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ChemicalBook CAS DataBase List Sulfalen
152-47-6

Sulfalen synthesis

3synthesis methods
Sulfalene, 3-methoxy-2-sulfanilamidopyrazine (33.1.41), like other sulfanilamides, is synthesized by the standard scheme from 4-acetylaminobenzenesulfonyl chloride, which is reacted with 3-amino-2-methoxypyrazine, which is synthesized by two technologically available methods. The first of these methods consists of direct bromination of 2-aminopyrazine using acetic acid as a solvent, which gives 3,5-dibromo-2-aminopyrazine (33.1.34). Reacting this with sodium methoxide gives 3-methoxy-5-bromo-2-aminopyrazine (33.1.35). Hydrogen reduction using a palladium on carbon catalyst replaces the bromine atom at C5 of the product with a hydrogen atom, giving 3-methoxy-2-aminopyrazine (33.1.36).
This same 3-methoxy-2-aminopyrazine (33.1.36) is synthesized from 3-hydroxypyrazin- 2-carboxamide. Reacting this with phosphorous oxychloride replaces the hydroxyl group with a chlorine atom while the carboxamide group simultaneously undergoes dehydration to form 3-chloro-2-cyanopyrazine (33.1.37). Next, reacting this with sodium methoxide gives 3-methoxy-2-cyanopyrazine (33.1.38). The cyano group in this compound is hydrolyzed by a base in the presence of hydrogen peroxide to a carboxamide group, giving 3-methoxy-2-carboxamideopyrazine (33.1.39). The resulting product undergoes a Hofmann rearrangement when reacted with sodium hypochlorite, giving the desired 3-methoxy-2 aminopyrazine (33.1.36). Reacting this with 4-acetylaminobenzenesulfonyl chloride and subsequent hydrolysis of the acetyl group with a base to (33.1.40) gives sulfalene.

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Yield:-

Steps:

Multi-step reaction with 2 steps
1: pyridine
2: sodium hydroxide / water

References:

Perlovich, German L.;Ryzhakov, Alex M.;Tkachev, Valery V.;Hansen, Lars Kr.;Raevsky, Oleg A. [Crystal Growth and Design,2013,vol. 13,# 9,p. 4002 - 4016]

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