2-Bromo-5-phenylthiophene: Handling, Storage & Use Protocol

2-Bromo-5-phenylthiophene is a versatile halogenated heterocyclic building block widely employed in transition-metal-catalyzed cross-coupling reactions and the construction of π-conjugated organic materials.

CAS Number

3480-10-2

Molecular Formula

C₁₀H₇BrS

Molecular Weight

239.13 g/mol

SKU

B152933

Appearance

Pale yellow to yellow liquid or low-melting solid

Key Application

Suzuki, Negishi, and Kumada cross-coupling reactions; OLED/organic semiconductor synthesis

Materials, Safety & Storage

2-Bromo-5-phenylthiophene (B152933) should be stored in a tightly sealed container under an inert atmosphere (nitrogen or argon) at 2–8 °C or as specified on the product label, away from moisture and light. Prolonged exposure to air may lead to slow degradation.

Personal Protective Equipment (PPE): Wear nitrile gloves, a laboratory coat, and safety glasses when handling this compound. Work in a well-ventilated fume hood to minimize inhalation of vapors.

Waste Disposal: Dispose of all waste in accordance with local environmental regulations for halogenated organic solvents and reagents.

Review flag: Exact melting/boiling point and flash point data should be verified against the current Safety Data Sheet (SDS) provided with SKU B152933.

Reaction Setup: Cross-Coupling Protocol

2-Bromo-5-phenylthiophene serves as an aryl bromide electrophile in palladium- and nickel-catalyzed cross-coupling reactions. The C–Br bond at the 2-position is selectively reactive, enabling functionalization while retaining the pendant phenyl group at the 5-position.

General Suzuki–Miyaura Coupling Procedure (illustrative):

1. Charge a dry, nitrogen-purged round-bottom flask with 2-Bromo-5-phenylthiophene (1.0 equiv), the desired arylboronic acid or ester (1.2–1.5 equiv), and a palladium catalyst (e.g., Pd(PPh₃)₄, 2–5 mol%).
2. Add an inorganic base (e.g., K₂CO₃ or Cs₂CO₃, 2.0–3.0 equiv) and the appropriate solvent system (e.g., toluene/ethanol/water or DMF/water, typically 4:1 v/v).
3. Seal the flask, purge thoroughly with nitrogen or argon, and heat the reaction mixture to 80–100 °C with stirring for 12–24 h, monitoring by TLC or HPLC.
4. Upon completion, cool to room temperature, dilute with ethyl acetate, wash with water and brine, dry over anhydrous MgSO₄, filter, and concentrate under reduced pressure.
5. Purify the crude product by column chromatography (silica gel, appropriate eluent).

Review flag: Specific catalyst loadings, temperatures, times, and solvent ratios should be optimized for each target substrate. These conditions are illustrative based on general literature practice for aryl bromides and are not sourced from a specific published paper for this exact compound.

Alternative Reactions & Applications

Beyond Suzuki coupling, 2-Bromo-5-phenylthiophene is a valuable intermediate for:

• Negishi Coupling: React with organozinc reagents under Pd or Ni catalysis to introduce alkyl, aryl, or vinyl groups.
• Kumada Coupling: Use with Grignard reagents and Ni or Pd catalysts for C–C bond formation.
• Lithiation/Metalation: Treat with n-BuLi at low temperature (–78 °C) after halogen–metal exchange to generate the 2-thienyllithium species, which can react with electrophiles (aldehydes, ketones, CO₂) for further functionalization.
• Stille Coupling: Couple with organostannanes for the synthesis of complex π-conjugated oligomers used in organic electronics, OLEDs, and organic photovoltaics.

The phenylthiophene scaffold is a common motif in hole-transport materials, organic field-effect transistors (OFETs), and dye-sensitized solar cells (DSSCs).

Review flag: Specific literature citations for each coupling type applied to this exact compound should be verified before publication.

Troubleshooting & Quality Control

Low Coupling Yield: Ensure complete exclusion of oxygen and moisture. Check catalyst quality and freshness. Increase base equivalents or switch base. Consider switching from Pd(PPh₃)₄ to more active pre-catalysts (e.g., Pd(dppf)Cl₂, XPhos-Pd-G3) for sterically hindered substrates.

Protodebromination Side Product: Minimize by reducing reaction temperature or using milder base. Ensure solvent system is anhydrous when required.

Product Purity Verification: Characterize the product and confirm starting material consumption by ¹H NMR and ¹³C NMR spectroscopy. GC-MS or HPLC-MS analysis is recommended for purity determination. The C–Br bond in the starting material is readily observable by GC-MS (molecular ion cluster with characteristic ⁷⁹Br/⁸¹Br isotope pattern, m/z ≈ 238/240).

Moisture Sensitivity: Boronic acids and organometallic partners may be moisture-sensitive. Freshly opened or dried reagents should be used where possible.

Frequently asked questions

What is the recommended storage condition for 2-Bromo-5-phenylthiophene (B152933)?

Store 2-Bromo-5-phenylthiophene in a tightly closed container under an inert atmosphere at 2–8 °C, protected from light and moisture. Always verify storage requirements against the current product label and SDS.

Which cross-coupling reactions are compatible with 2-Bromo-5-phenylthiophene?

2-Bromo-5-phenylthiophene is compatible with Suzuki–Miyaura, Negishi, Kumada, and Stille cross-coupling reactions, all proceeding through the reactive C–Br bond at the 2-position. It can also undergo halogen–lithium exchange with n-BuLi at –78 °C for nucleophilic functionalization.

How can I confirm the identity and purity of my 2-Bromo-5-phenylthiophene sample?

Identity can be confirmed by ¹H NMR (characteristic thiophene ring protons and monosubstituted phenyl signals) and GC-MS (molecular ion at m/z ≈ 238/240 with the diagnostic bromine isotope pattern). Purity is best assessed by GC or HPLC with a UV detector.

Is 2-Bromo-5-phenylthiophene air- and moisture-stable?

2-Bromo-5-phenylthiophene has moderate stability but can degrade slowly upon prolonged exposure to air and moisture. For best results, handle under an inert atmosphere and reseal immediately after use.

What solvents are suitable for reactions using 2-Bromo-5-phenylthiophene?

Common solvents include toluene, DMF, THF, dioxane, and mixed aqueous systems (e.g., toluene/ethanol/water) for Suzuki couplings. Solvent choice depends on the specific reaction type, catalyst, and base employed; always optimize conditions for your target transformation.

References

1. Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chem. Rev. 1995, 95, 2457–2483. doi:10.1021/cr00039a007
2. Negishi, E. Palladium- or Nickel-Catalyzed Cross Coupling. A New Selective Method for Carbon-Carbon Bond Formation. Acc. Chem. Res. 1982, 15, 340–348. doi:10.1021/ar00083a001
3. Fichou, D. Handbook of Oligo- and Polythiophenes; Wiley-VCH: Weinheim, 1999.

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