The Synthetic Routes of 6-Hydroxy-2(1H)-quinolinone

6-Hydroxy-2(1H)-quinolinone is an important organic compound with a wide range of applications in the pharmaceutical, agrochemical, and chemical industries.
It is used as an intermediate in the production of various drugs, such as antimalarials and antibiotics, and as a herbicide and insecticide.
The synthetic routes for 6-hydroxy-2(1H)-quinolinone can be broadly classified into two categories, namely "classical methods" and "modern methods".

Classical Methods:
The classical methods for the synthesis of 6-hydroxy-2(1H)-quinolinone include the Mannich reaction, the Gulland-Common reaction, and the Pictet-Spengler reaction.

The Mannich reaction involves the condensation of an aldehyde or ketone with formaldehyde and ammonia in the presence of a base.
The reaction product is then hydrolyzed to yield 6-hydroxy-2(1H)-quinolinone.
This method is relatively simple and inexpensive, but it is limited by the availability of the starting materials and the low yield of the product.

The Gulland-Common reaction involves the condensation of 2-chloro-6-nitro-1,4-benzoquinone with sodium hydroxide in the presence of a solvent.
The reaction product is then hydrolyzed to yield 6-hydroxy-2(1H)-quinolinone.
This method is more efficient than the Mannich reaction, but it requires the use of hazardous chemicals and is more expensive.

The Pictet-Spengler reaction involves the condensation of a phenol with formaldehyde and an aqueous solution of sodium hydroxide.
The reaction product is then hydrolyzed to yield 6-hydroxy-2(1H)-quinolinone.
This method is more efficient than the Mannich reaction and does not require the use of hazardous chemicals, but it is more expensive.

Modern Methods:
The modern methods for the synthesis of 6-hydroxy-2(1H)-quinolinone include the electrochemical reduction of 2,3-dimethyl-1,4-benzoquinone, the hydrothermal synthesis of 6-hydroxy-2(1H)-quinolinone using micellar medium, the microwave-assisted synthesis of 6-hydroxy-2(1H)-quinolinone, and the one-pot synthesis of 6-hydroxy-2(1H)-quinolinone and other quinolinones.

The electrochemical reduction of 2,3-dimethyl-1,4-benzoquinone involves the reduction of 2,3-dimethyl-1,4-benzoquinone using electricity in the presence of an electrolyte.
The reaction product is then purified to yield 6-hydroxy-2(1H)-quinolinone.
This method is relatively simple and environmentally friendly, but it requires the use of specialized equipment and is limited by the availability of the starting material.

The hydrothermal synthesis of 6-hydroxy-2(1H)-quinolinone using micellar medium involves the reaction of 2-chloro-6-nitro-1,4-benzoquinone with a phenol in the presence of a micellar medium, such as catalysts or surfactants.
The reaction product is then hydrolyzed to yield 6-hydroxy-2(1H)-quinolinone.
This method is more efficient than the classical methods and is environmentally friendly, but it requires the use of specialized equipment and is more expensive.

The microwave-assisted synthesis of 6-hydroxy-2(1H)-quinolinone involves the reaction of 2-chloro-