Meisenheimer Complexes

Abstract

This complex has been first reported from the reaction between picryl ether and potassium alkoxide and later it has been isolated and characterized. The stable or transient anionic σ complexes formed from electron‐deficient aromatic compounds and a variety of organic and inorganic bases are generally referred to as the Meisenheimer complexes. It has been reported that these complexes are formed as the intermediates of most nucleophilic aromatic substitution (S N Ar) reactions with two‐step mechanisms. Many nucleophiles have been categorized for the formation of this complex. Kinetically, the nucleophile would preferentially add to the meta ‐position of the leaving group but some of the places K3T1 regioselectivity has been observed. The formation of the Meisenheimer complexes has been modified using a micellar catalyst or by electrochemical reduction. This complex has been involved in various nucleophilic aromatic substitution reactions.