Abstract:Novel 2,4-dichloro-5-phenylcyclopent-4-ene-1,3-dione and 5-aryl-4-chlorocyclopent-4-ene-1,3-dione were synthesized by the Suzuki–Miyaura or Friedel–Crafts reactions of the di- and trichlorocyclopentenone monoketals and subsequent hydrolysis of the ketal function. Condensation of these diones with (hetero)aromatic aldehydes afforded multifunctional 1,3-cyclopentenediones that showed anticancer activity.Keywords: organochlorine compounds, cyclopentenones, ketals, Suzuki–Miyaura reaction, Friedel–Crafts reaction, Knoevenagel condensation, aldehydes, cross-conjugated cyclopentene-1,3-diones, cytotoxicity.