Synthesis of 3′,4′-Diaryl-4′H-spiro[indoline-3,5′-[1′,2′,4′]oxadiazol]-2-ones via DMAP-catalyzed Domino Reactions and Their Antibacterial Activity

A convenient and metal-free DMAP-catalyzed domino reaction of isatins, arylamines and hydroximoyl chlorides has been developed to achieve 1,3-dipolar cycloaddition of imines into aryl nitrile oxides at ambient temperature. In this one-pot transformation, a 1,2,4-oxadiazole skeleton was efficiently formed. This methodology needs no extra additives and features wide substrate scope, good functional group tolerance and mild reaction conditions. A plausible mechanism for this process was proposed. Moreover, the antibacterial activities of the products were evaluated towards Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae using the Broth microdilution method.