Nuclear Halogenopyrazines by Transhalogenation

This procedure is especially useful for converting easily available chloro- or bro-mopyrazines into less easily available iodo- or fluoropyrazines. Although neglected of recent years, there are several examples of the transhalogenation of chloro- into iodopyrazines. 

2-Chloropyrazine gave 2-iodopyrazine (Nal, AcOH, H2S04, MeCN, reflux, 5 h 80%).1613 

2-Chloropyrazine 1-oxide (66) gave 2-fluoropyrazine 1-oxide (67) (KF, Me2SO, reflux, 2 days 32%).276 Also other examples.1307 

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