A series of novel 10-phenylsulfonyl-2-substituted-4,10 dihydrobenzo[4,5]imidazo[1,2-a]pyrimidin-4-one derivatives obtained from N-sulfonation of 2-substituted-pyrimido[1,2-a]benzimidazol-4(10H)-ones and screened for for their in vitro anti-tuberculosis activities against Mycobacterium tuberculosis H37Rv by Microplate Alamar Blue Assay (MABA) method. The structures were established on the basis of their IR, ¹H-NMR, ¹³C-NMR, ESI-MS data and also the compound with 3f were crystallized and analysed by single crystal X-ray diffraction studies.