The Research Of Building C-S Bond Based On Oxidative Dehydrogenation In Visible Light Photocatalytic Systems

Visible light is an environmentally friendly ideal reagent,which is also highly compatible with the goals of green chemistry.Unlike many conventional reagents,visible light is non-toxic,clean,and can be obtained from renewable sources.However,the need for high-energy UV radiation in most organic photochemical processes has limited the practicality and environmental benefits of photochemical synthesis in industrially scales.Since the groundbreaking researches by MacMillan,Stephenson,and Yoon,visible light photocatalytic redox transformations have been established as a powerful strategy to promote the activation of organic molecules and develop novel synthetic methods.The C-S bond is an important structural motif in biologically active molecules and functional materials,the applications of thioether compounds is also very widespread.However,the traditional methods of constructing C-S bond developed in the past few decades,are still restricted to harsh reaction conditions,specificity to some substrates.Therefore,seeking a novel method for the construction of thioether compounds with mild conditions and broad substrate scope is a very important research.Because of the green,environmentally friendly,and high efficient of visible light photocatalysis processes,we made efforts to directly construct C-S bonds through photocatalytic oxidations of two C-H bonds.This article conducted an efficient and convenient visible light photocatalytic direct C-3 thioetherification of indoles with thiophenols,delivering functionalized indoles,which are very important,and widely used in antibacterial drugs and anti-allergic drugs.Therefore,it is particularly important to construct such compounds under mild conditions.This strategy uses thiophenols as the coupling reagents and cheap Rose Bengal as the visible light photocatalyst,and features the advantages of mild reaction conditions,easily available of raw materials,atom-economic and environmentally benign,etc.34 C-3 thioetherification of indoles were synthesized in medium yield under visible light irradiation.Based on the literatures and the control experiment,we proposed a possible mechanism of this reaction.This method provides a direct approach for C-S bond formation and has potential applications in the chemical and pharmaceutical industries.This article also developed the cross-dehydrogenative coupling(CDC)of 1,3-dicarbonyl compounds with both aromatic and aliphatic thilos under the visible light photocatalytic aerobic conditions.However,ketones and thiophenols are both nucleophiles,and either of them needs to be converted into the corresponding electrophiles prior to construct C-S bonds,so the reaction conditions are rather harsh.This method uses aromatic and aliphatic thilos as the coupling reagents and cheap Rose Bengal as the visible light photocatalyst,23a-carbonyl thioethers were synthesized in medium yield under visible light irradiation.and provides a direct route to the construction of C-S bonds to deliver a-carbonyl thioethers.Based on the literatures and the control experiment,we proposed a possible mechanism of this reaction.The mild reaction conditions,use of green air as the oxidant,and as well as the broad functional group compatibility and high yields,make this method particularly attractive.