My two previous explorations of aromatic substitutions have involved an electrophile (NO+ or Li+). Time now to look at a nucleophile, representing nucleophilic aromatic substitution. The mechanism of this is thought to pass through an intermediate analogous to the Wheland for an electrophile, this time known as the Meisenheimer complex. I ask the same question as before; are there any circumstances under which the mechanism could instead be concerted, by-passing this intermediate?
- J. Meisenheimer, "Ueber Reactionen aromatischer Nitrokörper", Justus Liebig's Annalen der Chemie, vol. 323, pp. 205-246, 1902. http://dx.doi.org/10.1002/jlac.19023230205