Reversible ArSE aroylation has been observed in the reaction of 2,7-dimethoxynaphthalene (1) with 4-chlorobenzoic acid/acid chloride 2 with the aid of discrete acidic mediators. The reaction readily gives 1-aroylated-, 3-aroylated-, and 1,8-diaroylated products. The product distribution clearly shows dependence oil the kind and strength of the acidic mediators and the time-course of the distribution manifests dearoylation of the productive aroylnaphthalenes. These reaction behaviors including, acid-strength-dependent reversibility are well interpreted from the viewpoint of highly congested noncoplanar geometry of the polyaromatic ketone products.