Study On The Oxidation Functionalization Of Benzylic C(sp~3)-H Bond Promoted By Ultraviolet Or DDQ

Aryl compounds play important roles in biomedicine,polymer materials,synthetic chemistry and other fields as an indispensable organic structure.The benzylic C-H bond has been proved to have good activity in the study,synthetic chemists have paid more attention to the oxidation functionalization of benzylic C?sp³?-H bond.How to transform the benzylic C?sp³?-H bond into C=O bond,C-C bond,C-N bond by simpler,more economical and environmentally friendly methods is a challenge at present.Based on the previous work of our group,this paper reports the oxidation functionalization of benzylic C?sp³?-H bond of two kinds of aryl compounds:xanthenes and diphenylmethanes.?1?Xanthene is a heterotricyclic compound,its oxidative product xanthone plays important roles in anti-hypertension and anti-tumor for its significant biological activity.In recent years,with the rapid development of photocatalysis,synthetic chemists's attention has gradually turned to the application of photocatalysis in oxidation of benzylic C?sp³?-H bond.In this paper,a ultraviolet-light-induced benzylic oxidation of xanthenes without external photocatalyst or chemical catalyst was developed.In the process of condition exploration,the effects of different wavelengths of light on the reaction were compared.After selecting the best light source,the best solvent of the reaction was selected.These factors including mild room temperature condition,high catalytic efficiency,good tolerance to a variety of substrates with different substituents make the ultraviolet catalytic strategy have a excellent research prospect.In addition,we propose a reasonable mechanism based on the demonstration of experiments and literatures,the reaction type is radical type,and oxygen source is from air.?2?Diphenylmethane is an important intermediate in organic synthesis,It is a challenging work to introduce heterocyclic aromatics through asymmetric direct functionalization of benzylic C?sp³?-H bond.In this paper,a catalytic oxidative system of Fe Cl₂/DDQ is reported,which promoted the cross dehydrogenative coupling reaction of diphenymethane and benzofuran.DDQ?2,3-dichloro-5,6-dicyano-1,4-benzoquinone?as a kind of highly active oxidant,can effectively oxidize to couple of diphenylmethane and benzofuran in nitrogen atmosphere and heating conditions after coordination with Fe Cl₂.This scheme provides a nevol strategy for the selective coupling of benzylic C?sp³?-H bond with C?sp²?-H bond at heterocyclic aromatics to form the C-C bond,which establishes a foundation for future research.The study of functionalization of benzylic C?sp³?-H bond is still to be developed,ultraviolet light and DDQ have good performance in this work,which can be used for reference.