Research On CS Bond Construction Based On CH Bond Functionalization Reaction

C-S bonds are widely spread in many natural products and biomacromolecules.Seeking novel and efficient approaches for C-S bond formations has always been a hot topic in organic chemistry.The direct coupling ofthiols or disulfides with organic halides,pseudo-halides or arylboronic acids under transition-metal-catalyzed conditions has been proven to be a common tool for the formation of C–S bonds.Recently,transition-metal-catalyzed decarboxylative cross-coupling reactions have also emerged as a versatile method for C–S bond formation starting from readily available and chemical stable carboxylic acids.However,these reactions could possess some limitations,including not easily available precursors,strong oxidants,harsh reaction conditions,and toxic metal salt catalysts.Recently,there are increasing demands in metal-free organic transformations owing to that trace-metal impurities could be avoided in the target compounds.This article foucuses on the C-S bond formation based on C-H functionalization,and the results were as follows:A facile and eco-friendly protocol for construction of the C-4 sulfenylated pyrazoles via a radical pathway was established for the first time.The reaction worked smoothly under catalyst-and additive-free conditions to afford a wide range of sulfenylated pyrazole derivatives in good to excellent yields.This reaction provides a new strategy for the formation of C-S bond.The developed protocol opens a new avenue towards the C-S bond-forming reactions,thus promising the broad applications in organic and pharmaceutical chemistry.Visible light and Eosin B-catalyzed the direct sulfenylation of sp~2 C-H bond with sulfinic acids through a photoredox process has been initially demonstrated at room temperature under transition-metal-free conditions.Diverse hetroaryl sulfides were obtained in moderate to good yields.More interestingly,a reductive product could be obtained under an visible-light-induced oxidative condition.This method would attract much attention in organic chemistry and medical chemistry.The first example of direct fixation of sulfur dioxide between heteroaryls and aryl halides has been developed via copper-catalyzed regioselective cleavage of C-X and C-H bonds under base-free and ligand-free conditions by using DABSO as a solid and bench-stable sulfur dioxide surrogate,and the present method exhibits tolerance of wide functional groups.Notably,the sulfonylation reaction proceeded well under base-free or ligand-free conditions.