Methyl 3-bromo-6-chloro-5- pyrazine

A mixture of 1- and 3-chloro, 1,3-dichloro, and 1,3,5-trichloro derivatives was obtained on chlorination of imidazo[l, 5-a]pyrazine (172). Bromination gave similar results (75JHC207,75JOC3373 84MI24). The 8-chloro compound is best made from the 8-oxy derivative of 172. When the 1-bromo-3-methyl derivative of 172 was treated in turn with aqueous bromine and excess dilute caustic soda, the pyrazine ring was destroyed to give 4-bromo-2-methylimidazole-5-aldehyde (75JOC3373). 

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