4-Methoxybenzo[d]oxazole-2(3H)-thione

4-Methoxybenzo[D]oxazole-2(3H)-thione can be used as a pharmaceutical intermediate to synthesize other compounds with certain activities, but its applications are currently rarely reported. The analogue of 4-methoxybenzo[D]oxazole-2(3H)-thione [5-methoxybenzo[d]oxazole-2(3H)-thione] is a key intermediate impurity of omeprazole, a first-generation benzimidazole proton pump inhibitor developed by AstraZen-eca in Sweden, primarily used to treat peptic ulcers and reflux gastritis. According to the European Pharmacopoeia EP8.0, there are nine known impurities of omeprazole (A-I, Chart 1): Impurity A is the key intermediate 5-methoxy-1H-benzo[d]imidazol-2-thiol, and impurities B-I are process impurities and degradation impurities of omeprazole.