The Minisci reaction ([miˈniʃi]) is a named reaction in organic chemistry. It is a radical substitution to an aromatic compound, in particular to a heteroaromatic base, that introduces an alkyl group. The reaction was published about in 1971 by F. Minisci. The aromatic compound is generally electron-deficient and with N-aromatic compounds the nitrogen atom is protonated. A typical reaction is that between pyridine and pivalic acid to 2-tert-butylpyridine with silver nitrate, sulfuric acid and ammonium persulfate. The reaction resembles Friedel-Crafts alkylation but with opposite reactivity and selectivity.
The Minisci reaction proceeds regioselectively and enables the introduction of a wide range of alkyl groups. A side-reaction is acylation. The ratio between alkylation and acylation depends on the substrate and the reaction conditions. Due to the simple raw materials and the simple reaction conditions the reaction has many applications in heterocyclic chemistry.
Mechanism
A free radical is formed from the carboxylic acid in an oxidative decarboxylation with silver salts and an oxidizing agent. The oxidizing agent reoxidizes the silver salt. The radical then reacts with the aromatic compound. The ultimate product is formed by rearomatization. The acylated product is formed from the acyl radical.