Microwave-assisted synthesis of new sulfonyl hydrazones, screening of biological activities and investigation of structure–activity relationship

Abstract

Sulfonyl hydrazone scaffold and the piperidine rings have important role in medicinal chemistry. This study shows the synthesis of two novel series of sulfonyl hydrazone having piperidine derivatives by condensing benzene sulfonyl hydrazides with ethyl 4-oxopiperidine-1-carboxylate and 2,6-diphenylpiperidin-4-one. Physical and chemical properties of compounds have been characterized and reported by utilizing their melting point, elemental analysis, IR, 1H-NMR, 13C NMR, 2D NMR and mass spectra results. Synthesized compounds were evaluated for antioxidant capacity and anticholinesterase activity. The antioxidant capacity of the compounds were screened through four complementary test, i.e., β-carotene–linoleic acid for lipid peroxidation, DPPH free radical (DPPH·), ABTS cation radical (ABTS+·) and CUPRAC assays. Assay results showed that N′-(2,6-diphenylpiperidin-4-ylidene)-4-bromobenzenesulfonohydrazide (11) has the highest lipid peroxidation inhibitory activity. Within the assay series, N′-(2,6-diphenylpiperidin-4-ylidene)-4-bromobenzenesulfonohydrazide (11) exhibited better activity than standard BHT in DPPH· scavenging, while N′-(2,6-diphenylpiperidin-4-ylidene)benzenesulfonohydrazide (10) showed the best ABTS+· scavenging assay. The CUPRAC assay revealed that ethyl 4-(2-(4-methoxyphenylsulfonyl)hydrazono)piperidine-1-carboxylate (5) indicated the best activity with A 0.50 value among the tested compounds than the antioxidant standard α-tocopherol. According to AChE assay, N′-(2,6-diphenylpiperidin-4-ylidene)-4-chlorobenzenesulfonohydrazide (12) had the best activity, while in BChE assay the highest activity was found for compound N′-(2,6-diphenylpiperidin-4-ylidene)-4-methylbenzenesulfonohydrazide (16). Electronic and structural characteristics and density functional studies of the all newly synthesized compounds have been reported for better understanding in molecular-level. NMR, molecular electrostatic potential (MEP), ΔE HOMO–LUMO band gap and the dipole moments of the molecules have been also analyzed and reported.