Elemental Sulfur Mediated Cyclization of Amidoximes and Sulfoxonium Ylides to Access 5‐Acyl‐1,2,4‐Oxadiazoles

ABSTRACT

We report herein a method for the synthesis of 1,2,4‐oxadiazoles via an annulation of amidoximes and sulfoxonium ylides. Elemental sulfur was utilized to activate the methine carbon in the sulfoxonium ylide, which then acts as an active electrophilic center. A wide range of functionalities, including halogen, ester, and tertiary amine groups, were compatible with the reaction conditions. Products were also obtained from alkyl sulfoxonium ylide starting materials, which overcame the current limitation of available methods.