Comparative conventional and microwave assisted synthesis of heterocyclic oxadiazole analogues having enzymatic inhibition potential

A comparative microwave assisted and conventional synthetic strategies were applied to synthesize heterocyclic 1,3,4‐oxadiazole analogues as active anti‐enzymatic agents. Green synthesis of compound 1 was achieved by stirring 4‐methoxybenzenesulfonyl chloride (a) and ethyl piperidine‐4‐carboxylate (b). Compound 1 was converted into respective hydrazide (2) by hydrazine and then into 1,3,4‐oxadiazole (3) by CS2 on reflux. The electrophiles, N‐alkyl/aralkyl/aryl‐2‐bromopropanamides (6a–p) were synthesized and converted to N‐alkyl/aralkyl/aryl‐2‐propanamide derivatives (7a–p) by reaction with 3 under green chemistry. Microwave assisted method was found to be effective relative to conventional method. 13C‐NMR, 1H‐NMR and IR techniques were availed to corroborate structures of synthesized compounds and then subjected to screening against lipoxygenase (LOX), α‐glucosidase, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. A number of compounds presented better potential against these enzymes. The most active compounds against LOX and α‐glucosidase enzymes were subjected to molecular docking study to explore their interactions with the active sites of the enzymes.