Condensation of naphthalenediols with benzene in the presence of aluminum bromide: an efficient synthesis of 5-, 6-, and 7-hydroxy-4-phenyl-1- and 2-tetralones

Isomeric 1,5-, 1,6-, 1,7-, 2,6-, and 2,7-naphthalenediols react smoothly with benzene at room temperature in the presence of an excess of aluminum bromide to give 5-, 6-, and 7-hydroxy-4-phenyl-1-tetralones and 5- and 6-hydroxy-4-phenyl-2-tetralones, respectively. The mechanism of these reactions is interpreted in terms of key di- or tri-cationic (superelectrophilic) intermediates.