5-Bromo-3-methoxypyrazin-2(1H)-one: Handling & Use Protocol

5-Bromo-3-methoxypyrazin-2(1H)-one is a brominated, methoxy-substituted pyrazinone heterocycle widely employed as a versatile synthetic building block in medicinal chemistry and drug-discovery research.

CAS / SKU

SKU B195634 (CAS to be confirmed by Aladdin certificate of analysis)

Molecular Formula

C5H5BrN2O2

Molecular Weight

205.01 g/mol (to be verified against CoA)

Appearance

Solid (color to be confirmed by CoA)

Key Functional Groups

Lactam N–H, C-5 bromo substituent, C-3 methoxy group

Primary Application

Synthetic building block for cross-coupling and nucleophilic substitution reactions

Storage

Store at 2–8 °C under inert atmosphere; keep away from light and moisture (verify with SDS)

Safety and Pre-Handling Considerations

Before handling 5-Bromo-3-methoxypyrazin-2(1H)-one (Aladdin SKU B195634), consult the current Safety Data Sheet (SDS) available from Aladdin Scientific. Standard laboratory precautions apply:

• Wear appropriate personal protective equipment (PPE): lab coat, chemical-resistant gloves (e.g., nitrile), and safety glasses.
• Work in a well-ventilated fume hood to avoid inhalation of fine powder or solvent vapours.
• The compound contains an aryl bromide moiety; treat as a potential irritant until full toxicological data are reviewed from the SDS.
• Dispose of all waste in accordance with local regulations for halogenated organic compounds.

Note: Specific hazard classifications should be confirmed from the official Aladdin SDS for B195634 prior to use.

Storage and Stability

Proper storage of 5-Bromo-3-methoxypyrazin-2(1H)-one is critical to maintaining reagent integrity:

• Temperature: Store at 2–8 °C. For long-term storage, confirm optimal conditions with the Aladdin CoA.
• Atmosphere: Keep under an inert atmosphere (nitrogen or argon) to prevent potential oxidation or hydrolysis of the lactam moiety.
• Light: Protect from direct light exposure; use amber vials or foil wrapping when practical.
• Moisture: The compound should be stored in a desiccated environment. Silica gel desiccant in the storage container is recommended.
• Container: Re-seal tightly after each use. Equilibrate cold samples to room temperature before opening to minimise condensation on the solid.

Review the CoA and SDS for verified stability data; specific shelf-life information is subject to confirmation.

Solubility and Solution Preparation

5-Bromo-3-methoxypyrazin-2(1H)-one is a solid heterocyclic compound. The following guidelines assist in solution preparation for synthetic or analytical use:

1. Solvent Selection: Polar aprotic solvents such as dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and tetrahydrofuran (THF) are generally suitable for pyrazinone derivatives. Solubility in aqueous media is expected to be limited due to the lipophilic methoxy and bromo substituents. Actual solubility should be determined experimentally.
2. Stock Solution Preparation:
   • Weigh the required amount of compound accurately using an analytical balance.
   • Transfer to a clean, dry vial and add a measured volume of chosen solvent.
   • Vortex or sonicate at room temperature until complete dissolution is confirmed visually.
   • Filter through a 0.2 µm PTFE syringe filter if a particulate-free solution is required.
3. Concentration Verification: For critical applications, verify stock concentration by UV-Vis spectrophotometry or HPLC using a validated method.
4. Working Solutions: Dilute stock solution with the appropriate buffer or co-solvent immediately before use. Avoid freeze-thaw cycles where possible.

Solubility values are not confirmed in the source material and should be determined empirically or sourced from validated references.

Applications in Synthesis

5-Bromo-3-methoxypyrazin-2(1H)-one is a multifunctional heterocyclic building block exploitable through several chemical transformations:

• Palladium-Catalysed Cross-Coupling Reactions: The C-5 aryl bromide is a suitable electrophilic partner in Suzuki–Miyaura, Negishi, Stille, and Buchwald–Hartwig coupling reactions, enabling introduction of aryl, vinyl, or amino substituents at the 5-position of the pyrazinone ring.
• Nucleophilic Substitution at C-3: The methoxy group at C-3 can function as a leaving group under appropriate nucleophilic conditions, allowing exchange with amines, thiols, or other heteroatom nucleophiles to generate 3-substituted pyrazinone analogues.
• N-Alkylation or N-Acylation: The lactam N–H can be selectively alkylated or acylated to modulate physicochemical properties and biological activity profiles of resulting derivatives.
• Medicinal Chemistry: Pyrazinone scaffolds are present in bioactive compounds targeting various biological pathways. This building block may serve as a core for structure–activity relationship (SAR) studies.

Specific reaction conditions, yields, and literature precedents are not confirmed in the provided source material. Researchers should consult primary literature and validate conditions experimentally.

Quality Control and Analytical Characterisation

To confirm identity and purity of 5-Bromo-3-methoxypyrazin-2(1H)-one (B195634) prior to use, the following analytical techniques are recommended:

• ¹H and ¹³C NMR Spectroscopy: Confirm the presence and integration of the methoxy singlet (~δ 3.9 ppm), the aromatic/vinyl proton of the pyrazinone ring, and the lactam N–H. ¹³C NMR should display signals consistent with the five ring and substituent carbons.
• Mass Spectrometry (MS): Electrospray ionisation (ESI-MS) or APCI-MS should show the expected molecular ion with characteristic bromine isotope pattern (M and M+2 in approximately 1:1 ratio).
• HPLC Purity: Reverse-phase HPLC (C18 column, UV detection at 254 nm or wavelength of maximum absorbance) should confirm purity ≥95% or as stated on the CoA.
• Melting Point: Determination of melting point and comparison with CoA values provides a rapid identity check.
• IR Spectroscopy: Characteristic lactam C=O stretch (~1660–1680 cm⁻¹) and C–O stretch of the methoxy group should be observable.

Reference spectral values are estimated from textbook-level knowledge of analogous pyrazinone structures; actual values must be confirmed against Aladdin CoA and/or primary literature.

Frequently asked questions

What solvents are recommended for dissolving 5-Bromo-3-methoxypyrazin-2(1H)-one?

Polar aprotic solvents such as DMSO, DMF, and THF are generally suitable for pyrazinone derivatives of this type. Aqueous solubility is expected to be limited due to the lipophilic bromo and methoxy substituents. Solubility should be confirmed experimentally for each specific application.

What chemical reactions can be performed using the C-5 bromo substituent of this compound?

The C-5 aryl bromide is an electrophilic handle well-suited for palladium-catalysed cross-coupling reactions, including Suzuki–Miyaura (with arylboronic acids), Negishi, Stille, and Buchwald–Hartwig amination reactions. These transformations enable introduction of diverse substituents at the 5-position of the pyrazinone ring.

How should 5-Bromo-3-methoxypyrazin-2(1H)-one be stored to maintain stability?

The compound should be stored at 2–8 °C under an inert atmosphere (nitrogen or argon), protected from light and moisture. After use, containers should be re-sealed tightly and cold samples equilibrated to room temperature before opening to prevent moisture condensation. Always confirm storage conditions with the Aladdin SDS and CoA for B195634.

How can I verify the purity and identity of 5-Bromo-3-methoxypyrazin-2(1H)-one upon receipt?

Identity and purity can be confirmed by a combination of ¹H/¹³C NMR spectroscopy, reverse-phase HPLC, and mass spectrometry with characteristic bromine isotope pattern. The Aladdin Certificate of Analysis (CoA) for SKU B195634 provides reference purity data and should be the primary verification document.

Can the methoxy group at C-3 be replaced by other nucleophiles?

Yes, the C-3 methoxy group in 3-methoxypyrazin-2(1H)-one systems can act as a leaving group under suitable nucleophilic substitution conditions, allowing introduction of amines, thiols, or other heteroatom nucleophiles. Specific reaction conditions should be optimised experimentally and validated against published procedures for analogous pyrazinone substrates.

References

1. Aladdin Scientific. Product Certificate of Analysis: 5-Bromo-3-methoxypyrazin-2(1H)-one, SKU B195634. Aladdin Scientific; [date to be confirmed].
2. Aladdin Scientific. Safety Data Sheet: 5-Bromo-3-methoxypyrazin-2(1H)-one, SKU B195634. Aladdin Scientific; [date to be confirmed].
3. Clayden J, Greeves N, Warren S. Organic Chemistry. 2nd ed. Oxford University Press; 2012. [General reference for cross-coupling reactions and heterocyclic chemistry.]

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