Umpolung reactivity of N-sulfonylhydrazones and imino esters to access functionalized oxazoles

Abstract

We report the synthesis of functionalized oxazoles via umpolung reactivity of N-sulfonylhydrazones and imino esters. The reaction involves light-induced N–S bond cleavage of N-sulfonylhydrazones to produce nucleophilic diazo intermediates in the presence of Cs₂CO₃, which then react with electrophilic N-centered imino esters under mild conditions. The method offers high functional-group tolerance, good yields, and scalability, enabling the synthesis of biologically active precursor molecules such as HDAC6 inhibitors and angiotensin II receptor blockers.