The Synthetic Routes of 4-Chloro-5-iodo-7H-pyrrol[2,3-d]pyrimidine

4-Chloro-5-iodo-7H-pyrrol[2,3-d]pyrimidine is an important intermediate in the synthesis of various pharmaceuticals, agrochemicals, and other chemical products.
The route to its synthesis has undergone significant changes over the years, from early manual methods to the present-day, highly efficient, and cost-effective synthetic routes.

One of the earliest methods of synthesizing 4-chloro-5-iodo-7H-pyrrol[2,3-d]pyrimidine involved the use of mercurochrome, which contained mercury.
This method produced the desired product, but the use of mercury was eventually discontinued due to its toxicity.

The next generation of synthetic routes involved the use of sodium hypochlorite, which was a cheaper and safer alternative.
However, this method had some limitations in terms of yield and purity.

The most widely used method today is the synthesis of 4-chloro-5-iodo-7H-pyrrol[2,3-d]pyrimidine via the intermediate 2-chloro-4,5,6,7-tetrachloro-3H-pyrrol[1,2-d]pyrimidine, which can be synthesized by treating 2,3,4,5-tetrachloro-6,7-dihydro-3H-pyrrol[1,2-d]pyrimidine with chlorine water.
The intermediate can then be treated with sodium iodide to produce the desired product.

This route has several advantages, such as high yield, high purity, and low cost.
The reaction can be carried out at room temperature, and the intermediate can be easily purified by simple precipitation with sodium sulfate.

Another synthetic route involves the use of hydrogen peroxide, which is a safe and green oxidizing agent.
This method involves the oxidation of 2,3,4,5-tetrachloro-6,7-dihydro-3H-pyrrol[1,2-d]pyrimidine with hydrogen peroxide in the presence of a solvent like acetone or ethyl ether.

In addition to the above methods, there are several other synthetic routes to 4-chloro-5-iodo-7H-pyrrol[2,3-d]pyrimidine, such as the N-chlorosuccinimide method, the N-chlorosuccinamide method, and the N-chloro-N'-nitroxylamide method.
These methods may vary in terms of efficiency, yield, and cost, but they all ultimately produce the desired product.

In conclusion, the synthetic routes to 4-chloro-5-iodo-7H-pyrrol[2,3-d]pyrimidine have undergone significant changes over the years, from manual methods to highly efficient and cost-effective synthetic routes.
The most widely used method today involves the synthesis of 2-chloro-4,5,6,7-tetrachloro-3H-pyrrol[1,2-d]pyrimidine, which can be converted to 4-chloro-5-iodo-7H-pyrrol[2,3-d]pyrimidine via sodium iodide treatment.
This route has high yield, high purity, and low cost, and is considered to be the most convenient and effective method for the synthesis of 4-chloro-5-iodo-7H-pyrrol[2,3-d]pyrimidine.