6-Chloro-4-methoxy-1H-indole: Handling & Use Protocol

6-Chloro-4-methoxy-1H-indole is a halogenated, methoxy-substituted indole building block widely employed in heterocyclic synthesis and medicinal chemistry research as a versatile electrophilic and nucleophilic reaction partner.

Chemical Name

6-Chloro-4-methoxy-1H-indole

SKU

C189921

Molecular Formula

C₉H₈ClNO

Molecular Weight

181.62 g/mol

Key Functional Groups

Indole NH, C-6 chloro substituent, C-4 methoxy substituent

Recommended Storage

Store in a cool, dry, well-ventilated place away from light; seal tightly after use

Typical Applications

Heterocyclic synthesis, pharmaceutical intermediate, cross-coupling reactions

Materials and Safety Precautions

Before beginning any work with 6-Chloro-4-methoxy-1H-indole (SKU C189921), gather the following materials and observe all applicable safety precautions:

• Personal Protective Equipment (PPE): Wear a laboratory coat, chemical-resistant gloves (nitrile recommended), and safety goggles at all times when handling this compound.
• Ventilation: All weighing, dissolution, and reaction steps must be performed inside a certified chemical fume hood to minimise inhalation exposure to fine particulates or vapours.
• Materials required: Analytical balance (0.1 mg readability), amber glass vials or Schlenk flasks, appropriate anhydrous solvents (e.g., DMSO, DMF, THF, or dichloromethane), inert gas supply (N₂ or Ar) if moisture-sensitive conditions are required, and standard volumetric glassware.
• Waste disposal: Collect all waste containing this compound in a labelled halogenated organic waste container and dispose of according to your institution's chemical waste regulations.
• SDS review: Consult the Safety Data Sheet for C189921 before first use. Pay particular attention to first-aid measures and spill procedures.

Stock Solution Preparation

Follow these steps to prepare a stock solution of 6-Chloro-4-methoxy-1H-indole for use in downstream assays or reactions:

1. Determine target concentration: Calculate the mass of compound required based on your desired stock concentration (e.g., 10 mM or 100 mM) and final volume, using the molecular weight of 181.62 g/mol.
2. Weigh accurately: Tare a clean, dry amber vial on the analytical balance. Transfer the required mass of 6-Chloro-4-methoxy-1H-indole using a clean stainless-steel spatula. Re-seal the original container immediately to prevent moisture uptake.
3. Select solvent: This compound is expected to dissolve in common organic solvents such as DMSO, DMF, THF, and dichloromethane. For biological assays, DMSO stock solutions (≤0.1% v/v final DMSO in assay) are commonly employed. Verify solubility empirically for your specific application.
4. Dissolve: Add the appropriate volume of solvent to the vial. Mix gently by vortexing or swirling. If the compound does not dissolve readily, gentle warming (≤40 °C) in a water bath may assist dissolution; avoid prolonged heating.
5. Filter if necessary: Pass the solution through a 0.22 µm PTFE syringe filter if a particle-free solution is required.
6. Label and store: Label the vial with compound name, SKU (C189921), concentration, solvent, preparation date, and your initials. Store stock solutions at −20 °C under inert atmosphere if not used immediately, and protect from light.

Note: Specific solubility data for this compound are not provided in the current source material. Users should verify solubility experimentally and consult the product specification sheet.

Synthetic Application Guidance

6-Chloro-4-methoxy-1H-indole is a difunctionalised indole scaffold offering multiple sites for chemical elaboration:

• C-3 electrophilic substitution: Like other 1H-indoles, this compound is activated at the C-3 position toward electrophilic attack. Standard electrophilic reactions (e.g., Mannich reactions, Pictet–Spengler cyclisations, acylation, and alkylation at C-3) can be explored, though the C-6 chloro and C-4 methoxy substituents will modulate reactivity relative to unsubstituted indole.
• Cross-coupling via C-6 chloro group: The aryl C–Cl bond at C-6 is amenable to transition-metal-catalysed cross-coupling reactions, including Suzuki–Miyaura, Buchwald–Hartwig, and Negishi couplings, enabling introduction of diverse aryl, heteroaryl, or amino substituents at that position.
• N-Functionalisation: The indole NH can be protected or alkylated using standard procedures (e.g., Boc protection, alkylation with NaH/alkyl halide) prior to further elaboration of other positions.
• C-4 methoxy group utility: The methoxy group at C-4 can be retained as a directing or electronic-modulating group, or converted to a free phenol under standard demethylation conditions (e.g., BBr₃ in DCM).

General reaction setup: Conduct reactions under inert atmosphere (N₂ or Ar) when moisture- or oxygen-sensitive reagents or catalysts are involved. Use dried solvents and degassed reaction mixtures as appropriate. Monitor reaction progress by TLC or HPLC.

Note: Specific reaction yields, conditions, and literature precedents for this exact compound are not available in the current source material. Researchers should consult primary literature for analogous indole chemistry and validate conditions empirically.

Quality Control and Analytical Characterisation

To confirm identity and purity of 6-Chloro-4-methoxy-1H-indole (C189921) upon receipt or after synthesis, the following analytical techniques are recommended:

• ¹H NMR: Record a proton NMR spectrum in a suitable deuterated solvent (e.g., CDCl₃ or DMSO-d₆). Key expected signals include the indole NH proton (broad singlet, typically 8–9 ppm), the C-2 vinyl proton, the C-3 vinyl proton, and aromatic protons at C-5 and C-7, as well as the methoxy singlet (approximately 3.8–3.9 ppm). Confirm the absence of unexpected impurity peaks.
• ¹³C NMR: Use ¹³C NMR to confirm the methoxy carbon (~55 ppm) and the aromatic/heteroaromatic carbon framework consistent with the assigned structure.
• HPLC purity: Determine purity by reversed-phase HPLC (C18 column, UV detection at 254 nm or 280 nm, acetonitrile/water gradient). A single major peak is expected for a pure sample.
• Mass spectrometry: Confirm molecular ion by ESI-MS or APCI-MS. Expected [M+H]⁺ at m/z 182.03 (monoisotopic, based on MW 181.62; note the characteristic chlorine isotope pattern at M and M+2 in approximately 3:1 ratio).
• Melting point: Determine melting point and compare with any reference value provided on the certificate of analysis (CoA). Flag deviations >2 °C for investigation.

Note: Reference spectral data for this specific compound are not available in the current source material. The analytical expectations described above are derived from general indole chemistry principles. Users should refer to the CoA supplied with SKU C189921 for vendor-confirmed purity and analytical data.

Troubleshooting Common Issues

The following table addresses common issues encountered when working with 6-Chloro-4-methoxy-1H-indole:

• Poor solubility: If the compound does not dissolve fully, try a more polar aprotic solvent (DMSO or DMF). Brief sonication or gentle warming (≤40 °C) may help. Avoid protic solvents if reactions require anhydrous conditions.
• Compound darkening on exposure to air/light: Indoles are susceptible to oxidation and photodegradation. Always store and handle under subdued light; use amber vials and inert atmosphere storage. If discolouration is observed, assess purity by HPLC before use.
• Low yield in cross-coupling: Ensure the catalyst loading, ligand, base, and temperature are optimised for aryl chloride substrates, which are generally less reactive than aryl bromides or iodides. Buchwald-type phosphine ligands (e.g., SPhos, XPhos) or Pd-PEPPSI-type pre-catalysts are often effective for aryl chlorides.
• Unwanted N-alkylation versus C-alkylation: Control selectivity by choice of base and conditions. N-alkylation is favoured under basic conditions with hard electrophiles; C-3 selectivity can be achieved under milder or Lewis-acid-mediated conditions.
• Incomplete reaction at C-3: Check that the electrophile is sufficiently reactive. Activating the electrophile or using a Lewis acid catalyst may improve conversion. Monitor by TLC.

Frequently asked questions

What solvents are recommended for dissolving 6-Chloro-4-methoxy-1H-indole?

Based on the general properties of halogenated methoxy-indoles, this compound is expected to dissolve in common polar aprotic organic solvents such as DMSO, DMF, THF, and dichloromethane. Solubility in aqueous media is expected to be low. Users should verify solubility empirically for their specific application and concentrations required.

How should 6-Chloro-4-methoxy-1H-indole (C189921) be stored to maintain stability?

Store the compound in a tightly sealed container in a cool, dry, well-ventilated location away from light and sources of heat or ignition. For long-term storage of stock solutions, −20 °C under an inert atmosphere is recommended. Always reseal the original container promptly after use to prevent moisture uptake and oxidation.

Can the C-6 chloro group of this indole be used in palladium-catalysed cross-coupling reactions?

Yes, the aryl C–Cl bond at C-6 is in principle amenable to palladium-catalysed cross-coupling reactions such as Suzuki–Miyaura, Buchwald–Hartwig amination, and Negishi coupling. Aryl chlorides typically require more active catalyst systems than aryl bromides; bulky phosphine ligands (e.g., SPhos, XPhos) or Pd-PEPPSI precatalysts are recommended starting points. Reaction conditions should be optimised and validated experimentally.

What is the molecular weight of 6-Chloro-4-methoxy-1H-indole and how do I calculate the amount needed?

The molecular weight of 6-Chloro-4-methoxy-1H-indole (C₉H₈ClNO) is 181.62 g/mol. To calculate the mass required for a given number of moles, use: mass (g) = moles (mol) × 181.62 g/mol. For example, to prepare 1 mmol, weigh out 0.18162 g (181.62 mg).

Is 6-Chloro-4-methoxy-1H-indole suitable for biological or cell-based assays?

This compound may serve as a synthetic intermediate or probe in biological research, but its suitability for any specific cell-based or biochemical assay must be established by the researcher. Key considerations include solubility in aqueous buffers, cytotoxicity, stability under assay conditions, and the final concentration of any co-solvent (e.g., DMSO ≤0.1% v/v is a common threshold). No biological activity data are available in the current source material; a review flag has been noted.

References

1. Aladdin Scientific. 6-Chloro-4-methoxy-1H-indole, SKU C189921, Product Specification Sheet. Aladdin Scientific.
2. Joule, J. A.; Mills, K. Heterocyclic Chemistry, 5th ed.; Wiley-Blackwell: Chichester, 2010. (General indole chemistry reference.)
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. Synlett 1997, 329–340.

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