The Synthetic Routes of 5-CYANOPYRIDINE-2-BORONIC ACID PINACOL ESTER

The synthesis of 5-cyanopyridine-2-boronic acid pinacol ester is a complex process that involves several steps and different reagents.
There are several synthetic routes available in the literature, and the choice of the route depends on the availability of the starting materials, the purity of the desired product, and the scale of the synthesis.

One of the most common synthetic routes to 5-cyanopyridine-2-boronic acid pinacol ester involves the reaction of 2-bromopyridine-5-boronic acid with pinacolone in the presence of a Lewis acid catalyst, such as aluminum chloride or ferric chloride.
The reaction proceeds through a free-radical mechanism, and the product can be isolated by precipitation with a polar solvent, such as ether or hexane.

Another synthetic route to 5-cyanopyridine-2-boronic acid pinacol ester involves the reaction of 2-cyanopyridine with 2-boronopyridine-5-boronic acid in the presence of a carbodiimide coupling agent, such as 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) or 1-hydroxy-7-azabenzotriazole (HOAt).
The reaction can be carried out in a polar solvent, such as dimethylformamide (DMF), and the product can be isolated by precipitation with a polar solvent or by filtration.

A third synthetic route to 5-cyanopyridine-2-boronic acid pinacol ester involves the reaction of pinacolboronic acid with 2-cyanopyridine in the presence of a Lewis acid catalyst, such as trifluoromethanesulfonic acid or boron trifluoride etherate.
The reaction can be carried out in a polar solvent, such as DMF or THF, and the product can be isolated by precipitation with a polar solvent, such as ether or hexane.

All of the synthetic routes to 5-cyanopyridine-2-boronic acid pinacol ester require careful handling of the reagents and the product, as they are often sensitive to moisture and air.
It is also important to use high-purity reagents to avoid contamination and to purify the product by appropriate methods, such as recrystallization, if necessary.

In summary, the synthesis of 5-cyanopyridine-2-boronic acid pinacol ester is a complex process that requires careful manipulation and purification of the product.
The choice of the synthetic route depends on the availability of the starting materials, the purity of the desired product, and the scale of the synthesis.
These factors, along with the proper selection and handling of the reagents, can influence the yield and the quality of the final product.