Abstract: In the present study 2-(4-Chlorophenyl)-6-iodo-3, 4-dihydroquinazolin-4-one 3 was prepared by the reaction of 2-(4-chlorophenyl)-6-iodo-4H-3,1-benzoxazin-4-one 2 with formamide. Treatment of 3 with phosphorus penta sulfide yielded the thione derivative 4. Alkylation of 3 and 4 with certain alkylhalides gave the target compounds. The structure of the new compounds was confirmed by 1H NMR, IR and MS. Some of the new compounds were screened for antitubercular activity, the 4-alkylthio derivatives were active while the 4-alkyloxy derivatives were inactive.