Ultrasound‐Mediated Synthesis of New (Piperazine‐Chromene)‐Linked Bis(thieno[2,3‐b]pyridine) Hybrids as Potential Anti‐acetylcholinesterase.

Using ultrasound irradiation and the eco‐friendly piperazine, two series of (piperazine‐chromene)‐linked bis(thieno[2,3‐b]pyridine) hybrids attached to various arene or chromene units were efficiently prepared. Therefore, the target hybrids were prepared by reacting bis(pyridine‐2(1H)‐thione) with two equivalents of the appropriate α‐haloketones in the presence of 1.4 equivalents of piperazine. The reaction mixture was subjected to ultrasonic irradiations at 60 °C for 20–40 min to produce the desired products in 87–96 % yields. At concentrations of 15 and 25 μM, new hybrids were tested for anti‐acetylcholinesterase activity, as well as their ability to quench DPPH free radicals at a concentration of 25 μg/mL. Generally, the chromene unit attached to thienopyridine‐C2 has a significant effect on the inhibitory activity of the new hybrids. Moreover, the electronic properties of the substituent attached to the chromene‐C6 unit influence the inhibitory activity. The bis(thienopyridine) hybrid attached to 6‐methoxy‐2H‐chromen‐2‐one units demonstrated the best anti‐acetylcholinesterase activity at the previous concentrations, with inhibition percentages of 69.1 and 85.4. Additionally, with an inhibition percentage of 84.4, the previous hybrid demonstrated the most effective anti‐DPPH activity. [ABSTRACT FROM AUTHOR]