Metal-free C-S Borylation Of Aryl Sulfides And C-C Borylation Of Aryl Amides

Arylboron compounds are important organic synthesis intermediates,which can be used as coupling components of Suzuki-Miyaura reaction and as starting materials for reactions such as oxidation,Chan-Lam coupling,halogenation and homologation.They are widely used in medical materials and other fields.Based on the importance of arylboron compounds,the synthesis of arylboron compounds has always been one of the research hotspots in the field of organic chemistry.The current methods for synthesizing arylboron compounds include borylation of aryl metal reagents,borylation of aryl carbon hetero-bonds and polar carbon-carbon bonds,borylation of aromatic hydrocarbons,and so on.In recent decades,impressive progress has been made in the synthesis of arylboron compounds under mild reaction conditions,although most required the use of transition metal catalysts.Aryl sulfide compounds have important application value in the fields of medicine,materials,dyes,etc.Aryl amide compounds are also widely used in the chemical industry,the activation and transformation of their chemical bonds have attracted extensive attention of organic chemists.In recent years,C-S borylation of aryl sulfides and C-C borylation of aryl amides have been reported as novel synthetic methods for arylboron compounds.However,most of these two types of reactions require the participation of transition metal catalysts,which have disadvantages such as high cost and heavy metal residues.Thus,it is of great scientific significance and practical value to develop metal-free C-S borylation of aryl sulfides and C-C borylation aryl amides.In this paper,the C-S bond activation of aryl sulfides and the C-C bond activation of aryl amides are systematically discussed,and the research on the borylation of aryl sulfides and aryl amides without transition metal are carried out.Here are the results:1.Photoinduced aerobic C–S borylation of aryl sulfides.Unlike previously reported methods without metal involvement,this method does not require precatalysis.In the reaction,mediated by a catalytic amount of benzoquinone and under the irradiation of blue light,the aryl sulfides and B₂pin₂can undergo C-S borylation at room temperature to obtain aryl boronate esters.The reaction condition is simple and mild,and has the advantages of good functional group compatibility.The study of the reaction mechanism shows that the reaction undergoes a radical borylation process involving the participation of superoxide radical anion.2.B（OMe）₃-mediated C-C borylation of aryl amides.Under the mediation of B（OMe）₃,N,N-dimethylbenzamide and B₂pin₂can undergo C-C borylation and yield aryl boronate esters in low yields.After continuous optimization of the reaction system,the yield of the target product still needs to be improved.Preliminary substrates range exploration showed good substrate suitability for this reaction.