Six 3-alkyl-5,6,7,8-tetrahydro[4,5]benzothieno[2,3-d]pyrimidin-4-one derivatives and seventeen 3-benzylideneaminotetrahydrobenzo[ 4,5]thieno[2,3-d]pyrimidin-4-one derivatives have been designed and synthesized via Gewald reaction under mild condition. The structures of synthesized compounds were characterized by 1H NMR, 13C NMR, IR and MS. Their antitumor activities were evaluated against human nasopharyngeal carcinoma (KB) and human nasopharyngeal carcinoma (CNE2) cell lines in vitro. These results revealed that four tested compounds showed modera...