Zincke–Suhl reaction
The Zincke–Suhl reaction is a special case of a Friedel-Crafts alkylation and was first described by Theodor Zincke and Suhl in 1906. Unlike the traditional Friedel-Crafts reaction, the reduction of the phenyl ring leads to a higher energy final product that can be used as starting material in the dienol–benzene rearrangement, among other reactions. The classic example of this reaction is the conversion of p-cresol to a cyclohexadienone (with the aid of aluminium chloride as a catalyst and tetrachloromethane as a solvent). Melvin Newman, a scientist from the U.S. intensively studied the reaction in the 1950s and reported several improved procedures as well as mechanistic studies. Since then, studies investigating the impact of alternate reagents have been conducted by others. Mechanism Aluminum chloride plays a range of functions in this reaction, first reacting with p-cresol to form phenoxy aluminum chloride along with a molecule of hydrogen chloride. Additionally, aluminum chloride activates a molecule of tetrachloride that in turn is subjected to a nucleophilic attack by the phenoxy aluminum chloride. Subsequently, the product interacts with aluminum chloride and tetrachloride again to form a loose complex. Finally, the product is treated with water, resulting in the final product. Catalysts During a series