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Medicinal chemistry and drug research require diverse chemical components to meet strict requirements not only in terms of physical and chemical properties but also in terms of chemical reactivity.
The chemists use the 'build–couple–pair' strategy of organic synthesis, which entails preparing molecular building blocks that contain several chemical groups.
The chemical building block (CBB) is a molecule which can be converted to various secondary chemicals and intermediates, and, in turn, into a broad range of different downstream uses.
Quinaldine, which is also called 2-methylquinoline, is a colorless liquid at room temperature and pressure, belonging to quinoline compounds. The freezing point of quinaldine is -2 ~ -1 oC and the boiling point is 247 oC. It is weakly alkaline and can form salt with inorganic acid. Quinaldine is slightly soluble in water, soluble in ethanol, acetone, ether, chloroform and other most organic solvent. Quinaldine is an important chemical raw material, widely used in the film and television industry, lubricants and antioxidants, also used in pharmaceutical production, dye. Meanwhile, it is the raw materials of semi-trace analysis reagent for zinc, copper, cadmium, uranium.
Quinaldine mainly exists in the washing oil fraction of coal tar. Currently, quinaldine is mainly extracted from coal tar in industrial production. Quinaldine can also be prepared by synthetic method. First, the neutral oil and other impurities are removed from coal tar. And then NaOH solution is added for decomposition, after filtration separation, dehydration of crude quinoline and its homologue in rectifying column distillation, for 243-247oC fraction, quinaldine can be obtained. The main impurities in the quinaldine mixture are quinoline, isoquinoline and 8-methyl quinoline.
Quinaldine derivatives are often used as intermediates in fine chemical industry and play an essential role in medicine field. For example, a primaquine derivative was synthesized by researchers for the treatment of malaria from 8-halogenated quinaldine. Deraeve et al. synthesized a polyquinoline metal complex for the treatment of neurological disorders. Jimin et al. reported a partial dopamine D3 receptor agonist from quinaldine. The synthesis of an antiviral HIV reverse transcriptase inhibitor Lavendamycin has also received considerable attention.
Quinaldine is used as transport live fish anesthetic, which is common in our country, especially in transportation of ornamental fish. At present, quinaldine cannot be directly applied in transportation of edible fish. The range of suitable concentration of anesthetic quinaldine is from 20 to 100 ppm. Quinaldines greatly improve the survival rate of the fish. The nylon bag filling oxygen are adopted during the transportation and with 2-methyl quinoline anesthetic, the fish are less likely to prick the nylon bag.
Quinaldine is able to produce quinoline yellow that is yellow food colorant. Synthetic pigment is mainly made from coal tar. Because of its low cost and bright color, it is widely used by manufacturers. Quinoline yellow is one of 22 approved synthetic pigments for food in China.