The Synthetic Routes of 6-[4-Aminophenyl]pyridazin-3(2H)-one

6-[4-Aminophenyl]pyridazin-3(2H)-one is an important intermediate in the synthesis of various pharmaceuticals and agricultural chemicals.
This compound can be synthesized through several routes in the chemical industry, and the selection of a particular route depends on various factors such as cost, availability of reagents, and desired yield.
In this article, we will discuss some of the most common synthetic routes for 6-[4-amino-phenyl]pyridazin-3(2H)-one.

Route 1: via 4-amino-3-chlorphenylamine

This route involves the synthesis of 4-amino-3-chlorphenylamine, followed by its oxidation to 6-[4-amino-phenyl]pyridazin-3(2H)-one.
The synthesis of 4-amino-3-chlorphenylamine can be achieved through a variety of methods, including the reduction of 4-chloro-3-nitrobenzaldehyde with ammonia or a metal hydride reducing agent, or by the reaction of 3-chloro-4-aminotoluene with sodium hydroxide.
The oxidation of 4-amino-3-chlorphenylamine to 6-[4-amino-phenyl]pyridazin-3(2H)-one can be achieved by treating the amine with a oxidizing agent such as potassium permanganate, sodium periodate, or mandelic acid.

Route 2: via 4-amino-3-bromphenylamine

In this route, 4-amino-3-bromphenylamine is synthesized, and then oxidized to 6-[4-amino-phenyl]pyridazin-3(2H)-one.
The synthesis of 4-amino-3-bromphenylamine can be achieved through a similar method as route 1, by reducing 4-bromo-3-nitrobenzaldehyde with ammonia or a metal hydride reducing agent, or by reacting 3-bromo-4-aminotoluene with sodium hydroxide.
The oxidation of 4-amino-3-bromphenylamine to 6-[4-amino-phenyl]pyridazin-3(2H)-one can be achieved using the same oxidizing agents as in route 1.

Route 3: via 2-chloro-6-[4-amino-phenyl]pyridine-3,5-dione

This route involves the synthesis of 2-chloro-6-[4-amino-phenyl]pyridine-3,5-dione, followed by its dehydration to 6-[4-amino-phenyl]pyridazin-3(2H)-one.
The synthesis of 2-chloro-6-[4-amino-phenyl]pyridine-3,5-dione can be achieved by the reaction of 6-chloro-2-aminopyridine-3,5-dione with potassium hydroxide, followed by treatment with a chlorinating agent such as phosphorus trichloride or thionyl chloride.
The dehydration of 2-chloro-6-[4-amino-phenyl]pyridine-3,5-dione to 6-[4-amino-phenyl]pyridazin-3(2H)-one can be achieved by treating the compound with a strong dehydrating agent such as sodium hydrate or calcium hydride.

Route 4: via 6-[4-azido-phenyl]pyrid