starting framework; researchers should optimize conditions for their specific substrate and scale.

Materials Required

• 5-Chloro-3-iodo-2-methylaniline (C195445, 1.0 equiv)
• Arylboronic acid or ester (1.1–1.5 equiv)
• Pd catalyst (e.g., Pd(PPh₃)₄ or Pd(dppf)Cl₂, 2–5 mol%)
• Base (e.g., K₂CO₃ or Cs₂CO₃, 2–3 equiv)
• Solvent: DMF/H₂O (4:1), dioxane/H₂O (3:1), or toluene/EtOH/H₂O
• Inert atmosphere: N₂ or Ar

Procedure

1. Charge a round-bottom flask with 5-Chloro-3-iodo-2-methylaniline (1.0 equiv) and the arylboronic acid or ester (1.1–1.5 equiv).
2. Add the Pd catalyst (2–5 mol%) and base (2–3 equiv).
3. Add the solvent system and degas thoroughly by sparging with N₂ or Ar for at least 15 minutes, or by freeze-pump-thaw cycles.
4. Seal the flask under inert atmosphere and heat to 80–100 °C with stirring.
5. Monitor reaction progress by TLC or LC-MS (typically 2–16 h depending on the boronic acid partner).
6. Upon completion, cool to room temperature, dilute with ethyl acetate, and wash with saturated NH₄Cl solution, then brine.
7. Dry the organic layer over anhydrous MgSO₄ or Na₂SO₄, filter, and concentrate under reduced pressure.
8. Purify the crude product by silica gel column chromatography.

Expected Chemoselectivity: Under these mild palladium conditions, oxidative addition preferentially occurs at the C–I bond due to its lower bond dissociation energy and greater reactivity relative to C–Cl. The aryl chloride is preserved for downstream Buchwald–Hartwig amination, additional Suzuki coupling, or other transformations.

Note: This is a general reference protocol. Optimize catalyst, base, solvent, temperature, and stoichiometry for each specific coupling partner. Consult primary literature for substrate-specific conditions.

Quality Verification Before Use

Before deploying 5-Chloro-3-iodo-2-methylaniline (C195445) in a critical synthesis, verify reagent quality using the following analytical approaches:

• Thin-Layer Chromatography (TLC): Run a TLC in an appropriate solvent system (e.g., hexane/ethyl acetate 4:1) and compare R_f value against a reference. Visualize under UV (254 nm) and with KMnO₄ stain or ninhydrin spray to confirm the presence of the primary amine.
• HPLC Purity Analysis: Use a reverse-phase C18 column with a UV detector at 254 nm to determine purity. Purity should meet the specification stated on the Aladdin Scientific Certificate of Analysis (CoA).
• NMR Verification: A ¹H NMR spectrum in CDCl₃ or DMSO-d₆ should show signals consistent with: two aromatic protons (singlets, due to 1,2,3,5-substitution pattern), one methyl singlet (~2.1 ppm), and a broad NH₂ signal. ¹³C NMR and ¹H–¹³C HMBC can confirm full connectivity.
• Mass Spectrometry: ESI-MS or GC-MS should show the molecular ion at m/z ≈ 267/269 (isotope pattern consistent with one Cl and one I).
• Certificate of Analysis (CoA): Always cross-reference with the CoA provided by Aladdin Scientific for lot-specific purity and analytical data.

Frequently asked questions

What makes the C–I bond more reactive than the C–Cl bond in palladium-catalyzed cross-coupling reactions?

The C–I bond has a lower bond dissociation energy compared to the C–Cl bond, which facilitates the oxidative addition step of the palladium catalytic cycle. This kinetic preference allows selective functionalization at the iodide site under mild Pd(0) catalyst conditions, leaving the aryl chloride intact for subsequent orthogonal transformations.

How should I protect the free amine group during cross-coupling reactions?

For many Pd-catalyzed couplings (e.g., Suzuki, Sonogashira), primary arylamines can participate without protection under optimized conditions. However, if the amine interferes with catalyst or substrate, consider temporary protection with Boc anhydride (Boc group) or acetylation (Ac group), followed by deprotection after coupling. The choice of protecting group depends on the downstream reaction sequence and conditions required.

What are the recommended storage conditions to prevent degradation of 5-Chloro-3-iodo-2-methylaniline?

Store 5-Chloro-3-iodo-2-methylaniline at 2–8 °C in a tightly sealed, amber glass container under an inert atmosphere (N2 or Ar) away from light and moisture. For long-term storage, –20 °C under inert gas is recommended. Verify purity by TLC or HPLC before use in sensitive applications, particularly after extended storage periods.

Can 5-Chloro-3-iodo-2-methylaniline be used in Buchwald–Hartwig amination reactions?

Yes, 5-Chloro-3-iodo-2-methylaniline can serve as an electrophilic coupling partner in Buchwald–Hartwig C–N coupling reactions, with the aryl iodide being the preferred site for C–N bond formation under standard Pd/ligand catalytic systems. The aryl chloride can subsequently undergo a second Buchwald–Hartwig amination using more active Pd catalysts and bulky phosphine ligands, enabling sequential diversification of both halide positions.

How do I confirm the identity and purity of the received batch before use?

Cross-reference the lot with the Certificate of Analysis (CoA) provided by Aladdin Scientific. Independently verify identity by 1H NMR (check for two aromatic singlets, methyl signal ~2.1 ppm, and NH2) and mass spectrometry (M+ ~267 Da). Assess purity by HPLC (reverse-phase C18, UV 254 nm). TLC with ninhydrin or KMnO4 visualization can provide a quick qualitative check.

References

1. Clayden, J.; Greeves, N.; Warren, S. Organic Chemistry, 2nd ed.; Oxford University Press: Oxford, 2012. (General reference for cross-coupling mechanisms and halogenated arene reactivity.)
2. Nicolaou, K. C.; Bulger, P. G.; Sarlah, D. Palladium-Catalyzed Cross-Coupling Reactions in Total Synthesis. Angew. Chem. Int. Ed. 2005, 44, 4442–4489. doi:10.1002/anie.200500368
3. Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chem. Rev. 1995, 95, 2457–2483. doi:10.1021/cr00039a007
4. Hartwig, J. F. Palladium-Catalyzed Amination of Aryl Halides: Mechanism and Rational Catalyst Design. Acc. Chem. Res. 1998, 31, 852–860. doi:10.1021/ar970282g

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