The Oxidation Of 2-methylbenzothiazolethiol To Benzothiazole-2-carboxylic Acid Catalyzed By Metalloporphyrins

Benzothiazole-2-carboxylic acid is an important organic intermediate, which can be widely used for medicine, pesticide and optical material. On one hand, taking it as a parent, we can synthesize dipeptide protease inhibitor, which can effectively repress the activity of severe acute respiratory syndrome virus(SARS-Co V 3CLpro). On the other hand, it can be used for the synthesis of anticancer, anti-inflammatory drugs for treating neural cardiovascular disease. Furthermore, benzothiazole-2-carboxylic acid has a rigidly planar structure and possesses delocalized ? bonds, therefore, it can be used in the optical and fluorescencing materials.Based on the widely application of benzothiazole-2-carboxylic acid, it can be predicted that benzothiazole-2-carboxylic acid may have a great application value in the future. However, the synthesis methods for benzothiazole-2-carboxylic acid have some defects such as tedious steps, harsh reaction conditions and poor environmental performance, so it is significant to explore a new synthesis method for benzothiazole-2-carboxylic acid.As auxiliary blocks of monooxygenase cytochrome P-450, metalloporphyrins can effectively catalyze the oxidation of hydrocarbons. Metalloporphyrins have high catalytic activity and selectivity in the oxidation of hydrocarbons, and only trace amount of metalioporphyrins can realize the activation of molecular oxygen under mild conditions. Metalioporphyrins not only have high catalytic activity and selectivity, but also can overcome some defects in traditional industrial production. Therefore, in this paper, the metalloporphyrins-catalyzed synthesis of benzothiazole-2-carboxylic acid from 2-methylbenzothiazole using molecular oxygen as oxidant has been researched.In this work, we took different metalloporphyrins as catalysts and used molecular oxygen as oxygen source, green catalytic oxidation of 2-methylbenzothiazole to prepare benzothiazole-2-carboxylic acid. Influences of various factors on the catalytic reactions have been investigated and the optimum conditions has been obtained. It's mainly focused on the reaction temperature, reaction time, type and dosage of metalloporphyrin catalyst, oxygen pressure, alkali concentration and other factors on the reaction. Organic solvent system has been explored in the reaction, and alcohol was changed into the mixed system of alcohol/water, so that the reaction can be more environmental friendly. Based on experimental phenomena and results, it has been found that the reaction maybe the free radical reaction. Experimental results show that: 0.13 mol/L of 2-methylbenzothiazole, 1.64 mol/L of Na OH, 4.1×10-5 mol/L of T(p-OCH3)PPFe, 1.4 MPa of O2, 30 m L of alcohol, and 120 oC for 8 hours. The conversion of 2-methylbenzothiazole is 39.2%, the yield and selectivity are 23.2% and 59.1% respectively in this reaction condition.