The Synthetic Routes of Ethyl 8-isoquinolinecarboxylate

Ethyl 8-isoquinolinecarboxylate is an important intermediate in the synthesis of various pharmaceuticals, agrochemicals, and other industrial chemicals.
The demand for this compound has been increasing steadily in recent years, hence there is a need for efficient and cost-effective synthetic routes to produce it.
In this article, we will discuss some of the commonly used synthetic routes for the synthesis of Ethyl 8-isoquinolinecarboxylate.

1. Hydrolysis of N-phenyl-8-methyl-8H-pyrido-[3,4-d] pyrimidine-2,5-diamine

One of the most commonly used synthetic routes for the synthesis of Ethyl 8-isoquinolinecarboxylate involves the hydrolysis of N-phenyl-8-methyl-8H-pyrido-[3,4-d] pyrimidine-2,5-diamine.
This route involves the following steps:

• N-phenyl-8-methyl-8H-pyrido-[3,4-d] pyrimidine-2,5-diamine is hydrolyzed using acid to produce N-phenyl-8-methyl-8H-pyrido[3,2-d]pyrimidine-2,5-diamine.
  
• The resulting compound is then treated with excess of ethyl bromide and sodium hydroxide to produce N-phenyl-8-ethyl-8H-pyrido[3,2-d]pyrimidine-2,5-diamine.
  
• The next step involves the reduction of the diazotized product using sodium borohydride to produce N-phenyl-8-ethyl-8H-pyrido[3,4-d]pyrimidine-2,5-diamine.
  
• Finally, the compound is treated with carbon disulfide and hydrochloric acid to produce Ethyl 8-isoquinolinecarboxylate.
  

2. Reductive Amination of N-Phenyl-8H-pyrido[3,2-d]picolinamide

Another commonly used route for the synthesis of Ethyl 8-isoquinolinecarboxylate involves the reductive amination of N-phenyl-8H-pyrido[3,2-d]picolinamide.
This route involves the following steps:

• N-phenyl-8H-pyrido[3,2-d]picolinamide is treated with excess of ethyl iodide and sodium hydroxide to produce N-phenyl-8-ethyl-8H-pyrido[3,2-d]picolinamide.
  
• The compound is then reduced using hydrogen in the presence of a palladium catalyst to produce N-phenyl-8-ethyl-8H-pyrido[3,4-d]picolinamide.
  
• The next step involves the treatment of the compound with carbon disulfide and hydrochloric acid to produce Ethyl 8-isoquinolinecarboxylate.
  

3. Reaction of 8-Methyl-8H-pyrido[3,4-d]pteridine-2,5-diamine with Ethyl Bromide

Another commonly used synthetic route for the synthesis of Ethyl 8-isoquinolinecarboxylate involves the reaction of 8-methyl-8H-pyrido[3,4-d]pteridine-2,5-diamine with ethyl bromide.
This route involves the following steps:

• 8-Methyl-8H-pyrido[3,4-d]pteridine-2,5-diamine is