Product Description
5-Methoxy-2-mercaptobenzimidazole (CAS 37052-78-1) is a heterocyclic organic intermediate with a benzimidazole core substituted by a methoxy group at the 5-position and a thiol group at the 2-position. It is best known as the key starting material for the proton-pump inhibitors omeprazole and esomeprazole, and is also listed as Omeprazole Related Compound B / Esomeprazole EP Impurity A.
Key features:
High-purity pharma intermediate (≥99% typical) for PPI synthesis.
Benzimidazole-thiol core provides the sulfur and methoxy handles needed for omeprazole side-chain coupling.
Low residual metals and controlled impurity profile for GMP downstream use.
Off-white to pale yellow crystalline powder, easy to handle and dry.
Also used as an antioxidant, metal corrosion inhibitor and rubber vulcanization intermediate.
Available in kg to drum quantities with COA and HPLC data.
Product Parameters
| Item | Specification |
|---|---|
| Product Name | 5-Methoxy-2-mercaptobenzimidazole |
| CAS No. | 37052-78-1 |
| Synonyms | 2-Mercapto-5-methoxybenzimidazole; Omeprazole Related Compound B |
| Molecular Formula | C₈H₈N₂OS |
| Molecular Weight | 180.23 |
| Appearance | Off-white to pale yellow crystalline powder |
| Purity (HPLC) | ≥ 99.0% |
| Melting Point | ~ 250 – 255 °C (decomp.) |
| Loss on Drying | ≤ 0.5% |
| Residue on Ignition | ≤ 0.1% |
| Heavy Metals | ≤ 10 ppm |
| Storage | Tight container, cool, dry, away from oxidizers |
| Packaging | 25 kg fiber drum / double PE bag |
Product Application
5-Methoxy-2-mercaptobenzimidazole is a specialized heterocyclic intermediate whose main commercial demand comes from pharmaceutical synthesis, with secondary uses in materials protection.
In pharmaceuticals, it is the critical starting material for omeprazole and esomeprazole (proton-pump inhibitors used for gastric ulcer and gastro-esophageal reflux). The 2-thiol group is oxidized and coupled with the pyridine side chain to build the sulfoxide core of these drugs, while the 5-methoxy group defines the benzimidazole half. It is also used as a reference standard / related compound (Omeprazole Related Compound B, Esomeprazole EP Impurity A) in QC laboratories for assay and impurity identification.
In materials and industrial applications, the thiolated benzimidazole structure gives good metal-chelating and antioxidant properties. It is used as a copper corrosion inhibitor, a high-temperature antioxidant in lubricating oils and greases, and an intermediate in rubber and polymer stabilizer formulations. It also serves as a building block for other benzimidazole derivatives and agrochemicals.
