The oxo-chromene-6-carbaldehyde derivative 1 was used as a starting material for the synthesis of some novel pyrano[3,2-b] xanthene-4,7-dione 2 and chromen-oxazol-5-(4H)-one derivatives 4,5. Furthermore, the oxazolone derivative 4 was used as key intermediates to synthesize some novel imidazol derivatives 6-14. The structures of target compounds were confirmed by elemental analyses and spectral data.  All the target compounds were subjected to in-vitro antitumor activity against breast and colon human tumor cell lines (MCF7 and HCT). Most of the screened compounds showed interesting cytotoxic activities compared to a reference drug.