Inorganic base-catalyzed formation of antivirally active N-substituted benzamides from α-amido sulfones and N-nucleophile

BACKGROUND Heteronucleophiles as well as carbanionic reagents can be used to react with α-amido sulfones, thus giving the opportunity to prepare a large array of amino derivatives. Since, novel 1,3,4-oxadiazole-2-thiol derivatives can serve as potent nucleophiles, we employed 5-subsititued phenyl-1,3,4-oxadiazole-2-thiols as the nucleophilic source of nitrogen in the reaction with α-amido sulfones. RESULTS A series of N-substituted benzamides bearing 1,3,4-oxadiazol unit were prepared for the first time by the reaction of in situ generated protected imine from α-amido sulfones with 5-subsititued phenyl-1,3,4-oxadiazole-2-thiols as the source of nitrogen nucleophile. Some of the synthesized products displayed favourable antiviral activity against cucumber mosaic virus (CMV) in preliminary antiviral activity tests. The title compounds 5c, 5o and 5r revealed curative activity of 42.2%, 48.7% and 40.5%, respectively against CMV (inhibitory rate) compared to the commercial standard Ningnanmycin (53.4%) at 500 μg/mL. CONCLUSION A practical synthetic route to N-benzoyl-α-amido sulfones by the reaction of 5-subsititued phenyl-1,3,4-oxadiazole-2-thiols as the source of nitrogen nucleophiles with in situ generated protected imine from N-benzoyl-α-amido sulfones is presented. The reaction catalyzed by an inorganic base has considerable significance to exploit the potential of α-amido sulfones in organic synthesis.