Diazole anions react with hexafluorobenzene to give hexa(diazo1-1-yl)benzenes in excellent yield, even with unfavorable reaction stoichiometries.In contrast, pyrrole anions give predominantly or exclusively 1,4-disubstituted products.This novel hexasubstitution reaction is discussed in terms of an S R N ~ mechanism.During the course of a herbicide discovery project we designed a series of 1,4-bis(azol-1-yl)benzenes as candidate herbicides.Our initial route of entry relied on the well described nucleophilic aromatic substitution chemistry characteristic of perlluoroaromatics2 and of hexafluorobenzene in particular, generally providing 1 ,Cdisubstituted products (eq.1).3Despite a recent report that imidazole anion fails to react with C6F6 even under relatively vigorous conditions (24 h.80 "C, DMSO or t-BuOH)~, we have found that diazole anions react readily with C6F6 at room temperature or slightly above to give the rnsubstitution products irrespective of reaction stoichiometry (eq.2).Products were characterized chiefly by mass spectrometry, together with 1 9 ~ nmr and elemental combustion analysis.
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Henrie et al. (1993) studied this question.