Guo, Qi published the artcileThe complete synthesis of favipiravir from 2-aminopyrazine, Category: pyrazines, the publication is Chemical Papers (2019), 73(5), 1043-1051, database is CAplus.
Favipiravir was synthesized from an inexpensive and com. available starting material, 2-aminopyrazine. The preferred route embedded within seven steps and was highlighted by the novel and efficient synthesis of 3,6-dichloropyrazine-2-carbonitrile. The intermediate 3,6-dichloropyrazine-2-carbonitrile was prepared in four successive steps which were regioselective chlorination of the pyrazine ring, bromination, Pd-catalyzed cyanation and Sandmeyer diazotization/chlorination. This protocol eliminated the hazardous POCl3 of previous synthetic methods and offered a better yield (48%) which was 1.3-fold higher than a recently published procedure. From intermediate 3,6-dichloropyrazine-2-carbonitrile, the subsequent nucleophilic fluorination, nitrile hydration and hydroxyl substitution efficiently afforded the target product. Another synthetic approach with the same starting material was also investigated to bypass the allergy-causing dichloro intermediate 3,6-dichloropyrazine-2-carbonitrile. The key step of monofluorination at the pyrazine C6 position of intermediate 6-chloro/bromo-3-aminopyrazine-2-carbonitriles and 6-chloro/bromo-3-hydroxylpyrazine-2-carbonitriles was not achieved.
Chemical Papers published new progress about 1257072-34-6. 1257072-34-6 belongs to pyrazines, auxiliary class Pyrazine,Chloride,Nitrile,Bromide, name is 6-Bromo-3-chloropyrazine-2-carbonitrile, and the molecular formula is C5HBrClN3, Category: pyrazines.
Referemce:
https://en.wikipedia.org/wiki/Pyrazine,
Pyrazine | C4H4N2 – PubChem