The condensation of 5-chloro-2-methylacetophenone with diethyl succinate in the presence of potassium t-butoxide gave a mixture of (Z)- and (E)-3-ethoxy-carbonyl-4-(3'-chloro-6'-methylphenyl) but-3-enoic acid. Cyclisation of (E)- and (Z)-half-esters afforded the naphthalene derivative and oxo-indenyl acid via the anhydride formation, respectively. The reaction of (E)-anhydride with aromatic hydrocarbons, amines and anhydrous aluminium chloride in acetylene tetrachloride was also investigated. The IR, 1N-NMR and mass spectra of the products were discussed.