Synthesis, X-ray Single Crystal, Conformational Analysis and Cholinesterase Inhibitory Activity of a New Spiropyrrolidine Scaffold Tethered Benzo[b]Thiophene Analogue

Described herein is a one-pot protocol for the synthesis of a substituted spiropyrrolidine scaffold tethered benzo[b]thiophene analogue from (E)-3-(benzo[b]thiophen-2-yl)-1-(4-fluoro- phenyl)-prop-2-en-1-one. The described protocol has the advantage of the high purity of the cyclized adduct and high chemical yield. To assign the chemical structure, different spectrophotometric tools have been applied, including H-1-NMR, C-13-NMR, FTIR, and the X-ray single crystal technique. The X-ray structure showed that the studied compound exist in two disordered parts with equal partial occupancies. The energies of the two conformers were found to be very similar and not exceed 1 kcal/mol, which justifies their coexistence in the crystal with equal percentage. The molecular packing in the crystal was analyzed using Hirshfeld topology analysis. The packing described as two dimensional hydrogen bond network extended along the ac-plane in both conformers but the intermolecular interactions included in each conformer are not similar. The synthesized spiropyrrolidine scaffold tethered benzo[b]thiophene analogue was examined against cholinesterase inhibitory activity and show moderate activity compared to standard drug galantamine.