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.