Studies On The Oxidation Of 2-methyl-quinoline To Quinoline-2-carboxylic Acid Catalyzed By Metalloporphyrins In The Presence Of Molecular Oxygen

Quinoline-2-carboxylic acid is a very important intermediate in organic synthesis. It is used to synthesize many organic matters such as quinoline-2-carbonitrile, 2-quinolinecarboxylic acid, methyl ester, and it can also be applied to the field of medicine to synthesize quinoline-polyamine derivatives which can protect injuried adrenal pheochromocytoma, and moreover it is also the important raw materials to synthesize the organotin compound which has an effect of anti-microbial and insecticide. Industrial demand for quinoline-2-carboxylic acid is growing, so its synthesis method has been received attention widely.Currently, the synthesis process of quinoline 2-carboxylic acid mainly has some problems of excessive residual reaction materials and intermediate products, and it seriously affects the yield of the product and increases the difficulty of separation and purification after the reaction; oxidant used in the reaction is expensive, and it leads to the environmental pollution in the process of recovery; reaction is required to carry out at high temperature and pressure, so energy consumption is increasing. Metall porphyrins, as a model catalyst cytochrome P-450, because of its specific structure, unique physical and chemical properties, high catalytic activity and environmental friendliness, can activate molecular oxygen at mild reation condition, so the above problems can be avoided. Therefore, the novel green synthesis method of 2-methyl-quinoline to quinoline-2-carboxylic acid catalyzed by metalloporphyrins under mild conditions with molecular oxygen is reported.This paper reports a process of catalysis and oxidation of 2-methyl-quinoline with different types of metalloporphyrins as biomimetic catalyst under basic conditions, and then optimizies the reaction conditions(reaction temperature, reaction time, alkali concentration, oxygen pressure, amount of metalporphyrins and the solvent type and ratio). The higher yield and selectivity of quinoline-2-carboxylic acid are achieved ultimately. The results are as follows:(1) For this reaction system, the paper studies the influence of all kinds of metalloporphyrins on the reaction of synthesis of 2-methyl-quinoline to quinoline-2-carboxylic acid. The results show that the metallporphyrin catalysts have good catalytic activity, and eventually T(p-OCH3) PPCoCl is selected as the optimal catalyst and the optimum catalyst concentration is 4.0 × 10-5 mol / L.(2) The effects of various process parameters of the reaction are systematically studied. The results show that the reaction temperature, oxygen pressure, reaction time, amount of alkali, the concentration of the raw material, the kind and ratio of solvent and other factors have a significant influence on the reaction. By performing optimization condition experiment, the optimum reaction conditions were obtained, namely reaction temperature 120 ℃,oxygen pressure 1.5 MPa, reaction time 8 h, concentration of NaOH 1.6 mol/L, concentration of 2-methyl-quinoline 0.125 mol/L, ethanol as solvent, and conversion rate of 2-methyl-quinoline reaches 40.8%, and the selectivity and the yield of quinoline-2-carboxylic acid reaches 24.5% and 10.0% respectively under the optimal conditions.