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 We used a new nickel catalyst to synthesize 11 unpublished compounds.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.