One‐pot Synthesis and Antitubercular Activity of Imidazo[2,1‐b]thiazol‐1H‐pyrazolylphosphonates

Abstract Herein, we present an effective one‐pot method for the synthesis of imidazo[2,1‐ b ]thiazole‐pyrazole phosphonates from 5‐imidazo[2,1‐ b ] thiazole carboxaldehydes. The reaction involves a 1,3‐dipolar cycloaddition between in situ generated α , β ‐unsaturated ketones and the Bestmann–Ohira reagent (BOR), facilitated by a base, leading to the formation of pyrazole phosphonates as the sole regioisomer with excellent yields. The in vitro evaluation of the newly synthesized compounds 4(a – x) against Mycobacterium tuberculosis H37Rv ( Mtb ) identified compound 4 o as the most effective analogue (MIC: 6.25 μg/mL; 10.40 μM).