Reactions of benzyl alcohol over oxide catalysts: A novel condensation to form anthracene

A novel heterogeneously catalyzed condensation of benzyl alcohol to form anthracene is reported. The reaction involves an orthoalkylation of a surface benzyl oxide species by the benzyl cation from a neighboring benzyl oxide to form o-hydroxymethyldiphenylmethane which undergoes cyclodehydration followed by aromatization to yield anthracene. Reactions have been carried out with alumina and modified alumina catalysts (fluorided and sodium ion-impregnated), HY-zeolite, phosphotungstic acid, and silicotungstic acid. Mechanistic features of the reaction are discussed. A simple and efficient synthesis of anthracene from benzyl alcohol over HY-zeolite is also described. © 1989.