The Synthetic Routes of 7,8-DIHYDROISOQUINOLIN-5(6H)-ONE

The synthesis of 7,8-dihydroisoquino(2,1-b)quinolin-5(6H)-one, also known as squarate, is an important synthetic target in the chemical industry.
Squarate is a versatile intermediate that can be used in the production of a variety of chemicals, including pharmaceuticals, dyes, and other industrial chemicals.
There are several synthetic routes that can be used to synthesize squarate, including both organic and inorganic methods.

One of the most common synthetic routes for squarate involves the use of a combination of chemical reactions.
This route typically involves the reaction of a substituted phenol with an appropriate isoquinolinone, such as 7-oxo-5-(2,3-dihydro-1H-isoindol-1-yl)-6,8-dihydro-4H-pyrano[3,2-d]pyrimidine-4-one.
The reaction is typically carried out in the presence of an acid catalyst, such as hydrochloric acid, and results in the formation of a substituted isoquinolinone.
This intermediate can then be reduced using a reducing agent, such as lithium aluminum hydride, to form the desired squarate.

Another synthetic route involves the use of a metal-catalyzed reaction between an appropriate substituted amide and an isoquinolinone.
This reaction typically involves the use of a metal catalyst, such as palladium, and is carried out in the presence of a solvent, such as acetonitrile.
The reaction results in the formation of an N-substituted isoquinolinone, which can then be converted to squarate using a reducing agent, such as sodium borohydride.

Inorganic synthetic routes for squarate involve the use of various metal-based reductions.
For example, the reaction of 7-oxo-5-(2,3-dihydro-1H-isoindol-1-yl)-6,8-dihydro-4H-pyrano[3,2-d]pyrimidine-4-one with lithium metal in the presence of an aprotic solvent, such as THF, can result in the formation of squarate.
This reaction typically requires the use of a base, such as tetrahydrofuran, to suppress the formation of unwanted side products.

Organic synthetic routes for squarate can also be used.
For example, the reaction of a substituted aniline with an isoquinolinone in the presence of a base, such as potassium carbonate, and a solvent, such as DMF, can result in the formation of squarate.
The reaction is typically carried out at an elevated temperature, such as 80-100°C, and requires the use of a coupling agent, such as pyridine, to facilitate the reaction.

Overall, the synthesis of 7,8-dihydroisoquino(2,1-b)quinolin-5(6H)-one is a well-established process that can be carried out using a variety of synthetic routes.
Each route has its own advantages and disadvantages, and the choice of route will depend on the specific requirements of the synthesis and the desired end product.
Regardless of the route chosen, the synthesis of squarate is an important step in the production of a variety of valuable chemicals and pharmaceuticals.