Quinoline/Isoquinoline

Introduction

Quinoline, also known as benzopyridine, is a compound in parallel with pyridine and benzene, and the molecular formula is C9H7N. Quinoline can also be regarded as a naphthaline-like nitrogen heterocyclic compound, that is, the nitrogen atom in the 1-position is replaced by the -CH group, so it is also known as azonaphthalene. The property of quinoline is similar to pyridine and naphthalene. The chemical synthesis of quinoline and its derivatives has attracted much attention from organic chemists and pharmaceutical chemists. In organic synthesis, there are theoretically three ways to form quinoline ring:

  1. Simultaneous formation of benzene ring and pyridine ring;
  2. Synthesis of benzene ring after pyridine ring;
  3. Pyridine ring was synthesized after the benzene ring was first formed. However, in actual synthesis, only the third approach is generally used, and the first and second approaches have few application examples.

The structure of isoquinoline is similar to that of quinoline and the position of nitrogen atom is different. There are seventeen kinds of Isoquinolines according to structures like simple isoquinolines, protoberbeines, bis-benzyl isoquinolines, phthalein isoquinolines, spiracyl-phenyl isoquinolines. Isoquinoline compounds have a wide range of biological activities including antibacterial, anti-tumor, analgesic, regulating immune function, anti-platelet aggregation, anti-arrhythmia, antihypertensive.

Applications

Pharmaceutical Chemistry:

A large amount of quinoline compounds including isquinoline are important pharmaceutical intermediates, and many new drugs containing quinoline rings have been developed in recent years. Quinoline was originally obtained by distillation of quinine, an antimalarial drug. In recent years, quinoline drugs emerge in endlessly, such as quinophan can be used as antipyretic and analgesic drugs. Dibuvacaine hydrochloride can be used as a local anesthetic. Dequalinium chloride can be used as an antibiotic. Oxyquinoline phthalyl sulfathiazole can be synthesized from quinoline ring and other heterocyclic rings.

Fluorescent Material:

Acid dye yellow 3, direct yellow 22, solvent yellow 33 and Palanil yellow 3G can be synthesized with quinoline and quinoline derivatives. Quinoline anthocyanins are still important photosensitive substances in color photography, and the composition of quinoline rings in different quantities can make the sensitive region of light from ultraviolet to infrared or any one of them.

Food Industry:

Niacin is obtained by oxidation of quinoline. Niacin is an important vitamin that can synthesize a variety of nicotinic acid drugs, such as niacin, cardiac stimulants, and so on. In addition to synthesizing a variety of drugs, it is also widely used as a food and feed additive.

Organic Synthesis:

Most antioxidants containing quinoline rings are 1, 2-dihydroquinoline derivatives. A variety of 1, 2-dihydroquinoline derivatives have long been produced and can be used as an antioxidant, anti-aging agent in the rubber processing industry.

References

  1. Lalit, Mohan, Nainwal, et al. Green recipes to quinoline: A review.[J]. European Journal of Medicinal Chemistry, 2018.
  2. Frédéric Louërat, Fort Y, Mamane V. Direct 1,4-difunctionalization of isoquinoline[J]. Tetrahedron Letters, 2009, 50(41):5716-5718.
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