23229-26-7

5-bromopyrazin-2-amine (3 g, 17.241 mmol) and bromine (8.2 g, 51.729 mmol) were added to aq. HBr solution at -15° C. Aq. solution of sodium nitrite (2.97 g, 43.0103 mmol) was then added to the mixture over a period of 1 h at -10° C. keeping the internal temperature below 5° C. during addition and stirred for 1 h at 0° C. Progress of reaction was monitored by TLC. After reaction completion reaction mass neutralised with 40percent NaOH solution and extracted with diethyl ether. The organic layer was dried over sodium sulphate and concentrated under reduced pressure (below 30° C.) to yield 2,5-Dibromopyrazine (1 g, 24.4percent) as brown oil.

[1] Patent: US2017/291910, 2017, A1. Location in patent: Paragraph 0592-0594
[2] Journal of the American Chemical Society, 1949, vol. 71, p. 2798
[3] Chemistry - A European Journal, 2010, vol. 16, # 19, p. 5645 - 5660
[4] Patent: WO2004/56369, 2004, A1. Location in patent: Page/Page column 24-25