The aim of the present work was to synthesise coumarinyl heterocycles and to elucidate the potential role of these compounds as antioxidants and cytotoxic agents against Dalton\u27s lymphoma ascites tumour cells (DLA) and Ehrlich ascites carcinoma cells (EAC). The synthesis of coumarin derivatives containing pyrazole, pyrazolone, thiazolidin-4-one, 5-carboxymethyl-4-thiazolidinone and 3-acetyl-1,3,4-oxadiazole ring is reported. 4-Methylcoumarinyl-7-oxyacetic acid hydrazide (1) reacted with arylazopropanes or hydrazono-3-oxobutyrate derivatives to form pyrazole (3a-c) and pyrazolone derivatives (5a-c). Heterocyclisation of Schiffs bases of 1 with thioglycolic acid, thiomalic acid or acetic anhydride afforded novel heterocyclic derivatives 4-thiazolidinones (7a-c), 5-carboxymethyl-4-thiazolidinones (8a-c) and oxadiazoles (9a-c), respectively. Some of the compounds showed promising results in in vitro antioxidant activity and cytotoxic activity against DLA cells and EAC cells.Cilj rada bio je sintetizirati kumarinske heterocikličke derivate i razjasniti njihovu potencijalnu ulogu kao antioksidativnih i citotoksičnih agenasa na tumorske stanice Daltonovog limfoma (DLA) i Ehrlichove tumorske stanice (EAC). U radu je opisana sinteza kumarinskih derivata s pirazolskim, pirazolonskim, tiazolidin-4-onskim, 5-karboksimetil-4-tiazolidinonskim i 3-acetil-1,3,4-oksadiazolskim prstenom. Hidrazid 4-metilkumarinil-7-oksioctene kiseline (1) dao je u reakciji s derivatima arilazopropana ili hidrazono-3-oksobutirata derivate pirazola (3a-c) i pirazolona (5a-c). Heterociklizacijom Schiffovih baza 1 s tioglikolnom kiselinom, tiojabučnom kiselinom ili anhidridom octene kiseline nastali su heterociklički derivati 4-tiazolidinoni (7a-c), 5-karboksimetil-4-tiazolidinoni (8a-c) i oksadiazoli (9a-c). Neki od spojeva pokazali su obećavajuće rezultate u in vitro testovima za antioksidativno i citostatsko djelovanje na DLA i EAC stanicama pokazali