Chemical Identity and Structure

5-Bromo-4-methyl-thiophene-2-carboxylic acid (SKU: B638297) is a halogenated thiophene derivative bearing three key substituents on the five-membered sulfur-containing aromatic ring: a bromine atom at the 5-position, a methyl group at the 4-position, and a carboxylic acid group at the 2-position. Its molecular formula is C₆H₅BrO₂S, with a molecular weight of approximately 221.07 g/mol.

The thiophene core is an electron-rich aromatic heterocycle. The combination of an electron-withdrawing carboxylic acid group and an electron-donating methyl group, alongside a reactive C–Br bond, gives this compound a distinctive reactivity profile that makes it highly valuable in synthetic chemistry. The bromine substituent at the 5-position is particularly amenable to palladium-catalyzed cross-coupling reactions, nucleophilic substitution, and metal-halogen exchange, enabling diverse downstream functionalization.

Synthesis and Reactivity

The carboxylic acid functionality of 5-bromo-4-methyl-thiophene-2-carboxylic acid can be readily converted into a range of derivatives including acid chlorides, esters, amides, and anhydrides under standard conditions. This versatility makes it a practical point of divergence in multi-step synthetic routes.

The C–Br bond at the 5-position enables a broad array of transformations. Palladium-catalyzed reactions such as Suzuki–Miyaura, Negishi, and Stille cross-couplings allow introduction of aryl, vinyl, or alkyl groups, expanding molecular complexity. Additionally, lithium–halogen exchange at low temperature provides access to the corresponding organolithium species, which can react with a wide variety of electrophiles.

The methyl group at the 4-position can serve as a handle for further functionalization via benzylic oxidation or radical bromination, further expanding the utility of this scaffold. The overall reactivity profile enables rapid construction of complex thiophene-containing frameworks from this single starting material.

Applications in Medicinal and Materials Chemistry

Thiophene-containing carboxylic acids occupy an important niche as building blocks in the pharmaceutical and agrochemical industries. The thiophene ring is a bioisostere of the benzene ring and is present in numerous approved drugs and drug candidates, conferring favorable metabolic stability, lipophilicity, and binding affinity.

5-Bromo-4-methyl-thiophene-2-carboxylic acid serves as a precursor for the synthesis of more complex heterocyclic systems, including thienopyrimidines, thienopyridines, and fused bicyclic scaffolds relevant to kinase inhibitor and anti-infective research. The carboxylic acid group facilitates coupling to amines for amide bond formation, a central transformation in drug discovery.

Beyond pharmaceuticals, brominated thiophene carboxylic acids find use as monomers or precursors in the synthesis of conjugated polymers and organic semiconductors, relevant to organic electronics and photovoltaic research. The well-defined substitution pattern supports regioselective polymerization strategies.

Handling, Storage, and Safety Considerations

As with all halogenated organic acids, standard laboratory safety precautions should be observed when working with 5-bromo-4-methyl-thiophene-2-carboxylic acid. This includes the use of appropriate personal protective equipment such as gloves, safety glasses, and a laboratory coat. Handling should be performed in a well-ventilated area or fume hood to minimize inhalation exposure.

The compound should be stored in a cool, dry environment, away from incompatible materials such as strong bases and strong oxidizing agents. Containers should be kept tightly sealed when not in use to prevent moisture uptake and degradation. Consult the Safety Data Sheet (SDS) for complete hazard information, first-aid measures, and disposal guidance prior to use.

Researchers should verify specific purity, physical form, and storage conditions from the product documentation supplied with SKU B638297, as these specifications may vary by lot.