Mechanistic insights for nickel catalyzed light‐assisted carbon–sulfur cross‐coupling reaction

Abstract

The C-S cross-coupling reaction is a very efficient and powerful tool for constructing C-S bonds. Despite the well-reported C-S cross-coupling protocols using aryl halides, this reaction using sp2-hybridized nonaromatic halides is still challenging. Herein, we report light-assisted C-S cross-coupling between thiols and 5-chlorobenzofurazan under blue LED irradiation. We used a new nickel catalyst to synthesize 11 unpublished compounds. Furthermore, we assessed the mechanism and the influence of light irradiation on this reaction and proposed a plausible mechanism that is mediated by the excited state of the nickel catalyst promoted by irradiation with blue light and the C-S coupling product formed. Notably, C-S cross-coupling under light irradiation was performed for the first time using a nickel catalyst in the absence of an external photocatalyst. We demonstrated that because nickel has a low energy barrier for oxidative addition, this protocol proceeded efficiently using chlorine as a leaving group, and the excited state of the nickel catalyst promoted reductive elimination with a lower energy barrier. It is important to mention that the procedure was tolerated by many functional groups within the thiol, affording a greater than 99% yield after reacting for 6 h.