An efficient and practical synthesis of the antipsoriatic drug Lonapalene is reported. This involves the thermal rearrangement of 4-(4-chlorophenyl)-4-hydroxy-2,3- dimethoxycyclobutenone to 6-chloro-1,4-dihydroxy-2,3-dimethoxynaphthalene which was converted to Lonapalene upon treatment with acetic anhydride/pyridine. © 1987.