Studies on pyrazines, 8. An improved syntheses of 2-amino-3,5-dibromo- and 2-amino-5-bromopyrazines

The titled dibromopyrazine ( 2 ) was prepared in 54% yield by the modified procedure for bromination of 2-aminopyrazine ( 1 ) using bromine and pyridine in chloroform solution. Similarly, 2-amino-5-bromopyrazine ( 3 ) was directly prepared in 36% yield by bromination using 1.2 equivalents of the above reagents.