5-Bromo-1-methyl-1,3-dihydro-2H-benzo[d]imidazol-2-one: Lab Protocol Guide

5-Bromo-1-methyl-1,3-dihydro-2H-benzo[d]imidazol-2-one is a brominated benzimidazolone building block widely employed in medicinal chemistry and heterocyclic synthesis as a versatile electrophilic or cross-coupling partner.

Chemical Name

5-Bromo-1-methyl-1,3-dihydro-2H-benzo[d]imidazol-2-one

CAS Number

Needs review — not specified in source material

Molecular Formula

C8H7BrN2O

Molecular Weight

227.06 g/mol

Appearance

Solid (exact form needs review)

Primary Application

Pharmaceutical intermediate and heterocyclic synthetic building block

Aladdin SKU

B590304

Safety and Handling Precautions

Before working with 5-Bromo-1-methyl-1,3-dihydro-2H-benzo[d]imidazol-2-one (Aladdin SKU: B590304), consult the current Safety Data Sheet (SDS) provided by Aladdin Scientific. As a brominated aromatic heterocycle, standard precautions for organic reagents apply:

• Wear appropriate personal protective equipment (PPE): nitrile gloves, safety glasses and a laboratory coat.
• Handle the compound in a well-ventilated fume hood to minimise inhalation of dust or vapours.
• Avoid contact with skin, eyes and mucous membranes. In the event of skin or eye contact, flush immediately with copious water and seek medical advice.
• Store in a cool, dry place, away from strong oxidisers and sources of ignition, in a tightly sealed container.
• Dispose of waste in accordance with local regulations governing halogenated organic waste streams.

Note: Specific GHS hazard classifications and first-aid measures should be verified against the official SDS prior to use.

Stock Solution Preparation

Preparing a high-quality stock solution ensures reproducible results in downstream reactions. Follow the steps below when dissolving 5-Bromo-1-methyl-1,3-dihydro-2H-benzo[d]imidazol-2-one:

1. Determine the required concentration and volume based on your experimental design before weighing.
2. Weigh accurately the required amount of compound on an analytical balance. Transfer to a clean, dry glass vial appropriate for the target volume.
3. Solvent selection: The compound is expected to show solubility in polar aprotic solvents such as DMSO, DMF and acetonitrile, consistent with its aromatic lactam structure. Solubility in aqueous media is anticipated to be limited; verify experimentally. (Exact solubility data not specified in source material — see review flags.)
4. Dissolution: Add the chosen solvent in small increments with gentle vortexing or sonication (room temperature, 1–5 min) until the solid is fully dissolved.
5. Final volume adjustment: Make up to the desired final volume and mix thoroughly.
6. Filtration (if needed): If any particulate matter remains, filter through a 0.22 µm PTFE syringe filter.
7. Storage of stock solution: Aliquot, label with compound name, concentration, date and solvent, and store according to SDS guidance. Avoid repeated freeze–thaw cycles.

Typical Synthetic Applications and Reaction Protocol

5-Bromo-1-methyl-1,3-dihydro-2H-benzo[d]imidazol-2-one serves as a valuable building block in several reaction classes. Its aryl C–Br bond makes it amenable to transition-metal-catalysed cross-coupling reactions, while the intact benzimidazolone core provides a pharmacophoric scaffold for drug discovery programmes.

Representative Palladium-Catalysed Cross-Coupling (General Procedure)

1. Charge a dry Schlenk flask or sealed vial with 5-Bromo-1-methyl-1,3-dihydro-2H-benzo[d]imidazol-2-one (1.0 equiv), the appropriate coupling partner (e.g., boronic acid for Suzuki–Miyaura, terminal alkyne for Sonogashira; 1.1–1.5 equiv), Pd catalyst (e.g., Pd(PPh3)4 or Pd(dppf)Cl2; 2–5 mol%), and base (e.g., K2CO3 or Cs2CO3; 2.0 equiv).
2. Add degassed solvent (e.g., DMF/H2O 9:1 for Suzuki, THF/Et3N for Sonogashira) and purge with N2 or Ar for 10 min.
3. Heat the reaction mixture at 80–100 °C with stirring for 12–24 h under inert atmosphere. Monitor by TLC or LC–MS.
4. Upon completion, cool to room temperature, dilute with ethyl acetate, wash with brine, dry over MgSO4, and concentrate under reduced pressure.
5. Purify the crude product by column chromatography (silica gel) or recrystallisation as appropriate.

Specific reaction conditions (temperature, solvent ratio, catalyst loading) should be optimised for each substrate combination. The above conditions are representative and require experimental validation.

Quality Control and Analytical Characterisation

Verify the identity and purity of 5-Bromo-1-methyl-1,3-dihydro-2H-benzo[d]imidazol-2-one (B590304) using the following techniques prior to use in sensitive applications:

• TLC: Run on silica gel plates with an appropriate solvent system (e.g., EtOAc/hexane) to check purity and confirm a single spot.
• HPLC: Reverse-phase HPLC (C18 column) with UV detection at 254 nm provides quantitative purity assessment. Target purity ≥ 97% for synthetic applications (verify against certificate of analysis).
• 1H NMR: Characteristic signals expected include the N-CH3 singlet (~3.3–3.5 ppm) and aromatic protons in the 6.9–7.5 ppm region consistent with the brominated benzimidazolone scaffold. The NH proton appears as a broad singlet. (Exact chemical shifts should be confirmed experimentally.)
• Mass Spectrometry (ESI-MS or EI-MS): The molecular ion cluster at m/z ~227/229 (1:1 pattern) is diagnostic for a mono-brominated compound with MW 227.06.
• Melting Point: Determination of melting point and comparison with literature values aids identity confirmation. (Literature value not specified in source material — needs review.)

Frequently asked questions

What solvents are recommended for dissolving 5-Bromo-1-methyl-1,3-dihydro-2H-benzo[d]imidazol-2-one?

Based on its aromatic lactam structure, this compound is expected to dissolve well in polar aprotic solvents such as DMSO, DMF and acetonitrile. Solubility in purely aqueous media is anticipated to be low. Exact solubility values are not specified in the source material and should be determined experimentally before preparing working solutions.

What cross-coupling reactions can be performed using 5-Bromo-1-methyl-1,3-dihydro-2H-benzo[d]imidazol-2-one as a starting material?

The aryl bromide functionality makes this compound suitable for palladium-catalysed cross-coupling reactions, including Suzuki–Miyaura (with boronic acids), Sonogashira (with terminal alkynes), Buchwald–Hartwig (amination) and Negishi couplings. The intact benzimidazolone NH can also participate in N-arylation or further functionalisation depending on reaction design. Specific conditions should be optimised empirically.

How should 5-Bromo-1-methyl-1,3-dihydro-2H-benzo[d]imidazol-2-one be stored to maintain stability?

Store the compound in a tightly sealed container in a cool, dry location, protected from moisture and light, and away from incompatible materials such as strong oxidisers. Refer to the Aladdin Scientific SDS for the specific recommended storage temperature and any additional stability information. Verify storage conditions on the product certificate of analysis.

What is the molecular weight and molecular formula of 5-Bromo-1-methyl-1,3-dihydro-2H-benzo[d]imidazol-2-one?

The molecular formula is C8H7BrN2O and the molecular weight is 227.06 g/mol. The presence of one bromine atom produces a characteristic 1:1 isotope pattern in the mass spectrum, which is useful for identity confirmation during analytical characterisation.

References

1. Aladdin Scientific Product Page: 5-Bromo-1-methyl-1,3-dihydro-2H-benzo[d]imidazol-2-one, SKU B590304.
2. General reference: Clayden, J.; Greeves, N.; Warren, S. Organic Chemistry, 2nd ed. Oxford University Press, 2012. (Benzimidazolone chemistry, cross-coupling methodology.)
3. Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chemical Reviews, 1995, 95(7), 2457–2483. doi:10.1021/cr00039a007

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