A novel series of pyrimidine/pyrazole linked β-lactams have been synthesized in excellent yields using a simple and efficient methodology involving conjunction of different heterocyclic substrates. All the new products were characterized on the basis of various spectroscopic techniques viz. FT-IR, 1 H NMR, 13 C NMR, elemental analysis (CHN), 1 H-1 H correlation spectroscopy ( 1 H-1 H COSY) and mass spectrometry (EIMS) in representative cases. Furthermore, theoretical calculations have also been performed on representative compounds and the results were compared with Cefuroxime axetil (a broad spectrum antibacterial agent). The phenomenon of tautomerism was also observed which was confirmed by different NMR experiments (D 2 O exchange study and 1 H-1 H correlation spectroscopy).