Copper promoted, direct sulfenylation of n-aryl pyrazoles

Abstract

Direct functionalization of N-heterocycles often attracts substantial attention, as the targeted compounds find ubiquitous uses in many applications. Among common N-heterocycles, substituted pyrazoles are still challenging compounds for functionalization, though commonly useful in bio- and material-related studies. Herein, we report a general method for direct sulfenylation at the C₄-H bonds of pyrazoles with diaryl disulfides. This transformation produces unsymmetrical thioethers, which often require the use of pre-functionalized starting materials and partners with unpleasant smells. Our reaction conditions involve the use of a CuCl₂ catalyst, K₂S₂O₈ oxidant, and CH₃COOH as the solvent. A wide range of functionalities, including bromo, chloro, and nitro groups, were well-compatible. A possible mechanism, including electrophilic sulfenylation, was proposed.