Heterocyclic compounds play an important role in the field of pharmaceutical chemistry, especially compounds containing hybrid bioactive moieties. So in continuation of our work, We focused mainly here on design, synthesis, and transformations of novel bio-active molecules bearing thieno[2,3-d]pyrimidine moiety which can be used as antibacterial and antifungal drugs after some modifications. The starting compound 2-chloromethyl-3H-7-p-tolylamino-4-oxo-9-phenyl-pyrimido[4',5':4,5]thieno[2,3-d]pyrimidine (1) which was prepared according to literature, was converted into many other derivatives bearing different functional groups to make a comparable study of their antimicrobial activity. The chemical constructions of all obtained compounds were well elucidated by the means of their analytical and spectral analyses (TLC, IR, ¹H NMR, ¹³C NMR, and MS). The title compounds have been chosen and screened