The key intermediate in this study is synthesis of pyrimidine-5-sulfonamides 2a,b. Further modification of starting material by treatment with ethanolamine, anthranilic acid and 3-bromopropanoic acid yielded the condensed pyrimidine derivatives incorporating sulfonamide moiety such as: imidazopyrimidine 3a,b, pyrimidoquinazoline 4a,b and pyrimidothiazine derivatives 5a,b, respectively, in good yields. S-Methylpyrimidine derivatives 6a,b were obtained and let to react either with morpholine and with phosphorous oxychloride to give 7a,b or 8a,b respectively. Compounds 9a,b or 10a,b were obtained via reaction of 8a,b and thiourea or hydrazine hydrate respectively. The condensed tetrazolopyrimidine derivatives 11a,b obtained by cyclocondensation of 10a,b with sodium nitrite and hydrochloric acid. Structures of newly synthesized compounds elucidated by: elemental analysis, IR, NMR and mass spectral data. The antitumor activities evaluated in vitro against four cell lines.