Makosza and Winiarski characterized a subclass of 
Makosza and Winiarski characterized a subclass of reactions with this mechanism that involves hydrogen, which they dubbed "vicarious". Metal amides and pyrimidines undergo a version of this mechanism called ANRORC, which also explains the Zincke reaction. Intermediates in one version of this complex can be isolated using a strongly colored enolate in the Zimmerman reaction, or simply using a ketone in the Janovski reaction. Another version goes through benzyne, while the aforementioned intermediate often contains nitro groups and is called the Meisenheimer complex. Often occurring in systems in which a halide is ortho or para to an electron-widthdrawing group, for 10 points, name this reaction mechanism which sees an attacking group replace a leaving group on benzene-like compounds.
Makosza and Winiarski characterized a subclass of reactions with this mechanism that involves hydrogen, which they dubbed "vicarious".
{Nucleophilic Aromatic Substitution} or {SnAr} (Prompt on partial)